Spectral characterisation of erbium doped microspherical lasers

We present continuing theoretical and experimental investigations into the characterisation of fibre taper coupled microspherical lasers. We investigate the spectral emissions of these micro resonators as a function of the wavelength and power of the pump radiation. We also consider various means of efficiently coupling radiation into and out of these devices. We are particularly interested in studying emissions about 1.55 μm with the aim of exploiting potential telecommunications applications of these devices. We study microspheres with diameters in the range 40-150 μm. Pump light about 980 nm or 1480 nm is coupled into the microsphere through evanescent wave coupling between microsphere and optical fibre. The resulting spatial and spectral distribution of radiation within the spheres is described by whispering gallery modes. Half and full-taper optical fibres are used to both couple the pump light into the sphere and to out couple the resulting infra red lasing. The physics of whispering gallery modes and the challenges of coupling to such modes is discussed. Experimental techniques and results will be presented and future directions indicated.