Temperature Tunable Optical Transmission control of VO2 nanostructures by IR based 1-D Photonic crystals as hybrid Photonic absorbers

Effect of 1-D photonic crystals on optical transmission of VO2 is studied by depositing thin films of VO2 nanoparticles on SiO2/TiO2 distributed Bragg reflectors (DBR) in the near infrared (IR) spectrum as per earlier theoretical predictions of J. Phys. D: Appl. Phys. 51 375102 (2018). Monoclinic VO2 nanoparticles with tuned crystallinity were synthesized by a facile solution processing method. Moderately crystalline (MC) and highly crystalline (HC) VO2 nanostructures were obtained by varying its synthesis temperature and post growth annealing conditions. Both MC VO2 and HC VO2 films exhibit expected reduction in optical transmission in the IR region due to its structural phase transition from monoclinic (insulator) to rutile (metallic) around critical temperature of 68 {\deg}C. By combining VO2 films on a 40% transmitting DBR structure, the average optical transmission further went down to ~ 20%. Number of stacks of DBR plays a key role in such effective reduction of optical transmission in IR. When the number of stacks of DBR is further increased from 4 to 7, optical transmission of metallic VO2 films on DBR nearly vanishes in NearIR spectrum in such vanadium dioxide/1D photonic crystal based composite photonic structures. Such temperature controlled, enhanced, broad band optical response can be a promising design for VO2 nanoparticle based hybrid photonic absorbers for various smart window applications.