Hydrogen Sensing with Long-Range Surface Plasmon Membrane Waveguides

Abstract

This integrated article thesis presents the full design, fabrication, characterization and testing of a long-range surface plasmon polariton (LRSPP) cladded membrane waveguide hydrogen gas (H 2 ) sensor with integrated grating couplers.The sensor, which is the first of its kind to be demonstrated in the literature, features a thin gold (Au) stripe embedded in an ultra-thin free standing Cytop membrane with palladium (Pd) transducer. The design is performed through finite element method (FEM) optical modeling of the LRSPP waveguide and gratings. The non-trivial fabrication process utilizes facilities at Carleton University and the University of Ottawa and is presented in detail. The process involves multi-layer dielectric deposition, blind double-sided wafer alignment, multiple metal depositions using photolithography and ebeam lithography as well as a through-wafer silicon wet etch step. The devices are passively characterized using an optical cutback technique comparing the observed waveguide attenuation to that of simulated values showing good agreement. Sensing tests are performed with hydrogen concentrations up to 3%. A best detection limit of 290 ppm is observed with a response time of 7 s to 0.6% H 2 (99.4%N 2 ). The sensor has the capability of a higher dynamic range than other thin film sensors while other simple adjustments are discussed that can be applied to improve overall performance.iii

Hydrogen Sensing Using Thin-Film Perfect Light Absorber

“…H ydrogen is highly flammable with low ignition energy at ambient temperature and pressure and concentrations ranging from 4 to 75%. 1 Consequently, hydrogen sensing is an important safety issue in industries where it is a crucial component or a byproduct. Gas chromatography and mass spectrometry systems are suitable for large scale industrial sensing; however, they may not be suitable for applications that require miniaturization, for example, detection of hydrogen in the breath that can indicate various diseases, such as lactose intolerance, and detection of hydrogen produced by bacteria in food industries.…”