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Wednesday, November 16, 2022

Nobel Prize

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Nobel_Prize

Nobel Prize
A golden medallion with an embossed image of Alfred Nobel facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then "MDCCCXXXIII" above, followed by (smaller) "OB•" then "MDCCCXCVI" below.
Awarded forContributions that have conferred the greatest benefit to humankind in the areas of Physics, Chemistry, Physiology or Medicine, Literature, Economics and Peace.
Country
  • Sweden (all prizes except the Peace Prize)
  • Norway (Peace Prize only)
Presented by
Reward(s)A gold medal, a diploma, and a monetary award of 10 million SEK
First awarded1901; 121 years ago
Last awarded2022
Number of laureates609 prizes to 975 laureates (as of 2021)
Websitenobelprize.org

The Nobel Prizes (/nˈbɛl/ noh-BEL; Swedish: Nobelpriset [nʊˈbɛ̂lːˌpriːsɛt]; Norwegian: Nobelprisen [nʊˈbɛ̀lːˌpriːsn̩]) are five separate prizes that, according to Alfred Nobel's will of 1895, are awarded to "those who, during the preceding year, have conferred the greatest benefit to humankind." Alfred Nobel was a Swedish chemist, engineer, and industrialist most famously known for the invention of dynamite. He died in 1896. In his will, he bequeathed all of his "remaining realisable assets" to be used to establish five prizes which became known as "Nobel Prizes." Nobel Prizes were first awarded in 1901.

Nobel Prizes are awarded in the fields of Physics, Chemistry, Physiology or Medicine, Literature, and Peace (Nobel characterized the Peace Prize as "to the person who has done the most or best to advance fellowship among nations, the abolition or reduction of standing armies, and the establishment and promotion of peace congresses"). In 1968, Sveriges Riksbank (Sweden's central bank) funded the establishment of the Prize in Economic Sciences in Memory of Alfred Nobel, to also be administered by the Nobel Foundation. Nobel Prizes are widely regarded as the most prestigious awards available in their respective fields.

The prize ceremonies take place annually. Each recipient (known as a "laureate") receives a gold medal, a diploma, and a monetary award. In 2021, the Nobel Prize monetary award is 10,000,000 SEK. A prize may not be shared among more than three individuals, although the Nobel Peace Prize can be awarded to organizations of more than three people. Although Nobel Prizes are not awarded posthumously, if a person is awarded a prize and dies before receiving it, the prize is presented.

The Nobel Prizes, beginning in 1901, and the Nobel Memorial Prize in Economic Sciences, beginning in 1969, have been awarded 609 times to 975 people and 25 organizations. Five individuals and two organisations have received more than one Nobel Prize.

History

A black and white photo of a bearded man in his fifties sitting in a chair.
Alfred Nobel had the unpleasant surprise of reading his own obituary, which was titled "The merchant of death is dead", in a French newspaper.

Alfred Nobel (listen ) was born on 21 October 1833 in Stockholm, Sweden, into a family of engineers. He was a chemist, engineer, and inventor. In 1894, Nobel purchased the Bofors iron and steel mill, which he made into a major armaments manufacturer. Nobel also invented ballistite. This invention was a precursor to many smokeless military explosives, especially the British smokeless powder cordite. As a consequence of his patent claims, Nobel was eventually involved in a patent infringement lawsuit over cordite. Nobel amassed a fortune during his lifetime, with most of his wealth coming from his 355 inventions, of which dynamite is the most famous.

In 1888, Nobel was astonished to read his own obituary, titled "The merchant of death is dead", in a French newspaper. It was Alfred's brother Ludvig who had died; the obituary was eight years premature. The article disconcerted Nobel and made him apprehensive about how he would be remembered. This inspired him to change his will. On 10 December 1896, Alfred Nobel died in his villa in San Remo, Italy, from a cerebral haemorrhage. He was 63 years old.

Nobel wrote several wills during his lifetime. He composed the last over a year before he died, signing it at the Swedish–Norwegian Club in Paris on 27 November 1895. To widespread astonishment, Nobel's last will specified that his fortune be used to create a series of prizes for those who confer the "greatest benefit on mankind" in physics, chemistry, physiology or medicine, literature, and peace. Nobel bequeathed 94% of his total assets, 31 million SEK (c. US$186 million, €150 million in 2008), to establish the five Nobel Prizes. Owing to skepticism surrounding the will, it was not approved by the Storting in Norway until 26 April 1897. The executors of the will, Ragnar Sohlman and Rudolf Lilljequist, formed the Nobel Foundation to take care of the fortune and to organise the awarding of prizes.

Nobel's instructions named a Norwegian Nobel Committee to award the Peace Prize, the members of whom were appointed shortly after the will was approved in April 1897. Soon thereafter, the other prize-awarding organizations were designated. These were Karolinska Institute on 7 June, the Swedish Academy on 9 June, and the Royal Swedish Academy of Sciences on 11 June. The Nobel Foundation reached an agreement on guidelines for how the prizes should be awarded; and, in 1900, the Nobel Foundation's newly created statutes were promulgated by King Oscar II. In 1905, the personal union between Sweden and Norway was dissolved.

Nobel Foundation

Formation of Foundation

A paper with stylish handwriting on it with the title "Testament"
Alfred Nobel's will stated that 94% of his total assets should be used to establish the Nobel Prizes.

According to his will and testament read in Stockholm on 30 December 1896, a foundation established by Alfred Nobel would reward those who serve humanity. The Nobel Prize was funded by Alfred Nobel's personal fortune. According to the official sources, Alfred Nobel bequeathed most of his fortune to the Nobel Foundation that now forms the economic base of the Nobel Prize.

The Nobel Foundation was founded as a private organization on 29 June 1900. Its function is to manage the finances and administration of the Nobel Prizes. In accordance with Nobel's will, the primary task of the foundation is to manage the fortune Nobel left. Robert and Ludvig Nobel were involved in the oil business in Azerbaijan, and according to Swedish historian E. Bargengren, who accessed the Nobel family archive, it was this "decision to allow withdrawal of Alfred's money from Baku that became the decisive factor that enabled the Nobel Prizes to be established". Another important task of the Nobel Foundation is to market the prizes internationally and to oversee informal administration related to the prizes. The foundation is not involved in the process of selecting the Nobel laureates. In many ways, the Nobel Foundation is similar to an investment company, in that it invests Nobel's money to create a solid funding base for the prizes and the administrative activities. The Nobel Foundation is exempt from all taxes in Sweden (since 1946) and from investment taxes in the United States (since 1953). Since the 1980s, the foundation's investments have become more profitable and as of 31 December 2007, the assets controlled by the Nobel Foundation amounted to 3.628 billion Swedish kronor (c. US$560 million).

According to the statutes, the foundation consists of a board of five Swedish or Norwegian citizens, with its seat in Stockholm. The Chairman of the Board is appointed by the Swedish King in Council, with the other four members appointed by the trustees of the prize-awarding institutions. An Executive Director is chosen from among the board members, a deputy director is appointed by the King in Council, and two deputies are appointed by the trustees. However, since 1995, all the members of the board have been chosen by the trustees, and the executive director and the deputy director appointed by the board itself. As well as the board, the Nobel Foundation is made up of the prize-awarding institutions (the Royal Swedish Academy of Sciences, the Nobel Assembly at Karolinska Institute, the Swedish Academy, and the Norwegian Nobel Committee), the trustees of these institutions, and auditors.

Foundation capital and cost

The capital of the Nobel Foundation today is invested 50% in shares, 20% bonds and 30% other investments (e.g. hedge funds or real estate). The distribution can vary by 10 percent. At the beginning of 2008, 64% of the funds were invested mainly in American and European stocks, 20% in bonds, plus 12% in real estate and hedge funds.

