Temperature-tunable Fabry-Pérot filter for miniaturization of high-resolution spectrometers

Abstract

This study introduces a new method for implementing large-gap, tunable Fabry-Pérot interferometers for high-resolution spectroscopy. The process utilizes solid resonance cavities obtained from commonly available, unaltered glass substrates. The transmitted wavelength is controlled via the thermo-optic effect and thermal expansion instead of intricate mechanical systems, streamlining miniaturization and enhancing device integration. Experimental results show a transmission wavelength shift of 5.7 pm/°C for a free spectral range of 137.1 pm, using 700 μm solid glass cavities. Exceptional linearity was observed, ensuring precise and predictable wavelength control. This concept was motivated by the need for miniaturizing Brillouin spectroscopy signal acquisition, which requires filters with extraordinary spectral resolution. The commonly used tunable Fabry-Pérot filter systems rely on complex piezoelectric-based actuators to adjust mirror spacing and alignment, making them impractical. The proposed alternative may lead to highly accurate, high-resolution, and low-maintenance filters, ideal for miniaturized spectrometry applications.