Intensity-moments characterization of general pulsed paraxial beams with the Wigner distribution function

On the basis of the space-time Wigner distribution function (STWDF), we use the matrix formalism to study the propagation laws for the intensity moments of quasi-monochromatic and polychromatic pulsed paraxial beams. The advantages of this approach are reviewed. Also, a least-squares fitting method for interpreting the physical meaning of the effective curvature matrix is described by means of the STWDF. Then the concept is extended to the higher-order situation, and what me believe is a novel technique for characterizing the beam phase is presented. (C) 1999 Optical Society of America [S0740-3232(99)001009-1].

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.

Influence of the chirp on the intensity distributions of an apertured pulse

Starting from the Huygens-Fresnel diffraction integral and the Fourier transform, the propagation expression of a chirped pulse passing through a hard-edged aperture is derived. Using the obtained expression, the intensity distributions of the pulse with different chirp in the near and far fields are analyzed in detail. Due to the modulation of the aperture, many intensity peaks emerge in the intensity distributions of the chirped pulse in the near field. However, the amplitudes of the intensity peaks decrease on increasing the chirp, which results in the smoothing effect in the intensity distributions. The beam smoothing brought by increasing the chirp is explained physically. Also, it is found that the radius of the intensity distribution of the chirped pulse decreases when the chirp increases in the far field. (c) 2005 Elsevier GmbH. All rights reserved.

Tunable three-dimensional intensity distribution by a pure phase-shifting apodizer

The three-dimensional distribution of light intensity that is modulated by a pure phase-shifting apodizer is studied. Results show that the Strehl ratio can be altered by the proposed apodizer and by the waist width of incident Gaussian beams. By changing geometrical parameters of the proposed apodizer, we can increase the focal depth to several times that of the original system. The proposed apodizer can also be used to realize focal splitting and local minimum of intensity, which may be advantageous for constructing an optical trap. Furthermore, the local minimum of intensity number is tunable by changing the parameters of the apodizer. (c) 2005 Optical Society of America

The intensity distribution and thermal stability of InnoSlab laser

Partially end-pumped slab laser is an innovative solid state laser, namely InnoSlab. Combining the hybrid resonator with partially end-pumping, the output power can be scaled with high beam quality. In this paper, the output intensity distributions are simulated by coordinate transformation fast Fourier transform (FFT) algorithm, comparing the thermal lens influence. As the simulated curves showed, the output mode is still good when the thermal lens effect is strong, indicating the good thermal stability of InnoSlab laser. Such a new kind of laser can be designed and optimized on the base of this simulation.

Judd-Ofelt intensity parameters of Er3+ doped mixed alkali aluminophosphate glasses

Lithium sodium mixed alkali aluminophosphate glasses of the composition xNa(2)O-(15-x)Li2O-4B(2)O(3)-11Al(2)O(3)-5BaO-65P(2)O(5) (where x=0, 3.75, 7.5, 11.25 and 15 mol%) containing 0.5 mol% Er2O3 were prepared by melt quenching. The absorption spectra of Er3+ were studied from the experimental oscillator strengths and the Judd-Ofelt intensity parameters were obtained. The variations of Judd-Ofelt intensity parameters (Omega(2), Omega(4) and Omega(6)), experimental oscillator strengths of certain excited states of Er3+ and hypersensitive band positions with different mixed alkali content have been discussed in detail. It was found that there were similar effects of mixed alkali on both Judd-Ofelt intensity parameter 02 and the experimental oscillator strength of the hypersensitive transition, I-4(15/2) -> H-2(11/2). No shifts in the peak wavelength of the studied transitions were found in different glasses. (c) 2006 Elsevier B.V. All rights reserved.

