High-energy, narrow-linewidth, pulsed 1083 nm laser system for metastable helium lidar

We present a high-energy, narrow-linewidth, pulsed 1083 nm laser source designed for ground-based metastable helium (He in the 23S state) fluorescence lidar systems to probe the thermosphere and lower exosphere. The system is pumped by a neodymium doped yttrium aluminum garnet (Nd:YAG) laser with a 532-1064 nm dual-wavelength output and consists of three home-made parts: (1) a second harmonic generation stage that produces a 532 nm pump laser from the residual 1064 nm output of Nd:YAG, (2) an injection-seeded optical parametric generation (OPG) stage employing two KTiOPO4 (KTP) crystals in series and a wavelength-stabilized continuous-wave seed laser, and (3) optical parametric amplification stages (A1 and A2) to amplify the signal and idler beams generated by the OPG stage. The constructed prototype system, operating at a repetition rate of 50 Hz, has achieved an output energy of ∼140 mJ/pulse with a typical pulse duration of 8 ns and a laser linewidth of less than 92 MHz. The output wavelength is continuously tunable between 1083 and 1084 nm, with a pulse-to-pulse frequency jitter of ∼±5 MHz, which is likely limited by the linewidth of the unlocked seed laser. By using a wave meter-based locking scheme for the seed laser wavelength, the central wavelength of the output 1083 nm pulses is stabilized with a long-term frequency jitter of about ±46 MHz. This work provides a technical solution for a high-energy 1083 nm laser for ground-based metastable helium lidars.