Obituary for Professor Dan Bradley

Dan Bradley, who died in Dublin on 7th February, was Head of the Department of Physics at Imperial College from 1976 to 1980.

Dan Bradley, who died in Dublin on 7th February, was Head of the Department of Physics at Imperial College from 1976 to 1980. As an international leader in the field of lasers and non linear optics he was responsible for establishing the UK as the major force in ultrashort-pulse laser physics and applications, a legacy that continues to the present day.

Dan was born in Derry in 1928. He worked as a telegraph boy and passed technical school examinations in electrical engineering before taking his secondary school senior certificate examinations at St. Columb’s College Derry in 1945. He subsequently attended St Mary’s Teacher Training College in Belfast as a King’s Scholar and then taught at a primary level in Derry from 1947 to 1953 during which time he completed an external University of London BSc degree in mathematics (graduated 1953) by part-time private study. From 1953-56 Dan held several secondary teaching posts in London and embarked on a second BSc degree at Birkbeck College (graduated 1957), this time in physics, studying initially in the evenings and then full-time for the final five terms.
In 1957 he commenced his research career, joining Royal Holloway College as an assistant lecturer and simultaneously enrolling as a PhD student under the supervision and mentorship of Professor Sam Tolansky FRS. He was awarded his PhD in 1961 for work on rapid scanning Fabry-Perot etalons for high high-resolution spectroscopy. These, of course, were very exciting times for optical physics, because of the invention of the laser in 1960, and Dan had the breadth of vision and expertise to apply his extensive knowledge of Fabry-Perot etalons and interferometers to the design of laser cavities and related spectral diagnostics.

From 1961-1964 he was a Lecturer at Imperial College where he extended his research palette to VUV interferometry and electron-optical imaging tubes. He was promoted to Reader at Royal Holloway College in 1964, where he undertook research in laser plasma diagnostics and solar physics. In 1966 he was appointed Professor and Head of the Department of Physics at the Queen’s University of Belfast and it was there that Dan, with exceptional vision and inspiration, set about establishing one of the largest laser research groups in Europe, carrying out research in selective excitation spectroscopy, ultrashort-pulse lasers and related measurement techniques, solar physics from rockets, laser interferometry, solid-state lasers and non linear optics. Some of his most influential work related to his application of the broad spectral coverage of the organic liquid dye laser for the generation of ultra short pulses. Dan’s group was acknowledged to be one of the international leaders in the production and application of frequency-tunable, picosecond optical pulses and many world firsts were achieved. In addition, he developed the only reliable direct and linear characterization of picosecond pulses using an electron-optical streak camera of his own design. It is of particular note that Dan, who had a remarkable gift for seeing the bigger picture, took the opportunity to establish a commercial outlet for these cutting-edge lasers and diagnostics, in an early university spinout in Belfast called Electro-Photonics Ltd.

In 1973 Dan returned to Imperial to take up a Chair in Laser Physics in the Optics Section and set about establishing another internationally leading laser research group, with influential programmes on semiconductor laser science, femtosecond organic dye lasers, femtosecond temporal diagnostics, electron-beam pumped excimer lasers and laser photochemistry. In 1976 he became Head of the Department of Physics, a post he held until 1980, when he decided to accept another new challenge, this time as the first incumbent of the Chair of Optical Electronics at Trinity College Dublin. He once again set out to build up a research group from scratch, within a vision that foresaw the vast interdisciplinary opportunities for laser applications in the biosciences as well as the wide potential of semiconductor laser technology in communications. This he rapidly achieved, but Dan’s longer term scientific aspirations were curtailed by a serious stroke that forced him to retire in 1984, although for many years thereafter he continued to actively engage in the academic life of Trinity College and also to travel quite extensively.

Throughout his career Dan Bradley received many prestigious honours and awards. He was the Institute of Physics Thomas Young Medalist in 1975 and was awarded the Royal Society Royal Medal in 1983, the Optical Society of America Townes Medal in 1989 and the Royal Irish Academy Cunningham Medal in 2001. He was elected a Fellow of the Royal Society (FRS) in 1976 and served as a member of Council from 1979 to 1980. He was also a Fellow of the Optical Society of America (FOSA), the Institute of Physics (FInstP) and Trinity College Dublin (FTCD), and a member of the Royal Irish Academy (MRIA). In addition, Dan received honorary DSc degrees from the University of Ulster in 1983 and from the Queen’s University of Belfast in 1986.
Complementing his talents as a researcher and entrepreneur, Professor Bradley was an inspirational teacher. He taught a range of undergraduate courses at all levels from his first appointment at Royal Holloway through to Trinity College. Many who joined his group did so as a result of listening to his undergraduate lectures, being inspired and directed towards a research career in laser-based science. He supervised more than sixty PhD students, many of whom have gone on to head up major international research groups in the field as well as underpin the industrial sector. Dan also played an active role in organizing conferences, advising funding agencies, consulting for government and industry and generally promoting the subject that he loved – one specific legacy is the Central Laser Facility at the Rutherford Laboratory that he was instrumental in establishing. The laser science and technology field owes him an enormous debt.
Dan Bradley is survived by his wife Winefride, a daughter and four sons, one of whom, Donal, followed his father’s footsteps as Head of the Department of Physics at Imperial College from 2005-2009.