Laser oscillation at an intended wavelength from a distributed feedback structure on anisotropic organic crystals

An organic laser device is constructed as distributed feedback (DFB) type using an anisotropic single crystal of an organic semiconductor oligomer BP3T. The DFB structure is formed on top of the crystal via an interference exposure technique of a positive type photoresist. In the DFB structure, both the phase matching condition and waveguide condition must be fulfilled. Under these conditions, the effective refractive indices can be precisely predicted for a BP3T crystal, and they vary depending upon the crystal thickness. As a result, the device produces a single-mode laser oscillation at an intended wavelength (typically ∼569 nm). The present study enables us to design a down-to-earth laser device based on an anisotropic organic semiconductor crystal toward practical use.