Compact mid-infrared tunable interband-cascade laser-based spectrometer: Characterization and outlook for Amide-I region chemical sensing

Abstract

This paper presents the development and evaluation of a compact mid-infrared (MIR) spectroscopy sensor system based on a tunable interband-cascade laser (tICL), intended for portable chemical sensing in field and industrial applications. The study focuses on the implementation, optimization and characterization of the optical system to provide an in-depth performance assessment of a customized spectrometer operating within a subset of the Amide-I region covering 1692 cm⁻¹ to 1640 cm⁻¹ (5.91 µm to 6.10 µm), using a novel tICL MIR laser. We performed a systematic evaluation of individual wavenumbers generated by the tICL laser to assess each single emission wavelength's performance. Aqueous ethanol and formic acid solutions at varying concentrations were utilized as test analytes to gauge the analytical capabilities of this system. We examined the signal strength and variability across all emission wavelengths by studying the absorbance values' dependence on various analyte mixture concentrations throughout the entire spectral range and find that most emission points have stable intensities. The performance of the new system was then benchmarked with a conventional FTIR spectrometer. The results demonstrate that compared to the reference FTIR spectrometer, the tICL laser-based system also achieves consistent trends and comparable results. Furthermore, it offers additional potential for miniaturization and feasibility for lab-on-a-chip applications. These findings highlight the potential of tICL-based MIR spectroscopy as a compact and highly sensitive tool for targeted applications where portable, narrow-range MIR sensing is sufficient, making it well-suited for field and industrial use cases.