Pyroelectric detector-based method for low uncertainty spectral irradiance and radiance responsivity calibrations in the infrared using tunable lasers

The standard uncertainty of detector-based radiance and irradiance responsivity calibrations in the short-wave infrared (SWIR) traditionally has been limited to around 1% or higher by the poor spatial uniformity of detectors used to transfer the scale from radiant power. Pyroelectric detectors offer a solution that avoids the spatial uniformity uncertainty but also introduces additional complications due to alternating current (AC) measurement techniques. Herein, a new, to the best of our knowledge, method for low uncertainty irradiance responsivity calibrations in the SWIR is presented. An absolute spectral irradiance responsivity scale was placed on two pyroelectric detectors (PED) at wavelengths λ from 500 to 3400 nm. The total combined uncertainty ( k = 1 ) was ≈ 0.28 % ( > 1000 nm ), 0.44% (900 nm), and 0.36% ( ≈ 950 nm and < 900 nm ) for PED #1 and 0.34% ( > 1000 nm ), 0.48% (900 nm), and 0.42% ( ≈ 950 nm and < 900 nm ) for PED #2. This was done by utilizing a demodulation technique to digitally analyze the time-dependent AC waveforms, which obviates the use of lock-in amplifiers and avoids associated additional uncertainty components.