Influence of pump-beam parameters and crystal optical properties on propagation of thermally affected Bessel–Gaussian beams generated by a solid-state laser

Abstract

In diode-pumped solid-state laser system, the generation and propagation of Helmholtz–Gaussian beam families such as Bessel–Gaussian (BG) beam can dramatically suffer from the effects of heat load. In this study, based on the ABCD matrix for BG beams passing through a graded-index medium, expressions for the thermal lens focal length and the output beam are obtained. Furthermore, to evaluate the impact of the pump-beam parameters and crystal optical properties, the intensity distribution of the zeroth- and first-order BG beams against radial distance together with its corresponding transverse intensity pattern on X–Y plane under different pump powers, pump beam waists, absorption coefficients, and thermal conductivities are simulated and compared. The simulation results indicate that for powerful narrow pump beam, the thermal-induced effects are so dramatic that the intensity profiles are altered, as the discernment of BG beams is not easily feasible; however, taking into account the large pump waist, high thermal conductivity and small absorption coefficient can partly cause the laser output similar to non-thermal one despite high pumping power is received. Therefore, the precise selection of laser parameters can considerably reduce the effects of induced heat on the generation and propagation of BG beams. The obtained results are a valuable hint to experimenters for beam identification and beam quality monitoring.