In Memoriam: William R. Bennett Jr., Laser Inventor and Collector of Data

William R. Bennett Jr., the C. Baldwin Sawyer Professor Emeritus of Engineering and Applied Science and Physics, who in 1960 co-invented the first gas (helium-neon) laser, died of esophageal cancer on June 29 at his home in Haverford, Pennsylvania. He was 78.

The calculations and ideas for the first gas lasers were based on Bennett’s Ph.D. research on spectroscopy and collisions of the second kind in the noble gases such as helium, neon, argon, krypton and xenon and on his work on optical pumping carried out as a junior faculty member at Yale. Lasers are devices which have had wide-ranging applications in the modern world, from compact disc players to supermarket scanners, surgical tools and spaced-based weaponry.

Bennett went on to invent nearly a dozen additional lasers including lasers using electron impact excitation in each of the noble gases and collision excitation in metal vapor.

His argon laser provided the first and still most effective treatment for the prevention of blindness in diabetes. It is the most widely used laser in the treatment of eye diseases. Bennett benefited many years later from the argon laser when it was used to treat his detached retina.

Over his 38 years at Yale, Bennett carried out research in diverse fields ranging from atomic physics to computer science and acoustics, and he taught a variety of courses designed along lines of his own interests.

Many of the approaches Bennett used to collect data for his projects provided much amusement to his students and colleagues. For one project, he rented a truck and filled it with equipment and a mattress and, together with his wife and dog, set out to measure the “Fifth Force” at a site where a large body of water changed height rapidly. The site he chose was the locks on the Snake River in Washington, which gave him special dispensation to camp there with his truck for the summer.

He was also frequently seen at various sites around the Yale campus collecting data for his popular course on “The Computer as a Research Tool.” For this course he was named one of the 10 best professors at Yale for many years in a row. His lectures in that course were multi-media events and included demonstrations of firestorms, removal of warts by laser, calculations of how long it would take monkeys sitting at the typewriter to produce phrases recognized from great works of literature, and comparisons of the sound waveforms of the French horn and the garden hose.

One time the professor was spotted dressed in scuba gear and pushing scales and other gadgets at the bottom of the Yale swimming pool, measuring drag coefficients.

Bennett was well known by members of the Yale Symphony Orchestra as he was an audiophile and regularly recorded their concerts. He used his expertise in physics and sound to make calculations on how to decrease the noise levels in the Yale dining halls and used those successfully to improve the ability to converse and to enjoy chamber music concerts there. He also measured magnetic fields around campus and around New Haven. With the magnetic field data, he showed that it was improbable that those fields could cause cancer.

Bennett received his B.A. in physics from Princeton University and completed his Ph.D. in physics at Columbia University. He taught in Yale’s Department of Physics 1957-1959, was a member of the technical staff in the physical research group at the Bell Laboratories 1959-1962 and returned to Yale as a tenured professor in 1962. He was named to the Charles Baldwin Sawyer Professorship in 1972 and retired in 1998. He was master of Silliman College 1981-1987 and received the DeVane Medal, Yale’s highest award for teaching and scholarship.

His work resulted in many prizes, six books, over 200 research papers and 15 patents. Bennett’s most recent paper was published in May of this year and clarified his discovery of the “tuning dip” based on hole-burning in laser spectroscopy [Bennett, WR, Jr, Physics Today 61(5):9 (2008)], a finding that had been erroneously credited to Willis Lamb. Bennett also recently completed the first several volumes of a five-volume book on “The Science of Musical Sound.” His research on the physics of musical instruments became the basis of a popular course he gave at Yale.
Beyond his academic interests, Bennett designed and built his own home in the Berkshires — including an 11-foot fireplace and a pipe organ. He was an accomplished amateur musician who enjoyed playing chamber music on piano and clarinet.

Bennett is survived by his wife of 55 years, Frances Commins Bennett; daughter Jean  of Bryn Mawr, Pennsylvania; son Bill of Berkeley, California; daughter Nancy of Los Angeles, California; a sister, Carol Anne Valles of Bedford, New York; and five grandchildren. A celebration of his life will be held at Yale University in the fall of 2008. In lieu of flowers, the family suggests that individuals make contributions in Bennett’s name to the charity of their choice.