In 2011, the total annual cost was approximately 120 million kronor, with 50 million kronor as the prize money. Further costs to pay institutions and persons engaged in giving the prizes were 27.4 million kronor. The events during the Nobel week in Stockholm and Oslo cost 20.2 million kronor. The administration, Nobel symposium, and similar items had costs of 22.4 million kronor. The cost of the Economic Sciences prize of 16.5 Million kronor is paid by the Sveriges Riksbank.

Inaugural Nobel prizes

A black and white photo of a bearded man in his fifties sitting in a chair.
Wilhelm Röntgen received the first Physics Prize for his discovery of X-rays.

Once the Nobel Foundation and its guidelines were in place, the Nobel Committees began collecting nominations for the inaugural prizes. Subsequently, they sent a list of preliminary candidates to the prize-awarding institutions.

The Nobel Committee's Physics Prize shortlist cited Wilhelm Röntgen's discovery of X-rays and Philipp Lenard's work on cathode rays. The Academy of Sciences selected Röntgen for the prize. In the last decades of the 19th century, many chemists had made significant contributions. Thus, with the Chemistry Prize, the academy "was chiefly faced with merely deciding the order in which these scientists should be awarded the prize". The academy received 20 nominations, eleven of them for Jacobus van 't Hoff. Van 't Hoff was awarded the prize for his contributions in chemical thermodynamics.

The Swedish Academy chose the poet Sully Prudhomme for the first Nobel Prize in Literature. A group including 42 Swedish writers, artists, and literary critics protested against this decision, having expected Leo Tolstoy to be awarded. Some, including Burton Feldman, have criticised this prize because they consider Prudhomme a mediocre poet. Feldman's explanation is that most of the academy members preferred Victorian literature and thus selected a Victorian poet. The first Physiology or Medicine Prize went to the German physiologist and microbiologist Emil von Behring. During the 1890s, von Behring developed an antitoxin to treat diphtheria, which until then was causing thousands of deaths each year.

The first Nobel Peace Prize went to the Swiss Jean Henri Dunant for his role in founding the International Red Cross Movement and initiating the Geneva Convention, and jointly given to French pacifist Frédéric Passy, founder of the Peace League and active with Dunant in the Alliance for Order and Civilization.

Second World War

In 1938 and 1939, Adolf Hitler's Third Reich forbade three laureates from Germany (Richard Kuhn, Adolf Friedrich Johann Butenandt, and Gerhard Domagk) from accepting their prizes. They were all later able to receive the diploma and medal. Even though Sweden was officially neutral during the Second World War, the prizes were awarded irregularly. In 1939, the Peace Prize was not awarded. No prize was awarded in any category from 1940 to 1942, due to the occupation of Norway by Germany. In the subsequent year, all prizes were awarded except those for literature and peace.

During the occupation of Norway, three members of the Norwegian Nobel Committee fled into exile. The remaining members escaped persecution from the Germans when the Nobel Foundation stated that the committee building in Oslo was Swedish property. Thus it was a safe haven from the German military, which was not at war with Sweden. These members kept the work of the committee going, but did not award any prizes. In 1944, the Nobel Foundation, together with the three members in exile, made sure that nominations were submitted for the Peace Prize and that the prize could be awarded once again.

Prize in Economic Sciences

Map of Nobel laureates by country

In 1968, Sweden's central bank Sveriges Riksbank celebrated its 300th anniversary by donating a large sum of money to the Nobel Foundation to be used to set up a prize in honour of Alfred Nobel. The following year, the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel was awarded for the first time. The Royal Swedish Academy of Sciences became responsible for selecting laureates. The first laureates for the Economics Prize were Jan Tinbergen and Ragnar Frisch "for having developed and applied dynamic models for the analysis of economic processes". The board of the Nobel Foundation decided that after this addition, it would allow no further new prizes.

Award process

The award process is similar for all of the Nobel Prizes, the main difference being who can make nominations for each of them.

Nominations

Nomination forms are sent by the Nobel Committee to about 3,000 individuals, usually in September the year before the prizes are awarded. These individuals are generally prominent academics working in a relevant area. Regarding the Peace Prize, inquiries are also sent to governments, former Peace Prize laureates, and current or former members of the Norwegian Nobel Committee. The deadline for the return of the nomination forms is 31 January of the year of the award. The Nobel Committee nominates about 300 potential laureates from these forms and additional names. The nominees are not publicly named, nor are they told that they are being considered for the prize. All nomination records for a prize are sealed for 50 years from the awarding of the prize.

Selection

The Nobel Committee then prepares a report reflecting the advice of experts in the relevant fields. This, along with the list of preliminary candidates, is submitted to the prize-awarding institutions. There are four awarding institutions for the six prizes awarded:

The institutions meet to choose the laureate or laureates in each field by a majority vote. Their decision, which cannot be appealed, is announced immediately after the vote. A maximum of three laureates and two different works may be selected per award. Except for the Peace Prize, which can be awarded to institutions, the awards can only be given to individuals.

Posthumous nominations

Although posthumous nominations are not presently permitted, individuals who died in the months between their nomination and the decision of the prize committee were originally eligible to receive the prize. This has occurred twice: the 1931 Literature Prize awarded to Erik Axel Karlfeldt, and the 1961 Peace Prize awarded to UN Secretary General Dag Hammarskjöld. Since 1974, laureates must be thought alive at the time of the October announcement. There has been one laureate, William Vickrey, who in 1996 died after the prize (in Economics) was announced but before it could be presented. On 3 October 2011, the laureates for the Nobel Prize in Physiology or Medicine were announced; however, the committee was not aware that one of the laureates, Ralph M. Steinman, had died three days earlier. The committee was debating about Steinman's prize, since the rule is that the prize is not awarded posthumously. The committee later decided that as the decision to award Steinman the prize "was made in good faith", it would remain unchanged.

Recognition time lag

Nobel's will provided for prizes to be awarded in recognition of discoveries made "during the preceding year". Early on, the awards usually recognised recent discoveries. However, some of those early discoveries were later discredited. For example, Johannes Fibiger was awarded the 1926 Prize in Physiology or Medicine for his purported discovery of a parasite that caused cancer. To avoid repeating this embarrassment, the awards increasingly recognised scientific discoveries that had withstood the test of time. According to Ralf Pettersson, former chairman of the Nobel Prize Committee for Physiology or Medicine, "the criterion 'the previous year' is interpreted by the Nobel Assembly as the year when the full impact of the discovery has become evident."

A room with pictures on the walls. In the middle of the room there is a wooden table with chairs around it.
The committee room of the Norwegian Nobel Committee

The interval between the award and the accomplishment it recognises varies from discipline to discipline. The Literature Prize is typically awarded to recognise a cumulative lifetime body of work rather than a single achievement. The Peace Prize can also be awarded for a lifetime body of work. For example, 2008 laureate Martti Ahtisaari was awarded for his work to resolve international conflicts. However, they can also be awarded for specific recent events. For instance, Kofi Annan was awarded the 2001 Peace Prize just four years after becoming the Secretary-General of the United Nations. Similarly Yasser Arafat, Yitzhak Rabin, and Shimon Peres received the 1994 award, about a year after they successfully concluded the Oslo Accords. The most recent controversy  was caused by awarding the 2009 Nobel Peace Prize to Barack Obama in his first year as US president.

Awards for physics, chemistry, and medicine are typically awarded once the achievement has been widely accepted. Sometimes, this takes decades – for example, Subrahmanyan Chandrasekhar shared the 1983 Physics Prize for his 1930s work on stellar structure and evolution. Not all scientists live long enough for their work to be recognised. Some discoveries can never be considered for a prize if their impact is realised after the discoverers have died.

