OSA | Living History

Rich Holmes Memoir

Rich Holmes

In late 1986, Allen Flusberg and I developed a theory of the polarization dependence of gain in stimulated rotational Raman scattering.  This dependence was poorly understood, because the standard polarization theory for spontaneous Raman scattering is complicated by Stokes-Anti-Stokes coupling.  The problem was (and is) also important because such scattering affects the propagation of intense lasers in the atmosphere. 

A manuscript was prepared for Physics Review Letters, and was sent off.  A few weeks later, we received a phone call from Hans Bethe asking to come to our labs in the Boston area (AVCO Research Labs) to hear of our latest work. Dr. Bethe would come to AVCO on an irregular basis to consult on laser isotope separation of uranium, and other topics.  

When Dr. Bethe came to visit, I was the one tagged to present our work on the stimulated Raman scattering.  The talk involved a discussion of spin-two phonons in gases to explain the polarization dependence of the electric-quadrupole interaction of rotational Raman scattering.  The theory's predictions matched up nicely with the results for spontaneous scattering from Landau and Lifshitz, but also included all the coherent coupling effects, and extended Bloembergen's scalar phonon theory of stimulated Raman scattering. The theory could also be applied to the magnetic dipole interaction using spin-one phonons. 

Dr. Bethe was a good listener.  At age 81, he was three times as old as I was, but still was very alert. He brought up a few insightful and supportive comments throughout the talk.  However, and to our mild surprise, we did not receive any significant negative criticisms. Because of this, towards the end of the talk, I decided to interject a more controversial statement.  Before I could complete the sentence, however, he said "Uh, uh, uh," to indicate I had gone into dangerous waters.  

We had the opportunity to interact with Dr. Bethe several times at AVCO, and his genius was always helpful and significant.  We in the optics community have much to be grateful for, because we "have stood on the shoulders of giants."  

It's worth mentioning that the paper was accepted for publication in PRL, and that subsequent experimental work provided verification of a number of predictions of the theory.