**6. Conclusions**

We fabricated a filter array spectroscope consisting of metamaterial color filters and Si photodiodes. The color filters based on guided-mode resonant metal gratings were newly designed. The peak wavelength of the transmission spectrum could be controlled mainly by the grating period. The filters were fabricated in 25 patterns, with grating periods between 220 and 460 nm at increments of 10 nm. SEM images of fabricated color filters confirmed that all the filters were fabricated accurately. The peak wavelength of the spectral sensitivity was found to be linearly dependent on the grating period. Several monochromatic lights were made incident on the fabricated device and the spectral characteristics of the incident light were reconstructed from the output signals obtained from the respective color sensors. The peak wavelengths of the reconstructed spectra were in good agreemen<sup>t</sup> with the center wavelengths of the monochromatic lights.

**Author Contributions:** Conceptualization, Y.K.; methodology, Y.K.; software, D.E.; validation, Y.K., D.E. and K.H.; formal analysis, Y.K. and D.E.; investigation, Y.K., D.E. and K.H.; resources, Y.K., D.E. and K.H.; data curation, D.E. and Y.K.; writing—original draft preparation, Y.K.; writing—review and editing, Y.K.; visualization, D.E. and Y.K.; supervision, K.H.; project administration, Y.K.; funding acquisition, Y.K.

**Funding:** A part of this research was funded by the MEXT KAKENHI 16K13648 and 16H04342.

**Acknowledgments:** Authors thank H. Sai for providing technical support for spectral response measurement. A part of this research was performed in Micro/Nano-Machining Research and Education Center (Tohoku University) and the Center for Integrated Nano Technology Support (Tohoku University) with assistance of MEXT Nanotechnology Platform.

**Conflicts of Interest:** The authors declare no conflict of interest.
