Random Fiber Laser

We investigate the effects of two-dimensional confinement on the lasing properties of a classical random laser system operating in the incoherent feedback (diffusive) regime. A suspension of 250 nm rutile (${\mathrm{TiO}}_2$) particles in a rhodamine 6G solution was inserted into the hollow core of a photonic crystal fiber generating the first random fiber laser and a novel quasi-one-dimensional random laser geometry. A comparison with similar systems in bulk format shows that the random fiber laser presents an efficiency that is at least 2 orders of magnitude higher.

Figure 1

Side view of the experimental setup. Variable neutral density filter (VNDF); 50 mm focal length cylindrical lens (CL); Sample holder (SH); 50 mm focal length spherical lens (SL); Spectrometer (SPEC). Inset: Scanning electron microscopy of the photonic crystal fiber used in the experiment (provided by Crystal Fibre A/S).

Figure 2

Emission spectra measured along the excitation region for different pump intensities and different configurations. (a) A ${10}^{-4}\mathrm{M}$ solution of Rh 6G in ethylene glycol containing ${10}^8{\mathrm{cm}}^{-3}$ rutile particles inside a cell. (b) A ${10}^{-4}\mathrm{M}$ solution of Rh 6G in ethylene glycol inside the photonic crystal fiber, without scattering particles. (c) A ${10}^{-4}\mathrm{M}$ solution of Rh 6G in ethylene glycol inside the photonic crystal fiber with ${10}^8{\mathrm{cm}}^{-3}$ rutile particles.

Figure 3

(a) Emission peak (open symbols) and spectrum-integrated (solid symbols) intensities for ${10}^{-4}\mathrm{M}$ Rh 6G in ethylene glycol with (squares/triangles) and without (circles) ${10}^8{\mathrm{cm}}^{-3}$ rutile particles in the core of the PCF. (b) Emission linewidth (FWHM) for the same configurations. Symbols represent the same conditions as in (a). The solid lines are guides to the eye.