III-V Semiconductor Materials for On-chip Optomechanical Resonators

Combining high sensitive displacement with on-chip radio frequency functionality is a strong trend in optomechanics. Piezoelectric materials are mandatory for such functionalities. Here, we present the potential use of III-V semiconductor materials for such integration.

Despite the difference of geometries in nano-optomechanics (micro-disk, toroid, photonic crystal), a great trend in optomechanics is to combine high sensitivity displacement with the radio frequency (RF) signal processing functionality on chip. This enables the optomechanical systems to be simultaneously probed and excited in the GHz range. Thus, piezoelectric materials are mandatory to achieve such functionality. Among piezoelectric materials, III-V semiconductors are more mature for potential on chip integration.

Here we present our work to achieve scalable III-V material nano-optomechanical resonators, integrating simultaneously mechanical and optical functionalities. With silicon based materials, photonic crystals have already reached several demonstrations in optomechanics. We took advantage of these developments and studied both 1D and 2D defect photonic crystal cavities with various III-V semiconductor piezoelectric materials such as GaAs, GaP or GaN. Accordingly, the cavities will act as an effective potential to confine both optical field at the telecom wavelength and displacement field in the GHz range, allowing for high optical and mechanical quality factors. Based on their intrinsic properties (piezoelectric properties, refractive index, Young’s modulus…), we investigated the different geometries of photonic crystal to improve optomechanical coupling. The different structures have been fabricated with these various materials and their optomechanical properties have been investigated.

Simultaneously, various electrical geometries have been developed in order to be able to resonantly excite mechanical modes in the GHz without degrading the optical and mechanical confinement. Thus, the envisioned geometry allows for fully integrated electro-optomechanical oscillators.