In this work, we study the effects of mechanical anisotropy in a 2D optomechanical crystal geometry. We fabricate and measure devices with different orientations, showing the dependence of the mechanical spectrum and the optomechanical coupling on the relative angle of the device to the crystallography directions of silicon. Our results show that the device orientation strongly affects its mechanical band structure, which makes the devices more susceptible to orientation fabrication imperfections. Finally, we show that our device is compatible with cryogenic measurements, reaching a ground state occupancy of 0.25 phonons at mK temperature.

We present a homodyne detection scheme to reliably measure the dissipative coupling in optomechanical systems. Our method is validated on silicon devices yielding GK_e/GΩ= -0.007 ± 0.001.