Normal-mode splitting in an optomechanical system enhanced by an optical parametric amplifier and coherent feedback

Abstract

Normal-mode splitting (NMS) is an evident signature of strong coupling interaction for observing quantum phenomena such as optomechanical squeezing and entanglement. In the previous literature, optical parametric amplifier (OPA) and coherent feedback are respectively proposed to enhance the NMS. Here, we combine OPA and coherent feedback into one optomechanical system to enhance the NMS. The controllable parameters such as input optical power, OPA gain and phase, coherent feedback strength are varied to observe the NMS variation. Especially, we consider the positive and negative feedback in terms of amplitude reflectivity of the beam splitter for coherent feedback. The NMS appears mostly with the positive coherent feedback rather than the negative. Furthermore, the largest mode separation occurs at an OPA phase of approximately −π/4 rather than zero, since the effective cavity detuning changes the effective intracavity round-trip phase, and therefore changes the OPA amplification/deamplification condition. The results indicate that the interplay between OPA and coherent feedback could enhance the NMS with more controllable parameter freedoms. This scheme provides a promising way to increase the optomechanical coupling strength, thereby has potential applications in the ground state cooling of a mechanical oscillator, preparation of optomechanical quantum states and sensitive detection of a weak force.

Tripartite entanglement in a detuned non-degenerate optical parametric oscillator

“…Recently, a detuned OPO is used to generate frequency-dependent squeezing which is required to achieve the GWD sensitivity beyond the standard quantum limit across the whole frequency band [26]. In the cavity optomechanics, the detuning is a feasible experimental parameter to control the optomechanical coupling strength [27][28][29].…”