Increased Sensitivity of Higher-Order Laser Beams to Mode Mismatches

Abstract

derives mode-mismatch-induced power losses, as a function of mode order, for Hermite-Gauss optical modes. Explicit factors are derived linking mode mismatch losses in a higher order mode to mismatch losses of the fundamental mode. This is particularly relevant for gravitational-wave detectors, where lasers employing higher-order optical modes have been proposed to mitigate thermal noise and quantum-enhanced detectors are very susceptible to losses. This work should inform mode matching and squeezing requirements for Advanced+ and Third Generation detectors.

Higher-order Hermite-Gauss modes as a robust flat beam in interferometric gravitational wave detectors

“…There remain some aspects of future gravitational-wave detector performance with higher-order HG modes that still require further study however. This includes HG mode generation at high powers and purities [4], squeezing of higher-order HG modes [16], alignment and mode matching requirements [15], alignment and mode matching sensing and control, and susceptibility to parametric instabilities. Nonetheless, we have demonstrated here that one of the main problems associated with higher-order LG modes for future gravitational wave detectors-fragility against mirror surface figure imperfections-can be effectively sidestepped for HG modes by using astigmatic cavity mirrors.…”