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Broadband dye laser

The basic experimental arrangement is shown in Figure 1. A Q-switched ruby pump laser is frequency doubled to pump a broadband dye laser with a piano-spherical cavity. The remaining ruby power and the dye pulse were then used for the non-linear spectroscopy experiments. Spectra were recorded on film or plates by means of a Spex Model 1701 spectrograph equipped with a camera. The smoothness of the dye output intensity with wavelength, which determines the sensitivity of the single-pulse spectra, varied from shot to shot and depended on the dye. [Pg.320]

With an iodine cell inside the resonator of a cw multimode dye laser, an enhancement factor of g = 10 could be achieved, allowing the detection of I2 molecules at concentrations down to n < 10 /cm [20]. This corresponds to a sensitivity limit of aL < 10 . Instead of the laser output power, the laser-induced fluorescence from a second iodine cell outside the laser resonator was monitored as a function of wavelength. This experimental arrangement (Fig. 1.16) allows demonstration of the isotope-specific absorption. When the laser beam passes through two external iodine cells filled with the isotopes l2 and l2, tiny traces of l2 inside the laser cavity are sufficient to completely quench the laser-induced fluorescence from the external l2 cell, while the l2 fluorescence is not affected [21]. This demonstrates that those modes of the broadband dye laser that are absorbed by the internal l2 are completely suppressed. [Pg.22]

A short pump pulse excites coherently different upper levels. The time evolution of the superposition of states following the coherent excitation causes time-dependent changes of the complex susceptibility x of the sample. Similar to the quantum beats in the fluorescence intensity the susceptibility x(t) is found to contain oscillating nonisotropic contributions which can be readily detected by placing the sample between crossed polarizers and transmitting a probe pulse with variable delay (see also Sect.10.3 on polarization spectroscopy). Even a cw broadband dye laser can be used for probing if the probe intensity transmitted by the polarizer is monitored with sufficient time resolution. [Pg.570]

The results displayed in Figures 13.2, 13.3, and 13.4 show that the most efficient result occurred when a relatively narrow-band laser pulse of moderate intensity was i applied at center frequency near the peak of the absorption spectrum of the dye -molecule. The most effective result occurred when a positively chirped broadband M laser pulse was applied. The positive chirp (i.e., an upward drift of the laser s central j frequency with time) is helpful because stimulated emission back to tire ground stale, which diminishes the number of excited state molecules, invariably occurs to the red of the absorbed photon. By rapidly shifting the laser center frequency more unci more to the blue, one can successively eliminate the frequencies causing stimulated emission from the excited state shortly after it is formed by photon absorption. - f ... [Pg.310]

The c.w. dye laser can also be passively mode-locked and two different arrangements have been used. The first employed two free flowing dye streams, one for the laser dye and the other for the absorber (see Fig. 4) [18, 19]. In the alternative arrangement, the saturable absorber dye flows in a narrow channel of variable thickness (0.2—0.5mm) and in contact with a 100% broadband reflectivity mirror. With an absorber thickness of 0.5 mm, output pulses of 1 ps duration have been obtained [20]. Pulses as short as 0.3ps were produced when the DODCI cell length was shortened to 0.2 mm. The subpicosecond pulses produced in this arrangement were transform-limited in bandwidth. [Pg.7]

In the above analysis, the pump frequency (cOp) and the Stokes frequency (coj have been assumed to be ideally monochromatic, which is applicable when each vibration-rotation line is scanned. In a broadband CARS system as described here the Stokes (dye) laser has a broad spectral profile so that the multiplexed CARS spectral profile of the probed species, is generated with each laser pulse. [Pg.291]

Mode-locked Nd-glass or ruby lasers have also been used to investigate hole-burning and intramolecular dynamics in molecules, as have intracavity dye laser techniques, which operate on the principle of transferring the loss of intensity at the frequency of the hole in the spectrum into the enhanced gain of a dye laser, whose broadband output overlaps that frequency. [Pg.547]

