Terahertz source with broad frequency tunability up to 3.8 THz using MZ-FCG for frequency reference in phase-locking of THz source devices

To simultaneously stabilize a series of terahertz (THz) source devices, we propose the use of optical combs as a frequency reference source. The optical combs provide a number of equally-spaced cw lights with high accuracy, so that it is suitable for generation of a series of frequency reference signals. To generate broadband optical combs, a combination of the Mach-Zehnder-modulator-based flat comb generator (MZ-FCG) and the highly nonlinear dispersion shifted fiber was used. Optical two-tones were extracted from the broadband optical combs by using a pair of optical tunable bandpass filters (TBPs). The optical two-tone was converted to THz waves by the unitraveling carrier photodiode (UTC-PD). As a result, THz waves with broad frequency tunability up to 3.8 THz were successfully demonstrated.