Buried channel optical waveguides, supporting orthogonal polarizations, have been fabricated in a neodymium doped yttrium aluminum borate nonlinear laser crystal by ultrafast laser inscription following the so-called "double line" approach. Confocal fluorescence and second harmonic imaging experiments have revealed that the original fluorescence and nonlinear properties have been not deteriorated by the waveguide inscription procedure. Preliminary laser experiments have shown the ability of the fabricated structures for green laser light generation under 808 nm optical pumping by self-frequency-doubling of the 1.06 m laser line of neodymium ions. © 2011 American Institute of Physics. ͓doi:10.1063/1.3584852͔Among the multifunctional optical systems currently proposed as building-blocks of integrated devices, selffrequency-converted ͑SFC͒ laser crystals are one of the most widely studied. SFC systems are constituted by a nonlinear crystal which is optically activated by laser ions ͑usually rare earth ions such as Nd 3+ or Yb 3+ ͒. 1 Under laser operation the nonlinear properties of the host matrix activate frequencymixing processes between the different intracavity laser radiations that propagate along the gain medium ͑pump and laser͒. These intracavity nonlinear processes lead to the generation of new laser frequencies without the requirement of additional intracavity optical components, i.e., allowing for highly compact multiwavelength laser sources. 1 Among the different SFC crystals reported up to now, neodymium doped yttrium aluminum borate ͑hereafter Nd:YAB͒ is, without doubts, a paradigm. 2 It combines the good thermal, mechanical, and nonlinear properties of the YAB host with the outstanding fluorescence properties of Nd ions. 3,4 Based on this unique combination, multifrequency laser light oscillation in the three fundamental colors ͑red, green, and blue͒ has been demonstrated from a unique Nd:YAB element operating at 1.3 m. 5 In its simplest version, involving only the second harmonic ͑SH͒ of the 1064 nm laser line of Nd 3+ ions, pumpto-green optical conversion efficiencies as high as 25% have been reported. 6 Further incorporation of Nd:YAB SFC lasers in miniaturized optical devices requires the controlled fabrication of optical waveguides ͑WGs͒ in the bulk material. Up to now, WGs in Nd:YAB crystals have been only reported by light ion implantation, without demonstrating any selffrequency-doubling ͑SFD͒ laser ability. 7 In order to achieve this goal the fabricated structures should satisfy following three main requirements: ͑i͒ the fabrication procedure should preserve the original fluorescence and nonlinear properties of the Nd:YAB system, ͑ii͒ the fabricated WGs should support both TE and TM modes so that birefringence-based phase matching ͑PM, requiring orthogonal polarizations for fundamental and second harmonic waves͒ will be possible, and ͑iii͒ light confinement should be achieved in a large spectral range so that spatial confinement of both fundamental and second order radiation would be achieve...

We report on tubular cladding optical waveguides fabricated in Neodymium doped WollastoniteTricalcium Phosphate glass in the eutectic composition. The glass samples were prepared by melting the eutectic powder mixture in a Pt-Rh crucible at 1600 C and pouring it in a preheated brass mould. Afterwards, the glass was annealed to relieve the inner stresses. Cladding waveguides were fabricated by focusing beneath the sample surface using a pulsed Ti:sapphire laser with a pulsewidth of 120 fs working at 1 kHz. The optical properties of these waveguides have been assessed in terms of near-field intensity distribution and transmitted power, and these results have been compared to previously reported waveguides with double-line configuration. Optical properties have also been studied as function of the temperature. Heat treatments up to 700 C were carried out to diminish colour centre losses where waveguide's modes and transmitted power were compared in order to establish the annealing temperature at which the optimal optical properties were reached. Laser experiments are in progress to evaluate the ability of the waveguides for 1064 nm laser light generation under 800 nm optical pumping. V C 2015 AIP Publishing LLC.

Abstract:In this work glass rods of (Mg x Ca 1-x ) 3 Al 2 Si 3 O 12 (x = 0, 0.5 and 1) doped with 1 wt% Nd 2 O 3 were produced by the laser floating zone technique. Thermo-mechanical and spectroscopic properties have been evaluated. The three glass samples present good thermo-mechanical properties, with similar hardness, toughness and glass transition temperatures. The spectroscopic characterization shows spectral shifts in absorption and emission spectra. These spectral shifts together with JuddOfelt intensity parameters and ionic packing ratio have been used to investigate the local structure surrounding the Nd 3+ ions and the covalency of the Nd-O bond. All obtained results agree and confirm the higher covalency of the Nd-O bond in the Ca 3 Al 2 Si 3 O 12 glass. Kozankova, "Er-and Nd-doped yttrium aluminosilicate glasses: preparation and characterization," Opt. Mater. 33(12), 1872-1878 (2011 42(1-3), 189-196 (1980). -78-XX-95, 1978). 36. T. Izumitani, H. Toratani, and H. Kuroda, "Radiative and nonradiative properties of Neodymium doped silicate and phosphate glasses," J. Non-Cryst. Solids 47(1), 87-99 (1982). 37. W. F. Krupke, "Induced-emission cross sections in Neodymium laser glasses," IEEE J. Quantum Electron. QE-10(4), 450-457 (1974). 38. M. J. Weber, D. C. Ziegler, and C. A. Angell, "Tailoring stimulated emission cross sections of Nd 3+ laser glass: observation of large cross sections for BiCl 3 glasses," J. Appl. Phys. 53(6), 4344-4350 (1982 66-78 (1998). 43. R. D. Shannon, "Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides," Acta Crystallogr. A 32(5), 751-767 (1976). 44. L. A. Riesberg and M. J. Weber, "Relaxation phenomena in rare-earth luminescence," Prog. Optics 14, 89-159 (1975 5799-5811 (1978).

Ridge waveguide lasers have been fabricated on Nd 3+ doped LiNbO 3 crystals. The fs-laser writing technique was used to define ridge structures on a gradient-index planar waveguide fabricated by Zn-diffusion. This planar waveguide was formed in a z-cut LiNbO 3 substrate homogeneously doped with a 0.23% of Nd 3+ ions. To obtain lateral light confinement, the surface was then micromachined using a multiplexed femtosecond laser writing beam, forming the ridge structures. By butting two mirrors at the channel waveguide end-facets, forming a waveguide laser cavity, TM-polarized laser action at 1085 nm was achieved by end-fire TM-pumping at 815 nm. The waveguide laser shows a threshold of 31 mW, with a 7% of slope efficiency.

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