Spectroscopy intracavity

Although most experiments have so far been performed with dye lasers, the color-center lasers or the newly developed vibronic solid-state lasers such as the Tiisapphire laser, with broad spectral-gain profiles (Vol. 1, Sect. 5.7.3) are equally well suited for intracavity spectroscopy in the near infrared. An example is the spectroscopy of rovibronic transitions between higher electronic states of the H3 molecule with a color-center laser [24]. The combination of Fourier spectroscopy with ICLAS allows improved spectral resolution, while the sensitivity can also be enhanced [25, 34, 35]. 

In the methods discussed in the preceding sections, the attenuation of the transmitted light (or of the laser power in intracavity spectroscopy) is monitored to determine the absorption coefficient a a>) or the number density of absorbing species. For small absorptions this means the measurement of a small difference of two large quantities, which limits, of course, the signal-to-noise ratio. 

V.M. Baev, Intracavity spectroscopy with diode lasers. Appl. Phys. B 55, 463 (1992)... 

W. Schrepp, H. Bigger, H. Walther, Intracavity spectroscopy with a color-center laser, l ser Appl 77 (1984)... 

N. Picqe, F. Gueye, G. GuelachviU, E. Sorokin, l.T. Sorokina, lime-resolved Fourier-Transform Intracavity spectroscopy with a Cr + ZnSe-laser. Opt. l tt. 30,24 (2005)... 

V.M. Baev, K.J. Boiler, A. WeUer, P.E. Toschek, Detection of spectrally narrow light emission by laser intracavity spectroscopy. Opt. Commun. 62,380 (1987) ... 

V.M. Baev, A. Weiler, P.E. Toschek, Ultrasensitive intracavity spectroscopy with multimode... 

The main part of the book presents various applications of lasers in spectroscopy and discusses the different methods that have been developed recently. Chapter 6 starts with Doppler-limited laser absorption spectroscopy with its various high-sensitivity detection techniques such as frequency modulation and intracavity spectroscopy, cavity ring-down techniques, excitation-fluorescence detection, ionization and optogalvanic spectroscopy, optoacoustic and optothermal spectroscopy, or laser-induced fluorescence. A comparison between the different techniques helps to critically judge their merits and limitations. 

New absorption methods, like intracavity spectroscopy, cavity-ring-down and cavity-enhanced spectroscopy, have demonstrated very high sensitivities in laboratory measurements with DLs. An ultrasensitive technique that combines external cavity enhancement and FM spectroscopy has been developed recently. This method, which has been called NICE-OHMS. or noise-immune cavity-enhanced optical heterodyne molecular spectroscopy, is based on frequency modulation of the laser at the cavity free-spectral-range frequency or its multiple. The MDA of 5x 10 1 X 10 cm ) in the detection of narrow... 

Although most experiments have so far been performed with dye lasers, the colour-center lasers or the newly developed vibronic solid-state lasers with broad spectral-gain profiles (Sect.5.7.3) are equally well suited for intracavity spectroscopy in the near infrared. An example is the spec-... 

We considered the effect of placing the reactor inside the eavity of multimode lasers (ICLS). Evidently, the sensitivity will increase also when the gas mixture under study is plaeed into the cavity of a laser. Let us consider the case of intracavity spectroscopy for external passive cavities, which contain no active medium. Such passive cavities are, in fact, reactors with the corresponding edge mirrors. The use of an external cavity, which represents an improved modification of multiway cells, was developed when the technology of creation of mirrors with a high reflection coefficient was improved. This new type of spectroscopy was named Ring-Down spectroscopy. 

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