Pumping, of laser

We assume strong coherent pumping of laser modes and replace the operators aLj with corresponding complex amplitudes [Pg.558]

In 1974 two independent experiments in pumping of laser media by nuclear explosives were reported briefly. 

The previous edition of this chapter added a section on laser pumping of lasers. This method has remained a laboratory specialty that has never matured outside the scientific marketplace due to the very small overall efiiciency and system complexity it entails. A possible exception in the future might be bleach pumping, where not only a very small fraction of the active ions present in the active medium are being inverted, as is usually the case, but essentially most of them. The result is that there are basically few uninverted ions left in the active medium. This is a useful effect for ions whose lasing transition terminates in, or... 

This paper deals with the control of weld depth penetration for cylinders in gold-nickel alloy and tantalum. After introducing the experimental set-up and the samples description, the study and the optimization of the testing are presented for single-sided measurements either in a pulse-echo configuration or when the pump and the probe laser beams are shifted (influence of a thermal phenomenon), and for different kind of laser impact (a line or a circular spot). First, the ultrasonic system is used to detect and to size a flat bottom hole in an aluminium plate. Indeed, when the width of the hole is reduced, its shape is nearly similar to the one of a slot. Then, the optimization is accomplished for... 

The dynamics of fast processes such as electron and energy transfers and vibrational and electronic deexcitations can be probed by using short-pulsed lasers. The experimental developments that have made possible the direct probing of molecular dissociation steps and other ultrafast processes in real time (in the femtosecond time range) have, in a few cases, been extended to the study of surface phenomena. For instance, two-photon photoemission has been used to study the dynamics of electrons at interfaces [ ]. Vibrational relaxation times have also been measured for a number of modes such as the 0-Fl stretching m silica and the C-0 stretching in carbon monoxide adsorbed on transition metals [ ]. Pump-probe laser experiments such as these are difficult, but the field is still in its infancy, and much is expected in this direction m the near fiitiire. 

Figure B2.5.8. Schematic representation of laser-flash photolysis using the pump-probe technique. The beam splitter BS splits the pulse coming from the laser into a pump and a probe pulse. The pump pulse initiates a reaction in the sample, while the probe beam is diverted by several mirrors M tluough a variable delay line.

Gortschakov G, Loffhagen D and Winkler R 1998 The homogeneity of a stabilized discharge-pumped XeCI laser Appl. Phys B 66 313-22... 

The timing of the emission is clearly dependent on the system in use. For example, if pumping is relatively slow and stimulated emission is fast, then the emergent beam of laser light will appear as a short pulse (subsequent lasing must await sufficient population inversion). This behavior is... 

A schematic representation of a PR apparatus is shown in Figure 2. In PR a pump beam (laser or other light source) chopped at frequency 2 creates photo-injected electron-hole pairs that modulate the built-in electric field of the semiconductor. The photon energy of the pump beam must be larger than the lowest energy gap of the material. A typical pump beam for measurements at or below room temperature is a 5-mW He-Ne laser. (At elevated temperatures a more powerful pump must be employed.)... 

Iral modes within the narrow peak. However, mode structure was not observed in any of our measurements. Since both ASE and lasing are based on stimulated emission, the difference is not very important in the context of the electrically pumped organic laser. Moreover, because the distinction is not a key issue here, we consider the gain phenomena observed in systems without external feedback to be mirmrless lasing. 

Sum-frequency mixing of two diode pumped fiber lasers (938 and 1583 nm) in a nonlinear crystal. CW format has been demonstrated at low power levels higher powers and pulsed formats are under development. 

Since there are a large number of different experimental laser and detection systems that can be used for time-resolved resonance Raman experiments, we shall only focus our attention here on two common types of methods that are typically used to investigate chemical reactions. We shall first describe typical nanosecond TR spectroscopy instrumentation that can obtain spectra of intermediates from several nanoseconds to millisecond time scales by employing electronic control of the pnmp and probe laser systems to vary the time-delay between the pnmp and probe pnlses. We then describe typical ultrafast TR spectroscopy instrumentation that can be used to examine intermediates from the picosecond to several nanosecond time scales by controlling the optical path length difference between the pump and probe laser pulses. In some reaction systems, it is useful to utilize both types of laser systems to study the chemical reaction and intermediates of interest from the picosecond to the microsecond or millisecond time-scales. 

The advent of ultrafast pump-probe laser techniques62 and their marriage with the TOF method also enables study of internal ion-molecule reactions in clus-ters.21,63-69 The apparatus used in our experiments is a reflectron TOF mass spectrometer coupled with a femtosecond laser system. An overview of the laser system is shown in Figure 4. Femtosecond laser pulses are generated by a colliding pulse mode-locked (CPM) ring dye laser. The cavity consists of a gain jet, a... 

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