Stabilization of a Lasing Frequency of a THz-QCL in Free Running for Long-Term Phase-Locking

We have successfully demonstrated a continuous phase-locking of a terahertz quantum cascade laser (THz-QCL) in ~5 days by suppressing a slow drift of the lasing frequency in free running from ~150 to 5~10 MHz/day. The THz-QCL was covered with an enclosure to prevent the gas adsorption. The holding time of the phase-locking is expected to be longer.