  Visible-wavelength very large-scale integration (VLSI) photonic circuits have
potential to play important roles in quantum information and sensing
technologies. The realization of scalable, high-speed, and low-loss photonic
mesh circuits depends on reliable and well-engineered visible photonic
components. Here we report a low-voltage optical phase shifter based on
piezo-actuated mechanical cantilevers, fabricated on a CMOS compatible, 200 mm
wafer-based visible photonics platform. We show linear phase and amplitude
modulation with 6 V$_{\pi}$-cm in differential operation, -1.5 dB to -2 dB
insertion loss, and up to 40 dB contrast in the 700 nm - 780 nm range. By
adjusting selected cantilever parameters, we demonstrate a low-displacement and
a high-displacement device, both exhibiting a nearly flat frequency response
from DC to a peak mechanical resonance at 23 MHz and 6.8 MHz respectively,
which through resonant enhancement of Q~40, further decreases the operating
voltage down to 0.15 V$_{\pi}$-cm.
