Asymmetric photonic resonances in GaN slab waveguide for mid infrared selective filters.

We demonstrate a spectrally selective reflector that exploits asymmetric photonic resonances of a 1D photonic crystal. The proposed spectrally selective reflector has a very simple structure - essentially just a single high-index slab of GaN, properly perforated, and supported by a transparent sapphire substrate. With the proper 1D array design, nearly 100% reflection is achieved with a narrow spectral width between 10 cm⁻¹ - 18 cm⁻¹, while the background reflection remains low across the entire mid-IR range. The reflection peak can be tuned over a large wavelength span based on physical parameters. Resonant transmission dips in the experimentally measured spectra corroborate the device theory and simulation, exhibiting the narrowband low-background mid-IR reflection as predicted.

Mid-infrared doping tunable transmission through subwavelength metal hole arrays on InSb.

Doping-tunable mid-infrared extraordinary transmission is demonstrated from a periodic metal hole array patterned on n-InSb. The polarization-dependent transmission was measured at room temperature and 77 K. In addition, the extraordinary transmission was measured for incident angles from 0 degrees to 35 degrees in 5 degrees steps. A fundamental resonance shift of approximately 123 cm-1 (1.4 microm) is observed by varying the doping from 1 x 10(16) to 2 x 10(18) cm(-3). The calculated transmission resonances were in good agreement with the experimental results. This suggests that InSb semiconductor-based plasmonic structures may be suitable for a variety of tunable mid-infrared device applications.