High contrast mid-infrared chalcogenide waveguides for biosensing applications

Abstract

Mid-infrared spectral band from 2 µm - 20 µm is ideal for label-free biosensing as the fundamental vibrations of many significant biomolecules take place in this region. Mid-infrared absorption spectroscopy using FTIR has been exploited for the last few decades to provide sensing capabilities for biomedical diagnostics. However, the sensitivity and the detection limit of the sample under test can be tremendously improved by using the evanescent field based integrated planar waveguide devices. In this paper, we present the fabrication and characterization results of chalcogenide waveguides transparent in the mid-infrared region for such applications. GeTe4 waveguides on ZnSe substrates were fabricated using lift-off technique. Lift-off resist was used to create the patterns on ZnSe substrate using photolithography and GeTe4 was deposited on these patterned samples using RF sputtering. The lift-off resist was stripped off to obtain the desired channels. The waveguides were characterized in both mid wave (2.5 µm - 3.7 µm) and long wave (6.4 µm - 7.5 µm) spectral bands using optical parametric oscillator-based laser source and quantum cascade laser, respectively [1]. Fig. 1 (a) and (b) show the cross-section and top view of the infrared camera images of the output facet of a GeTe4 channel waveguide showing light guidance at lambda = 3.5 µm and lambda = 6.5 µm, respectively.

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Identifiers

ORCID for Vinita Mittal: orcid.org/0000-0003-4836-5327

ORCID for James S. Wilkinson: orcid.org/0000-0003-4712-1697

ORCID for Ganapathy Senthil Murugan: orcid.org/0000-0002-2733-3273

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