Fig. 1. Schematics of Fresnel lens and FPI. (a) Side view of Fresnel lens; (b) front view of Fresnel lens; (c) schematic of FPI

Fig. 2. Structural diagrams of FPI. (a) 3D structural diagram of FPI frame; (b) photograph of FPI

Fig. 3. Displacement-voltage curve of PZT used in FPI

Fig. 4. Calibration method of cavity length of FPI cavity. (a) Setup for measuring cavity length of FPI cavity; (b) interference pattern on observation screen

Fig. 5. Optical path and results for measuring free spectral range and resolution of FPI. (a) Device for measuring FPI performance; (b) relationship between measured optical power and time when PD is 10 cm away from FPI; (c) relationship between optical power and cavity length variation measured by PD when distance between PD and FPI is different

Fig. 6. Experimental setup for measuring remote weak light spectrum by Fresnel lens and FPI

Fig. 7. Images of mercury lamp after passing through Fresnel lens and FPI. (a)(b) Recorded interference patterns by CCD; (c)(d) interference patterns observed on screen

Fig. 8. Variation of radial position of fringe M under different PZT voltages. (a) 1 V; (b) 4 V; (c) 7 V; (d) 10 V

Fig. 9. Intensity distribution along x direction in Fig. 8(a)

Fig. 10. Images detected by FPI when mercury lamp is 30 m away from Fresnel lens. (a) Image recorded by CCD; (b) image after filtering out background noise; (c) intensity distribution along dotted arrow direction in Fig. 10(b)

Fig. 11. Experimental setup for measuring fluorescence spectrum of NaCl aerogel induced by femtosecond laser filament

Fig. 12. Time-resolved fluorescence spectra of NaCl aerosol excited by femtosecond laser filaments recorded using grating monochromator and ICMOS camera. (a) Fluorescence spectra with time delay of 5-25 ns; (b) fluorescence spectra with time delay of 85-120 ns

Fig. 13. Interference pattern of backscattered He-Ne laser after passing through FPI recorded by ICMOS camera

Fig. 14. Time-resolved F-P interference patterns of NaCl aerogel fluorescence induced by femtosecond laser filament

Fig. 15. Detection results of fluorescence of NaCl aerosol excited by femtosecond laser. (a) Fluorescence interference pattern of NaCl aerosol excited by femtosecond laser recorded by ICMOS camera; (b) intensity distribution along dotted arrow direction in Fig. 15(a)