Acoustic modulation on a fiber laser based on dissipative coupling of a microcavity

Imparting information on a light wave by signal modulation is fundamental for all forms of optical sensors. Here, we use a microfiber coupled whispering-gallery microcavity as a feedback element and experimentally demonstrate the intensity modulation on a fiber laser based on dissipative acousto-optic interaction where the acoustic wave modulates the coupling strength of suspended microfiber and microcavity, and accordingly modulates the decay rate of laser cavity. As high as 35% modulation depth is realized and the laser is then explored for the sensitive detection of an acoustic wave in air and a noise equivalent pressure of less than 0.9 Pa is found at frequency of 35 kHz. The microcavity with a higher mutual coupling rate of counterpropagating degenerate modes and higher Q factor resonance is anticipated for more sensitive detection on the acoustic wave.