Mid-infrared waveguide evanescent wave sensing

Murugan, Ganapathy Senthil, Mittal, Vinita, Vlk, Marek, Jágerská, Jana and Wilkinson, James S (2019) Mid-infrared waveguide evanescent wave sensing. Photonics West, The Moscone Center, San Francisco, United States. 01 - 06 Feb 2019. pp. 10914-13 . (doi:10.1117/12.2508591).

Abstract

Mid-Infrared (Mid-IR) techniques have gained considerable attention because of their inherent molecular selectivity and their potential for rapid label-free detection in applications such as water quality and environmental monitoring, security, food safety, and point-of-care diagnostics. Waveguide evanescent-field-based Mid-IR spectroscopy can detect analytes at very low concentrations using molecular absorption fingerprints, potentially offering high sensitivity and selectivity over a wide range of compounds. Moreover, significant footprint reduction compared to ATR-based FTIR measurements can be achieved with optical waveguide-based Mid-IR sensing through integration of various optoelectronic and microfluidic components realizing fully packaged lab-on-a-chip systems.
Recently we have developed low-loss chalcogenide optical waveguides and demonstrated waveguiding in the mid-wave and long-wave infrared spectral bands. High contrast GeTe₄ and ZnSe channel waveguides were fabricated on bulk substrates and on silicon wafers (with suitable optical isolation layers) using lift-off and dry etching techniques after photolithographically patterning the thin films. These waveguides were exhibiting optical losses as low as 0.6 dB/cm in the mid-wave IR band and were validated for the Mid-IR evanescent wave spectroscopy with water and IPA. We have also demonstrated the effectiveness of simple paper-based fluidics with our waveguides.
In addition, we investigate a new family of free-standing Ta₂O₅ rib waveguides for trace gas detection with evanescent field overlap with the surrounding medium (air) up to about 70%. The waveguides are being fabricated and the fabrication and characterization results will be presented.

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Contributors

Author: Ganapathy Senthil Murugan

Author: Vinita Mittal

Author: James S Wilkinson

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