Speaker
Description
The high-frequency sensitivity of ground-based gravitational-wave detectors is fundamentally limited by quantum noise, dominated by shot noise, while increasing the circulating optical power is constrained by thermal effects and optomechanical instabilities. Extending detector sensitivity into the kilohertz band is particularly important, as it may enable observations of post-merger signals from binary neutron star coalescences and potential signatures of supernovae, offering access to currently unexplored physics.
Signal recycling with detuning modifies the interferometer response and can locally enhance sensitivity through the optical spring effect.
In this study, we introduce intracavity optical parametric amplification (OPA) to enhance the optical spring via modified ponderomotive interactions. The phase-sensitive amplification of signal sidebands modifies the optomechanical response and enables the optical spring resonance and response to be extended toward higher frequencies. By appropriately choosing the squeeze angle and detuning phase, we demonstrate that the sensitivity can be improved over a broader bandwidth in the high-frequency region compared to the conventional optical spring.
We perform a parameter study based on configurations relevant to current ground-based detectors and show that the proposed scheme remains effective even in the presence of realistic optical losses. These results indicate that intracavity OPA provides a promising approach to extending high-frequency sensitivity through enhanced optomechanical interactions.