Polimer optik mikrodisk çınlaç tabanlı hidrojen gazı algılayıcısı

Hydrogen gas is an attractive energy source since its energy conversion efficiency is higher than conventional oil and its side products after combustion are non?toxic. However, it has a very small lower flammable limit (4% by volume) and its storage is difficult because of small molecular volume. Therefore even low concentration leakages become very dangerous to the public health and the safety of property. Hence, selective detection of small concentrations of hydrogen gas is required. In this work, we propose a hydrogen sensor based on polymer optical microdisk resonators fabricated using UV photolithography. The sensing mechanism relies on the shift of optical whispering gallery modes (WGMs) due to the size change of the resonator in the presence of hydrogen gas. The size change is induced by volume expansion of palladium layer coated on the microdisk resonator. We fabricated microdisk structures together with optical waveguides using SU?8 photoresist on Si substrates possessing a 5 ?m?thick thermal oxide. A tunable laser was coupled into the waveguides using end?face coupling. When laser transmission was measured as a function of wavelength, transmission dips were observed revealing the WGMs. A maximum quality factor (Q?factor) of 2000 was measured for the observed WGMs of 200 ?m?diameter microdisks. Palladium layer was coated on the fabricated microstructures using lift?off technique. Experiments are now underway for characterizing hydrogen gas sensitivity of these structures. Our estimates reveal sensitivities better than 1000 ppm for the fabricated structures. In parallel to these efforts using microdisks fabricated by UV photolithography, two-photon polymerization was employed for fabricating microdisks and microrings. For these structures, maximum Q?factors of around 120 were measured. Relatively low Q?factors were attributed to small diameters (30 ?m) of these structures.