GaAs Detection Principle

The measurement principle is based on white light absorption/transmission by a GaAs (gallium arsenide) semiconductor. The impacts of temperature variations on this semiconductor are well known and predictable. As the temperature of the semiconductor changes, the semiconductor’s transmission spectrum (i.e. the light that is not absorbed) also shifts. At any given temperature, there will be a wavelength at which the transmission essentially jumps from 0% to 100%. This jump is called the absorption shift, and the relationship between the specific wavelength where the absorption shift takes place and the temperature is predictable.



The sensor consists of a tiny GaAs semiconductor crystal that is bonded to one end of a well-polished fiber optic.

Temperature Sensor

The white light launched from the monitor into the fiber optic travels through to the GaAs crystal, passing through it while being partially absorbed, and is then reflected to the monitor by a mirror located at the very tip of the sensor. The light reflected to the monitor is coupled into an optical spectrum analyzer, which then measures the optical power transmission versus the wavelength. The position of the absorption shift is determined by the monitor using a proprietary signal analysis algorithm and is then correlated to the temperature of the GaAs crystal.



Furthermore, since the semiconductor will not change over time, all sensors can be interchanged with no need for calibration or entry of factors when swapping sensors. For the same reason monitors never need recalibration after leaving the factory when used under normal operating conditions.

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