When using laser light sources and some optical devices, beam expansion and contraction are common application requirements. LBTEK large aperture fixed magnification laser beam expander is an optical system based on a telescope structure that can expand (or reduce) the diameter of a parallel incident light spot to a certain magnification. Through the low-aberration and air-gap structure design, it can achieve a transmitted wavefront difference less than λ/4@633nm (i.e., reaching the diffraction limit). The single-sided anti-reflection coating on the beam expander lens can minimize the reflection at the air and glass interface between the specified bands. Compared with the typical reflectivity of 4% on the surface of uncoated optical components, the anti-reflection coating can reduce the average reflectivity of each surface to less than 0.5% in the specified band. LBTEK UV fused silica beam expanders provide threaded input apertures and output apertures. The input end of the beam expander has an SM1.5 internal thread and the output end has an SM3 external thread, which is convenient for use with LBTEK lens tubes and other optical components. When adjusting the fine-tuning rotating ring with magnification at the input end, the thread end and the mounting surface will not be driven, and the stability of other components in the optical path will not be affected during the adjustment of the divergence angle. LBTEK also provides a variety of customized services, including customization of special sizes, design wavelengths, beam expansion magnifications and other indicators. For specific customization needs, please contact LBTEK technical support.