Daniel J. Bradley, physicist and laser pioneer, died 7 February in Sandymount, Dublin, Ireland.
Bradley held chairs at Queen's Univ. Belfast from 1966-1973, Imperial College London from 1973-1980, and Trinity College Dublin from 1980-1984. He was a leader in the development of ultrafast pulsed lasers until his retirement in 1984.
SPIE CEO and Executive Director Eugene G. Arthurs said of his former Ph.D. supervisor that "Dan Bradley was a late bloomer in the physics world, having first been a schoolteacher before studying under Sam Tolansky at Royal Holloway College. Prof. Bradley was an inspirational mentor, a global thinker from the north of Ireland who in the late '60s and early '70s built a leading group in the relatively new 'laser physics' at Queen's University. His pioneering work in tunable lasers and ultrashort pulses was world leading."
"One of his great gifts was his ability to master different challenges," Arthurs said. "Dissatisfied with the interpretation of correlation pulse-width measurement techniques for pulse trains, such as two photon fluorescence, he developed and patented picosecond streak cameras, and founded a company, Electro-photonics, in Belfast, a city with no support infrastructure for such a venture. He bridged the academic-industry gulf long before this became acceptable."
"Dan Bradley created the first major effort in laser development and their applications in the UK. His vision, tenacity and boundless energy in those early days of lasers inspired a whole generation of laser scientists. I had the good fortune to be one of his first graduate students, and have never lost that enthusiasm," said Martin Richardson, Director of the Townes Laser Center at the College of Optics & Photonics, University of Central Florida. "I well remember my first presentation at a scientific meeting, a one-day symposium at a defense laboratory at Malvern, UK. I had been working with him only a few months on the spectral characterization of Q-switched lasers, but he knew how petrified I was in those days of speaking publically. He was scheduled to talk about our work right after the lunch break. Midway through the morning session he leaned over to me and in his broad Irish accent said, "Martin, I think you should give this talk". I don't remember at all giving the talk, but still have a vivid imprint of the fear before it! He knew how to get the best out of people."
"My first work as a graduate student with Dan was to time resolve, with the then-new streak cameras, the axial modes of high power ruby lasers. Using the high-resolution spherical Fabry-Perot interferometers he had developed for his thesis we observed for the first time the spectral shifting of individual modes with time. It was published in Nature, and later at the Royal Society. He aimed high, and he taught those around him to do likewise," Richardson continued.
After the political climate in Belfast deteriorated, Bradley moved his group in 1973 to Imperial College, where he became head of the physics department. His worked there with the then-new excimer lasers and researched nonlinear phenomena. He moved to Trinity College in part to assist in Ireland's renaissance, and led work in diode lasers there before suffering a disabling stroke in 1984.
At the 1967 Belfast Science Fair Bradley illustrated the practical significance of laser technology in a demonstration of the power of a laser beam.
In 1969, as head of the laser research team at Queen's Univ., Bradley predicted that, "Lasers would be used 'in the not-too-distant future' to increase radically the speed of computer operations and facilitate faster and cheaper printing of books and newspapers," Arthurs said. "By the end of the century lasers could be used to create displays that would show an up-to-the-minute newspaper or colour magazine on the living-room wall, activated by a wave of the hand. Photographic cameras could have a 'crystal layer' that would allow high-capacity storage of holographic colour images."
Arthurs touts Prof. Bradley as the catalyst behind him joining SPIE and other scientific societies at an early age. "Dan Bradley was a strong proponent of having his students attend international technical meetings and he fostered productive transnational linkages when Belfast was relatively insular. I was very fortunate to have had him as a Ph.D. supervisor," said Arthurs. "Not only did he find the funds for students to go to international meetings but he encouraged his students to join international societies, and so I came to SPIE around 1970."
Bradley received many honors during his career, including a Cunningham Medal from the Royal Irish Academy for his outstanding contribution to scholarship and to the objectives of the Academy. A special tribute to Bradley was held at SPIE OptoIreland in 2005.
Bradley is survived by his wife and 5 children.
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Photo Captions
Top: Bradley and students at Queens University, Belfast
Center: Roy Taylor, Imperial College; Bradley; Eugene Arthurs, SPIE
Bottom: Frank Imbusch, Kevin Carroll, Thomas Glynn, James Lunney, Eugene Arthurs, Bradley (seated)
