Frequency stabilized laser source at around 2.09 μm by locking to H79Br and CO2 transitions

A tunable Tm-Ho:YAG laser was fabricated, characterized and used to perform high-resolution spectroscopy of several molecular absorption lines of HBr and CO₂ at around 2090 nm. Frequency locking of this laser source to the H⁷⁹Br P(12) transition at 2097.222 nm and to the CO₂ P(22) transition at 2087.844 nm was then achieved using the fringe side locking technique. The frequency stability obtained was first evaluated by monitoring the error signal of the control loop, giving a root mean square (rms) value of ∼30 kHz for the residual frequency fluctuations with both molecular frequency references. A further stability analysis was performed by monitoring the beat note between two independently stabilized Tm-Ho:YAG lasers, giving a two-sample deviation of the beat frequency below 100 kHz for all integration times between 1 μs and 0.1 s.