Modeling of compact Pd coated VCSELs for hydrogen sensing

We report on designs for compact VCSEL sensors for use in hydrogen gas detection. We discuss 980nm VCSELs coated with Pd, which has been proven to react with hydrogen. During this reaction, the device undergoes hydrogen induced lattice expansion (HILE) which causes two distinct effects that can be detected at the output. These two effects are a red-shift in the emission wavelength and a decrease in the output power. The compact VCSELs will be positioned into a 2D array with varying mesa diameters and palladium thickness in order to distinguish and track the specific level of hydrogen present in the atmosphere.