  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.
