Wavelength tuning

Another possibility for laser wavelength tuning is based on the shift of the energy levels in the active medium by external perturbations, which can cause a corresponding spectral shift in the gain profile and, therefore, in the laser wavelength. For instance, this shift may be caused by a temperature variation, as in the aforementioned case of semiconductor lasers. 

Figure 12. Laser configuration for SHG experiments, incorporating four single-narrow-stripe (SNS) red laser diodes and a prism (P) for wavelength tuning (DM dichroic mirror HWP half-wave plate PC polarization cube HR high reflector 1.5% output coupler).

One principally different method of photoexcitation consists in the so-called two-color, two-laser flash photolysis. This method allows exciting ion-radicals already generated during the first laser (first color) flash photolysis. With a short-time delay after the first laser flash, the ion-radicals are selectively excited by the second laser (second color) flash. This flash is of the wavelength tuned to the absorption of the ion-radical initially formed. As a result, the ion-radical transforms into... 

FIGURE 5.2 (a) Experimental (filled circles) wavelength tuning curve and accessible Raman freqnencies as a fnnction of the crystal temperatnre. The solid curves are a result of the calculations. (b) OPO output power versus pump power at the crystal facet (c) and (d) show the typical signal pulse spectrum and autocorrelation trace at the OPO cavity detuning of minus 36 (xm, respectively. 

The interference of the eigenfunction given by Eq. (7.5) was observed for each vibrational level by scanning r with the probe wavelength tuned to a specific E <- B vibronic transition. The results are shown in Figure 7.10a for t l.OTyib... 

Fig. 4 Excitation and emission spectra of complex 16 in CHCI3, CH3CN, CH3OH and buffer at room temperature (A,ex = 400 nm). The solid line shows the excitation anisotropy spectrum in 100% glycerol at - 60 °C with the emission wavelength tuned to 550 nm [51]...

The interpretation of these results is not obvious since the substitution reaction competes with van der Waals fragmentations (vdWF). The size of the parent cluster ion can be deduced from the R2PI spectra shown in Figure 4-19 the anisole+ ion product is monitored as a function of laser wavelength tuned on the Si - S0 transition of the precursor FB(CD3OD) clusters. From the position of the different bands on the spectra, the assignment of the neutral precursors has... 

Excited-state intramolecular proton transfer (ESIPT) processes are important for both practical and fundamental reasons. o-Hydroxybenzaldehyde (OHBA) is the simplest aromatic molecule displaying ESIPT and serves as a model system for comparison with theory. TRPES was used to study ESIPT in OHBA, monodeuterated ODBA and an analogous two-ring system hydroxyacetonaph-tone (HAN) as a function of pump laser wavelength, tuning over the entire enol... 

Through the availability of tunable diode laser sources the set-up used for atomic absorption (see Section 4.2.2) can be simplified considerably. In this way, several additional advantages can be realized. As through wavelength tuning, measurements in the wings of the absorption profile can also be made, and possible improvements to the linear dynamic range in a number of cases could be expected. 

Fig. 1.20. Comparison of the experimental far infrared spectrum of Vs with calculated IR absorption spectra of some geometric isomers. The experimental spectrum displayed in the lowest panel was obtained by resonant multiphoton dissociation of VeAr with the FELIX light source and mass-selective detection of the VsAr" -complex depletion during wavelength tuning of the laser [127]...

In CLCs induced by single chiral photoresponsive dopant, the reflection wavelength tuning is mainly determined by the HTP change of the chiral dopant... 

Wavelength tuning over a larger spectral range can be achieved in the following way (Fig. 6.44). 

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