Thermal deformation reduction in high-power interferometry with higher-order laser modes
Phys. Rev. D 114, 022004 – Published 16 July, 2026
DOI: https://doi.org/10.1103/qlx1-xc9k
Abstract
Test-mass thermal noise is a limiting noise source for current and next-generation ground-based gravitational-wave observatories in their most sensitive frequency band. In addition to ongoing efforts to reduce coating mechanical loss, complementary approaches such as the use of uniform-intensity laser beams, including higher-order Laguerre–Gaussian (LG) and Hermite–Gaussian (HG) modes, have been proposed as alternatives to the fundamental Gaussian beam due to their thermal-noise advantages. As the interferometer operating power increases toward the megawatt regime, as anticipated for next-generation detectors, thermal aberrations arising from absorption in the high-reflectivity coatings of the test masses become an increasingly severe challenge. In parallel, the spatially more extended intensity profiles of higher-order modes, which enable their thermal-noise benefits, modify the thermal loading of the test masses, making it essential to assess their behavior under absorption-induced self-heating. In this work, we quantify the robustness of higher-order incident beams against thermal deformation. We show that, under identical operating conditions, higher-order modes produce significantly more uniform thermally induced mirror distortions compared to the sharply peaked aberrations generated by the fundamental mode. As a result, substantially less thermal compensation power is required for their active correction, with the required optimal curvature correction reduced to 33% of that of the fundamental mode for the mode and to 24% for the mode. In addition, we show that the residual thermal deformation for higher-order modes leads to significantly lower optical power loss and enables larger power buildup and enhanced modal purity in an aLIGO-like optical cavity. We further demonstrate that astigmatism compensation enhances the intracavity modal purity of HG modes under self-heating-induced thermal deformation. These results highlight that higher-order laser modes mitigate thermal noise while intrinsically suppressing beam self-heating-induced thermal distortions, making them more thermally robust and well suited for operation in high-power gravitational-wave interferometers.
