Fig. 1. Basic structure and working principle of MEMS-FP filtering chips

Fig. 2. Comparison of MEMS-FP filtering chips based on bulk micromachining and surface micromachining. (a) Bulk micromachining; (b) surface micromachining

Fig. 3. MEMS-FP filtering chips based on different actuation strategies. (a) Electrostatic actuation^[45]; (b) piezoelectric actuation^[52]; (c) thermal actuation^[53]; (d) electromagnetic actuation^[54]

Fig. 4. Reflectance of different metallic films with different thicknesses. (a) Au film; (b) Ag film; (c) Al film

Fig. 5. Reflectance of DBR with different film compositions. (a) Schematic structure; (b) TiO₂/SiO₂ film; (c) TiO₂/Al₂O₃ film

Fig. 6. Phase shift of MEMS-FP filtering chip based on DBR

Fig. 7. Photonic-crystal reflector based on sub-wavelength periodic hole-array^[60]. (a) Schematic structure; (b) SEM picture; (c) measured reflectance

Fig. 8. Electrostatically tunable MEMS-FP filtering chip working in mid-infrared wavelength developed by NASA in US^[62]

Fig. 9. Electrostatically tunable MEMS-FP filtering chip working in visible wavelength and spectral imaging system developed by US Army Research Laboratory^[64-66]

Fig. 10. Infrared MEMS-FP filtering chip and tunable pyroelectric detector^[68]. (a) Schematic structure; (b) optical performance; (c) tunable pyroelectric detector

Fig. 11. Dual-band MEMS-FP filtering chip and detector module^[43,70-72]. (a) Schematic structure and spectral performance of filtering chip; (b) optical design and assemble process of detector module

Fig. 12. Visible light MEMS-FP filtering chip based on Si₃N₄ film^[73]. (a) Schematic structure and working principle; (b) filtering chips with different aperture size; (c) optical performance

Fig. 13. MEMS-FP filtering chip based on photonic-crystal reflector^[75]

Fig. 14. Surface-machined MEMS-FP filtering chip working in visible light^[78]

Fig. 15. Surface-machined MEMS-FP filtering chip based on Ag mirror^[83]

Fig. 16. Piezo-actuated MEMS-FP filtering chip series developed by VTT^[77]

Fig. 17. Spectral imager used for UAV^[84-86]

Fig. 18. Spectral sensor for mobile gas detection^[87]

Fig. 19. Spectral imaging module assembled with iPhone 5s^[88]

Fig. 20. Aalto-1 cube nanosatellite and its miniaturized spectral imager payload (AaSI)^[92-93]

Fig. 21. Hand-held spectral detection systems based on MEMS-FP filtering chips^[81]. (a) Hand-held spectral imager^[94]; (b) miniaturized spectral imager^[95]; (c) point source type miniaturized spectrometer

Fig. 22. MEMS-FP filtering chips developed by domestic different research institutes. (a)(b) Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences^[96-97]; (c)(d) Huazhong University of Science and Technology^[98-99]

Fig. 23. Electromagnetic actuation MEMS-FP filtering chips and miniature spectral imagers applied to different wavebands developed by Northwestern Polytechnical University. (a) Visible light waveband;(b) long-wave infrared waveband

Fig. 24. Common optical materials and their properties. (a) Transmission range; (b) transmittance of typical infrared optical materials

Fig. 25. MEMS-FP filtering structures based on GST phase-change material. (a) FP tunable filtering structure^[104]; (b) metasurface filtering structure^[105]