Laser Power Sensors
Thermal sensors have a series of bimetallic junctions called a thermopile. Radial or axial heat flow through the sensor creates a voltage proportional to the power absorbed as it flows through the thermopile.
Photodiode sensors saturate for light levels above 2mW, this could lead to erroneously low reads. Therefore, most Ophir PD sensors have a built-in and removable attenuator allowing measurement of up to 3 W without saturation.