Linear Laser Tuning Using a Pressure-Sensitive Microbubble Resonator

The tunability of an optical cavity is an essential requirement for many areas of research. Here, we use the Pound–Drever–Hall technique to lock a laser to a whispering gallery mode (WGM) of a microbubble resonator, to show that linear tuning of the WGM, and the corresponding locked laser, display almost zero hysteresis. By applying aerostatic pressure to the interior surface of the microbubble resonator, optical mode shift rates of around 58 GHz/MPa are achieved. The microbubble can measure pressure with a detection limit of
$2\times 10^{-4}$
MPa, which is an improvement made on pressure sensing using this device. The long-term frequency stability of this tuning method for different input pressures is measured. The frequency noise of the WGM measured over 10 min for an input pressure of 0.5 MPa has a maximum standard deviation of 36 MHz.