Metasurface-Embedded Ultracompact On-Chip Spectrometer for Mobile Applications

We have developed an extremely compact and efficient spectrometer based on metasurface structures. The spectrometer consists of a mobile phone image sensor and dielectric nano post-embedded Fabry-Perot bandpass filters are directly integrated on top of the image sensor pixels. Each filter has a different peak transmission wavelength in the near IR region. Spectrum information is directly retrieved by intensity map of image sensor, i.e, image captured by sensor.<br/><br/>Embedded metasurface structures greatly simplify monolithic fabrication processes in constructing multiple bandpass filters having different transmission spectra. Also, metasurface provides superior optical performance of spectral filters since the dependence of incident angle onto the filter is reduced that the peak wavelength is not changed much compared to conventional Fabry Perot Filter. The spectrometer shows good transmission efficiency and excellent spectral resolution up to 1nm. <br/>We applied the spectrometer technology to 1) Raman spectroscopy applications and 2) hyperspectral imaging. <br/> For Raman spectroscopy application, we built handheld and smartphone-attachable Raman modules with some external optics to collect and transport Raman scattered photons onto the spectrometer chip. We will present applications of meat and vegetable freshness sensing. Also application for a drug classification will be shown . For hyperspectral imaging, optimized optical bandpass filters are pixel-wisely integrated on the image sensor so snapshot hyperspectral imaging method is possible in the mobile devices including smartphones. We will present applications of material identification for agriculture and skincare.<br/>The spectrometer chip can be directly combined into smartphone and used as portable spectral analyzer. This new device will open new business opportunities and research fields for diverse applications.