Award ceremonies

Two men standing on a stage. The man to the left is clapping his hands and looking towards the other man. The second man is smiling and showing two items to an audience not seen on the image. The items are a diploma which includes a painting and a box containing a gold medal. Behind them is a blue pillar clad in flowers.
A man in his fifties standing behind a desk with computers on it. On the desk is a sign reading "Kungl. Vetensk. Akad. Sigil".
Right: Giovanni Jona-Lasinio presenting Yoichiro Nambu's Nobel Lecture at Aula Magna, Stockholm in 2008; Left: Barack Obama after receiving the Nobel Peace Prize in Oslo City Hall from the hands of Norwegian Nobel Committee Chairman Thorbjørn Jagland in 2009

Except for the Peace Prize, the Nobel Prizes are presented in Stockholm, Sweden, at the annual Prize Award Ceremony on 10 December, the anniversary of Nobel's death. The recipients' lectures are normally held in the days prior to the award ceremony. The Peace Prize and its recipients' lectures are presented at the annual Prize Award Ceremony in Oslo, Norway, usually on 10 December. The award ceremonies and the associated banquets are typically major international events. The Prizes awarded in Sweden's ceremonies are held at the Stockholm Concert Hall, with the Nobel banquet following immediately at Stockholm City Hall. The Nobel Peace Prize ceremony has been held at the Norwegian Nobel Institute (1905–1946), at the auditorium of the University of Oslo (1947–1989), and at Oslo City Hall (1990–present).

The highlight of the Nobel Prize Award Ceremony in Stockholm occurs when each Nobel laureate steps forward to receive the prize from the hands of the King of Sweden. In Oslo, the chairman of the Norwegian Nobel Committee presents the Nobel Peace Prize in the presence of the King of Norway and the Norwegian royal family. At first, King Oscar II did not approve of awarding grand prizes to foreigners. It is said that he changed his mind once his attention had been drawn to the publicity value of the prizes for Sweden.

Nobel Banquet

A set table with a white table cloth. There are many plates and glasses plus a menu visible on the table.
Table at the 2005 Nobel Banquet in Stockholm

After the award ceremony in Sweden, a banquet is held in the Blue Hall at the Stockholm City Hall, which is attended by the Swedish Royal Family and around 1,300 guests. The Nobel Peace Prize banquet is held in Norway at the Oslo Grand Hotel after the award ceremony. Apart from the laureate, guests include the president of the Storting, on occasion the Swedish prime minister, and, since 2006, the King and Queen of Norway. In total, about 250 guests attend.

Nobel lecture

According to the statutes of the Nobel Foundation, each laureate is required to give a public lecture on a subject related to the topic of their prize. The Nobel lecture as a rhetorical genre took decades to reach its current format. These lectures normally occur during Nobel Week (the week leading up to the award ceremony and banquet, which begins with the laureates arriving in Stockholm and normally ends with the Nobel banquet), but this is not mandatory. The laureate is only obliged to give the lecture within six months of receiving the prize, but some have happened even later. For example, US President Theodore Roosevelt received the Peace Prize in 1906 but gave his lecture in 1910, after his term in office. The lectures are organized by the same association which selected the laureates.

Prizes

Medals

The Nobel Foundation announced on 30 May 2012 that it had awarded the contract for the production of the five (Swedish) Nobel Prize medals to Svenska Medalj AB. Between 1902 and 2010, the Nobel Prize medals were minted by Myntverket (the Swedish Mint), Sweden's oldest company, which ceased operations in 2011 after 107 years. In 2011, the Mint of Norway, located in Kongsberg, made the medals. The Nobel Prize medals are registered trademarks of the Nobel Foundation.

Each medal features an image of Alfred Nobel in left profile on the obverse. The medals for physics, chemistry, physiology or medicine, and literature have identical obverses, showing the image of Alfred Nobel and the years of his birth and death. Nobel's portrait also appears on the obverse of the Peace Prize medal and the medal for the Economics Prize, but with a slightly different design. For instance, the laureate's name is engraved on the rim of the Economics medal. The image on the reverse of a medal varies according to the institution awarding the prize. The reverse sides of the medals for chemistry and physics share the same design.

A heavily decorated paper with the name "Fritz Haber" on it.
Laureates receive a heavily decorated diploma together with a gold medal and the prize money. Here Fritz Haber's diploma is shown, which he received for the development of a method to synthesise ammonia.

All medals made before 1980 were struck in 23 carat gold. Since then, they have been struck in 18 carat green gold plated with 24 carat gold. The weight of each medal varies with the value of gold, but averages about 175 grams (0.386 lb) for each medal. The diameter is 66 millimetres (2.6 in) and the thickness varies between 5.2 millimetres (0.20 in) and 2.4 millimetres (0.094 in). Because of the high value of their gold content and tendency to be on public display, Nobel medals are subject to medal theft. During World War II, the medals of German scientists Max von Laue and James Franck were sent to Copenhagen for safekeeping. When Germany invaded Denmark, Hungarian chemist (and Nobel laureate himself) George de Hevesy dissolved them in aqua regia (nitro-hydrochloric acid), to prevent confiscation by Nazi Germany and to prevent legal problems for the holders. After the war, the gold was recovered from solution, and the medals re-cast.

Diplomas

Nobel laureates receive a diploma directly from the hands of the King of Sweden, or in the case of the peace prize, the chairman of the Norwegian Nobel Committee. Each diploma is uniquely designed by the prize-awarding institutions for the laureates that receive them. The diploma contains a picture and text in Swedish which states the name of the laureate and normally a citation of why they received the prize. None of the Nobel Peace Prize laureates has ever had a citation on their diplomas.

Award money

The laureates are given a sum of money when they receive their prizes, in the form of a document confirming the amount awarded. The amount of prize money depends upon how much money the Nobel Foundation can award each year. The purse has increased since the 1980s, when the prize money was 880,000 SEK per prize (c. 2.6 million SEK altogether, US$350,000 today). In 2009, the monetary award was 10 million SEK (US$1.4 million). In June 2012, it was lowered to 8 million SEK. If two laureates share the prize in a category, the award grant is divided equally between the recipients. If there are three, the awarding committee has the option of dividing the grant equally, or awarding one-half to one recipient and one-quarter to each of the others. It is common for recipients to donate prize money to benefit scientific, cultural, or humanitarian causes.

Controversies and criticisms

Controversial recipients

When it was announced that Henry Kissinger was to be awarded the Peace Prize, two of the Norwegian Nobel Committee members resigned in protest.

Among other criticisms, the Nobel Committees have been accused of having a political agenda, and of omitting more deserving candidates. They have also been accused of Eurocentrism, especially for the Literature Prize.

Peace Prize

Among the most criticised Nobel Peace Prizes was the one awarded to Henry Kissinger and Lê Đức Thọ. This led to the resignation of two Norwegian Nobel Committee members. Kissinger and Thọ were awarded the prize for negotiating a ceasefire between North Vietnam and the United States in January 1973. However, when the award was announced, both sides were still engaging in hostilities. Critics sympathetic to the North announced that Kissinger was not a peace-maker but the opposite, responsible for widening the war. Those hostile to the North and what they considered its deceptive practices during negotiations were deprived of a chance to criticise Lê Đức Thọ, as he declined the award. The satirist and musician Tom Lehrer has remarked that "political satire became obsolete when Henry Kissinger was awarded the Nobel Peace Prize."

Yasser Arafat, Shimon Peres, and Yitzhak Rabin received the Peace Prize in 1994 for their efforts in making peace between Israel and Palestine. Immediately after the award was announced, one of the five Norwegian Nobel Committee members denounced Arafat as a terrorist and resigned. Additional misgivings about Arafat were widely expressed in various newspapers.

Another controversial Peace Prize was that awarded to Barack Obama in 2009. Nominations had closed only eleven days after Obama took office as President of the United States, but the actual evaluation occurred over the next eight months. Obama himself stated that he did not feel deserving of the award, or worthy of the company in which it would place him. Past Peace Prize laureates were divided, some saying that Obama deserved the award, and others saying he had not secured the achievements to yet merit such an accolade. Obama's award, along with the previous Peace Prizes for Jimmy Carter and Al Gore, also prompted accusations of a liberal bias.

