Highly Sensitive Hydrogen Sensor Based on an Optical Driven Nanofilm Resonator.

Nanofilm resonators combine ultracompact and highly mechanically sensitive properties, making them intriguing devices for sensing applications. For trace hydrogen detection, we demonstrate an optomechanical nanofilm resonator by employing a Pd- and Au-decorated graphene onto a fiber end facet. The Pd layer is a sensitive layer for selective absorption of hydrogen. Hydrogen sensing is achieved by all-optical measuring of the resonant frequencies shift of the optomechanical nanofilm resonator induced by hydrogen-related mechanical stress change. Using the approach, we realize highly sensitive hydrogen sensing at room temperature with a low detection limit, challenging the state-of-the-art. When the measured hydrogen concentration increases from 0 to 1000 ppm (v/v), the mechanical resonance frequencies of the sensor at 511.7 kHz, 1253.4 kHz, and 2231.7 kHz blue-shift by 100.4 kHz, 257.5 kHz, and 400.6 kHz, respectively. The response and recovery time are 120.3 and 91.3 s at a 1000 ppm hydrogen concentration. Such a sensor exhibits a low detection limit of 741 ppb and good repeatability in the measurement process, which makes the practical application of the sensor possible.