Optical properties of transparent alkali gallium silicate glass-ceramics containing Ni2+-doped beta-Ga2O3 nanocrystals

Broadband near-infrared (IR) luminescence in transparent alkali gallium silicate glass-ceramics containing N2+-doped beta-Ga2O3 nanocrystals was observed. This broadband emission could be attributed to the T-3(2g) (F-3) -> (3)A(2g) (F-3) transition of octahedral Ni2+ ions in glass-ceramics. The full width at half-maximum (FWHM) of the near-IR luminescence and fluorescent lifetime of the glass-ceramic doped with 0.10 mol% NiO were 260 nm and similar to 1220 mu s, respectively. It is expected that transparent Ni2+-doped beta-Ga2O3 glass-ceramics with this broad near-IR emission and long fluorescent lifetime have potential applications as super-broadband optical amplification media.

Broad-bandwidth semi-noncollinear optical parametric amplification in periodically poled LiNbO3 based on tilted quasi-phase-matched gratings

On the basis of noncollinear optical parametric amplification in periodically poled lithium niobate (PPLN) which is realized by quasi-phase matching (QPM) technology, we consider the possibility of semi-noncollinear phase matching between collinear and noncollinear geometries by tilting a PPLN-crystal's parallel grating at a sure angle. Numerical simulation with proper parameters shows that we can achieve a broader optical parametric amplification (OPA) bandwidth than that of noncollinear geometry. About 121 nm at a signal wavelength of 800 and 70 nm at a signal wavelength of 1064 nm under optimal conditions are obtained when the crystal length is 9 mm.

Transparent Ni2+-doped ZnO-Al2O3-SiO2 system glass-ceramics with broadband infrared luminescence

We report transparent Ni2+-doped ZnO-Al2O3-SiO2 system glass-ceramics with broadband infrared luminescence. After heat-treatment, ZnAl2O4 crystallite was precipitated in the glasses, and its average size increased with increasing heat-treatment temperature. No infrared emission was detected in the as-prepared glass samples, while broadband infrared luminescence centered at 1310 nm with full width at half maximum (FWHM) of about 300 nm was observed from the glass-ceramics. The peak position of the infrared luminescence showed a blue-shift with increasing heat-treatment temperature, but a red-shift with an increase in NiO concentration. The mechanisms of the observed phenomena were discussed. These glass-ceramics are promising as materials for super broadband optical amplifier and tunable laser. (c) 2006 Elsevier Ltd. All rights reserved.

Coherent enhancement of broadband frequency up-conversion in BBO crystal by shaping femtosecond laser pulses

An optimal feedback control of broadband frequency up-conversion in BBO crystal is experimentally demonstrated by shaping femto-second laser pulses based on genetic algorithm, and the frequency up-conversion efficiency can be enhanced by similar to 16%. SPIDER results show that the optimal laser pulses have shorter pulse-width with the little negative chirp than the original pulse with the little positive chirp. By modulating the fundamental spectral phase with periodic square distribution on SLM-256, the frequency up-conversion can be effectively controlled by the factor of about 17%. The experimental results indicate that the broadband frequency up-conversion efficiency is related to both of second harmonic generation (SHG) and sum frequency generation (SFG), where the former depends on the fundamental pulse intensity, and the latter depends on not only the fundamental pulse intensity but also the fundamental pulse spectral phase. (c) 2006 Elsevier B.V. All rights reserved.

Transverse intensity distributions of a broadband laser modulated by a hard-edged aperture

By means of the Huygens-Fresnel diffraction integral, the field representation of a laser beam modulated by a hard-edged aperture is derived. The near-field and far-field transverse intensity distributions of the beams with different bandwidths are analyzed by using the representation. The numerical calculation results indicate that the amplitudes and numbers of the intensity spikes decrease with increasing bandwidth, and beam smoothing is achieved when the bandwidth takes a certain value in the near field. In the far field, the radius of the transverse intensity distribution decreases as the bandwidth increases, and the physical explanation of this fact is also given. (c) 2005 Optical Society of America.

Smoothing effect in the broadband laser through a dispersive wedge

The propagation expression of a broadband laser passing through a dispersive wedge is derived on the basis of the Huygens-Fresnel diffraction integral, Smoothing effects caused by the phase perturbation of the dispersive wedge on the intensity profiles are investigated in detail. The phase perturbation of the dispersive wedge induces a relative transverse position shift between the diffraction patterns of different frequency components. The relative transverse position shift is of great benefit to the fill of the intensity peaks of some patterns in the valleys of others when these patterns are overlapped and thus the smoothing effect is achieved. (c) 2006 Elsevier B.V. All rights reserved.

Smoothing the side lobes of a focused pattern by spectral dispersion in the broadband laser

Starting from the Huygens-Fresnel diffraction integral, the propagation equations of a broadband laser passing through a dispersive lens and a dispersive wedge are derived. Smoothing effect on the side lobes of the focused pattern is achieved as the broadband laser passes through the lens because of the spectral dispersion of the lens. By inserting a dispersive wedge behind the lens, better smoothing effect is realized because a relative position shift between focused patterns of different frequency components is generated due to the spectral dispersion of the wedge. Smoothing effect on the side lobe is obtained even with small bandwidth of the broadband laser as the wedge is used. (c) 2006 Elsevier GmbH. All rights reserved.

Optimization of Pulse Temporal Contrast in Optical Parametric Chirped Pulse Amplification

In optical parametric chirped pulse amplification (OPCPA), the degradation of temporal contrast of the compressed signal pulse mainly results from spectral clipping in the grating stretcher with finite size of the optics, parametric fluorescence (PF) and the spectral variations transferred from temporal fluctuation of the pump pulse. The temporal contrast of the recompressed amplified pulse in the OPCPA system is studied numerically and a number of solutions are considered and optimized to achieve the highest temporal contrast.