Frequency stabilized Tm-Ho:YAG laser by locking to H79Br and CO2 transitions at around 2.09 μm

A diode-pumped Tm-Ho:YAG laser, widely tunable at around 2090 nm, was fabricated and used to perform high-resolution spectroscopy of several molecular absorption lines of HBr and CO₂. The laser source was then frequency locked, using the fringe side locking technique, to the H⁷⁹Br P(12) transition at 2097.222 nm and to the CO₂ P(22) transition at 2087.844 nm. The obtained laser frequency stabilities evaluated by monitoring the error signal of the control loop were ∼30 kHz root mean square (rms) values, with both the molecular frequency references. Additional frequency stability measurements were performed by monitoring the beat note between two independently stabilized Tm-Ho:YAG lasers. The two-sample frequency deviation of the beat frequency below 200 kHz was measured over different integration times of interest in Lidar and differential absorption Lidar system applications.