  We demonstrate a CMOS-foundry-fabricated piezo-optomechanical photonic
integrated circuit platform for ultraviolet and blue wavelengths, using alumina
waveguides that are strongly mechanically coupled to monolithically integrated
aluminum nitride piezoelectric actuators. Low waveguide losses are measured
down to at least 320 nm, where we achieve 1.6 dB/cm. This allows us to
demonstrate broadband amplitude modulators based on piezoelectrically actuated
MEMS cantilever phase-shifters down to 320 nm, with a high extinction ratio of
30 dB. We further demonstrate the versatility of the platform by designing and
demonstrating a modulator that can work with high extinction and low loss at
320 nm and 420 nm, simultaneously, demonstrating control of multiple, disparate
wavelengths in one device. We also demonstrate narrow-band resonant racetrack
modulators with quality factors of 4.7E5 and a tuning rate of 27.5 MHz/V. These
results should open doors for a range of novel applications in UV photonics,
quantum science, sensing and spectroscopy.
