Patent ID: 7826510

Claim:
A laser oscillation element, comprising: a first cholesteric liquid crystal layer containing cholesteric liquid crystals; a second cholesteric liquid crystal layer containing cholesteric liquid crystals facing said first cholesteric liquid crystal layer; a defect layer containing a dye which emits fluorescence upon optical excitation disposed between said first cholesteric liquid crystal layer and said second cholesteric liquid crystal layer; a first alignment substrate provided on the first cholesteric liquid crystal layer on the opposite side to the defect layer; and a second alignment substrate provided on the second cholesteric liquid crystal layer provided on the opposite side to the defect layer, wherein the first and second alignment substrates each comprises an alignment film composed of a material selected from a polyamide, a polyvinyl alcohol or a silane coupling agent; the selective reflection wavelength band in said cholesteric liquid crystals and the fluorescence emission band of the fluorescence emitted from said dye overlap with each other in at least a part of the wavelength range; the helical winding directions of the cholesteric liquid crystals in said first cholesteric liquid crystal layer and said second cholesteric liquid crystal layer are identical; the transition moments of said dye are parallel to the surfaces of said first cholesteric liquid crystal layer and said second cholesteric liquid crystal layer, said defect layer is composed of an anisotropic medium, and said first cholesteric liquid crystal layer and said second cholesteric liquid crystal layer are aligned such that the directors of the cholesteric liquid crystals in the surface on the defect layer side of said first cholesteric liquid crystal layer, and the directors of the cholesteric liquid crystals in the surface on the defect layer side of said second cholesteric liquid crystal layer, are parallel to each other.