Effects of heat transfer characteristics of atmospheric horizontal buoyant jets on optical aberrations in a laser system

Abstract

An effective thermal monitoring and management strategy is required to ensure stable performance of an optical system. Although forced convection cooling systems help to maintain the temperature within an appropriate range, such systems always exhibit temperature gradients and turbulence. The resulting thermal lensing effects degrade optical performance. An understanding of the convective heat transfer characteristics and thermal lensing effects is essential for optimizing optical system performance. This study analyzes the independent thermo-optical effects of convective heat transfer by a horizontal buoyant jet. The results showed that the buoyancy of the jet induced an increase in the core flow. Rays passing through the flow exhibited various aberrations including a negative Y-tilt, positive defocus, and negative vertical astigmatism. These effects intensified as the discharge temperature increased. Turbulent dissipation rate analysis revealed that the variability of these aberrations was attributable to fluctuations in the thermodynamic parameters of air. The variability increased at turbulent dissipation rates. Based on the theoretical background of thermo-optical phenomena in air, the effect of convective heat transfer on these aberrations was explored via numerical simulations and experimentally validated using a Shack–Hartmann wavefront sensor. These findings indicate that quantitative aberration-based analytical methods aid optical quality evaluation in terms of the thermal management of optical systems.