Boyd has made significant contributions to the research field known colloquially as slow and fast light. Shortly after the development of great interest in this field in 2000, he realized that it is possible to produce slow and fast-light effects in room-temperature solids.[11][12][13] Until that time, most workers had made use of systems of free atoms such as atomic vapors and Bose-Einstein condensates to control the group velocity of light. The realization that slow light effects can be obtained in room temperature solids has allowed the development of many applications of these effects in the field of photonics. In particular, with his students he pioneered the use of coherent population oscillations as a mechanism for producing slow and fast light in room temperature solids.[11][12][13] His work has led to an appreciation of the wide variety of exotic effects that can occur in the propagation of light through such structures, including the observation of “backwards” light propagation.[14] Boyd has also been instrumental in developing other slow light methods such as stimulated Brillouin scattering.[15] More recently, he has moved on to the investigation of applications of slow light for buffering[16] and signal regeneration.[17] He also came to the realization that slow light methods can be used to obtain enormous enhancements in the resolution of interferometric spectrometers,[18][19] and he is currently working on the development of spectrometers based on this principle. As just one indication of the impact of Robert's work on slow and fast light, his Science paper[12] has been cited 523 times.
Quantum imaging
Boyd has been instrumental in the creation and development of the field of quantum imaging. This field utilizes quantum features of light, such as squeezing and entanglement, to perform image formation with higher resolution or sensitivity than can be achieved through use of classical light sources. His research contributions in this area have included studies of the nature of position and momentum entanglement,[20] the ability to impress many bits of information onto a single photon,[21] and studies to identify the quantum or classical nature of coincidence imaging.[22][23] This latter work has led the community to realize that classical correlations can at times be used to mimic effects that appear to be of a quantum origin, but using much simpler laboratory implementations.
Local field effects and the measurement of the Lorentz red shift
Boyd has performed fundamental studies of the nature of local field effects in optical materials including dense atomic vapors. A key result of this work was the first measurement[24] of the Lorentz red shift, a shift of the atomic absorption line as a consequence of local field effects. This red shift had been predicted by Lorentz in the latter part of the nineteenth century, but had never previously been observed experimentally. In addition to confirming this century-old prediction, this work is significant in confirming the validity of the Lorentz local-field formalism even under conditions associated with the resonance response of atomic vapors.
Development of composite nonlinear optical materials
Boyd has taken a leading role in exploiting local field effects to tailor the nonlinear optical response of composite optical materials and structures. Along with John Sipe, he predicted that composite materials could possess a nonlinear response exceeding those of their constituents[25] and demonstrated this enhanced nonlinear optical response in materials including nonlinear optical materials,[26] electrooptic materials,[27] and photonic bandgap structures.[28] Similar types of enhancement can occur for fiber and nanofabricated ring-resonator systems,[29] with important applications in photonic switching[30] and sensing of biological pathogens.[31]
Foundations of nonlinear optics
Boyd has also made contributions to the overall growth of the field of nonlinear optics.[32] Perhaps his single largest contribution has been in terms of his textbook Nonlinear Optics.[33] The book has been commended for its pedagogical clarity. It has become the standard reference work in this area, and thus far has sold over 12,000 copies. Moreover, in the 1980s he performed laboratory and theoretical studies of the role of Rabi oscillations in determining the nature of four-wave mixing processing in strongly driven atomic vapors.[34][35] This work has had lasting impact on the field with one particular paper having been cited 293 times.[34]
^Boyd, Robert William (1977). An Infrared Upconverter for Astronomical Imaging (PhD thesis). University of California, Berkeley. OCLC21059058. ProQuest302864239.
^Shi, Z.; Schweinsberg, A.; Vornehm, J. E.; Martínez Gámez, M. A.; Boyd, R. W. (2010). "Low distortion, continuously tunable, positive and negative time delays by slow and fast light using stimulated Brillouin scattering". Physics Letters A. 374 (39): 4071–4074. Bibcode:2010PhLA..374.4071S. doi:10.1016/j.physleta.2010.08.012.
^Heebner, J. E.; Lepeshkin, N. N.; Schweinsberg, A; Wicks, G. W.; Boyd, R. W.; Grover, R; Ho, P. T. (2004). "Enhanced linear and nonlinear optical phase response of Al GaAs microring resonators". Optics Letters. 29 (7): 769–71. Bibcode:2004OptL...29..769H. doi:10.1364/ol.29.000769. PMID15072386. S2CID6681651.
