The All-Solid-State Narrowband Lidar Developed by Optical Parametric Oscillator/Amplifier (OPO/OPA) Technology for Simultaneous Detection of the Ca and Ca⁺ Layers

We report an all-solid-state narrowband lidar system for the simultaneous detection of Ca and Ca+ layers over Yanqing (40.41 degrees N, 116.01 degrees E). The uniqueness of this lidar lies in its transmitter, which is based on optical parametric oscillation (OPO) and optical parametric amplification (OPA) techniques. The injection seeded OPO and the OPA are pumped by the second harmonic of an injection-seeded Nd:YAG laser, which can generate coherent light at the wavelength of 786 nm or 846 nm lasers, whose second harmonics in turn generate the 393 nm or 423 nm pulses, respectively, for the detection of thermospheric and ionospheric Ca+ and Ca layers. Compared to the conventional dye-based system, this lidar transmitter is a narrowband system (bandwidth < 200 MHz), which has produced a factor of two more output power with higher stability and reliability. The lidar system in Yingqing demonstrated Ca+ detection sensitivity of 0.1 atoms-cm(-3) for long-term observation and reached a height of similar to 300 km. Potential applications and further improvements in this lidar technique are also discussed in this paper.