Laser Beam Matching Detector

Photo-diode-based detectors utilize a doped semiconducting material (typically silicon) which absorbs incident light of a given wavelength (or range of wavelengths), thereby exciting electrons and generating an electric current commensurate with the wavelength and intensity of the incident light. Laser photodiode detectors tend to have a fast response time and are less sensitive to temperature than thermal-based laser power detectors. For detection of varying wavelengths, different semiconducting materials can be used, such as Germanium, of InGaAsP, which provide different (and complementary) spectral ranges for laser detection. Photodiode detectors are typically used for low-power lasers when compared to thermal power detectors.

Thermopile laser power detectors work on a wholly different principle altogether than photodiode detectors: instead of incident light exciting electrons directly, a laser beam instead is applied to a heat absorbent end of the detector, which creates a temperature gradient between the detector absorption end and the colder heat sink end of the detector. This temperature gradient then drives a voltage proportional to the magnitude of the temperature gradient, in an electronic device known as a thermopile. Thermopile power detectors are able to characterize the laser power of a typically wide range of applied lasers (in terms of both spectral range and power).

Pyroelectric laser power detectors work on a similar principle to thermal power detectors, in that the outputted laser power is a function of temperature change due to an incident laser beam, but instead of arising from a spatial temperature gradient in a thermopile, pyroelectric detectors rely on voltage generated from a pyroelectric material forming the basis of the detector. A pyroelectric material is a material that, upon experiencing a temperature change, modifies the positions of atoms in its crystal lattice to produce differences in polarization, ultimately resulting in an electric current proportional to the amount of heating applied.