Laser intensity, function

Karlov etal. investigated inversion kinetics in a pulsed CO2 laser, which was Q-switched with a rotating mirror, by shifting the time delay between excitation and Q-switch pulses and measuring the laser intensity as a function of delay time and discharge conditions 377) Similar experiments were performed by Lee era/.378). 

Fig. 2. Left experimental photoelectron spectra as a function of the delay time r. Right Measured photoelectron spectra as a function of the laser intensity at a fixed delay time.

Figure 12. Transient Na2+ spectra as a function of delay between identical 80-fs, 620-nm pump-probe pulses for three different laser intensities (top) and corresponding Fourier transforms (bottom).

The laser output intensity of the C153 and R6G ORMOSIL gels was studied as a function of the number of laser pump pulses. Both materials could be pulsed for more than 3000 shots with a reduction of the emission amplitude of about a factor of four. Specifically, the C153 gel laser intensity decreased by a factor of 6 after more than 6000 pulses of 500 MW/cmA The plot of the intensity versus number of shots has a double exponential decay. This phenomenon is not yet completely understood, but it could be associated with microscopic phase separation in the medium. The R6G decay plot shows that the intensity undergoes a 90% reduction after 5300 laser pulses. 

Figure 3. The observed intensity of the phase-conjugate reflection as a function of laser intensity for PdPcCP4 (6 x 10 3 M in CHC13). The line is a fit to a curve of the form Signal = a3I3 + a5I5. The dashed line is the cubic term only. The deviations from a cubic dependence can be seen at high intensity.

Figure 4. Ionization yield as a function of laser intensity for a radiation pulse with a linear tum-on of 1007 //. The field frequency is an = 10 a.u.. These yields are computed at t = 11007 //. The line represents the results for the time-dapendent Schrodinger equation treatment while the dots are the results of the Klein-Gordon equation treatment,...

Fig. 11. Log-log plots for the intensities of the green and red upconversion emission of NaYF4 Ybo.2/Ero.015 as a function of pumping laser intensity (redrawn after (Wang et al., 2007)).

FIGURE 26 Nomogram of the dimensionless alignment parameter A > as a function of laser intensity, field strength, and polarizability anisotropy. [Reproduced with permission from Freidrich, B., and Herschbach, D. R. (1995). J. Phys. Chem. 99,15686. Copyright American Chemical Society.]... 

Figure 2. Ratio of populations (groundtexcited) in the two levels connected by the laser as a function of inverse laser intensity for three assumed values of

Figure 3. Dummy (vibrationally excited)-level population, as a fraction of the total, as a function of assumed transfer Cross section av (insquare angstroms) to v = 0 of X2H for three values of laser intensity...

Dummy level population. With no laser, the population of the dummy level is set at 11% of the total, the thermal equilibrium fraction in v=l at 2000°K. Because vibrational energy transfer rates are generally slow, the laser excitation causes a sizeable fraction of the total to be pumped into the dummy level. Fig. 3 shows the dummy level population for three laser intensities as a function of assumed a. (In the imensionless notation used in the computer, 1=1 corresponds to 10 erg sec- cm Hz-, or that of the unfocussed output of the fundamental from an efficient dye pumped by a powerful doubled Nd YAG laser). At the nominal 0.4 A, nearly 40% of the population is driven into the dummy level at high I. Clearly the value of C, a poorly known parameter, is important for a quantitative description of fluorescence saturation. 

Laser-induced fluorescence is a sensitive, spatially resolved technique for the detection and measurement of a variety of flame radicals. In order to obtain accurate number densities from such measurements, the observed excited state population must be related to total species population therefore the population distribution produced by the exciting laser radiation must be accurately predicted. At high laser intensities, the fluorescence signal saturates (1, 2, 3 ) and the population distribution in molecules becomes independent of laser intensity and much less dependent on the quenching atmosphere (4). Even at saturation, however, the steady state distribution is dependent on the ratio of the electronic quenching to rotational relaxation rates (4, 5, 6, 7). When steady state is not established, the distribution is a complicated function of state-to-state transfer rates. 

Fig. 2.8. Left Ratio of doubly to singly charged (7, = 2, , ) and triply to doubly charged (Z = 3, o, ) molecular ions are plotted as a function of effective laser intensity. Circles and squares indicate them by circularly and linearly polarized lights, respectively. Right figure Ratio of the sum of molecular ions of all charge states (JO Mz+) to the total ions (Total). Signals by circularly polarized light are indicated by (o) and for linearly polarized light by ( )...

Fig. 11.4. Energy distribution functions of the radiation produced by nonlinear Thomson scattering in a laser field for two laser intensities. Radiation above 1 keV can be achieved for laser intensities larger than 1020 W/cm2...

Fig. 11.5. Experimental setup (left) and spatial distribution function (right) of the radiation observed for a laser intensity ao = 5.6...

Fig. 11.7. X-ray intensity as a function of the electronic density of the plasma and the laser strength parameter. The process of nonlinear Thomson scattering for the production of X-ray emission can be observed for the highest laser intensities and along the laser axis (ao = 5.6 for the two first figures)...

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