Opto-Electro-Mechanical Reconfigurable Control of Resonances in Diamond Photonic Crystal Nanobeam Coupled-Cavity System

Among solid-state spin qubits, diamond color centers stand out for their long coherence times, robust optical and microwave control, and stable spin-photon interfaces. Realizing efficient single-photon generation and photon-mediated entanglement requires embedding these emitters in high-Q, low-mode-volume photonic crystal cavities to harness Purcell enhancement. However, fabrication induced variations cause spectral mismatches between cavity resonances and emitter transitions, hindering scalability and uniformity in integrated quantum networks.

We present a coupled-cavity system enabling opto-electro-mechanical tuning of cavity resonances. Two nomically identical diamond nanobeam cavities are positioned in proximity to form a supercavity with symmetric and antisymmetric modes. By varying inter-cavity gap, both resonance frequency and Q-factor are dynamically controlled. The cavities are released through Faraday cage etching. One cavity is linked to a suspended electrode via support arms, while the counter electrode is affixed to the substrate. Applying voltage generates an electrostatic force that modulates the gap from a few tens up to 300 nanometers, achieving resonance shift over 10 nm and tunable mode splitting.

This gap-tunable coupled-cavity architecture enables deterministic spectral alignment with color-center emission frequencies, offering a scalable and reconfigurable platform for integrated quantum photonics and cavity-QED-based quantum technologies.