Correction of spectral deformation by second-order diffraction overlap in a mid-infrared range grating spectrometer using a PbSe array detector

Conventional diffraction gratings suffer from order overlap problems, especially for a mid-infrared optical emission spectrometer (mid-IR OES) using a detector array. Because of diffraction order overlap, ambiguous spectroscopic data are inevitably acquired. This shortcoming motivated us to devise an order-sorting method. We predicted a second-order diffraction overlap and corrected the deformation of signal measured with a mid-IR OES using an array detector. It is found that the first-order signal separated from the overlapped spectrum fit well with the intrinsic signal of incident light. We determined the system response function of a mid-IR OES and confirmed the validity of the compensation method by comparing the measured spectrum with Planck's curve of blackbody radiation at two different temperatures. In addition, for accuracy verification, the uncertainty factors that could affect the compensation procedures were carefully considered.