Analysis on fluorescence intensity reverse photonic phenomenon between red and green fluorescence of oxyfluoride nanophase vitroceramics

An interesting fluorescence intensity reverse photonic phenomenon between red and green fluorescence is investigated. The dynamic range. of intensity reverse between red and green fluorescence of Er( 0.5) Yb( 3): FOV oxyfluoride nanophase vitroceramics, when excited by 378.5nm and 522.5nm light respectively, is about 4.32 x 10(2). It is calculated that the phonon- assistant energy transfer rate of the electric multi- dipole interaction of {(4)G(11/2)( Er3+) -> F-4(9/2)( Er3+), F-2(7/2)( Yb3+). F-2(5/2)( Yb3+)} energy transfer of Er( 0.5) Yb( 3): FOV is around 1.380 x 10(8) s(-1), which is much larger than the relative multiphonon nonradiative relaxation rates 3.20 x 10(5) s(-1). That energy transfer rate for general material with same rare earth ion's concentration is about 1.194 x 10(5) s(-1). These are the reason to emerge the unusual intensity reverse phenomenon in Er( 0.5) Yb( 3): FOV. (C) 2007 Optical Society of America.

Far-field intensity distribution of a beam generated by a resonator with a phase-unifying mirror

The far-field intensity distribution (FFID) of a beam generated by a phase-unifying mirror resonator was investigated based on scalar diffraction theory. Attention was paid to the parameters, such as obscuration ratio and reflectivity of the phase-unifying mirror, that determine the FFID. All analyses were limited to the TEM00 fundamental mode. (c) 2005 Optical Society of America.

Far-field intensity distribution and M-2 factor of hollow Gaussian beams

The far-field intensity distribution of hollow Gaussian beams was investigated based on scalar diffraction theory. An analytical expression of the M-2 factor of the beams was derived on the basis of the second-order moments. Moreover, numerical examples to illustrate our analytical results are given. (c) 2005 Optical Society of America.

Far-field intensity distribution of beam generated by Gaussian mirror resonator

Based on scalar diffraction theory, we investigated far-field intensity distribution (FFID) of beam generated by Gaussian mirror resonator. We found usable analytical expressions of diffracted field with respect to variation of diffraction parameters. Particular attention was paid to the parameters such as mirror spot size and radius of the Gaussian mirror, which determine the FFID. All analyses were limited to TEM00 fundamental mode. (c) 2004 Elsevier B.V. All rights reserved.

Far-field intensity distribution, M-2 factor of beams generated by Gaussian mirror resonator

We investigated M-2 factor and far-field distribution of beams generated by Gaussian mirror resonator. And we found usable analytical expressions of the M2 factor and the far-field distribution intensity with respect to variation of diffraction parameters. Particular attention was paid to the parameters such as mirror spot size and reflectance of the Gaussian mirror. (c) 2006 Elsevier GrnbH. All rights reserved.

Effects of cadmium on chlorophyll content, photochemical efficiency, and photosynthetic intensity of Canna indica Linn.

The effects of cadmium (Cd2+) on growth status, chlorophyll (Chl) content, photochemical efficiency, and photosynthetic intensity were studied on Canna indica Linn. Plant specimens that were produced from a constructed wetland and precultivated hydroponically in 20 L of 1/10 Hoagland solution under greenhouse conditions for I week were exposed to cadmium in concentrations of 0, 0.4, 0.8, 1.6 and 3.2 mg L- Cd2+, respectively. The results show that leaves were injured in the Cd2+ solution by the third day of exposure and the injury became more serious with an increase in the applied heavy metal. Under 3.2 mg L-1 Cd2+ treatment, growth retardation, the decrease of chlorophyll content from 0.70 to 0.43 mg g(-1) FW, and a decrease in Chl a/b ratio from 2.0 to 1.2 were observed. Chl a was more sensitive than Chl b to Cd2+ stress. The decrease was the same with photochemical efficiency. Photosynthetic intensity decreased by 13.3% from 1.5X10(4) mumol m(-2)s(-1) CO2 in control to 1.3x10(4) mumol m(2)s(-1) CO2 in the treatment of 3.2 mg L-1. Because Canna species are used in heavy metal phytoremediation, these results show that C. indica can tolerate 0.4 to 0.8 mg L-1 Cd2+. Therefore, it is a potential species for phytoremediation of cadmium with some limitations only at higher concentrations.