Research On Filtering And Radiation Characteristics Of One-dimensional Photonic Crystals

Photonic crystal structure has a strong selective control ability on spectral reflection,absorption and transmission.It can selectively adjust and tailor the spectrum according to human needs to obtain the required spectral signal,which can be widely used in many fields,such as spectrum detection and new energy.In this thesis,the optical properties of different one-dimensional photonic crystal structures with spectrum ranging from the visible to the infrared band are designed theoretically and then applied to fabricate narrow band filter and radiation cooling devices.The specific results are as follows:1.A 1064nm ultra-narrow band filter with full width at half maximum?FWHM?of less than 1nm and a high transmittance was designed and prepared.Its FWHM can even reach as narrow as 0.31nm and it's good at narrow-band filtering.To explore the optimization of coating process conditions to obtain the Ta₂O₅ and SiO₂ film materials with the lowest extinction coefficient for the preparation of narrow-band filters,an online detection method for the optical constants of optical film materials is proposed,where the optical constants of deposited films with varying film thickness under the real-time preparation process can be obtained by fitting the optical transmittance of light intensity in the coating process.Finally,four optical elements of narrow-band filters made from Ta₂O₅ and SiO₂ film materials with low extinction coefficient are obtained using this method,which verified experimentally that the FWHM and the peak transmittance of the narrow band filter gradually decrease with the increasing number of periods.What is more,it still maintain 75%transmittance when FWHM is below 1nm.2 The Ag+SiO₂ structure was selected as the main structure of the radiation cooling based on the radiation cooling power calculation program first.Secondly,theoretically simulating the absorption spectrum of Ag+SiO₂ structure at different angles and calculating its radiant cooling power.The results show that the hemispherical integrated daytime radiant cooling power is 132.8W/m².Then,based on this,the Ag+SiO₂ structure is processed by micro-nano fabrication to overcome some of the shortcomings that are not conducive to the spectral characteristics of radiation cooling.By plating a one-dimensional photonic crystal DBR reflective layer between Ag and the glass substrate,the solar energy absorption can be reduced as much as 5W/m².At the same time,the small absorption valley of the Ag+SiO₂structure near 10?m can be almost overcome by a periodic pyramid structure with a length of 1?m and a height of 4?m plated on the surface of the Ag+SiO₂ structure.Finally,a radiant cooling structure with a net radiant cooling power of 182.1 W/m²during the day in the direction of 0°was obtained.