Heterojunction structures consisting of a dye-doped low-molecular-weight liquid-crystalline blue phase (low-BP) sandwiched between polymer cholesteric liquid crystal films with same handedness were fabricated, and its lasing characteristics were experimentally evaluated. As observed, the excitation lasing threshold value for the fabricated structure is extremely lower than that in a simple dye-doped low-BP. This is because the defect states emerge, and the photonic density of state is resonantly enhanced when the defect mode coincides with the edge mode in our structure.