Waveguide grating mirror in a fully suspended 10 meter Fabry-Perot cavity

Area of Science:

• Optics and Photonics
• Interferometry
• Materials Science

Background:

• Fabry-Perot cavities are crucial for high-precision measurements.
• Traditional mirrors can be bulky and challenging to integrate into compact systems.
• Waveguide gratings offer a potential alternative for miniaturized optical components.

Purpose of the Study:

• To demonstrate the first fully suspended 10 m Fabry-Perot cavity using a waveguide grating as a coupling mirror.
• To evaluate the performance and reflectivity of the waveguide grating in a low-noise environment.
• To assess the potential of waveguide gratings in high-precision interferometry.

Main Methods:

• Fabrication of a waveguide grating using tantala, fused silica, and an Al2O3 etch stop layer.
• Integration of the waveguide grating into a 10 m suspended Fabry-Perot cavity.
• Maintaining cavity resonance using the Pound-Drever-Hall method and laser frequency feedback.
• Measuring cavity finesse to determine grating reflectivity.

Main Results:

• Achieved a finesse of 790 for the suspended cavity.
• Determined waveguide grating reflectivity to exceed 99.2% at 1064 nm.
• Demonstrated stable operation of the waveguide grating in a suspended low-noise cavity.
• Results show good agreement with rigorous simulations.

Conclusions:

• Waveguide gratings can function as high-reflectivity mirrors in suspended optical cavities.
• This technology is suitable for applications requiring high-precision interferometry.
• The demonstrated system is a significant step towards future gravitational wave observatories.