Literature Prize

The award of the 2004 Literature Prize to Elfriede Jelinek drew a protest from a member of the Swedish Academy, Knut Ahnlund. Ahnlund resigned, alleging that the selection of Jelinek had caused "irreparable damage to all progressive forces, it has also confused the general view of literature as an art". He alleged that Jelinek's works were "a mass of text shovelled together without artistic structure". The 2009 Literature Prize to Herta Müller also generated criticism. According to The Washington Post, many US literary critics and professors were ignorant of her work. This made those critics feel the prizes were too Eurocentric. The 2019 Literature Prize to Peter Handke received heavy criticisms from various authors, such as Salman Rushdie and Hari Kunzru, and was condemned by the governments of Bosnia and Herzegovina, Kosovo, and Turkey, due to his history of Bosnian genocide denialism and his support for Slobodan Milošević.

Science prizes

In 1949, the neurologist António Egas Moniz received the Physiology or Medicine Prize for his development of the prefrontal leucotomy. The previous year, Dr. Walter Freeman had developed a version of the procedure which was faster and easier to carry out. Due in part to the publicity surrounding the original procedure, Freeman's procedure was prescribed without due consideration or regard for modern medical ethics. Endorsed by such influential publications as The New England Journal of Medicine, leucotomy or "lobotomy" became so popular that about 5,000 lobotomies were performed in the United States in the three years immediately following Moniz's receipt of the Prize.

Overlooked achievements

Mahatma Gandhi, although nominated five times, was never awarded a Nobel Peace Prize.

Although Mahatma Gandhi, an icon of nonviolence in the 20th century, was nominated for the Nobel Peace Prize five times, in 1937, 1938, 1939, 1947, and a few days before he was assassinated on 30 January 1948, he was never awarded the prize.

In 1948, the year of Gandhi's death, the Norwegian Nobel Committee decided to make no award that year on the grounds that "there was no suitable living candidate".

In 1989, this omission was publicly regretted, when the 14th Dalai Lama was awarded the Peace Prize, the chairman of the committee said that it was "in part a tribute to the memory of Mahatma Gandhi".

Geir Lundestad, 2006 Secretary of Norwegian Nobel Committee, said,

The greatest omission in our 106 year history is undoubtedly that Mahatma Gandhi never received the Nobel Peace Prize. Gandhi could do without the Nobel Peace Prize. Whether the Nobel committee can do without Gandhi, is the question.

Other high-profile individuals with widely recognised contributions to peace have been overlooked. In 2009, an article in Foreign Policy magazine identified seven people who "never won the prize, but should have". The list consisted of Gandhi, Eleanor Roosevelt, Václav Havel, Ken Saro-Wiwa, Sari Nusseibeh, Corazon Aquino, and Liu Xiaobo. Liu Xiaobo would go on to win the 2010 Nobel Peace Prize while imprisoned.

In 1965, UN Secretary General U Thant was informed by the Norwegian Permanent Representative to the UN that he would be awarded that year's prize and asked whether or not he would accept. He consulted staff and later replied that he would. At the same time, Chairman Gunnar Jahn of the Nobel Peace prize committee, lobbied heavily against giving U Thant the prize and the prize was at the last minute awarded to UNICEF. The rest of the committee all wanted the prize to go to U Thant, for his work in defusing the Cuban Missile Crisis, ending the war in the Congo, and his ongoing work to mediate an end to the Vietnam War. The disagreement lasted three years and in 1966 and 1967 no prize was given, with Gunnar Jahn effectively vetoing an award to U Thant.

James Joyce, one of the controversial omissions of the Literature Prize

The Literature Prize also has controversial omissions. Adam Kirsch has suggested that many notable writers have missed out on the award for political or extra-literary reasons. The heavy focus on European and Swedish authors has been a subject of criticism. The Eurocentric nature of the award was acknowledged by Peter Englund, the 2009 Permanent Secretary of the Swedish Academy, as a problem with the award and was attributed to the tendency for the academy to relate more to European authors. This tendency towards European authors still leaves many European writers on a list of notable writers that have been overlooked for the Literature Prize, including Leo Tolstoy, Anton Chekhov, J. R. R. Tolkien, Émile Zola, Marcel Proust, Vladimir Nabokov, James Joyce, August Strindberg, Simon Vestdijk, Karel Čapek, the New World's Jorge Luis Borges, Ezra Pound, John Updike, Arthur Miller, Mark Twain, and Africa's Chinua Achebe.

Candidates can receive multiple nominations the same year. Gaston Ramon received a total of 155 nominations in physiology or medicine from 1930 to 1953, the last year with public nomination data for that award as of 2016. He died in 1963 without being awarded. Pierre Paul Émile Roux received 115 nominations in physiology or medicine, and Arnold Sommerfeld received 84 in physics. These are the three most nominated scientists without awards in the data published as of 2016. Otto Stern received 79 nominations in physics 1925–1943 before being awarded in 1943.

The strict rule against awarding a prize to more than three people is also controversial. When a prize is awarded to recognise an achievement by a team of more than three collaborators, one or more will miss out. For example, in 2002, the prize was awarded to Koichi Tanaka and John Fenn for the development of mass spectrometry in protein chemistry, an award that did not recognise the achievements of Franz Hillenkamp and Michael Karas of the Institute for Physical and Theoretical Chemistry at the University of Frankfurt.

According to one of the nominees for the prize in physics, the three person limit deprived him and two other members of his team of the honor in 2013: the team of Carl Hagen, Gerald Guralnik, and Tom Kibble published a paper in 1964 that gave answers to how the cosmos began, but did not share the 2013 Physics Prize awarded to Peter Higgs and François Englert, who had also published papers in 1964 concerning the subject. All five physicists arrived at the same conclusion, albeit from different angles. Hagen contends that an equitable solution is to either abandon the three limit restriction, or expand the time period of recognition for a given achievement to two years.

Similarly, the prohibition of posthumous awards fails to recognise achievements by an individual or collaborator who dies before the prize is awarded. The Economics Prize was not awarded to Fischer Black, who died in 1995, when his co-author Myron Scholes received the honor in 1997 for their landmark work on option pricing along with Robert C. Merton, another pioneer in the development of valuation of stock options. In the announcement of the award that year, the Nobel committee prominently mentioned Black's key role.

Political subterfuge may also deny proper recognition. Lise Meitner and Fritz Strassmann, who co-discovered nuclear fission along with Otto Hahn, may have been denied a share of Hahn's 1944 Nobel Chemistry Award due to having fled Germany when the Nazis came to power. The Meitner and Strassmann roles in the research was not fully recognised until years later, when they joined Hahn in receiving the 1966 Enrico Fermi Award.

Emphasis on discoveries over inventions

Alfred Nobel left his fortune to finance annual prizes to be awarded "to those who, during the preceding year, shall have conferred the greatest benefit on mankind". He stated that the Nobel Prizes in Physics should be given "to the person who shall have made the most important 'discovery' or 'invention' within the field of physics". Nobel did not emphasise discoveries, but they have historically been held in higher respect by the Nobel Prize Committee than inventions: 77% of the Physics Prizes have been given to discoveries, compared with only 23% to inventions. Christoph Bartneck and Matthias Rauterberg, in papers published in Nature and Technoetic Arts, have argued this emphasis on discoveries has moved the Nobel Prize away from its original intention of rewarding the greatest contribution to society.

Gender disparity

There have been a total of 57 women Nobel laureates compared to 873 male laureates. Most female laureates received them in the peace and literature categories. Marie Curie was the first female to receive the Nobel Prize in 1903 and the only woman to receive it twice.
 

