Update: 2019-08-10 16:50 Source: LUFTMY
Laser power sensor is a kind of detector which absorbs laser beam and outputs the signal proportional to the beam power. The type of laser power sensor to be used depends on various elements of the measured laser beam, including power level, spectral region, beam size, etc.
When the photon source of the laser is directed at the photodiode detector, a current is generated proportional to the intensity of the light and depends on the wavelength. Since the power of many low-power lasers is about 5 to 30mW, and the saturation of most photodiode detectors is about 2mW, the laser power sensor sensor is built with built-in filters that can measure up to 30mW without saturation. The power meter unit amplifies the signal and indicates the power level received by the sensor.
Commonly used in the laser power sensor are: photodiode sensor and thermal power sensor. Photodiode sensors are used from power up to hundreds of milliwatts and up to 3W of low power. Thermal sensors can be used for fractions of microwatts to tens of thousands of watts. The thermal sensor can also measure a single source of energy at a pulse rate of no more than one pulse every five seconds.
Photodiode sensors are highly linear over a wide range of optical power levels: from nava-level fractions up to about 2mW. Above this light level, corresponding to a current of about 1mA, the sensor is saturated and erroneously reads low. As a result, most laser photodiode sensors have built-in and removable attenuators that measure saturation up to 3W.
The heat sensors have a series of bimetallic junctions called thermopile. The voltage generated by the radial or axial heat flow through the sensor is proportional to the power absorbed as it flows through the thermopile. The reading does not depend on the ambient temperature, as only the temperature difference is measured, not the absolute temperature. Thermopile elements are arranged so that readings are almost independent of beam size and position.