Precise scale of spectral responsivity for InGaAs detectors based on a cryogenic radiometer and several laser sources

Abstract

The Physikalisch-Technische Bundesanstalt (PTB) has developed a spectral responsivity scale in the spectral range 0.95 µm to 1.6 µm. The responsivity scale was established by calibrating InGaAs photodiodes against the PTB radiation thermometry cryogenic radiometer (RTCR) using several laser sources: a Ti:sapphire laser (0.850 µm to 1.02 µm); a Nd:YAG laser (1.064 µm); and two diode lasers (1.31 µm, 1.55 µm). At intermediate wavelengths the responsivity was interpolated with the help of thermal cavity detectors of high emissivity. In this way the high accuracy of the scale at the laser wavelengths can be maintained over almost the entire spectral region. A detailed discussion is given of the uncertainties achieved in the calibration with the RTCR and the interpolation with the thermal detector.

Infrared Filter Radiometers for Thermodynamic Temperature Determination below 660 °C

“…Hitherto, the spectral responsivity scale between 950 nm and 1,650 nm was realized by calibrating InGaAs photodiodes at four laser lines using the PTB laser-based radiation thermometry cryogenic radiometer (RTCR) and interpolating the spectral responsivity with thermal detectors [2]. However, the interpolation with conventional thermal detectors is very time-consuming and of limited accuracy.…”

“…To fulfil these conditions, we used custom interference filters with a center wavelength of 1,310 nm or 1,550 nm (respectively), a spectral bandwidth of about 50 nm (FWHM), and an out-of-band blocking of more than five orders of magnitude. With these filter parameters, the corrections due to water-vapor absorption remain below 4 × 10 −4 (1,310 nm) and 4 × 10 −5 (1,550 nm), respectively, and the temperature coefficient (TC) [2,10] and nonlinearity of the spectral responsivity of the filter radiometer are minimized. The InGaAs photodiodes used in the filter radiometer were selected from a batch of InGaAs photodiodes previously characterized with respect to their shunt resistance and the homogeneity of their spectral responsivity at 1,300 nm and 1,550 nm (Fig.…”

“…The first step is the calibration of transfer detector standards (i.e., single photodiodes or trap detectors) against the cryogenic radiometer [2][3][4][5][6]. The spectral responsivity of the transfer detectors to radiant power is determined at this step.…”

“…Therefore, the PTB has developed an InGaAs photodiode-based filter radiometer with a center wavelength at 1,595 nm and a bandwidth (FWHM) of 100 nm [1] as a first step to extend the range of radiometric high-accuracy thermodynamic temperature measurements down to temperatures as low as the Sn-FP (232 • C). This filter radiometer was absolutelycalibrated in terms of spectral irradiance responsivity and applied to thermodynamic temperature determinations of a blackbody at 419 • C, 457 • C, and 600 • C. The results presented in [1] are based on an interpolated scale of spectral responsivity in the wavelength range from 0.95 µm to 1.65 µm maintained with InGaAs photodiodes as transfer detector standards [2]. However, the uncertainty of this interpolated scale is more than one order of magnitude higher than the spectral responsivity scale maintained with trap detectors consisting of silicon photodiodes in the wavelength range from 500 nm to 900 nm [3].…”

Spectral phase shaping for non-linear spectroscopy and imaging

“…The temperature dependence of the sensitivity of a Siphotodiode is large for wavelengths over 1 μm (in the order of 0.8% change in sensitivity per degree Kelvin for operation at 1064 nm) whereas it is negligible for wavelengths under 0.95 μm [106]. For InGaAs-photodiodes the temperature dependence of the sensitivity at 1064 nm is less than 0.05% per degree Kelvin [107]. The higher harmonics of the photodiode signals are reduced by means of a short pass filter with a cutoff frequency of 91 MHz, because the variable amplifiers are not specified at those frequencies.…”