Michelson interferometer with diffractively-coupled arm resonators in second-order Littrow configuration.

Area of Science:

• Optics and Photonics
• Astrophysics and Cosmology
• Gravitational Wave Detection

Background:

• Gravitational-wave (GW) observatories require high laser powers and Fabry-Perot arm resonators for sensitivity.
• Absorption in transmissive optics causes thermal lensing, limiting usable laser power in current GW detectors.

Purpose of the Study:

• To propose and demonstrate an all-reflective Michelson-type interferometer for GW detection.
• To overcome the limitations of thermal lensing caused by transmissive optics in high-power laser interferometers.

Main Methods:

• Utilized second-order Littrow gratings as all-reflective coupling components for Fabry-Perot arm resonators.
• Theoretically analyzed the signal response of the proposed grating-based interferometer.
• Conducted a proof-of-principle experiment to generate and detect phase-modulation signals.

Main Results:

• The proposed all-reflective topology theoretically matches the signal response of conventional Michelson-type interferometers.
• Experimental detection of phase-modulation signals at two output ports was achieved simultaneously.
• The sum signal from the two ports replicated the performance of a single-output-port interferometer, accounting for optical losses.

Conclusions:

• The all-reflective Littrow grating design effectively eliminates bulk transmission and associated thermal beam distortions.
• This topology offers a viable path for future gravitational-wave observatory designs seeking higher laser power and sensitivity.
• The demonstrated approach provides an alternative for advanced, all-reflective GW detector configurations.