J. Miguel Hickmann

Two-photon-resonant photoinduced second-harmonic generation in Er 3+ -doped germano-aluminosilicate optical fibers pumped at 1.319 μm

The growth of a two-photon-resonant photoinduced second-harmonic signal at 660 nm in Er(3+)-doped GeO(2)-Al(2)O(3)-SiO(2) single-mode optical fibers pumped by a Nd:YAG laser at 1.319 microm is reported. Defect states in the band gap are optically excited through a resonant two-photon absorption process connecting the (4)I(15/2)-(4)F(9/2) energy levels of the erbium ions present in the fiber core. As a result a periodic X((2)) grating is formed, and efficient second-harmonic generation takes place. For erbium-free GeO(2)-doped silica test fibers no second-harmonic signal has been detected, even after hours of seeded preparation process.

Space-time break-up in the self-focusing of ultrashort pulses

We investigate the effect of rapidly varying perturbations on the initial stage of the three-dimensional propagation of ultrashort pulses through a nonlinear dispersive medium, in the limit and beyond the slowly varying envelope approximation. We have found a space-time coupling effect which distorts and reduces the range for which sidebands appear on far-field and temporal spectrum.

Weak signal pulse compression and amplification through stimulated Raman scattering and cross-phase modulation in optical fibers

Abstract Simulataneous amplification and temporal compression of low intensity signal pulses of a few μWs peak powers in single-mode optical fibers is reported. The process was achieved by means of the combined effects of synchronous Raman amplification and cross-phase modulation induced chirp on a weak signal copropagating with a strong pump pulse in an optical fiber. Experimental results agree quite well with numerical simulations.

Cross-phase modulation of incoherent light in single-mode optical fibers.

When two optical incoherent beams copropagate in an optical fiber, the intensity-dependent refractive index couples the two beams through a nonlinear process known as cross-phase modulation. We show, for the first time to our knowledge, experimental evidence on cross-phase-modulation-induced correlation time reduction and a concomitant growth of the frequency components of the two copropagating incoherent waves in a singlemode optical fiber. Theoretical analysis agrees well with experimental data.

440 nm light generation by frequency tripling in germanosilicate glasses

Generation of 120 μW average power blue‐violet light at 440 nm through efficient frequency tripling of 1.319 μm Nd:YAG laser pulses in bulk GeO2‐SiO2 and Er3+‐doped GeO2‐SiO2 glasses is reported. Third‐harmonic signal light enhancement owing to two‐ and three‐photon resonant pumping of erbium ions in doped samples is also reported.

Control of soliton interaction in a coherently excited three-level system embedded in a nonlinear waveguide

We have investigated the interaction between a pair of solitons that originate from the breakup of a high-order soliton propagating through a cylindrical waveguide in the presence of three-level resonance associated with a dopant. We found that one can control the nature of this interaction by varying the initial intensity ratio and the overlap between the pump and the signal from which the pair originated.

Spatial instabilities in the propagation of a cylindrical beam in a Kerr medium

We study the development of spatial instabilities during the propagation of a cylindrically-symmetric beam in a medium with Kerr nonlinearity. Analytical results show that the initial evolution of the associated ring structure can be described by a Bessel function. Numerical simulations confirm these results and show that the rings increase very rapidly in sharpness and intensity. Their radii decrease as the beam propagates and the central ring collapses after a short distance.

SOLITON PROPAGATION IN THE VICINITY OF A TWO-PHOTON RESONANCE

Abstract We investigate the effects of frequency dispersion of the nonlinear susceptibility associated to the two-photon resonance, obtaining the necessary conditions for a solitary wave solution, even in the presence of a self-steepening term.

Intense picosecond pulse generation in the 580–610 nm region from a pure SiO2-core fiber ring oscillator synchronously pumped by a Nd: YAG laser at 1.319 µm

Abstract Generation of intense picosecond pulses in the 580–610 nm region, from a frequency upconversion pure Si0 2 -core fiber ring oscillator, is described. The single-mode fiber ring oscillator was synchronously pumped by a Q-switched and mode-locked Nd: YAG laser operated at 1.319 µmm. The oscillator produced pulses at 100 MHz with less than 90 ps duration and peak powers as high as 120 W. The pulses resided in 300 ns duration Gaussian shaped Q-switch bursts at repetition rates of up to 1.5 kHz.