Design and Optimization of a Variable-Divergence Galilean Laser Optical System Using a Kerr-Based Nonlinear Aspherical Lens

Abstract

This paper presents the design and optimization of a Galilean laser optical system incorporating a Kerr-based nonlinear aspherical lens (NAL) for variable beam divergence control. The system retains the classical axial-shift zoom principle while replacing the conventional precision-polished positive aspherical lens with a Kerr nonlinear element modeled as an equivalent aspherical surface. The Kerr effect introduces an intensity-dependent refractive index modulation that compensates for spherical aberrations, thereby improving wavefront quality. The optical design was developed and optimized using Zemax in multi-configuration mode. A compact afocal beam-expanding and collimating system is proposed for a 1064 nm laser source with an initial divergence of approximately 5 mrad and an input beam diameter of 1 mm. The system provides a continuously tunable expansion ratio from 4× to 20×, reducing the output divergence to as low as 0.25 mrad. Across all configurations, the optimized design achieves a root means square (RMS) wavefront aberration below λ /14, reaching the diffraction limit. Compared with conventional zoom systems, the proposed configuration offers comparable optical performance with reduced alignment sensitivity and improved manufacturability, demonstrating the practical potential of Kerr-based nonlinear aspherical lenses for variable-divergence laser applications.