James P. Gordon

Picture of James P. Gordon with Charles H. Townes behind maser components, at the exhibit in National Museum of American History, Washington, DC, USA.

During his doctoral training period with C.H. Townes at Columbia University, Gordon worked on the design, analysis and construction of the maser.[6] This work produced the first prototype of what later evolved into the laser (originally called ``optical maser") and became one of the most important workhorses in 20th-century technology.[7] Gordon's later contribution to lasers included the analysis of the confocal, or curved mirror laser resonator. He joined with G. Boyd, to introduce the concept of Hermite-Gaussian modes into resonator study,[8] influencing all subsequent research conducted on laser resonators. In his work with R.L. Fork and O.E. Martinez in 1994, a mechanism for generating tunable negative dispersion using pairs of prisms was proposed. This invention was instrumental in achieving ultra-short laser pulses, critical in many applications using laser technology.[9]

In 1962, Gordon studied the implications of quantum mechanics on Shannon's information capacity.[10] He pointed out the main effects of quantization and conjectured the quantum equivalent of Shannon's formula for the information capacity of a channel.[11] Gordon's conjecture, later proven by Alexander Holevo and known as Holevo's theorem, became one of the central results in the modern field of quantum information theory.[12] In his work with W.H. Louisell published in 1966, Gordon addressed the problem of measurement in quantum physics, focusing in particular on the simultaneous measurement of noncommuting observables.[13] The concept of "measurement operator," which was introduced in that work was an early version of what is currently referred to as positive-operator valued measure (POVM) in the context of quantum measurement theory. After his retirement, Gordon re-engaged with the topic of quantum information and his last paper on the subject, titled ``Communication and Measurement," was published on arxiv one year after his death.[14]

Having joined Arthur Ashkin's efforts of manipulating microparticles with laser beams, Gordon wrote the first theory describing radiation forces and momenta in dielectric media.[15] Later, jointly with Ashkin, he modeled the motion of atoms in a radiation trap.[16] This work together with Ashkin's experiments, was the basis for what later developed into the fields of atom trapping and optical tweezers.

Much of Gordon's later career focused on the study of soliton transmission in optical fibers. He reported the first experimental observation of solitons in optical fibers in a paper co-authored with R.H. Stolen and L.F. Mollenauer.[17] In a seminal 1986 paper Gordon explained and formulated the theory of the soliton self-frequency shift that had been observed prior to that in experiments.[18] In the same year, together with Prof. H. A. Haus of the Massachusetts Institute of Technology (MIT) he predicted and quantified the timing-jitter effect resulting from the coupling between solitons and optical amplification noise in amplified optical systems.[19] This effect was shown to be one of the most fundamental factors in determining the performance of soliton systems and it is now broadly recognized as the Gordon-Haus effect.[20] In 1990 J.P. Gordon and L.F. Mollenauer predicted and analyzed the enhancement of phase-noise as a result of the optical nonlinearity of fibers.[21] This phenomenon, often referred to as the Gordon-Mollenauer effect, was a key factor in preventing the use of solitons in coherent optical communications.

Gordon's most recent major contribution to the field of fiber-optic communications was in the mathematical formulation of the phenomenon of polarization mode dispersion (PMD), which constitutes one of the most important factors in determining the performance of fiber-optic systems. His paper, coauthored with H. Kogelnik, appeared in the Proceedings of the National Academy of Sciences, and the formulation presented therein became standard in many of the subsequent texts dealing with polarization phenomena in optical fibers.[22]