Ultra-Stable, spatially uniform monochromatic beam generation via active flux stabilization and fractional Talbot Self-Imaging

Abstract

Laser-based stable and uniform sources are necessary in various radiometry applications such as spectroradiometry, imaging, materials processing and various device characterizations. This study presents an optical system that produces a highly stable and homogeneous monochromatic beam using commercially available optical components. The stabilized laser flux fluctuates within ± 40 ppm over multiple hours of operation. Beam homogenization is achieved through a microlens array-based beam integrator, expanding the beam into a uniform square profile exceeding 45 × 45 mm² with a spatial uniformity above 99.6 %. For a coherent source, the homogenized expanded beam is an array of regularly spaced, narrowly packed light spots (beamlets) of identical intensity. A computational model based on Fresnel diffraction, Fourier analysis, and fractional Talbot self-imaging phenomenon has been used here to predict the beam’s irradiance distribution and behaviour. The model showed good agreement with experimental results. With an output irradiance expanded uncertainty falling as low as 0.46 %, the system provides a precise and reliable platform for optical measurements calibration and device characterization.