Ultraviolet light detection using an optical microcavity

Ultraviolet (UV) light exposure is connected to both physical and psychological diseases. As such, there is significant interest in developing sensors that can detect UV light in the mW/cm2 intensity range with a high signal-to-noise ratio. In this Letter, we demonstrate a UV sensor based on a silica integrated optical microcavity that has a linear operating response in both the forward and backward directions from 14 to 53  mW/cm2. The sensor response agrees with the developed predictive theory based on a thermodynamic model. Additionally, the signal-to-noise ratio is above 100 at physiologically relevant intensity levels.