A construction method of the quasi-monolithic compact interferometer based on UV-adhesives bonding

Abstract

Quasi-monolithic interferometers play a crucial role in high-precision measurement experiments, including gravitational wave detection, inertial sensing, vibrometry, and seismology. Achieving high stability and accuracy in such interferometers requires a method for bonding optical components to a baseplate. While optical contact bonding and silicate bonding are common methods, UV adhesives offer advantages such as controlled curing and low geometrical requirements for optical components and baseplates. This paper presents a detailed construction method for a quasi-monolithic compact interferometer based on UV-adhesive bonding. We built two types of interferometers using this method: a $100\mathrm{mm}\times 100\mathrm{mm}\times 20\mathrm{mm}$ Mach-Zender homodyne interferometer with unequal arm lengths of about $100\mathrm{mm}$ for laser frequency noise monitoring, and a heterodyne interferometer as a displacement sensing head sizing $20\mathrm{mm}\times 30\mathrm{mm}\times 20\mathrm{mm}$. Our Mach-Zender interferometer achieved a phase noise level of $2\hat{I}¼\mathrm{rad}\sqrt{\mathrm{Hz}}$ at $1\mathrm{Hz}$ and a equivalent laser frequency noise monitoring sensitivity of about $1\mathrm{kHz}/\sqrt{\mathrm{Hz}}$ at $1\mathrm{Hz}$. The compact heterodyne interferometer sensing head showed a sensitivity level of $1\mathrm{pm}/\sqrt{\mathrm{Hz}}$ in translation and $0.2\mathrm{nrad}/\sqrt{\mathrm{Hz}}$ in two tilts above $0.4\mathrm{Hz}$. Our tests demonstrate that quasi-monolithic compact interferometers based on UV-adhesive bonding can achieve high sensitivity levels at the pico-meter and nano-radian scales.

7 pages, 11 figures