A smaller, faster and more sensitive laser power meter in the form of a folding mirror uses a capacitor-based force transducer and merges optical elements, namely a high reflectivity mirror, and sensing elements into a compact cube package. The four-centimeter-on-a-side cubes can be conveniently embedded into laser optical systems or laser-welding systems for point-of-use, realtime laser power measurement and calibration.
The key part of the design is a capacitor-based compact force transducer. It consists of a spiral planar silicon spring supporting a circular plate with a high reflectivity mirror on one side and an electrode on the other. An identical silicon spring with an electrode is placed close to the first spring such that the two electrodes face each other, forming a variable capacitor. A laser beam reflecting off the mirror on the first spring pushes the first spring to move toward the second and change the capacitance between the two electrodes. By comparing to a fixed reference capacitor, radiation pressure and laser power can be calculated. After reflecting off the mirror, the laser beam can be used directly for work, making real-time monitoring of laser power or laser calibration possible.
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