A miniature photonic integrated pressure sensor based on a suspended waveguide Bragg grating

This paper presents the development of a miniature photonic integrated pressure sensor based on a suspended waveguide Bragg grating. The sensor leverages microfabrication techniques to create an ultra-compact sensor die, that interfaces seamlessly with a single optical fiber. The design features a silicon waveguide Bragg grating integrated onto a circular membrane, which is pressure-sensitive. The photonic circuit involving the Bragg grating sensor, interconnecting silicon waveguide and grating coupler was fabricated using the ISIPP50G technology and underwent post-processing to create the suspended Bragg grating sensors. The post-processing involved bonding the photonic integrated circuit (PIC) to a fused silica lid with cylindrical cavities, followed by the removal of the silicon substrate to form an approximately 10 µm thick oxide membrane. The cylindrical cavities were created using femtosecond laser-induced chemical etching, and the PIC was bonded to the fused silica carrier using an adhesive layer. The sensor's performance was characterized using a custom-designed clamping setup, demonstrating a clear shift in the reflection spectrum of the Bragg grating as a function of applied pressure making it a promising candidate for applications in environments where traditional electrical sensors are unsuitable.