Dual-wavelength Q-switched Er:YAG laser around 1.6 μm for methane differential absorption lidar

A pulsed Er:YAG laser with resonant in-band diode pumping was demonstrated. Laser pulses with 6.6 mJ energy and 50 ns pulse duration were generated. With an intra-cavity etalon a broad wavelength tuning range from 1643.47 to 1646.78 nm was obtained. A stable dual-wavelength operation was observed by fine tuning of the etalons. The separation of the two wavelengths was 0.78 nm. One of them was located within a methane absorption line and the other was off the line. The frequency stability of the narrow linewidth Er:YAG laser was less than 40 MHz. It is a very compact laser source for methane differential absorption lidar.