Volume Bragg grating with tunable reflectivity and the bandwidth assisted Fabry-Pérot cavity

The rigid Fabry-Pérot (F-P) cavity has emerged as the preferred core sensing component for optical pressure, vibration, and acoustic sensing in harsh environments, owing to its high reliability and structural stability. However, due to the inadequate temperature resistance of the optical dielectric film, maintaining a high level of precision in the rigid F-P cavity at elevated temperatures proves to be challenging. Volume Bragg grating (VBG) is a three-dimensional optical element modified by a femtosecond laser within a transparent glass medium to create a periodic refractive index distribution. Based on its structure's similarity to fiber grating and optical film, the VBG was proposed as a reflection component for a fully rigid F-P cavity, and its structure and reflection properties were researched and analyzed. The results indicate that the reflectivity and reflective bandwidth of the VBG are primarily influenced by the variation of single or double parameters among the four key parameters: grating period, grating linewidth, number of layers, and refractive index change. These analytical results can assist in selecting appropriate parameters based on application requirements during the preparation of the VBG and provide data support for its practical measurement.