How to Shrink Raman Spectrometer to CIS Chip Size

Imec article "How to shrink a Raman spectroscope and analyze complex samples on-the-go?" proposes a way to fit a spectrometer onto CIS chip:

"The spectrometer chip is based on SiN-based waveguide photonics, implemented on top of a CMOS image sensor (CIS) used for electrical readout. The spectrometer chip as used in the current design consists of an array of massively parallel evanescently-coupled Fabry-Perot interferometers, varying in length in the range 2.2-152.8µm (in linear steps of 0.2µm). Incident light is coupled into the waveguide structures using a grating based in-coupler (GC). Sloped metal output mirrors are used to couple the light from the waveguide to the readout pixels of the CIS (see also insert with a crosssection of the chip in figure above). An illustration of the layout showing a top view of the F-P resonators together with the grating incoupler and sloped metal output mirror is shown in the figure below.”