Silicon photonics temperature and refractive index sensor for curing process monitoring in composite material industry

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. We investigate, a photonic solution, able of measure key monitoring values that facilitate optimization of the curing process. Simulation and evaluation results on a bragg grating based photonic integrated sensor, developed in 220 nm Silicon-on-Insulator platform, are presented. A multi-sensor deployment is considered, enabling monitoring of the temperature and the refractive index of the resin. Serially coupled bragg grating photonic elements will enable concurrent monitoring of both temperature and refractive index. Several bragg configurations have been investigated and experimentally evaluated, specifically regular and phase-shifted ones. Both TE and TM polarization operation sensors that have been designed and fabricated, will be presented. Their sensitivity on resin temperature and refractive index variation will be discussed, resulting in a comparative study outlining the benefits and disadvantages of each solution. Refractive index sensors are realized by employing post-processing etching techniques on Multi-Project-Wafer run fabricated silicon chips, on top of the periodic bragg grating element. The comparative study takes into consideration TE and TM polarization operation, regular and phase-shifted bragg grating configuration elements, while evaluating their sensitivity in temperature and refractive index variations. Temperatures considered are in the range of 27 °C to 200 °C, while refractive index values lay between 1.5 and 1.6. A Figure-of-Merit is proposed to facilitate the selection of multi-sensor deployment for specific temperature and refractive index ranges.

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

“…Although the phase-shifted Bragg grating sensor signature is still clearly visible, the signal-to-noise ratio reduced at higher temperatures. A first reason that explains this is the different optical behavior of the grating coupler, which was confirmed by recording the sensor reflection spectrum as a function of the temperature on bare PICs, to exclude the effect of packaging 13 . The main reason for the reduced reflectivity is the red shifting of the grating coupler spectrum for increasing the temperature (in the order of 0.1 nm/°C) 24 .…”

“…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.…”

“…A first reason that explains this is the different optical behavior of the grating coupler, which was confirmed by recording the sensor reflection spectrum as a function of the temperature on bare PICs, to exclude the effect of packaging. 13 The main reason for the reduced reflectivity is the red shifting of the grating coupler spectrum for increasing the temperature (in the order of 0.1 nm∕°C). 24 Therefore, a solution to improve the high-temperature performance could be to optimize the coupling angle for this expected red-shifted behavior.…”

“…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.…”

Demonstration of photonic temperature sensor for RTM-6 composite manufacturing process (180°C) integrated with PMOC system

“…For the packaged chips characterization, most of the optical components of the experimental testbed presented in previous sensor iterations can be made redundant [7], so a single polarization controller (PC) is used, a single SMF fiber to couple the interrogator to the PC, as well as the heat block containing the Pt100 temperature sensor with an accuracy of 0.1℃.…”