title: Mercury-cadmium-telluride waveguides--a novel strategy for on-chip mid-infrared sensors.
abstract: We report the first planar waveguides made from mercury-cadmium-telluride (MCT)-a material to date exclusively used for mid-infrared (MIR) detector elements-serving as on-chip MIR evanescent field transducers in combination with tunable quantum cascade lasers (tQCLs) emitting in the spectral regime of 5.78-6.35 μm. This novel MIR sensing approach utilizes structured MCT chips fabricated via molecular beam epitaxy (MBE) as waveguide enabling sensing via evanescent field absorption spectroscopy, as demonstrated by the detection of 1 nL of acetone. Complementary finite difference time domain (FDTD) simulations fit well with the experimentally obtained data and predict an improvement of the limit of detection by at least 2 orders of magnitude upon implementation of thinner MCT waveguides. With the first demonstration of chemical sensing using on-chip MCT waveguides, monolithically fabricated IR sensing systems directly interfacing the waveguide with the MCT detector element may be envisaged.
authors.affiliation: Institute of Analytical and Bioanalytical Chemistry, University of Ulm , Albert-Einstein-Allee 11, 89075 Ulm, Germany.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Wang
authors.forename: Jarek
authors.initials: J
authors.lastname: Antoszewski
authors.forename: Gino
authors.initials: G
authors.lastname: Putrino
authors.forename: Wen
authors.initials: W
authors.lastname: Lei
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Faraone
authors.forename: Boris
authors.initials: B
authors.lastname: Mizaikoff