Current status of terahertz frequency metrology at NICT

NICT has commenced development of an accurate and stable frequency standard for THz frequency band. We succeeded in phase-locking a single-mode 3THz quantum cascade laser (THz-QCL) to a THz reference. Using the phase-locked THz-QCL and a hot electron bolometer mixer, a THz wave generated by photomixing was evaluated. The result showed that the phase-locked THz-QCL and the optically generated THz wave had the same sability as the microwave references at the 10
^-15
level and also that imposed noises during heterodyne mixing were negligibly small.