Applications of Dye Lasers

In recent years dye lasers operating in the spectral region of 600-750 mn have been of particular interest as they have found applications in photodynamic therapy of 

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In this section the types of dye lasers, the mechanism of lasing as applied to dyes, structural types of laser dyes and a few of the applications of dye lasers will be dis-cussed. ... 

For spectroscopic applications of dye lasers, where the dye laser has to be tuned through a large spectral range, the intensity change, caused by the... 

F. P. Schafer Principles of Dye Laser Operation. -B. B. Snavely Continuous-Wave Dye Lasers. -C V. Shank, E. P. Ippen Mode-Locking of Dye Lasers. -K.H. Drexhage SiniciUTQm6 Properties of Laser Dyes. - T. W. Hansch Applications of Dye Lasers. - FP Schafer Progress in Dye Lasers September 1973 till March 1977. 

Direct determination of the rate of the C- or Y-Dye formation reaction in the individual microdroplets has been made possible by potential application of the laser trapping-spectroscopy-electrochemistry technique. Furthermore, the dye formation reaction efficiency in each droplet could be controlled arbitrarily by the distance between the droplet and the electrode. Under the present experimental conditions (i.e., pH 10 and [SO] ] =20mM), the diffusion length of QDI within its lifetime is only several micrometers, so the distance dependence of the reaction is unique in the micrometer dimension. The present approach will therefore lead to a new methodology to control chemical reaction in micrometer-size volumes. 

In addition to the continuum sources just discussed, line sources are also important for use in the UV/visible region. Low-pressure mercury arc lamps are very common sources that are used in liquid chromatography detectors. The dominant line emitted by these sources is the 253.7-nm Hg line. Hollow-cathode lamps are also common line sources that are specifically used for atomic absorption spectroscopy, as discussed in Chapter 28. Lasers (see Feature 25-1) have also been used in molecular and atomic spectroscopy, both for single-wavelength and for scanning applications. Tunable dye lasers can be scanned over wavelength ranges of several hundred nanometers when more than one dye is used. 

In order to visualize the limits of the application of longer laser pulses for the structuring of a nonabsorbent composite material, a result of ablation experiments on human enamel with a 7-ns dye laser (2=600 nm) is presented in Fig. 29. The lateral ablation precision is unsatisfactory (Fig. 29a). Collagen fiber bundles were disrupted (Fig. 29b). The application of high laser fluences above 20 J cm-2 is necessary to achieve a relatively uncontrolled material removal. The constituents of enamel, water, collagen, and the hydroxyapatite matrix, are practically nonabsorbent for wavelengths in the visible region at 2=600 nm. 

Typical lithographic applications of dye-sensitized photopolymerization today include direct laser imaging of printed wiring boards, based on a visible laser-sensitive resist (Riston LV ) developed by Dupont. ... 

These few numbers illustrate the very different properties of laser systems as they exist today. The laser is,in principle, a light source with fixed and stable frequency. The emission frequency is determined by the optical transition of the laser medium and the frequencies of the modes of the laser resonator. In fact the monochromaticity and the high stability of the frequency is the basis of many spectroscopic experiments with lasers. For this reason systems with high frequency stability have been developed. In addition the spectroscopy requires, however, light sources with tunable frequency. The broad application of lasers for spectroscopy is thus closely related to the development of dye lasers, since this laser provided for the first time coherent light of broadly tunable wavelength. 

Major Applications inks, dye lasers, in manufacture of vinyl polymers, textiles determination of iron, calcium, aluminum, -" tantalum, monitoring hardness in industrial water," measuring chlorine dioxide in drinking water, hypoglycemic agents, nuclear fluorochrome Safety/Toxicity Mutagenicity"... 

Common applications of excimer lasers are their use as pump lasers for tuneable dye lasers, and as light sources in photo-fragmentation experiments (see the chapters in Part 4). 

For spectroscopic applications of multimode lasers one has to keep in mind that the spectral interval Ay within the bandwidth of the laser is, in general, not uniformly filled. This means that, contrary to an incoherent source, the intensity 7(y) is not a smooth function within the laser bandwidth but exhibits holes. This is particularly true for multimode dye lasers with Fabry-Perot-type resonators where standing waves are present and hole burning occurs (Sect. 5.3.4). 

With three-photon spectroscopy, states with the same parity are reached as in single-photon transitions. The advantage is, however, that transitions in the vacuum-ultraviolet region can be excited with visible light [10.79]. Since single-photon laser spectroscopy in this region is impeded by the lack of suitable and easy to handle laser systems, the application of nitrogen laser-pumped dye lasers to Doppler-free three-photon spectroscopy will cer-... 

Thus dye lasers have led to an enormous increase in activity in many areas of atomic physics. In the sections which follow we will briefly discuss the principles of dye laser operation and the construction of some typical laser systems. We will then consider a few of the recent applications of these devices to atomic spectroscopy. Further information on dye lasers and their spectroscopic applications is contained in the excellent collections of review articles edited by Schafer (1973), Walther (1976) and Shimoda (1976). 

Organic colors caused by this mechanism are present in most biological colorations and in the triumphs of the dye industry (see Azinedyes Azo dyes Eluorescent whitening agents Cyanine dyes Dye carriers Dyes and dye intert diates Dyes, anthraquinone Dyes, application and evaluation Dyes, natural Dyes, reactive Polymethine dyes Stilbene dyes and Xanthenedyes). Both fluorescence and phosphorescence occur widely and many organic compounds are used in tunable dye lasers such as thodamine B [81-88-9], which operates from 580 to 655 nm. 

To carry out a spectroscopy, that is the structural and dynamical determination, of elementary processes in real time at a molecular level necessitates the application of laser pulses with durations of tens, or at most hundreds, of femtoseconds to resolve in time the molecular motions. Sub-100 fs laser pulses were realised for the first time from a colliding-pulse mode-locked dye laser in the early 1980s at AT T Bell Laboratories by Shank and coworkers by 1987 these researchers had succeeded in producing record-breaking pulses as short as 6fs by optical pulse compression of the output of mode-locked dye laser. In the decade since 1987 there has only been a slight improvement in the minimum possible pulse width, but there have been truly major developments in the ease of generating and characterising ultrashort laser pulses. 

We have applied FCS to the measurement of local temperature in a small area in solution under laser trapping conditions. The translational diffusion coefficient of a solute molecule is dependent on the temperature of the solution. The diffusion coefficient determined by FCS can provide the temperature in the small area. This method needs no contact of the solution and the extremely dilute concentration of dye does not disturb the sample. In addition, the FCS optical set-up allows spatial resolution less than 400 nm in a plane orthogonal to the optical axis. In the following, we will present the experimental set-up, principle of the measurement, and one of the applications of this method to the quantitative evaluation of temperature elevation accompanying optical tweezers. 

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