Storing light as a mechanical excitation in a silica optomechanical resonator (1106.4512v1)

Abstract: We report the experimental demonstration of optomechanical light storage in a silica resonator. We use writing and readout laser pulses tuned to one mechanical frequency below an optical cavity resonance to control the coupling between the mechanical displacement and the optical field at the cavity resonance. The writing pulse maps a signal pulse at the cavity resonance to a mechanical excitation. The readout pulse later converts the mechanical excitation back to an optical pulse. The light storage lifetime is determined by the relatively long damping time of the mechanical excitation.

• The paper demonstrates a novel experimental method that maps optical signals to mechanical excitations with a 3.5 μs storage lifetime.
• It employs writing and readout laser pulses under resolved sideband conditions to achieve controlled optomechanical coupling and near-unity conversion efficiency.
• The study further enables wavelength conversion, opening new possibilities for heterogeneous quantum networks and optical information routing.

Storing Light as a Mechanical Excitation in a Silica Optomechanical Resonator

This paper presents an experimental demonstration of storing light in a silica optomechanical resonator. The paper introduces a novel approach by leveraging optomechanical processes to map an optical signal into a mechanical excitation and subsequently retrieve it. The research represents a significant step in the development of optomechanical systems as potential candidates for light storage, with implications for optical information networks and long-distance quantum communication.

Experimental Setup and Methodology

The researchers utilized a silica microsphere resonator with whispering gallery modes (WGM) and conducted experiments at room temperature. The mechanism of light storage involves the interaction between optical fields and mechanical modes mediated by radiation pressure. They used writing and readout laser pulses, tuned below the mechanical frequency relative to the optical cavity resonance, to control the coupling. The writing pulse converts an optical signal into a mechanical excitation, effectively storing the light. The readout pulse retrieves the optical signal from the mechanical mode.

The optomechanical interactions were explored under the resolved sideband condition—where the mechanical frequency is much larger than the optical cavity decay rate—to facilitate coherent mapping between optical and mechanical states. This setup approximates a coupled oscillator system with an interaction Hamiltonian characterized by the effective optomechanical coupling rate.

Key Results

1. Storage Lifetime: The paper demonstrates an optomechanical light storage with a lifetime of 3.5 μs, corroborated by the mechanical linewidth of γ/2π = 38 kHz.
2. Conversion Efficiency: Investigated under different conditions, the signal-to-retrieval conversion efficiency shows dependence on the intensity and detuning of the writing and readout pulses. The results suggest that near-unity efficiency is achievable with optimized coupling conditions.
3. Wavelength Conversion: The experimental setup enables storage and retrieval of light across different wavelengths, an attribute beneficial for heterogeneous quantum networks.

Theoretical Implications

The approach integrates concepts from quantum optics, relating closely to electromagnetically-induced transparency (EIT) but with key distinctions: notably, the coherent coupling controlled by the pulse area of writing pulses and retrieval processes akin to laser cooling.

Theoretically, the researchers modeled the system as a beam-splitter Hamiltonian under a mean-field approximation, allowing for a clear analysis of optomechanical state transfer. This mathematically robust framework aligns well with the experimental data.

Implications and Future Prospects

Optomechanical systems, as shown, can serve as effective light storage media, offering advantages such as the ability to couple mechanical modes with multiple optical resonances. This becomes crucial for practical applications in quantum communication where frequency conversion and signal routing across varying channels are required.

Thermal background noise at room temperature is identified as a limitation for quantum regime applications. However, advancements in cooling mechanical oscillators to their ground states open avenues for quantum-level operations.

The research lays foundational work for further exploration in quantum memory and wavelength conversion within optomechanical frameworks. Future directions may involve enhancing storage lifetimes and improving conversion efficiencies by exploring different materials or resonance geometries, potentially integrating with other quantum systems.

In conclusion, this work provides a comprehensive demonstration of light storage via mechanical excitations, contributing significantly to optomechanical technology and its emergent applications in photonic networks and quantum communication.