31 May 2012 Planar integrated plasmonic mid-IR spectrometer
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Abstract
The convergence of silicon photonics and infrared plasmonics allows compact, chip-scale spectral sensors. We report on the development of a compact mid-IR spectrometer based on a broad-band IR source, dielectric waveguides, a transformer to convert between waveguide modes and surface plasmon polaritons (SPP), an interaction region where analyte molecules are interrogated by SPPs, an array of ring resonators to disperse the light into spectral components, and photodetectors. The mid-IR light source emits into a dielectric waveguide, leading to a region that allows coupling of the incident photons into SPPs. The SPPs propagate along a functionalized metal surface within an interaction region. Interactions between the propagating SPP and any analytes bound to the surface increase loss at those wavelengths that correspond to the analyte vibrational modes. After a suitable propagation length the SPP will be coupled back into a dielectric waveguide, where specific wavelength components will be out-coupled to detectors by an array of ring resonators. We have selected a 3.4 micron LED as the IR source, based on both cost and performance. Initial experiments with circular waveguides formed from GLSO glass include measurement of the loss per mm. Electrodynamic simulations have been performed to inform the eventual Si taper design of the proposed photonic/plasmonic transformer. The SPP propagation length necessary for a discernible change in the signal due to absorption in the interaction region has been estimated to be on the order of 1 mm, well within the bounds of calculated propagation lengths for SPPs on Au.
© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Christopher J. Fredricksen, Justin W. Cleary, Walter R. Buchwald, Pedro Figueiredo, Farnood Khalilzadeh-Rezaie, Gautam Medhi, Imen Rezadad, Monas Shahzad, Mehmet Yesiltas, Janardan Nath, Javaneh Boroumand, Evan Smith, Robert E. Peale, "Planar integrated plasmonic mid-IR spectrometer", Proc. SPIE 8353, Infrared Technology and Applications XXXVIII, 835321 (31 May 2012); doi: 10.1117/12.918671; https://doi.org/10.1117/12.918671
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