Robert Keith Bullough ("Robin"), who has died at the age of 78, was a mathematical physicist best known as one of the discoverers of the soliton, a remarkable kind of self-reinforcing and solitary wave. Bullough proposed the idea of a soliton-based transmission system to increase performance of optical telecommunications and this is now commonly used in trans-oceanic optical fibre communication. His discoveries also led to revolutions in nonlinear mathematics and nonlinear physics and may ultimately play a role in the new sciences of quantum computing.
Bullough, whose parents were Quakers, attended Newcastle High School before leaving at 16 with a scholarship to Emmanuel College, Cambridge. National Service in the RAF intervened in 1948-49 and just three days before demobilisation he was blinded in one eye. Nevertheless, he went on to study a BA in Natural Sciences. This led to postgraduate work at Leeds and a first job in rayon research. In 1961 he moved to a lectureship at UMIST and was promoted to the Chair of Mathematical Physics in 1973. Since his retirement in 1995 he had held a position as Emeritus Professor at Manchester University.
Bullough was a great traveller, starting with pre-war holidays with his parents in the Austrian Alps, at a time when overseas travel was unknown to most. He was to develop a passion for mountaineering and had a particular fascination for the early Victorian alpinists, building a remarkable collection of books from this era. However, in the early 1970s Bullough developed chronic asthma, which severely curtailed physical activity.
Nonetheless, he travelled widely across Europe, the Middle East, the Americas, India, the Soviet Union and China before the economic boom. He was impressed by the intellectual talent he found in the developing world and became mentor to many international students. His journeys could never have been undertaken without the unstinting support of his wife and travel companion, Louise, who was a native of Denmark. This was a country to figure prominently in his early career; he worked in Copenhagen with Léon Rosenfeld, one of the pioneers of modern quantum mechanics.
Bullough's extensive work led him towards novel problems in nonlinear and quantum optics. He discovered spectacular phenomena such as transmission of light through a dispersive medium without any attenuation, which became known as self-induced transparency. In addition he worked out conditions under which light can essentially be brought to a standstill by interaction with a dispersive medium. He was very much ahead of his time: these problems only became fashionable 30 years later.
In recognition of his work he was honoured to give the Special Foundation Lecture at the Quantum Electronics and Photonics Conference held at the University of Manchester in 1999. Only Steven Chu, Nobel Laureate and recently nominated Energy Secretary in the new Obama administration, was similarly honoured at this conference.
From being one of the founders of soliton theory, Bullough continued to work on associated problems for the rest of his career, even having ideas on quantum computing; but in this area he did not have time to realise his dreams. While Bullough continued to work hard almost to the end of his life, in his last two years the onset of dementia made it increasingly difficult to remain focused. He leaves a wife and two sons.
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