Fast calibration of photodiodes in the near-infrared, visible and ultraviolet using a Fourier-transform spectrometer

A new, fast method for broadband secondary calibrations of photodiodes against a calibrated reference diode has been developed. It is based on a Fourier-transform spectrometer (FTS) and does not require any exchange of the light source, grating or higher-order filter. With the present set-up, it takes only 10 minutes to measure the spectral responsivity ratios of three unknown photodiodes compared with a reference photodiode from 200 nm to 1000 nm. The estimated uncertainty of 0.05% of the responsivity ratios was confirmed by independent measurements using intensity-stabilized laser radiation at twelve wavelengths between 238 nm and 1000 nm. The combination of the uncertainties of the new secondary FTS calibration method and those of the reference diode's primary calibration at the cryogenic radiometer shows that an efficient, practicable way has been found to provide customers with photodiodes as working standards of spectral responsivity for wavelengths from 1000 nm to 200 nm with uncertainties of 0.05% to 0.2% (near-infrared and visible to ultraviolet).