In terms of the most prestigious awards in STEM fields, only a small proportion have been awarded to women. Out of 210 laureates in Physics, 181 in Chemistry and 216 in Medicine between 1901 and 2018, there were only three female laureates in physics, five in chemistry and 12 in medicine. Factors proposed to contribute to the discrepancy between this and the roughly equal human sex ratio include biased nominations, fewer women than men being active in the relevant fields, Nobel Prizes typically being awarded decades after the research was done (reflecting a time when gender bias in the relevant fields was greater), a greater delay in awarding Nobel Prizes for women's achievements making longevity a more important factor for women (one cannot be nominated to the Nobel Prize posthumously), and a tendency to omit women from jointly awarded Nobel Prizes. Despite these factors, Marie Curie is to date the only person awarded Nobel Prizes in two different sciences (Physics in 1903, Chemistry in 1911); she is one of only three people who have received two Nobel Prizes in sciences (see Multiple laureates below). Malala Yousafzai is the youngest person ever to be awarded the Nobel Peace Prize. When she received it in 2014, she was only 17 years old.

Status of the Economic Sciences Prize

Peter Nobel describes the Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel as a "false Nobel prize" that dishonours his relative Alfred Nobel, after whom the prize is named, and considers economics to be a pseudoscience.

Statistics

  1. Marie Curie, Pierre Curie (along with Henri Becquerel). Received Nobel Prize in Physics (1903).
  2. Irène Joliot-Curie, Frédéric Joliot. Received Nobel Prize in Chemistry (1935).
  3. Gerty Cori, Carl Cori. Received Nobel Prize in Medicine (1947).
  4. Gunnar Myrdal received Nobel Prize in Economics Sciences (1974), Alva Myrdal received Nobel Peace Prize (1982).
  5. May-Britt Moser, Edvard I. Moser. Received Nobel Prize in Medicine (2014)
  6. Esther Duflo, Abhijit Banerjee (along with Michael Kremer). Received Nobel Prize in Economics Sciences (2019).

Specially distinguished laureates

Multiple laureates

A black and white portrait of a woman in profile.
Marie Curie, one of five people who have received the Nobel Prize twice (Physics and Chemistry)

Five people have received two Nobel Prizes. Marie Curie received the Physics Prize in 1903 for her work on radioactivity and the Chemistry Prize in 1911 for the isolation of pure radium, making her the only person to be awarded a Nobel Prize in two different sciences. Linus Pauling was awarded the 1954 Chemistry Prize for his research into the chemical bond and its application to the structure of complex substances. Pauling was also awarded the Peace Prize in 1962 for his activism against nuclear weapons, making him the only laureate of two unshared prizes. John Bardeen received the Physics Prize twice: in 1956 for the invention of the transistor and in 1972 for the theory of superconductivity. Frederick Sanger received the prize twice in Chemistry: in 1958 for determining the structure of the insulin molecule and in 1980 for inventing a method of determining base sequences in DNA. Karl Barry Sharpless was awarded the 2001 Chemistry Prize for his research into chirally catalysed oxidation reactions, and the 2022 Chemistry Prize for click chemistry.

Two organizations have received the Peace Prize multiple times. The International Committee of the Red Cross received it three times: in 1917 and 1944 for its work during the world wars; and in 1963 during the year of its centenary. The United Nations High Commissioner for Refugees has been awarded the Peace Prize twice for assisting refugees: in 1954 and 1981.

Family laureates

The Curie family has received the most prizes, with four prizes awarded to five individual laureates. Marie Curie received the prizes in Physics (in 1903) and Chemistry (in 1911). Her husband, Pierre Curie, shared the 1903 Physics prize with her. Their daughter, Irène Joliot-Curie, received the Chemistry Prize in 1935 together with her husband Frédéric Joliot-Curie. In addition, the husband of Marie Curie's second daughter, Henry Labouisse, was the director of UNICEF when he accepted the Nobel Peace Prize in 1965 on that organisation's behalf.

Although no family matches the Curie family's record, there have been several with two laureates. The Nobel Prize in Physiology or Medicine was awarded to the husband-and-wife team of Gerty Cori and Carl Ferdinand Cori in 1947 Prize, and by the husband-and-wife team of May-Britt Moser and Edvard Moser in 2014 (along with John O'Keefe). The Physics Prize in 1906 was won by J. J. Thomson for showing that electrons are particles, and in 1937 by his son, George Paget Thomson, for showing that they also have the properties of waves. William Henry Bragg and his son, William Lawrence Bragg, shared the Physics Prize in 1915 for inventing X-ray crystallography. Niels Bohr was awarded the Physics Prize in 1922, as was his son, Aage Bohr, in 1975. The Physics Prize was awarded to Manne Siegbahn in 1924, followed by his son, Kai Siegbahn, in 1981. Hans von Euler-Chelpin, who received the Chemistry Prize in 1929, was the father of Ulf von Euler, who was awarded the Physiology or Medicine Prize in 1970. C. V. Raman was awarded the Physics Prize in 1930 and was the uncle of Subrahmanyan Chandrasekhar, who was awarded the same prize in 1983. Arthur Kornberg received the Physiology or Medicine Prize in 1959; Kornberg's son Roger later received the Chemistry Prize in 2006. Arthur Schawlow received the 1981 Physics prize, and was married to the sister of 1964 Physics laureate Charles Townes. Two members of the Hodgkin family received Nobels in consecutive years: Sir Alan Lloyd Hodgkin shared in the Nobel for Physiology or Medicine in 1963, followed by Dorothy Crowfoot Hodgkin, the wife of his first cousin, who won solo for Chemistry in 1964. Jan Tinbergen, who was awarded the first Economics Prize in 1969, was the brother of Nikolaas Tinbergen, who received the 1973 Physiology or Medicine Prize. Gunnar Myrdal who was awarded the Economics Prize in 1974, was the husband of Alva Myrdal, Peace Prize laureate in 1982. Economics laureates Paul Samuelson and Kenneth Arrow were brothers-in-law. Frits Zernike, who was awarded the 1953 Physics Prize, is the great-uncle of 1999 Physics laureate Gerard 't Hooft. In 2019, married couple Abhijit Banerjee and Esther Duflo were awarded the Economics Prize. Christiane Nüsslein-Volhard was awarded the Prize in Physiology or Medicine in 1995, and her nephew Benjamin List received the Chemistry Prize in 2021. Sune Bergström was awarded the Prize in Physiology or Medicine in 1982, and his son Svante Pääbo was awarded the same prize in 2022. Edwin McMillan, who was awarded the Prize in Chemistry in 1951, is the uncle of John Clauser, who was awarded the Prize in Physics in 2022.

Refusals and constraints

A black and white portrait of a man in a suit and tie. Half of his face is in a shadow.
Richard Kuhn, who was forced to decline his Nobel Prize in Chemistry

Two laureates have voluntarily declined the Nobel Prize. In 1964, Jean-Paul Sartre was awarded the Literature Prize but refused, stating, "A writer must refuse to allow himself to be transformed into an institution, even if it takes place in the most honourable form." Lê Đức Thọ, chosen for the 1973 Peace Prize for his role in the Paris Peace Accords, declined, stating that there was no actual peace in Vietnam. George Bernard Shaw attempted to decline the prize money while accepting the 1925 Literature Prize; eventually it was agreed to use it to found the Anglo-Swedish Literary Foundation.

During the Third Reich, Adolf Hitler hindered Richard Kuhn, Adolf Butenandt, and Gerhard Domagk from accepting their prizes. All of them were awarded their diplomas and gold medals after World War II.

In 1958, Boris Pasternak declined his prize for literature due to fear of what the Soviet Union government might do if he travelled to Stockholm to accept his prize. In return, the Swedish Academy refused his refusal, saying "this refusal, of course, in no way alters the validity of the award." The academy announced with regret that the presentation of the Literature Prize could not take place that year, holding it back until 1989 when Pasternak's son accepted the prize on his behalf.

Aung San Suu Kyi was awarded the Nobel Peace Prize in 1991, but her children accepted the prize because she had been placed under house arrest in Burma; Suu Kyi delivered her speech two decades later, in 2012. Liu Xiaobo was awarded the Nobel Peace Prize in 2010 while he and his wife were under house arrest in China as political prisoners, and he was unable to accept the prize in his lifetime.

