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Obituary of Richard Brewer (1928-2012)

6 December 2012

Richard G. (Dick) Brewer passed away on July 22, 2012, following a long illness. Dick was one of the pioneers in the field of nonlinear laser spectroscopy, noted for his applications of advanced techniques in the study of a variety of laser induced steady state and transient phenomena. He was born in Los Angeles on December 8, 1928 and attended Caltech as an undergraduate, obtaining his Bachelor of Science degree in 1951. After his graduate studies at UC Berkeley were interrupted by his military service, he returned to Berkeley and obtained his PhD degree in Chemistry in 1958 under the supervision of Leo Brewer (no relation). He was an Instructor at Harvard and an Assistant Professor at UCLA before joining the research staff at IBM, Almaden, in 1963 and remained there until his retirement in 1994. He became an IBM Fellow in 1973 and a Consulting Professor of Applied Physics at Stanford University in 1978.

In his early work at IBM, Dick used a ruby laser to demonstrate stimulated Brillouin scattering in liquids. He insisted in looking for the effect after he doggedly confirmed that nowhere in the literature was such a scattering reported in liquids. Following work on laser trapping and filamentation carried out in collaboration with the group of Charles Townes, Dick entered the field of nonlinear infrared spectroscopy during an extended research visit with the group of Ali Javan at MIT in 1968-69 where he discovered a method he was to exploit in his future research at IBM. Dick observed molecular transitions in naturally abundant 14NH2D molecules using a standing wave cw CO2 and a Stark electric field that tuned the transitions into resonance with the laser field. By sweeping the Stark field instead of the laser field frequency through resonance, he discovered that an extremely narrow Lamb dip occurs in absorption, providing a sensitive method for high resolution laser spectroscopy of gases that display Lamb dips.  

On returning to IBM, Dick now realized that he could simulate a pulsed electric field interacting with a molecular electric dipole by Stark switching the molecular transition frequency into and out of resonance with the fields. Dick believed that he could see a photon echo and explore other optical coherent transient effects as well by using this technique. As stated by Richard Shoemaker, who was a postdoc working with Dick at that time: It was one of those rare events where an experiment not only worked the first time it was put together, but also worked far better than expected.  I don't think it was until a little while later we realized that the primary reason the experiment worked so well is that we had a built-in heterodyne detection system. The heterodyne signal was produced by classes of molecules that were switched both into and out of resonance by the Stark fields, also producing coherent optical free induction decay and Rabi nutation.

Together with Jan Schmidt, Joel Levy, and Paul Berman, Dick carried out a theoretical and experimental study of the role played by velocity-changing collisions in diminishing the photon echo signal. He began a systematic study of the theory of coherent transient spectroscopy in two and three level systems with Stig Stenholm, and again later with Erwin Hahn concerning special solutions of Bloch type NMR equations. Dick developed a method to study coherent transient Raman beats after first preparing a coherent superposition of states among degenerate sublevels in a molecule, and then suddenly lifting the degeneracy by Stark switching . 

 Dick realized that he could extend the observation of coherent optical transient effects to molecules without a permanent dipole moment by switching the laser frequency instead of the molecular transition frequency, as had been done with the Stark effect. He and Azriel Genack developed the method of laser frequency switching in which the laser frequency was rapidly switched by applying a voltage to intra-cavity electro-optic crystal. This made it possible to observe optical coherent transients and separate elastic and inelastic scattering in atoms, molecules and solids.

Dick and his IBM colleague Ralph DeVoe collaborated on a number of important projects. Together with Alex Szabo and Stephen Rand, they carried out one of the first experiments in which ultra-long lifetimes of optical coherence were observed in solids doped with rare earth ions. The rare earth ion work led to the discovery of the breakdown of the optical Bloch equations at high field intensities: the intense fields reduce the dephasing attributed to relaxation processes in which the transition frequency of the ions undergoes stochastic jumps. 

Another pioneering study by DeVoe and Brewer was the demonstration of sub and super radiance in the spontaneous emission of two ions as a function of their separation. By using nano-fabrication techniques they were able to position ions at varying distances on the order of a transition wavelength and observe an oscillation of the decay rate as a function of separation. This remains one of the only studies of this nature.

Dick was the recipient of many awards and honors. He was elected as an IBM Fellow in 1973 and a member of the National Academy of Sciences in 1980. He received the Albert A. Michelson Gold Medal of the Franklin Institute in 1979, the California Institute of Technology Distinguished Alumni Award in 1994, and the Charles Hard Townes Silver Medal of the Optical Society in 2000. In 1992 symposiums in honor of Dick were held at Stanford University and at IBM. In 1997 he endowed the Brewer prize at Caltech, which is awarded annually to a freshman who is deemed the best at overcoming two 'hurdles' that are a prerequisite for admission into a Research Tutorial where the student carries out an independent research project. With Aram Mooradian, Dick organized the first International Laser Spectroscopy Conference, a conference that continues to be held in world wide venues. 

Tragically, Dick's work was cut short by the progression of a debilitating neurological disease that was first diagnosed in the early eighties. For someone who loved to travel, hike, and explore the outdoors, this disease might be viewed as a death blow. Fortunately, Dick's quick mind, curiosity, love of learning, his interest in people and sense of humor were immune from the attack on his body. Throughout his career Dick had an unusual tenacity for carrying out what he wanted to get done, to do what he enjoyed, no matter the road blocks. He continued to study, keep up with developments in physics, perfect his Italian, and offer reminiscences about many of his colleagues. 

Dick is survived by his wife Lillian, whom he met at Berkeley in 1954. Although the courtship lasted only three months, the marriage endured for another 57 years. He is also survived by his son Laurence and his daughters, Emily and Cathy. It was the loving and caring of his family that helped sustain him in the difficult years of his disease. The importance of Dick's love of family and physics is evident in the wonderful Memoir he wrote in 2003 that is available at the AIP History of Physics web site.  

We thank Ralph DeVoe, Azi Genack, Rick Shoemaker, and Stig Stenholm for their input in composing this obituary.

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