Robert W. Hellwarth
About Optica
In Memoriam: Robert W. Hellwarth, 1930 - 2021
20 January 2021
Robert “Bob” W. Hellwarth, OSA Fellow and recipient of the Charles Hard Townes Award, has passed away at the age of 90. Hellwarth was a renowned researcher, having made significant contributions in the area of nonlinear optical devices. He was best known for inventing and demonstrating "Q-switching," a contribution that led to the field of high-power lasers. Hellwarth’s research also identified stimulated Raman scattering, which he was the first to explain. Hellwarth was co-discoverer of a new kind of laser action, to which he gave its theoretical basis and the name, "stimulated scattering."
Hellwarth was born in Ann Arbor, Michigan, USA, and studied electrical engineering at Princeton University (1952). He was a Rhodes Scholar at Oxford University, where he obtained his Ph.D. in physics in 1955. Hellwarth spent a year as a postdoctoral researcher working with Richard Feynman at the California Institute of Technology, followed by positions at Hughes Research Laboratories and Caltech from 1956-1970. Hellwarth then joined the faculty of the University of South California (USC). He went onto to hold the George T. Pfleger Chair in Electrical Engineering and be a Professor of Physics.
Hellwarth's research was focused on understanding and developing materials for nonlinear optical devices, and particularly concentrated on polymers, suspensions, and photorefractive crystals, physics of optical glasses (especially acoustic attenuation in glass), nonlinear imaging devices, wave front reversal, and nonlinear optics for systolic-architecture computers. His work in nonlinear materials demonstrated the surprisingly low power thresholds for nonlinear effects that may be expected to be found at microwave and longer wavelengths. Hellwarth made the first observation of the hyperfine resonance absorption of a radioactive isotope. He was co-developer of the precessing-vector model of two-level atoms. While at USC, Hellwarth developed a new, and now widely employed method for reversing the lightwave pattern of an optical image, a process known as optical beam phase conjugation.
Hellwarth was recognized with the OSA Charles Hard Townes Award in 1983 for his invention of the Q-switched laser, co-discovery of the Raman laser and explanation of stimulated scattering phenomena, and the theory of optical phase conjugation. He was made an OSA Fellow in 1987 and was named an OSA Honorary Member in 2014 for pioneering the introduction of Q-switches to lasers and profoundly influential contributions to the science of nonlinear optics, including stimulated light scattering, origins of nonlinear refractive index, photo-refractivity and phase conjugation. Hellwarth was a Fellow of the U.S. National Academies of Sciences and Engineering, American Association for the Advancement of Science, the American Physical Society and IEEE.
Bob was a beloved colleague, mentor, and friend to many within the scientific community and will be dearly missed. His research advanced the field of optics along numerous pathways and his humor, kindness, and curiosity made him a true original.
OSA and the scientific community mourn the loss of Robert Hellwarth.
