Pd coated edge-emitting lasers for hydrogen sensing applications

A novel type of hydrogen (H₂) sensor utilizing a thin film of palladium (Pd) deposited on the ridge of an edge-emitting laser has been designed, fabricated, and tested. This Pd film is known to react to H₂, yielding a change in the complex refractive index and thus also the laser´s output power. As the propagating wave travels through the device, the evanescent portions of the wave interact with these changing optical properties, yielding a change in optical output power as a function of H₂ concentration. The measurement results show that there is a definite change in output power as the H₂ concentration is increased. The measured sensitivity of these devices is shown to be about a 2% fractional power change per percent H₂.