Speaker
Description
Alignment sensing and control are essential for maintaining the stability of laser interferometric gravitational-wave detectors. Wavefront sensing (WFS) is an effective technique for detecting the misalignment between the cavity axis and the incident beam axis. However, the conventional WFS, which relies on the beat between the carrier and phase-modulated (PM) sidebands, is dominated by arm cavity-axis signals when the carrier resonates in the full interferometer. This dominance limits the sensing of other optical axes.
In this presentation, we propose a new sensing technique that demodulates the beat signal at the difference frequency between two anti-resonant PM sidebands. We present its theoretical response and present experimental results using the power-recycled X-arm configuration of KAGRA.