Fiber Cavity Optomechanics

The Fiber Cavity Optomechanics - FCO project focuses on the development of a Cavity Optomechanics platform that combines fiber Fabry-Perot cavities with 3D laser written polymer structures. This unites the advantages of fiber-coupled, small mode-volume optical resonators with the extremely flexible fabrication method of Nanoscribe 3D laser-writing provided in collaboration with the group of Prof. Linden.

The field of optomechanics explores the interaction of light with mechanical elements and more specifically Cavity Optomechanics that of optical with mechanical resonators. This interplay of light and vibration is mediated by the radiation-pressure and can be found in systems of all sizes. It affects the sensitivity of gravitational wave interferometers with large kilogram-sized mirrors, but is also present in picometer sized cavities interacting with the vibrations of molecules.

Close-up on the two opposing mirrors of a fiber Fabry-Perot cavity inside a carved glass ferrule.

Fiber Fabry-Perot cavities (FFPCs) are optical resonators made from two opposing mirrors on the end facets of optical fiber. As they combine small optical mode volumes with direct fiber access, they are an ideal platform for light-matter interfaces. Recent progress in their fabrication techniques led to the development of compact and passively stable devices easing their application within various experiments. To combine such optical cavity with a mechanical resonator, we are using a 3D laser-writing system (Nanoscribe) that creates solid polymer structures from a liquid photoresist by two photon absorption in a strongly focused laser beam. It is used to fabricate thin, semi-transparent membranes that combined with the FFPC form a membrane-in-the-middle (MIM) setup.

The advantage of our approach is the combination of large optomechanical coupling strengths caused by the small size of the optical cavity with competitive mechanical and optical resonator properties. The direct fiber coupling allows for an easy integration in vacuum or cryogenic environments. The flexible Nanoscribe fabrication technique can be used to add functionalities like tunability through electrical elements or even coupling to microwave circuits. Adding more mechanical resonators within the same optical cavity or coupled resonators on a larger substrate mirror will allow us to perform multimode optomechanical experiments ultimately leading to optomechanical arrays. Also, combinations with solid state emitters can be envisioned.

Suspended polymer membrane structure on the tip of an optical fiber.