Development of a novel beam profiling prototype with laser self-mixing via the knife-edge approach

Abstract

Laser is widely used in industry, biomedical and other kinds of fields. Beam size is the most important parameter among the laser variables. Typical state-of-the-art profiling techniques employ either a scanning-based or camera-based system, using photodiodes or image sensors as the signal receiver. Despite their profiling capabilities, these systems do not tend to be budget-friendly and easy to operate. In this paper, a novel cost-effective beam profiling prototype based on self-mixing interference was developed to measure the Full Width Half Maximum (FWHM) of a range of laser diodes by the knife-edge approach. The difference between our prototype and other systems is that the photodiode is placed behind the laser source, and beam size is calculated by analyzing the feedback signal. A commercial camera beam profiler was used to benchmark our prototype. Results show that though there is a variation of 45.29 % and 65.44 % between the measured beam size and the integrated beam size in the x and y directions due to diffuse and specular reflection, our USD 200 prototype has an accuracy ranging from 89.59 % to 98.74 % on the prediction of laser beam sizes. Our prototype could provide accurate predicted beam size both for Gaussian-alike beam and top-hat-alike beam. This is the very first study to explore the application of self-mixing interference in laser beam profiling. It is believed that our proposed approach has contributed to the on-going development of laser beam profiling methodology.