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Opto-Mechanical and Electronic Design of a Tunnel-Trap Si-Radiometer



George P. Eppeldauer, D C. Lynch


A transmission-type light-trap silicon-radiometer has been developed for the Spectral irradiance and Radiance Response Calibrations with Uniform Sources (SIRCUS) Facility of NIST to hold the spectral power and irradiance responsivity scales between 406 nm and 920 nm. The transfer standard irradiance-type radiometer performs uncertainties similar to that of the primary standard cryogenic radiometer. Illuminance and irradiance meters, holding the SI units (candela, color- and radiance-temperature), will be calibrated directly against the transfer standard to obtain improved accuracy in the base-units. The device was built from replaceable imput apertures and tightly packed different-size silicon photodiodes positioned inside of a triangular shape tunnel. A second light trap was attached to the output of the device to collect the transmitted radiation and to minimize pickup of ambient light. The photodiodes, selected for equal shunt resistance, were connected parallel. The capacitance and the resultant shunt resistance of the device were measured and frequency compensations were applied in the feedback network of the photocurrent-to-Voltage converter to optimize performance. The trap-radiometer can measure either dc or ac (chopped) optical radiation with high sensitivity. The noise-equivalent power of the noise optimized device was 47 fW in dc mode and 5.2 fW at 10 Hz chopping. The radiometric characterization of the device and the spectral responsivity calibration based on the physical model will be described in a following paper.
Journal of Research (NIST JRES) -
105 No. 6


detector, irradiance, photocurrent, photodiode, radiant power, reference detector, responsivity, spectral response, transfer standard


Eppeldauer, G. and Lynch, D. (2000), Opto-Mechanical and Electronic Design of a Tunnel-Trap Si-Radiometer, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD (Accessed April 20, 2024)
Created November 1, 2000, Updated February 17, 2017