A compact and continuously operating CO₂ pumped HCOOH dual laser

A compact terahertz continuous wave (CW) CO
2
pumped formic acid (HCOOH) dual laser has been developed for higher time resolution and long continuous operation, with active power and intermediate frequency (IF) control. The output power of more than 20 mW on 0.69 THz line is obtained by using a 1.5 m long dual-waveguide with an inner diameter of 38 mm. The air supply system of the laser is designed for continuous air intake, so that the laser system can operate continuously and stably for at least 24 hours. Two high precision ($1~{\mu }\mathrm{m}$) moving frames are used to control the output power and IF of the dual laser. The whole dual laser system has been successfully operated, with output power exceeding 20 mW and IF stable at around 1 MHz in more than 24 hours.