Cladded optical fiber laser made from a-axis Nd:MgO:LiNbO₃ single crystal fiber with Mg-ion indiffusion

We report the implementation of a low loss core-cladding waveguide structure of an a-axis Nd:MgO:LiNbO₃ single crystal fiber and the demonstration of a frequency-doubled laser made from such a cladded crystal fiber. The laser-heated pedestal grown a-axis single crystal fiber, which has an elliptical cross sectional area of about 200 μm×150 μm, was further treated with a Mg-ion indiffusion process. An electron probe microanalysis was used to measure the Mg-ion concentration distribution of the Mg diffused layer. After a number of trials, the diffusion parameters suitable for forming a core-cladding waveguide structure have been obtained. The optical and structural properties of the cladded crystal fibers were also characterized. A diode pumped external cavity frequency doubled laser has been made from the cladded crystal fiber, At room temperature, a CW green laser output with a power of 10 μW at the wavelength of 0.532 μm has been obtained. The origins of the relatively low frequency-doubled conversion efficiency will also be discussed.