IG2 Transmission Grating - 3 um - Fourier Transform Spectrometer spectral transmission measurement
These data were obtained in August 2016 using the Bruker Vertex 80v Fourier Transform Spectrometer in the High-resolution Spectroscopy facility, RAL Space, Rutherford Appleton Laboratory, UK. The spectrometer was configured using the mid-infrared glowbar broadband source, with optical data collected over 1.5-6 um. The beamsplitter was KBr, and the detector was nitrogen cooled HgCdTe. The double-sided interferogram was defined to run from 0.25 cm-1 to 15000 cm-1. The resolution was 0.5 cm-1. The pinhole size was 3 mm. The averaging period was calculated by observing the Allan variance of the spectrometer under these conditions; an averaging period of 2 minutes, or 40 scans, was used for noise reduction, to achieve SNR~500 in transmission. The data was collected using the Bruker OPUS software, and exported as a .dat file to Origin Pro 2017 for processing. The grating is an ultrafast laser inscribed transmission grating fabricated by Heriot-Watt University project partners.
The data contains 10 columns. The first column is the wavelength in microns, which was calculated from the wavenumber in cm-1 value provided by the spectrometer. The following columns contain the normalized transmission (measured signal divided by individual background measurement) for each wavelength, obtained by setting the grating such that the incoming beam interacts with the grating at a specific angle of incidence. These are (in order, degrees): 20, 25, 30, 35, 40, 45, 50, 55, 0. A short header summarizes this information.