Strain Tuning a Nonplanar Ring Oscillator by 3.5 GHz: Theory and Experiment

We tuned the oscillating frequency of a nonplanar ring oscillator by 3.5 GHz by applying strain to the monolithic resonator using a piezoelectric element. The voltage applied to the piezoelectric element was 192 volts, corresponding to a tuning coefficient of 18.2 MHz/volt. Useful bandwidth was limited by a resonance at 323 kHz and an anti-resonance at 420 kHz. Performance improvement relative to previous work was achieved primarily by using a resonator design with a small distance between the piezoelectric element and the resonant laser beam, but also by using a piezoelectric material with favorable properties and reducing the thickness of the resonator. A theoretical analysis of strain tuning supported the design.