Dual wavelength waveguide lasers fabricated using femtosecond laser inscription in Yb doped phosphate glass

The paper reports on the combination of waveguide and fibre technologies to create phase modulated sampled grating based multiwavelength lasers in Yb phosphate glass. In a π-phase shifted grating the fundamental Bragg resonance is suppressed leaving the sampled grating sidebands. When manifest in a DFB waveguide laser this results in a dual wavelength laser in which the absolute wavelength and laser line spacing is controlled by the phase-shifted grating´s parameters. By fabricating a range of waveguide Bragg gratings around the gain peak at 1030 nm, a dual wavelength laser operation was obtained with separation of 10 to 20 nm. Wavelength separations less than this exhibit strong mode competition which elucidate details of the material´s broadened gain bandwidth. Improvements are possible using more complicated DFB structures where individual gain regions are separated.