Many researches and inventions of non-linear optical material have been stimulated for these decades by the publications on the optical properties of three-dimensionally arrayed dielectric materials by Yablonovitch and John in 1987. The optical materials allow us to control the flow of light, providing a new technology of optical devices, such as low-energy consumption laser resonator, high-speed computers, light storage and so on. We have succeeded in fabrication of a photonic crystal (PhC) by self-assembly of block copolymers (BCP) that generally form one-, two-, three-dimensional periodic nanostructures, i.e., lamellar, cylindrical, spherical, gyroids microdomains, etc. Lattice spacings of the microdomain structures are dependent on molecular sizes of BCPs. In order to obtain a large spacing on the order of wavelength of visible light, we should utilize BCPs with ultra-high-molecular weight (UHMW) such as 106 g/mol. They, however, are highly entangled and hence too viscous in bulk to attain structural equilibrium. We have found that even in a semi-dilute solution at several percent microphase separation is strongly induced by solvent selectivity. At such low concentrations, BCPs can easily form equilibrated structures with high order because of their high mobility. In the vicinity of the boundary of lyotropic order-disorder transition, large grains on the order of centimeters were obtained. These phenomena was well analyzed by computer simulation using “SUSHI”. We have successfully applied these structures in a THF/water mixture to a laser resonator. They successfully inhibit the spontaneous emission of dyes, and laser emission was generated. The laser threshold was 0.1μJ/pulse and is dependent on the refractive index difference between the phases and the number of the stacked lattice planes. In this talk, I will introduce our solution systems for photonic crystals and discuss how to inprove the functionality.