Cultural impact

Being a symbol of scientific or literary achievement that is recognisable worldwide, the Nobel Prize is often depicted in fiction. This includes films like The Prize (1963), Nobel Son (2007), and The Wife (2017) about fictional Nobel laureates, as well as fictionalised accounts of stories surrounding real prizes such as Nobel Chor, a 2012 film based on the theft of Rabindranath Tagore's prize.

The statue and memorial symbol Planet of Alfred Nobel was opened in Alfred Nobel University of Economics and Law in Dnipro, Ukraine in 2008. On the globe, there are 802 Nobel laureates' reliefs made of a composite alloy obtained when disposing of military strategic missiles.

Despite the symbolism of intellectual achievement, some recipients have embraced unsupported and pseudoscientific concepts, including various health benefits of vitamin C and other dietary supplements, homeopathy, HIV/AIDS denialism, and various claims about race and intelligence. This is sometimes referred to as Nobel disease.

Optical amplifier

From Wikipedia, the free encyclopedia

Optical amplifiers are used to create laser guide stars which provide feedback to the adaptive optics control systems which dynamically adjust the shape of the mirrors in the largest astronomical telescopes.

An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback from the cavity is suppressed. Optical amplifiers are important in optical communication and laser physics. They are used as optical repeaters in the long distance fiberoptic cables which carry much of the world's telecommunication links.

There are several different physical mechanisms that can be used to amplify a light signal, which correspond to the major types of optical amplifiers. In doped fiber amplifiers and bulk lasers, stimulated emission in the amplifier's gain medium causes amplification of incoming light. In semiconductor optical amplifiers (SOAs), electron-hole recombination occurs. In Raman amplifiers, Raman scattering of incoming light with phonons in the lattice of the gain medium produces photons coherent with the incoming photons. Parametric amplifiers use parametric amplification.

History

The principle of optical amplification was invented by Gordon Gould on November 13, 1957. He filed patent No. 804,539 on April 6, 1959 titled "Light Amplifiers Employing Collisions to Produce Population Inversions" (subsequently amended as a continuation in part and finally issued as No. 4,746,201A on May 4, 1988). The patent covered “the amplification of light by the stimulated emission of photons from ions, atoms or molecules in gaseous, liquid or solid state.” In total, Gould obtained 48 patents related to the optical amplifier that covered 80% of the lasers on the market at the time of issuance.

Gould co-founded an optical telecommunications equipment firm, Optelecom Inc., that helped start Ciena Corp with his former head of Light Optics Research, David Huber and Kevin Kimberlin. Huber and Steve Alexander of Ciena invented the dual-stage optical amplifier (US Patent 5,159,601) that was a key to the first dense wave division multiplexing (DWDM) system, that they released in June 1996. This marked the start of optical networking. Its significance was recognized at the time by optical authority, Shoichi Sudo and technology analyst, George Gilder in 1997, when Sudo wrote that optical amplifiers “will usher in a worldwide revolution called the Information Age” and Gilder compared the optical amplifier to the integrated circuit in importance, predicting that it would make possible the Age of Information. Today optical amplification WDM systems are the common basis of all local, metro, national, intercontinental and subsea telecommunications networks and the technology of choice for the fiber optic backbones of the Internet (e.g. fiber-optic cables form a basis of modern day computer networking).

Laser amplifiers

Almost any laser active gain medium can be pumped to produce gain for light at the wavelength of a laser made with the same material as its gain medium. Such amplifiers are commonly used to produce high power laser systems. Special types such as regenerative amplifiers and chirped-pulse amplifiers are used to amplify ultrashort pulses.

Solid-state amplifiers

Solid-state amplifiers are optical amplifiers that uses a wide range of doped solid-state materials (Nd: Yb:YAG, Ti:Sa) and different geometries (disk, slab, rod) to amplify optical signals. The variety of materials allows the amplification of different wavelength while the shape of the medium can distinguish between more suitable for energy of average power scaling. Beside their use in fundamental research from gravitational wave detection to high energy physics at the National Ignition Facility they can also be found in many of today’s ultra short pulsed lasers.

Doped fiber amplifiers

Schematic diagram of a simple Doped Fiber Amplifier

Doped fiber amplifiers (DFAs) are optical amplifiers that use a doped optical fiber as a gain medium to amplify an optical signal. They are related to fiber lasers. The signal to be amplified and a pump laser are multiplexed into the doped fiber, and the signal is amplified through interaction with the doping ions.

Amplification is achieved by stimulated emission of photons from dopant ions in the doped fiber. The pump laser excites ions into a higher energy from where they can decay via stimulated emission of a photon at the signal wavelength back to a lower energy level. The excited ions can also decay spontaneously (spontaneous emission) or even through nonradiative processes involving interactions with phonons of the glass matrix. These last two decay mechanisms compete with stimulated emission reducing the efficiency of light amplification.

The amplification window of an optical amplifier is the range of optical wavelengths for which the amplifier yields a usable gain. The amplification window is determined by the spectroscopic properties of the dopant ions, the glass structure of the optical fiber, and the wavelength and power of the pump laser.

Although the electronic transitions of an isolated ion are very well defined, broadening of the energy levels occurs when the ions are incorporated into the glass of the optical fiber and thus the amplification window is also broadened. This broadening is both homogeneous (all ions exhibit the same broadened spectrum) and inhomogeneous (different ions in different glass locations exhibit different spectra). Homogeneous broadening arises from the interactions with phonons of the glass, while inhomogeneous broadening is caused by differences in the glass sites where different ions are hosted. Different sites expose ions to different local electric fields, which shifts the energy levels via the Stark effect. In addition, the Stark effect also removes the degeneracy of energy states having the same total angular momentum (specified by the quantum number J). Thus, for example, the trivalent erbium ion (Er3+) has a ground state with J = 15/2, and in the presence of an electric field splits into J + 1/2 = 8 sublevels with slightly different energies. The first excited state has J = 13/2 and therefore a Stark manifold with 7 sublevels. Transitions from the J = 13/2 excited state to the J= 15/2 ground state are responsible for the gain at 1500 nm wavelength. The gain spectrum of the EDFA has several peaks that are smeared by the above broadening mechanisms. The net result is a very broad spectrum (30 nm in silica, typically). The broad gain-bandwidth of fiber amplifiers make them particularly useful in wavelength-division multiplexed communications systems as a single amplifier can be utilized to amplify all signals being carried on a fiber and whose wavelengths fall within the gain window.

An erbium-doped waveguide amplifier (EDWA) is an optical amplifier that uses a waveguide to boost an optical signal.

Basic principle of EDFA

A relatively high-powered beam of light is mixed with the input signal using a wavelength selective coupler (WSC). The input signal and the excitation light must be at significantly different wavelengths. The mixed light is guided into a section of fiber with erbium ions included in the core. This high-powered light beam excites the erbium ions to their higher-energy state. When the photons belonging to the signal at a different wavelength from the pump light meet the excited erbium ions, the erbium ions give up some of their energy to the signal and return to their lower-energy state.

A significant point is that the erbium gives up its energy in the form of additional photons which are exactly in the same phase and direction as the signal being amplified. So the signal is amplified along its direction of travel only. This is not unusual – when an atom "lases" it always gives up its energy in the same direction and phase as the incoming light. Thus all of the additional signal power is guided in the same fiber mode as the incoming signal. An optical isolator is usually placed at the output to prevent reflections returning from the attached fiber. Such reflections disrupt amplifier operation and in the extreme case can cause the amplifier to become a laser.

The erbium doped amplifier is a high gain amplifier.

Noise

The principal source of noise in DFAs is Amplified Spontaneous Emission (ASE), which has a spectrum approximately the same as the gain spectrum of the amplifier. Noise figure in an ideal DFA is 3 dB, while practical amplifiers can have noise figure as large as 6–8 dB.

