Characteristic molecular vibrational absorption wavelengths in mid-infrared (mid-IR) have been discovered for various applications, and as a result, a faster summary of an MIR spectrum can be gained by probing a set of discrete spectral fingerprints only, enabling many applications including fast early cancer diagnostics, real-time spectroscopic observation, on-chip chemical sensing, and simple/compact mid-IR instrumentation. In this ‘discrete-frequency infrared’ (DF-IR) spectroscopy approach, there is no Fourier transform infrared (FT-IR) interferometer that continuously scans a spectrum, and acquisition of spectral information can be made rapidly by combining an MIR detector and a tunable single-peak narrowband light source, such as selective thermal emitters, quantum cascade (QC) lasers, or a combination of a broadband incandescent globar and filters.This thesis explores the DF-IR approach by using photonic filtering that is based on guided mode resonance (GMR). First, a useful analytical framework for optimal design of GMR devices is established based on a sound understanding of the underlying physics, and can be used to complement numerical electromagnetic simulations. Then, guided by this judicious design, the thesis presents experimental realization of high-performance GMR filters in the C-H stretching region (3-4 µm or 2500-3300 cm-1) of the mid-IR, and demonstrates GMR-filter-based DF-IR microspectroscopy for the first time. Last but not the least, this thesis introduces a new type of high-refractive-index photonic filter in the challenging but important molecular fingerprint mid-IR (6-10 µm or 1000-1600 cm-1) that shows behaviors distinct from conventional GMR. The combination of the high-index photonic devices and the recently developed QC emitters is proposed as a novel, promising solution to high-quality DF-IR microspectroscopy.
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