Electro-mechanically tunable, waveguide-coupled photonic-crystal cavities with embedded quantum dots

Abstract

On-chip micro-cavities with embedded quantum emitters provide an excellent platform for high-performance quantum technologies. A major difficulty for such devices is overcoming the detrimental effects of fluctuations in the device dimensions caused by the limitations of the fabrication processes. We present a fully tunable system based on a 1D photonic-crystal cavity with an embedded quantum dot, which enables tuning of both the quantum dot emission energy and the cavity mode wavelength. A micro-electromechanical cantilever is used to tune the cavity mode wavelength via index modulation and the quantum-confined Stark effect is used to tune the quantum dot emission energy, mitigating the effect of fabrication imperfections. To demonstrate the operation of the device, a maximum, voltage-controllable cavity tuning range of $\Delta \lambda = 1.8$ nm is observed. This signal is measured at the end of a bus waveguide which side-couples to the cavity, enabling the coupling of multiple cavities to a common waveguide, a key requirement for scale-up in these systems. Additionally, a quantum dot is tuned into resonance with the cavity mode, exhibiting an enhanced emission rate with a resolution limited Purcell factor of $F_P = 3.5$.