A fibre optic wedge type microcavity random laser

In this work, a fibre optic wedge type microcavity with arbitrarily distributed scattering centres is employed to construct a flexible, cost effective, and low threshold random laser. The wedge cavity is constructed within an optical fiber of 125 mu m in diameter, using a conventional fibre drawing technique. The sharp edge corners of the triangularly shaped of the air holes are filled with a phenol-rhodamine 6 G mixture via a capillary effect to form the gaining medium. Randomly distributed air-bubbles are naturally formed in different sizes and shapes during the filling process of the phenol-rhodamine mixture, which serve as the scattering centres for obtaining the random lasing. By making a fine spatial tuning of the excitation beam spot towards the apex of the wedge, a single mode lasing is obtained at wavelength of 585 nm, with 1.4 nm of the FWHM.