Parametric laser rangefinder with a passive thermal stabilization system

Subject of study. The development of a small-sized pulsed laser rangefinder with a passive thermal stabilization system is studied. Objective. The objective is the creation of a prototype of a laser rangefinder generating pulsed laser radiation with a wavelength of λ=(1.57±0.04)µm. Method. A theoretical study of the influence of the rangefinder operating wavelength on the propagation of laser radiation in the atmosphere and extinction losses was performed using the finite difference method in a time-nonstationary formulation. The mode composition of radiation was estimated using a standard numerical solution of the Fresnel–Kirchhoff diffraction integral. The methods of pyroelectric registration were used for the estimation of the energy parameters of laser radiation. Main results. A small-sized laser rangefinder generating laser radiation in the near-IR range at a wavelength of (1.57±0.04) µm with a pulse repetition rate of up to 20 Hz and pulse energy of up to 17 mJ was developed. The rangefinder emitter was constructed utilizing a composite stable semi-confocal optical resonator. Within one segment of the resonator, a nonlinear passive conversion of the radiation λ=(1.064±0.025)µm emitted by an active medium based on a stoichiometric Nd:YAG single crystal led to the formation of a signal wave with a wavelength of λ=(1.57±0.04)µm. Scientific novelty. The research demonstrates the possibility of maintaining stable generation with a temperature mismatch between the absorption spectrum of the active media and the emission spectrum of the laser diode bar by up to 22 nm, which makes it possible to eliminate the use of a thermal stabilization system for the diode bar. Practical significance. It is shown that radiation with a wavelength of λ=(1.57±0.04)µm is preferable for tasks of pulsed laser ranging in comparison with radiation with a wavelength of λ=(1.064±0.025)µm because there is less scattering on atmospheric aerosol. The active medium is pumped by a quasi-continuous wave multispectral array of laser diodes with a total average radiation pulse power of 2200 W, which makes it possible to abandon active thermal stabilization and optimize the mass and dimensional parameters of the product.