Optical dispersion spectroscopy using optical frequency comb applied to dual-heterodyne mixing

The optical dispersion can be obtained from the adjacent relative phase between neighbor peaks in the optical frequency comb. Thus, the dispersion measurement becomes possible by measuring the relative phase spectrum. Our group has experimentally confirmed the operation principle by parallel capturing of the dispersion spectrum using an arrayed waveguide grating. We have proposed a dual-heterodyne mixing that obtained relative phases (ΔΦ) by fitting data of beat intensity versus optical path length difference. The path difference was applied by a delay line. In this study, we removed the delay line to realize a fast measurement by measuring simultaneous three relative phases with path length differences corresponding to π⁄2 or π, with which we have measured the dispersion in millisecond speed (250 sec. in previous ). In general, it is effective to measured chromatic dispersion using high-speed signal transmission in the fundamental scientific research, such as the analysis of material properties and telecommunications. It is, however, that limit of cutoff frequency using measurement is the restriction on increasing of the speed. Our proposed method to observe it on a frequency domain is effective for the high-speed signal processing.