One-dimensional planar topological laser

Topological interface states are formed when two photonic crystals with overlapping band gaps are brought into contact. In this work, we show a planar binary structure with such an interface state in the visible spectral region. Furthermore, we incorporate a thin layer of an active organic material into the structure, providing gain under optical excitation. We observe a transition from fluorescence to lasing under sufficiently strong pump energy density. These results are the first realization of a planar topological laser, based on a topological interface state instead of a cavity like most of other laser devices. We show that the topological nature of the resonance leads to a so-called “topological protection”, i.e. stability against layer thickness variations as long as inversion symmetry is preserved: even for large changes in thickness of layers next to the interface, the resonant state remains relatively stable, enabling design flexibility superior to conventional planar microcavity devices.

Study of Edge Emission and its Induced Photo Pumping by Using Microcavity Organic Light Emitting Diodes

The authors have investigated the edge emission of microcavities which are formed by low-molecular organic light emitting diodes sandwiched between dielectric mirrors and the metal cathode. The edge emission relative to the surface emission is found to significantly depend on the layer number of alternating high and low refractive index films in dielectric mirrors. The enhancement of cavity devices can reach a factor of ~3.0 compared with noncavity devices. Spectra of organic film pumped by edge emission of microcavity devices have been observed, a mechanism of achievement of an amplified spontaneous emission has been discussed theoretically.