Spectral responsivity uncertainty of silicon photodiodes due to calibration spectral bandwidth

A systematic study on the uncertainty in spectral responsivity of silicon photodiodes due to the calibration spectral bandwidth is presented. Two of the most common types of silicon photodiodes in the field of optical power measurements have been used in this work: one with thickness of about 100 nm of SiO₂ and the other with thickness about 27 nm of SiO₂. It is shown that the spectral responsivity error will be negligible (≤5×10^-4) using a spectral bandwidth up to 20 nm in the calibration if the effective wavelength of the spectral transfer function, including the distribution of the radiation source, is calculated and the measured responsivity is assigned to that effective wavelength. In other cases, the error depends not only on the extent of the interval isolated by the spectral analysis system but also on the shape of the spectral isolation function.