As well as decaying via stimulated emission, electrons in the upper energy level can also decay by spontaneous emission, which occurs at random, depending upon the glass structure and inversion level. Photons are emitted spontaneously in all directions, but a proportion of those will be emitted in a direction that falls within the numerical aperture of the fiber and are thus captured and guided by the fiber. Those photons captured may then interact with other dopant ions, and are thus amplified by stimulated emission. The initial spontaneous emission is therefore amplified in the same manner as the signals, hence the term Amplified Spontaneous Emission. ASE is emitted by the amplifier in both the forward and reverse directions, but only the forward ASE is a direct concern to system performance since that noise will co-propagate with the signal to the receiver where it degrades system performance. Counter-propagating ASE can, however, lead to degradation of the amplifier's performance since the ASE can deplete the inversion level and thereby reduce the gain of the amplifier and increase the noise produced relative to the desired signal gain.

Noise figure can be analyzed in both the optical domain and in the electrical domain. In the optical domain, measurement of the ASE, the optical signal gain, and signal wavelength using an optical spectrum analyzer permits calculation of the noise figure. For the electrical measurement method, the detected photocurrent noise is evaluated with a low-noise electrical spectrum analyzer, which along with measurement of the amplifier gain permits a noise figure measurement. Generally, the optical technique provides a more simple method, though it is not inclusive of excess noise effects captured by the electrical method such multi-path interference (MPI) noise generation. In both methods, attention to effects such as the spontaneous emission accompanying the input signal are critical to accurate measurement of noise figure.

Gain saturation

Gain is achieved in a DFA due to population inversion of the dopant ions. The inversion level of a DFA is set, primarily, by the power of the pump wavelength and the power at the amplified wavelengths. As the signal power increases, or the pump power decreases, the inversion level will reduce and thereby the gain of the amplifier will be reduced. This effect is known as gain saturation – as the signal level increases, the amplifier saturates and cannot produce any more output power, and therefore the gain reduces. Saturation is also commonly known as gain compression.

To achieve optimum noise performance DFAs are operated under a significant amount of gain compression (10 dB typically), since that reduces the rate of spontaneous emission, thereby reducing ASE. Another advantage of operating the DFA in the gain saturation region is that small fluctuations in the input signal power are reduced in the output amplified signal: smaller input signal powers experience larger (less saturated) gain, while larger input powers see less gain.

The leading edge of the pulse is amplified, until the saturation energy of the gain medium is reached. In some condition, the width (FWHM) of the pulse is reduced.

Inhomogeneous broadening effects

Due to the inhomogeneous portion of the linewidth broadening of the dopant ions, the gain spectrum has an inhomogeneous component and gain saturation occurs, to a small extent, in an inhomogeneous manner. This effect is known as spectral hole burning because a high power signal at one wavelength can 'burn' a hole in the gain for wavelengths close to that signal by saturation of the inhomogeneously broadened ions. Spectral holes vary in width depending on the characteristics of the optical fiber in question and the power of the burning signal, but are typically less than 1 nm at the short wavelength end of the C-band, and a few nm at the long wavelength end of the C-band. The depth of the holes are very small, though, making it difficult to observe in practice.

Polarization effects

Although the DFA is essentially a polarization independent amplifier, a small proportion of the dopant ions interact preferentially with certain polarizations and a small dependence on the polarization of the input signal may occur (typically < 0.5 dB). This is called Polarization Dependent Gain (PDG). The absorption and emission cross sections of the ions can be modeled as ellipsoids with the major axes aligned at random in all directions in different glass sites. The random distribution of the orientation of the ellipsoids in a glass produces a macroscopically isotropic medium, but a strong pump laser induces an anisotropic distribution by selectively exciting those ions that are more aligned with the optical field vector of the pump. Also, those excited ions aligned with the signal field produce more stimulated emission. The change in gain is thus dependent on the alignment of the polarizations of the pump and signal lasers – i.e. whether the two lasers are interacting with the same sub-set of dopant ions or not. In an ideal doped fiber without birefringence, the PDG would be inconveniently large. Fortunately, in optical fibers small amounts of birefringence are always present and, furthermore, the fast and slow axes vary randomly along the fiber length. A typical DFA has several tens of meters, long enough to already show this randomness of the birefringence axes. These two combined effects (which in transmission fibers give rise to polarization mode dispersion) produce a misalignment of the relative polarizations of the signal and pump lasers along the fiber, thus tending to average out the PDG. The result is that PDG is very difficult to observe in a single amplifier (but is noticeable in links with several cascaded amplifiers).

Erbium-doped optical fiber amplifiers

The erbium-doped fiber amplifier (EDFA) is the most deployed fiber amplifier as its amplification window coincides with the third transmission window of silica-based optical fiber. The core of a silica fiber is doped with trivalent erbium ions (Er3+) and can be efficiently pumped with a laser at or near wavelengths of 980 nm and 1480 nm, and gain is exhibited in the 1550 nm region. The EDFA amplification region varies from application to application and can be anywhere from a few nm up to ~80nm. Typical use of EDFA in telecommunications calls for Conventional, or C-band amplifiers (from ~1525 nm to ~1565 nm) or Long, or L-band amplifiers (from ~1565 nm to ~1610 nm). Both of these bands can be amplified by EDFAs, but it is normal to use two different amplifiers, each optimized for one of the bands.

The principal difference between C- and L-band amplifiers is that a longer length of doped fiber is used in L-band amplifiers. The longer length of fiber allows a lower inversion level to be used, thereby giving emission at longer wavelengths (due to the band-structure of Erbium in silica) while still providing a useful amount of gain.

EDFAs have two commonly used pumping bands – 980 nm and 1480 nm. The 980 nm band has a higher absorption cross-section and is generally used where low-noise performance is required. The absorption band is relatively narrow and so wavelength stabilised laser sources are typically needed. The 1480 nm band has a lower, but broader, absorption cross-section and is generally used for higher power amplifiers. A combination of 980 nm and 1480 nm pumping is generally utilised in amplifiers.

Gain and lasing in Erbium-doped fibers were first demonstrated in 1986–87 by two groups; one including David N. Payne, R. Mears, I.M Jauncey and L. Reekie, from the University of Southampton and one from AT&T Bell Laboratories, consisting of E. Desurvire, P. Becker, and J. Simpson. The dual-stage optical amplifier which enabled Dense Wave Division Multiplexing (DWDM) was invented by Stephen B. Alexander at Ciena Corporation.

Doped fiber amplifiers for other wavelength ranges

Thulium doped fiber amplifiers have been used in the S-band (1450–1490 nm) and Praseodymium doped amplifiers in the 1300 nm region. However, those regions have not seen any significant commercial use so far and so those amplifiers have not been the subject of as much development as the EDFA. However, Ytterbium doped fiber lasers and amplifiers, operating near 1 micrometre wavelength, have many applications in industrial processing of materials, as these devices can be made with extremely high output power (tens of kilowatts).

Semiconductor optical amplifier

Semiconductor optical amplifiers (SOAs) are amplifiers which use a semiconductor to provide the gain medium. These amplifiers have a similar structure to Fabry–Pérot laser diodes but with anti-reflection design elements at the end faces. Recent designs include anti-reflective coatings and tilted wave guide and window regions which can reduce end face reflection to less than 0.001%. Since this creates a loss of power from the cavity which is greater than the gain, it prevents the amplifier from acting as a laser. Another type of SOA consists of two regions. One part has a structure of a Fabry-Pérot laser diode and the other has a tapered geometry in order to reduce the power density on the output facet.

Semiconductor optical amplifiers are typically made from group III-V compound semiconductors such as GaAs/AlGaAs, InP/InGaAs, InP/InGaAsP and InP/InAlGaAs, though any direct band gap semiconductors such as II-VI could conceivably be used. Such amplifiers are often used in telecommunication systems in the form of fiber-pigtailed components, operating at signal wavelengths between 850 nm and 1600 nm and generating gains of up to 30 dB.

