Miniaturization of Bragg-multiplexed membrane transducers

This paper reports the miniaturization of Bragg-multiplexed pressure sensing membranes for integrated photonic chips. The analysis compares a novel Fabry-Pérot Bragg grating (FPBG) design that integrally spans a thin (54 µm) silica membrane to a recently reported single Bragg grating (BG) design that resides within the membrane. Unlike the single BG, the FPBG maintains spectral integrity as the dimensions of the membrane become sub-millimetre. In addition it is shown that the FPBG structure can also be used for inherent temperature referencing, having a Bragg thermal sensitivity of 13.5 pm °C-1, which can be decoupled from pressure effects. For the reported sub-millimetre membrane, pressure resolution was enhanced by a factor of three and spectral bandwidth reduced by over five-fold.