Portable THz Frequency Standard using Difference-Frequency Generation of Acetylene-Stabilized Telecom Diode Lasers

We have developed a portable THz frequency standard. It is based on difference-frequency generation (DFG) of two telecom lasers in a uni-traveling-carrier photodiode (UTC-PD). Both lasers were simultaneously stabilized to acetylene $(^{13}\mathrm{C}_{2}\mathrm{H}_{2})$ transitions by modulation transfer spectroscopy using one reference gas cell. The fractional instability of the THz standard at 288GHz was attained to be $1\times ^{10-8}$ over 400s averaging time. This THz standard serves as a new wavelength reference for THz spectroscopy equipments and consequently improves their measurement accuracy.