Engineering high cooperativity diamond optomechanical devices robust to optical absorption heating for applications in quantum information and networks

Diamond mechanical systems in the quantum regime provide powerful functionality in quantum sensing, networking, and information. Diamond combines superb mechanical and thermal properties with highly coherent, optically addressable, defect-based qubits, such as the nitrogen vacancy (NV) center and silicon vacancy (SiV) center. Here I present high-quality-factor, high-frequency, diamond optomechanical resonators with embedded, coherent defect centers. We measure record high mechanical quality factors as high as 1.9 million and optical quality factors up to 43,000 at 4K. We measure an optomechanical coupling as high as 216 kHz at a circulating photon number of 40,000 that corresponds to an optomechanical cooperativity of 54. However, parasitic optical absorption, which plagues optomechanical devices across different material platforms, poses a challenge for efficient operation in the quantum ground state. We characterize optical absorption heating in these diamond devices to understand its origin and mitigate its effects through improved design, geometry, and fabrication.