Miniaturized silicon photonics multi-sensor operating at high temperatures for use in composite materials industrial applications

Abstract

Composite materials offer significant performance advantages due to their lightweight, high-strength, and high stiffness. This led to their adoption in several industrial sectors with particular emphasis on the aerospace industry which has undergone a transformation towards a composite-dominated new standard. In order to respond to the increased demand, it is mandatory to focus on an efficient and well-controlled curing cycle of the resin, which will lead to a significant reduction of cost and an increase in production speed. Currently, manufacturers use filling and curing cycles with high safety margins which can be optimized by applying process monitoring techniques, which up to now use thermocouples and dielectric sensors. However, these electric solutions suffer in terms of operating capabilities and the facilitation of integrating them in composite materials (due to their size and electrically conductive aspect when using carbon fibers). We present the design and evaluation of a miniaturized novel photonic integrated sensor, fabricated in 220 nm top SOI platform, capable of measuring key monitoring values that facilitate optimization of the curing process. The operation principle is the spectral shift of a silicon Bragg grating component's resonant wavelength. Bragg grating design and postprocessing of the integrated chip allows for measuring different key values such as temperature, refractive index and pressure all in ~1.5 mm diameter. The fabricated temperature sensors achieve a significant 0.084 nm/°C thermo-optic efficiency with high accuracy (0.5 °C) and repeatability across a very wide dynamic range (temperature 27 to 180 °C).

Compact packaged silicon photonic Bragg grating sensor based on a ball lens interface

“…When fitting a linear function through the measured data, a sensitivity of 73 pm/°C was found, which was very close to the simulated sensitivity (i.e. 70 pm/°C) for Bragg gratings in the current technology [13]. Because a Bragg grating sensor with a different pitch (i.e.…”

“…Those variations yield nearly identical reflection spectra, but 5.2 nm blue-shifted or red-shifted in Bragg wavelength respectively. The simulated shift in Bragg wavelength as a function of temperature was previously reported to be 70 pm/°C [13] for the adopted technology.…”

Silicon photonic temperature sensor: from photonic integrated chip to fully packaged miniature probe

“…The influence of the design parameters (corrugation width, number of periods, pitch, effective index, and fill factor) on the spectral response of the Bragg grating can be studied analytically 17 or using the eigenmode expansion propagation solver (Ansys Lumerical) as detailed in Refs. 13 and 14. In summary, increasing the fill factor has a minor influence on the Bragg wavelength, increasing the number of periods increases peak reflectivity, and increasing the corrugation width increases the bandwidth.…”

“…The design of the silicon Bragg grating sensor was detailed in Refs. 13 and 14, and a high-level overview of the packaging process was reported in Ref. 9.…”

A fully packaged silicon photonic Bragg grating temperature sensor with a compact back side interface based on a ball lens

“…In our previous publications, we have described in detail how the grating pitch, corrugation width etc. have an impact on the Bragg grating response [6,7]. Firstly, due to the large refractive index contrast, the bandwidth of the reflection peak is much larger (several nanometer) than in optical fibers (<<1 nm).…”