J. R. Vázquez de Aldana

Continuous wave laser generation at 1064 nm in femtosecond laser inscribed Nd:YVO4 channel waveguides

We report on continuous wave 1064 nm laser generation from an ultrafast laser inscribed neodymium-doped yttrium orthovanadate channel waveguide with pumping at 808 nm. Single-mode stable laser operations have been observed with pump powers at threshold as low as 14 mW and with laser slope efficiencies as high as 38.7%.

Femtosecond-laser-written, stress-induced Nd:YVO 4 waveguides preserving fluorescence and Raman gain

We report the formation of optical waveguides in the self-Raman Nd:YVO(4) laser crystal by femtosecond laser inscription. The confocal fluorescence and Raman images have revealed that the waveguide is constituted by a locally compressed area in which the original fluorescence and Raman gains of the Nd:YVO(4) system are preserved. Thus the obtained structures emerge as promising candidates for highly efficient self-Raman integrated laser sources.

Transferring orbital and spin angular momenta of light to atoms

Light beams carrying orbital angular momentum (OAM), such as Laguerre–Gaussian (LG) beams, give rise to the violation of the standard dipolar selection rules during interaction with matter, yielding, in general, an exchange of angular momentum larger than per absorbed photon. By means of ab initio three-dimensional (3D) numerical simulations, we investigate in detail the interaction of a hydrogen atom with intense Gaussian and LG light pulses. We analyze the dependence of the angular momentum exchange with the polarization, the OAM and the carrier-envelope phase of light, as well as with the relative position between the atom and the light vortex. In addition, a quantum-trajectory approach based on the de Broglie–Bohm formulation of quantum mechanics is used to gain physical insight into the absorption of angular momentum by the hydrogen atom.

Thermally resistant waveguides fabricated in Nd:YAG ceramics by crossing femtosecond damage filaments

We report on femtosecond laser writing of channel waveguides in Nd(3+) ion doped YAG ceramics by multiple inscriptions of damage filaments. Waveguiding between filaments was found to resist annealing temperatures as high as 1500 degrees C. Microluminescence imaging experiments have been carried out to elucidate the potential application of the obtained waveguides as integrated laser sources as well as to elucidate the waveguiding mechanisms.

Photoionization with Orbital Angular Momentum Beams

Intense laser ionization expands Einsteins photoelectric effect rules giving a wealth of phenomena widely studied over the last decades. In all cases, so far, photons were assumed to carry one unit of angular momentum. However it is now clear that photons can possess extra angular momentum, the orbital angular momentum (OAM), related to their spatial profile. We show a complete description of photoionization by OAM photons, including new selection rules involving more than one unit of angular momentum. We explore theoretically the interaction of a single electron atom located at the center of an intense ultraviolet beam bearing OAM, envisaging new scenarios for quantum optics.

Saturation of ablation channels micro-machined in fused silica with many femtosecond laser pulses.

We investigate the effect of saturation in the propagation of ablation channels performed in fused silica with many incident femtosecond pulses and laser fluence slightly above the ultrafast ablation threshold. A 110 fs Ti:Sapphire laser system is used in the experiments and the results are compared with theoretical predictions performed with a numerical model developed by the authors. Diffraction of the incoming pulses at the entrance of the channel as well as reflections at the walls of the channel play a crucial role in the progress of the crater as it is shown by means of the numerical results. The effect of the pulse duration in the shape of the ablation channel is also investigated.

Self-frequency-doubling of ultrafast laser inscribed neodymium doped yttrium aluminum borate waveguides

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 μm laser line of neodymium ions.

Propagation of ablation channels with multiple femtosecond laser pulses in dielectrics: numerical simulations and experiments

We present numerical simulations for the propagation of the ablation channel in dielectrics for multiple incident femtosecond laser pulses with fluences slightly above ultrafast ablation threshold. The theoretical model is based on the direct numerical integration of the wave equation for the laser pulse propagation together with coupled equations for the polarization and ionization of the medium. The progress of the ablation channel predicted by our calculations shows fairly good agreement with that observed in experiments, reproducing quite well other features of the process, namely, formation of optical damage areas aside the channel.

Femtosecond laser writing of multifunctional optical waveguides in a Nd:YVO4 KTP hybrid system

We report on the fabrication of optical channel waveguides supporting both visible and IR TE and TM confinement in a hybrid system composed of a Nd:YVO4 laser gain medium glued to a potassium titanyl phosphate (KTP) nonlinear crystal. The microphotoluminescence and second harmonic confocal images of the fabricated waveguides have revealed that the laser and nonlinear properties of the constituent crystals have not been deteriorated because of the waveguide inscription. The resulting structures emerge as promising candidates for the development of multifrequency waveguide lasers.

Integrated-grating-induced control of second- harmonic beams in frequency-doubling crystals

We report a novel type of integrated nonlinear photonic device for controlling the generation of several second-harmonic beams. Two-dimensional diffraction gratings are recorded with femtosecond laser pulses at the entrance surface of a frequency-doubling crystal. This periodic spatial modulation of the material surface induces noncollinear propagation of the fundamental input signal in the crystal. By slightly changing the angle of incidence of the seed beam, collinear and noncollinear phase matching can be achieved between different diffraction orders, in this way allowing the efficient generation of several second-harmonic beams.