Laser spot measurement using simple devices

• Published in: AIP advances Vol. 11; no. 7; pp. 075016 - 075016-9
• Main Authors: Bonnett Del Alamo, M., Soncco, C., Helaconde, R., Bazo Alba, J. L., Gago, A. M.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01.07.2021; AIP Publishing LLC
• Subjects: Automation; CMOS; Error analysis; Gaussian beams (optics); Imaging techniques; Knife-edge; Laser beams; Lasers; Photodiodes; Sensors; Webcams
• ISSN: 2158-3226; 2158-3226
• DOI: 10.1063/5.0046287

We have designed and tested an automated simple setup for measuring the profile and spot size of a Gaussian laser beam, which exhibits a similar performance to ready-made optical devices, using three light sensors. We use a light dependent resistor as a novel instrument in this approach with good accuracy. We provide the setup in detail in order to be reproduced with the current technology at a standard laboratory. Two profiling techniques were implemented: the imaging technique for the CMOS 2D array (webcam) and scanning knife-edge-like technique using a single photodiode and a light dependent resistor. We apply up-to-date devices, such as a Raspberry Pi, for automation. The methods and sensors were compared to determine their accuracy using lasers of two different wavelengths and technologies. We verify that it is possible to use a webcam to determine the profile of a laser with 1% uncertainty on the beam waist, 1.5% error on the waistline position, and less than 3% error in determining the minimum spot radius. We show that it is possible to use a light dependent resistor to estimate the laser spot size with an 11% error. The photodiode measurement is the most stable since it is not affected by the change in laser intensity.