Photodiode Sensors convert incident laser photons into charge carriers (electron and holes), which are afterwards measured as voltage or current. Their behaviour of having low noise and high sensitivity enables Photodiodes to detect very low light levels and makes them ideal for low power measurements of CW lasers.
Compared to thermal sensors, Photodiodes have a much more confined spectral range and lower spatial uniformity, which can affect the measurement repeatability of very small beams or of beams that are not stable on the detector surface. In general, Photodiode Sensors are the best choice when very low power measurement and when a fast response time is required.
Photodiode sensors have a saturation limit at, approximately, 1mW / cm2; to operate at higher powers attenuating filters must then be used. Laser Point’s series of Photodiode Sensors for laser power measurement was designed to cover a range of powers up to 500mW and a wavelength range that extends from UV to the near IR. These sensors are offered in a slim case that provides enhanced shielding against EM interference and can be supplied with a set of fiber adapters to connect them to standard optical fiber patch cords.