No detector has a constant spectral responsivity under all conditions of use. For instance, the responsivity of photodiode detectors falls off above a certain incident power level due to saturation effects. Full evaluation of a detector requires characterisation of such effects. This information allows the identification of the detector with the best performance for a particular application. Also, a detector to be used for calibration purposes should be fully characterised in order to evaluate the uncertainty of such calibrations.
In all cases the detector under test is compared with a standard detector of known spectral responsivity / quantum efficiency.
300F Monochromator is used to select a narrow wavelength band from a broad band quartz halogen lamp. Wavelength range of monochromator is between 380 - 1100 nm (Optional wavelength ranges are available on request). The wavelength can readily be tuned continuously allowing measurement of spectral responsivity across the wavelength range for which the detector is used.
|Photocurrent measurement range||:||0.1 nA to 50 uA|
|Bias voltage||:||+10V to -10V|
|Bias voltage step size||:||100 mV|
|Light Source||:||50 W tungsten halogen lamp|
|Monochromator type||:||Czerny Turner with two holographic gratings and 2nd order filters|
|Wavelength range||:||380 - 1100 nm (Optional wavelength ranges are available on request)|
|Maximum sample size||:||50 mm|
|Sample holder with manual three axis positioning using knobs|
|Pogo pins or multimeter like probe tips to make contact with the sample|
|Note : PC is not in the scope of supply|
HOLMARC Model: HO-PDC-01 designed for characterisation / measurement of the following detector parameters:
Linearity range : This is the range of incident radiant power levels over which the detector output varies linearly with incident power. (Laser-based methods is used for measuring saturation threshold of a detector).
Spatial non-uniformity of response : The variation of responsivity across the active area of a detector is determined by scanning a small spot of radiation at a selected wavelength over the surface.
Noise Equivalent Power (NEP) : the incident radiant power at a specific wavelength and modulation frequency necessary to produce a signal-tonoise ratio of 1 at the detector output.
Temperature coefficient of response : the variation of responsivity with temperature
Detector shunt resistance : the slope of the current-voltage curve of a photovoltaic detector at zero-volt bias.
Spectral response of a photodiode
Solar cell response at different temperatures