Laser light characteristics

The following laser light characteristics play a key part in both these approaches. 

The importance of laser light, in brief, is tliat its base characteristics, coherence, spectral and polarization purity, and high brilliance allow us to manipulate its properties. Gain switching [i, 10] and mode locking [16] are prime examples of our ability to very specifically control tire laser output. It is easy to see why lasers are tire ideal sources for optoelectronic applications. 

Figure 10-15. Output vs. input energy characteristic of our laser device. The horizontal dashed curve indicates the zero line. A clear laser threshold behavior at an excitation pulse energy ol 1.5 nJ is observed. Below the lasing threshold only isotropic phololuminesccncc is entitled. Above threshold the device emits low divergence single mode laser emission perpendicular to the surface, as schematically shown in the inset. The laser light is polarized parallel to the grating lines.

At the moment, one recommends to determine the molecular characteristics of pectins using SEC chromatography equipped with a differential refractometer, a multiangle laser light scattering detector and a viscometer as previously described [25]. This technique needs no calibration with the usual molecular weight standards such dextrans and pullulans... 

Figure 14 Most characteristic small-angle laser light scattering patterns (Hv) observed with linear polyethylene fractions. Reproduced by permission of The Royal Society of Chemistry from Ref. [224].

The most obvious characteristics of laser light are its brightness, its spectral purity, and the directionality of the beam. It is not so obvious how extreme these properties are. It has been pointed out ( 7) that a one-milliwatt He-Ne laser, virtually a toy laser, is 100 times brighter than the surface of the sun in terms of luminous intensity per unit area. Considering only light at the laser wavelength of 632.8 nm, the laser is 2 x 10 times brighter than the sun ... 

Describe the mode of action of a laser and the characteristic properties of laser light. 

Determination of changes in the absorbance (AA) of a solution of the complex containing a quencher can be investigated when a pulse of laser light excites Ru(bpy)j+. The principal spectral characteristics of the complex and its derived transient species are given in Table 10.3. 

It is already a fact that lasers are replacing conventional lamps in a great variety of spectroscopic applications. The origin of this substitution lies in their superior performance over incoherent light in many experimental situations. Many spectroscopic experiments have been improved, and moreover new techniques have been developed due to the particular advantages provided by lasers. The characteristics of laser radiation on their own constitute real advantages and justify their widespread use in many applications. 

The intensity of Rayleigh scattering is on the order of 10 times the intensity of the incident light, and the Raman intensities are at least 10 less than that of the Rayleigh scatter. Thus, the Raman effect is obviously a weak phenomenon which requires a high intensity monochromatic excitation source (a laser) and a high dispersion spectrometer with excellent stray-light characteristics to observe it. 

Contents Spectroscopy with Lasers Introduction. Characteristic Features of Lasers as Spectroscopic light Sources. Spectroscopic Applications of Lasers. High-Resolution Spectroscopy Based on Saturation Effects. Spectroscopy of Laser Media. Conclusion. Zusammen-fassung. (418 references). 

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