Abstract
We present a simple and convenient, high-resolution solution for automated laser-beam profiling with axial translation. The device is based on a Raspberry Pi computer, Pi Noir CMOS camera, stepper motor, and commercial translation stage. We also provide software to run the device. The CMOS sensor is sensitive over a large wavelength range between 300 and 1100 nm and can be translated over 25 mm along the beam axis. The sensor head can be reversed without changing its axial position, allowing for a quantitative estimate of beam overlap with counter-propagating laser beams. Although not limited to this application, the intended use for this device is the automated measurement of the focal position and spot-size of a Gaussian laser beam. We present example data of one such measurement to illustrate device performance.
Highlights
There are a vast number of situations in experimental atomic and optical physics where precise measurement of laser beam profiles is required, from measurements of absolute beam intensity in determining atomic transition dipole matrix elements,1 evaluating trap depths in optical dipole traps,2 and laser beam shaping applications,3 amongst others
The smallest and largest beam sizes that can be detected are set by the total area of the sensor and the size of a single pixel
In the remainder of the paper, we illustrate the use of the beam profiler through example data
Summary
There are a vast number of situations in experimental atomic and optical physics where precise measurement of laser beam profiles is required, from measurements of absolute beam intensity in determining atomic transition dipole matrix elements, evaluating trap depths in optical dipole traps, and laser beam shaping applications, amongst others. A labour-saving alternative is to use a CMOS image sensor to map the 2D spatial profile of the laser beam. This approach is widely used; there have been recent demonstrations using a webcam or the camera built into a smart phone device for this application.. For a focussed laser beam, one often needs to measure both the beam size at the focus and the axial position of the focus, which necessitates translating the camera or knife-edge along the axial dimension and repeating the profile measurements, which quickly becomes laborious if done manually. A recent novel approach used a spatial light modulator to negate the need for any physical translation of the beam, but this was only demonstrated for relatively large (of order 1 mm) beam sizes
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