In this paper, we introduce an innovative proposal for a low cost micro Raman spectrometer for non-invasive glucose monitoring. In this design, an Array Waveguide Grating (AWG) chip integrated with PIN photodiodes and a prism coupling are proposed to replace fiber micro alignment in packaging and to reduce system cost. Experiments were designed and conducted to evaluate the impact of thickness of the waveguides and the incident angle of the laser beam on the efficiency of the prism coupling. Considerable light coupling was observed when the waveguide core is 2mm thick. An updated fabrication process was designed and test chip was also fabricated to determine the critical feature size to solve the problem of air bubble resulted in trench filling.
In this study, we designed and simulated an array of bandpass filters as a spectral separator for mid-infrared self-emission noninvasive glucose monitoring, using the human body as the background radiation emitter. The filters were based on the guided-mode resonance (GMR) effect. The human body is a good black body radiator that provides a stable temperature and continuous radiation energy in the mid-infrared range. We can thus use self-emission from the human body to measure certain fingerprint peaks of glucose spectrum between 8 μm to 10 μm, which allows estimation of glucose concentration. The GMR filter set includes at least four filters on one chip fabricated at the same time. By using fixed thicknesses and the same thin-film material for all the filters on the chip, a structure period adjustment alone can theoretically achieve multiple bandpass filters between the glucose fingerprint ranges - and achieve these coplanar filters on a single chip. By using all CMOS-compatible materials, COMSOL simulations show that a series of peaks with transmittances up to 70% and bandwidths of around 200nm can be achieved. This filter set can be fabricated with just a few thin layers that can simplify the typical thin-film deposition process. The proposed GMR filter array can then be combined with a thermometer array to achieve the non-invasive glucose monitoring. We compare the results obtained with the first version of the fabricated filter set with the measurements of Fourier transform infrared (FT-IR) spectroscopy.