Engineers have developed a compact, single-shot, free-space-coupled spectrometer with hyperspectral imaging capabilities. The miniaturized spectrometer is fabricated on top of and integrated with a CMOS chip. The device measures 200 microns on each side. It can lie directly on a sensor from a typical digital camera.
The miniaturized spectrometer and hyperspectral imager are based on photonic-crystal (PC) slabs. The device uses arrays of photodetectors with different responsivities. Optical interference in PC slabs positioned immediately on top of the photodetector pixels create these arrays. The PC slabs enable a nonscanning, single-shot imaging method on a compact chip.
Compact and low-cost devices like this miniaturized spectrometer could help turn ordinary cellphones into advanced analytical tools. The PC slabs could be applied to any wavelength range by scaling the dimension of the PC. The PC slabs are compact, with sizes similar to light-sensing pixels in CMOS image sensors.
The researchers hope to boost the device’s spectral resolution and the clarity of the images the miniaturized spectrometer captures. For example, they could improve spectral resolution by replacing silicon PC with silicon nitride or silicon carbide, creating more diverse spectral features due to the lack of light absorption. Smaller PC slabs could improve spatial resolution and angle tolerance by using even smaller PC slabs.