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An optical scheme of an optical parametric oscillator with a master laser based on an Nd : KGW active element excited by two orthogonally oriented diode side pump modules is proposed to form radiation pulses with energies above 30 mJ and a repetition rate of 1 – 20 Hz in the eye-safe spectral range of 1.5 – 1.6 μm. The two-module excitation of the active medium makes the distribution of the master laser radiation intensity in the output beam cross section more uniform and provides a reliable operation of the optical parametric oscillator.

A -switched Nd : YAG laser with a high-power transverse diode pumping and injection of seed radiation generated by a single-frequency semiconductor laser is described. The threshold seed radiation power at which the -switched Nd : YAG switches to the single-frequency mode is (radiation intensity . With increasing injection power, the spectral and power characteristics of the -switched laser almost do not change at a constant excitation of its active medium. The spectral linewidth of the -switched Nd : YAG laser with injection from a TLD-1060-14BF single-frequency semiconductor laser module does not exceed (wavelength .

The features of the correlation processing of a speckle pattern obtained after transmission of radiation from a single-fibre multimode interferometer (SMI) with few modes through a diffusion transparency are studied theoretically and experimentally. It is shown that this approach eliminates the influence of polarisation mode beats and of higher-order modes typical for the two-mode excitation of a SMI and allows the measurement of the elongation of a sensitive fibre piece by exciting few modes in a multimode interferometer.