Diode laser generating 3-ns pulses for a high resolution lidar

An AlGaAs laser (907 nm, 0.2 μJ) with a 3-ns pulse duration and eye-safe energy density below 1 μJ cm^-2 is developed for lidar application. The laser is composed of three stacked diodes in a plastic housing. An external pump current generator based on discrete elements with an FMMT417 bipolar transistor switch is assembled on a printed circuit board together with the laser. A lidar based on this laser and a single photon avalanche diode (SPAD) as a detector is used to monitor aerosols with a resolution of 10 cm inside the tunnel of the Baksan Neutrino Observatory near the Elbrus volcano. An abrupt three-fold increase in aerosol emanation of yet unknown nature is recorded for the first time. The absence of the Earth's crust disturbance traces in the signal of a laser interferometer with a resolution of 1.6 × 10^-11 m testifies to a high sensitivity of the lidar for monitoring geodynamic processes.