The semiconductor optical amplifier is of small size and electrically pumped. It can be potentially less expensive than the EDFA and can be integrated with semiconductor lasers, modulators, etc. However, the performance is still not comparable with the EDFA. The SOA has higher noise, lower gain, moderate polarization dependence and high nonlinearity with fast transient time. The main advantage of SOA is that all four types of nonlinear operations (cross gain modulation, cross phase modulation, wavelength conversion and four wave mixing) can be conducted. Furthermore, SOA can be run with a low power laser. This originates from the short nanosecond or less upper state lifetime, so that the gain reacts rapidly to changes of pump or signal power and the changes of gain also cause phase changes which can distort the signals. This nonlinearity presents the most severe problem for optical communication applications. However it provides the possibility for gain in different wavelength regions from the EDFA. "Linear optical amplifiers" using gain-clamping techniques have been developed.

High optical nonlinearity makes semiconductor amplifiers attractive for all optical signal processing like all-optical switching and wavelength conversion. There has been much research on semiconductor optical amplifiers as elements for optical signal processing, wavelength conversion, clock recovery, signal demultiplexing, and pattern recognition.

Vertical-cavity SOA

A recent addition to the SOA family is the vertical-cavity SOA (VCSOA). These devices are similar in structure to, and share many features with, vertical-cavity surface-emitting lasers (VCSELs). The major difference when comparing VCSOAs and VCSELs is the reduced mirror reflectivity used in the amplifier cavity. With VCSOAs, reduced feedback is necessary to prevent the device from reaching lasing threshold. Due to the extremely short cavity length, and correspondingly thin gain medium, these devices exhibit very low single-pass gain (typically on the order of a few percent) and also a very large free spectral range (FSR). The small single-pass gain requires relatively high mirror reflectivity to boost the total signal gain. In addition to boosting the total signal gain, the use of the resonant cavity structure results in a very narrow gain bandwidth; coupled with the large FSR of the optical cavity, this effectively limits operation of the VCSOA to single-channel amplification. Thus, VCSOAs can be seen as amplifying filters.

Given their vertical-cavity geometry, VCSOAs are resonant cavity optical amplifiers that operate with the input/output signal entering/exiting normal to the wafer surface. In addition to their small size, the surface normal operation of VCSOAs leads to a number of advantages, including low power consumption, low noise figure, polarization insensitive gain, and the ability to fabricate high fill factor two-dimensional arrays on a single semiconductor chip. These devices are still in the early stages of research, though promising preamplifier results have been demonstrated. Further extensions to VCSOA technology are the demonstration of wavelength tunable devices. These MEMS-tunable vertical-cavity SOAs utilize a microelectromechanical systems (MEMS) based tuning mechanism for wide and continuous tuning of the peak gain wavelength of the amplifier. SOAs have a more rapid gain response, which is in the order of 1 to 100 ps.

Tapered amplifiers

For high output power and broader wavelength range, tapered amplifiers are used. These amplifiers consist of a lateral single-mode section and a section with a tapered structure, where the laser light is amplified. The tapered structure leads to a reduction of the power density at the output facet.

Typical parameters:

  • wavelength range: 633 to 1480 nm
  • input power: 10 to 50 mW
  • output power: up to 3 W

Raman amplifier

In a Raman amplifier, the signal is intensified by Raman amplification. Unlike the EDFA and SOA the amplification effect is achieved by a nonlinear interaction between the signal and a pump laser within an optical fiber. There are two types of Raman amplifier: distributed and lumped. A distributed Raman amplifier is one in which the transmission fiber is utilised as the gain medium by multiplexing a pump wavelength with signal wavelength, while a lumped Raman amplifier utilises a dedicated, shorter length of fiber to provide amplification. In the case of a lumped Raman amplifier, a highly nonlinear fiber with a small core is utilised to increase the interaction between signal and pump wavelengths, and thereby reduce the length of fiber required.

The pump light may be coupled into the transmission fiber in the same direction as the signal (co-directional pumping), in the opposite direction (contra-directional pumping) or both. Contra-directional pumping is more common as the transfer of noise from the pump to the signal is reduced.

The pump power required for Raman amplification is higher than that required by the EDFA, with in excess of 500 mW being required to achieve useful levels of gain in a distributed amplifier. Lumped amplifiers, where the pump light can be safely contained to avoid safety implications of high optical powers, may use over 1 W of optical power.

The principal advantage of Raman amplification is its ability to provide distributed amplification within the transmission fiber, thereby increasing the length of spans between amplifier and regeneration sites. The amplification bandwidth of Raman amplifiers is defined by the pump wavelengths utilised and so amplification can be provided over wider, and different, regions than may be possible with other amplifier types which rely on dopants and device design to define the amplification 'window'.

Raman amplifiers have some fundamental advantages. First, Raman gain exists in every fiber, which provides a cost-effective means of upgrading from the terminal ends. Second, the gain is nonresonant, which means that gain is available over the entire transparency region of the fiber ranging from approximately 0.3 to 2µm. A third advantage of Raman amplifiers is that the gain spectrum can be tailored by adjusting the pump wavelengths. For instance, multiple pump lines can be used to increase the optical bandwidth, and the pump distribution determines the gain flatness. Another advantage of Raman amplification is that it is a relatively broad-band amplifier with a bandwidth > 5 THz, and the gain is reasonably flat over a wide wavelength range.

However, a number of challenges for Raman amplifiers prevented their earlier adoption. First, compared to the EDFAs, Raman amplifiers have relatively poor pumping efficiency at lower signal powers. Although a disadvantage, this lack of pump efficiency also makes gain clamping easier in Raman amplifiers. Second, Raman amplifiers require a longer gain fiber. However, this disadvantage can be mitigated by combining gain and the dispersion compensation in a single fiber. A third disadvantage of Raman amplifiers is a fast response time, which gives rise to new sources of noise, as further discussed below. Finally, there are concerns of nonlinear penalty in the amplifier for the WDM signal channels.

Optical parametric amplifier

An optical parametric amplifier allows the amplification of a weak signal-impulse in a nonlinear medium such as a noncentrosymmetric nonlinear medium (e.g. Beta barium borate (BBO)) or even a standard fused silica optical fiber via the Kerr effect. In contrast to the previously mentioned amplifiers, which are mostly used in telecommunication environments, this type finds its main application in expanding the frequency tunability of ultrafast solid-state lasers (e.g. Ti:sapphire). By using a noncollinear interaction geometry optical parametric amplifiers are capable of extremely broad amplification bandwidths.

Recent achievements

The adoption of high power fiber lasers as an industrial material processing tool has been ongoing for several years and is now expanding into other markets including the medical and scientific markets. One key enhancement enabling penetration into the scientific market has been the improvements in high finesse fiber amplifiers, which are now capable of delivering single frequency linewidths (<5 kHz) together with excellent beam quality and stable linearly polarized output. Systems meeting these specifications have steadily progressed in the last few years from a few watts of output power, initially to the tens of watts and now into the hundreds of watts power level. This power scaling has been achieved with developments in the fiber technology, such as the adoption of stimulated brillouin scattering (SBS) suppression/mitigation techniques within the fiber, along with improvements in the overall amplifier design including large mode area (LMA) fibers with a low-aperture core, micro-structured rod-type fiber helical core, or chirally-coupled core fibers, and tapered double-clad fibers (T-DCF). The latest generation of high finesse, high power and pulsed fiber amplifiers now deliver power levels exceeding what is available from commercial solid-state single frequency sources and are opening up new scientific applications as a result of the higher power levels and stable optimized performance.

Implementations

There are several simulation tools that can be used to design optical amplifiers. Popular commercial tools have been developed by Optiwave Systems and VPI Systems.

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