In order to detect the intensity change of one mode in the presence of many others, the laser output has to be dispersed by a monochromator or an interferometer. The absorbing molecules may have many absorption lines within the broadband gain profile of a multimode dye laser. Those laser modes that overlap with absorption lines are attenuated or are even completely quenched. This results in spectral holes in the output spectrum of the laser and allows the sensitive simultaneous recording of the whoie absorption spectrum within the laser bandwidth, if the laser output is photographically recorded behind a spectrograph or if an optical multichannel analyzer (Vol. 1, Sect. 4.5) is used. [Pg.19]

Fig. 1.43 Optogalvanic spectrum (a) of a neon discharge (1 mA, p = 1 mbar) generated with a broadband cw dye laser [117] (b) of Al, Cu, and Fe vapor sputtered in a hollow cathode illuminated with a pulsed dye laser [120]... Fig. 1.43 Optogalvanic spectrum (a) of a neon discharge (1 mA, p = 1 mbar) generated with a broadband cw dye laser [117] (b) of Al, Cu, and Fe vapor sputtered in a hollow cathode illuminated with a pulsed dye laser [120]...
Often a broadband laser (for example, a pulsed dye laser without etalons), or a multiline laser (for example, a CO2 or CO laser without grating) may simultaneously cover several absorption lines of different molecules. In such cases the reflected beam is sent to a polychromator with a diode array or an optical multichannel analyzer (OMA, Vol. 1, Sect. 4.5). If a fraction of the laser power Po(< ) is imaged onto the upper part of the OMA detector and the transmitted power onto the lower part (insert in Fig. 10.17), electronic difference and ratio recording allows the simultaneous determination of the concentrations V/ of all absorbing species. A retroreflector arrangement is feasible for measurements at low altitudes above ground, where buildings or chimneys can support the construction. Examples are measurements of fluorine concentrations in an aluminum plant [1452], or the detection of different constituents in the chimney emission of power plants, such as NOjc and SOj components [1453]. Often, ammonia is added to the exhaust of power stations in order to reduce the amount of NO emission. In such cases, the optimum... [Pg.608]

Flash induced absorbance changes were recorded at 1250 nm using a germanium diode. The measuring beam was filtered before and after the cuvette by broadband interference filters (maximum of transmission = 1250 nm). A 10 ns flash from a dye laser (595 nm) excited the sample at a repetition rate of 0.1 Hz. Cells were suspended in 50 mM Mops/lOO mM KCl buffer (pH7), ficoll (10% w/v), 1 mM Na ascorbate... [Pg.198]

The solution to this problem appears to lie in the use of narrow-band optical excitation using dye lasers (Szabo, 1970). Several workers have shown the power of optical-site selection spectroscopy (Eberly et al., 1974 Abram et al, 1974 Dinse et al, 1976,1978). The resulting emission spectrum is often dramatically sharper than that obtained with broad band excitation. Using this method, Dinse et al (1976,1978) have observed sharp ( 1 MHz) zf ODMR transitions of several triplets in different organic glasses. It was also indicated that insofar as ODMR linewidths are concerned, very narrow band selective detection ( 1 cm ) is equivalent to broadband detection combined with selection laser excitation. [Pg.171]

What is serendipitious in combustion is that if the Stokes sources are positioned to observe the major products of hydrocarbon-air reactions, namely CO2 and H2O, the dual broadband frequency differences cover all the important diatomic constituents, i.e. N2, CO and NO if sufficiently abundant. If the CO2 Stokes laser is centered near 1320 cm midway between the and 21/2 modes, then O2 can be observed as well in the low frequency tall of the dye laser. Most broadband dyes possess unnarrowed FWHH on the order of 150 to 200 cm and base widths at least double this value. We have found that the dye DCM dissolved in DMSO, well suited to the H2O Raman freqtiencles, possesses a FWHH of 350 cm . Using this dye, a very broad frequency difference range can be achieved. [Pg.228]


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