Intracavity saturation

Fig. 2.18 Schematic arrangement for third-derivative intracavity saturation spectroscopy...

Figure 2.46 illustrates the advantages of this technique. The upper spectrum represents a Lamb peak in the intracavity saturation spectrum of the neon line (l 2p) at A. = 588.2 nm (Sect. 2.3.3). Due to the collisional redistribution of the atomic velocities, a broad and rather intense background appears in addition to the narrow peak. This broad structure is not present in the dichroism and birefrin-gent curves (Fig. 2.46b, c). This improves the signal-to-noise ratio and the spectral resolution. 

Fig.7.41a-c. Comparison of different techniques for measuring the neon transition ls2 — 2p2 at X = 588.2 nm (a) intracavity saturation spectroscopy (Lamb peak of the laser output Il cd) with Doppler-broadened background) (b) laser-induced dichroism and (c) laser-induced birefringence [7.72]... 

Figure 7.41 illustrates the advantages of this technique. The upper spectrum represents a Lamb peak in the intracavity saturation spectrum of the neon line (Is—>2p) at A = 588.2 nm (Sect.7.3.3). Due to the collisional... 

Fiq.l0.24a-c. Intracavity saturated absorption spectroscopy, (a) Experimental setup, (b) "Lamb peak" in the laser output, (c) derivative of a Lamb peak obtained by modulation of the laser frequency... 

The blue satellite peak associated with resonance line of rubidium (Rb) saturated with a noble gas was closely examined by Lepoint-Mullie et al. [10] They observed SL from RbCl aqueous solution and from a 1-octanol solution of rubidium 1-octanolate saturated with argon or krypton at a frequency of 20 kHz. Figure 13.4 shows the comparison of the SL spectra of the satellite peaks of Rb-Ar and Rb-Kr in water (Fig. 13.4b) and in 1-octanol (Fig. 13.4c) with the gas-phase fluorescence spectra (Fig. 13.4a) associated with the B —> X transition of Rb-Ar and Rb-Kr van der Waals molecules. The positions of the blue satellite peaks obtained in SL experiments, as indicated by arrows, exactly correspond to those obtained in the gas-phase fluorescence experiments. Lepoint-Mullie et al. attributed the blue satellites to B — X transitions of alkali-metal/rare-gas van der Waals species, which suggested that alkali-metal atom emission occurs inside cavitating bubbles. They estimated the intracavity relative density to be 18 from the shift of the resonance line by a similar procedure to that adopted by Sehgal et al. [14],... 

One method which employs the saturable absorption of intracavity gaseous absorbers has turned out to be strikingly successful333) As explained in the last section, the absorption profile of a gas interacting with a monochromatic standing wave inside the laser cavity exhibits a sharp minimum at the center of the unsaturated ab-... 

Radicals.—The measurement of emission intensities from electronically excited small free radicals has become an important means of determining radical concentrations in hostile environments such as flames. When combined with laser excitation, the technique is very powerful, offering temporal, spectral, and spatial resolution. Just has reviewed laser techniques for the measurement of both radical concentrations and local temperatures in flames, and has demonstrated the use of laser-induced saturated fluorescence to measure the concentrations of CH and OH radicals in low-pressure acetylene-oxygen flames. Vanderhoff ei al. used a novel Kr " and Ar laser intracavity technique to... 

In the case of a homogeneous profile g(v —vo)> all molecules in the upper level can contribute to stimulated emission at the laser frequency Ua with the probability Bikpgiva I d), see (5.8). Although the laser may oscillate only with a single frequency v, the whole homogeneous gain profile a(v) = ANa v) saturates until the inverted population difference AN has decreased to the threshold value AAthr (Fig- 5.23a). The saturated amplification coefficient asat(v) at the intracavity laser intensity / is, according to Sect. 3.6,... 

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