Visible laser radiation

In a conventional Raman spectrometer (Figure 4.19), a visible laser radiation is used as the source of exciting photons these photons are typically of much higher energies than those of the fundamental vibrations of most chemical bonds or systems of bonds. 

Interaction and Effects of UV IR Laser Radiation on Biologic Tissues Penetration and Effects of UV IR Laser Radiation into Biologic Tissue Effects of Mid-IR Laser Radiation Effects of Near-IR Laser Radiation Effects of Visible-Range Laser Radiation Effects of UV Laser Radiation Effects of Continuous and Pulsed IR-Visible Laser Radiation and Associated Temperature Rise General Description and Operation of Lasers Biomedical Laser Beam Delivery Systems Defining Terms References Further Information... 

Effects of Continuous and Pulsed IR-Visible Laser Radiation and Associated Temperature Rise... 

THE INFLUENCE OF UV AND VISIBLE LASER RADIATION ON LAYERED ORGANIC-INORGANIC NANOCOMPOSITES ZINC AND COPPER... 

In contrast to UV laser radiation, visible laser radiation can be only used for material processing, e.g. drilling, cutting and for welding. [1580]. However, ruby laser radiation can cause the destruction of polymers with crystalline structures [1248]. 

There are several requirements for this to be a suitable deteetion method for a given moleeule. Obviously, tire moleeule must have a transition to a bound, exeited eleetronie state whose wavelength ean be reaehed with tunable laser radiation, and the band system must have been previously speetroseopioally assigned. If the moleeules are fonned with eonsiderable vibrational exeitation, the available speetroseopie data may not extend up to these vibrational levels. Transitions in the visible ean be aeeessed direetly by the output of a tunable dye laser, while transitions in the ultraviolet ean be reaehed by Ifequeney-doubled radiation. The... 

In contrast to the ionization of C q after vibrational excitation, typical multiphoton ionization proceeds via the excitation of higher electronic levels. In principle, multiphoton ionization can either be used to generate ions and to study their reactions, or as a sensitive detection technique for atoms, molecules, and radicals in reaction kinetics. The second application is more common. In most cases of excitation with visible or UV laser radiation, a few photons are enough to reach or exceed the ionization limit. A particularly important teclmique is resonantly enlianced multiphoton ionization (REMPI), which exploits the resonance of monocluomatic laser radiation with one or several intennediate levels (in one-photon or in multiphoton processes). The mechanisms are distinguished according to the number of photons leading to the resonant intennediate levels and to tire final level, as illustrated in figure B2.5.16. Several lasers of different frequencies may be combined. 

From the Heisenberg uncertainty principle as stated in Equation (1.16) estimate, in cm and Hz, the wavenumber and frequency spread of pulsed radiation with a pulse length of 30 fs, typical of a very short pulse from a visible laser, and of 6 ps, typical of pulsed radiofrequency radiation used in a pulsed Fourier transform NMR experiment. 

The first, and still the most commonly used, of the tunable lasers were those based upon solutions of organic dyes. The first dye laser was developed by Sorokin and Lankard 05), and used a "chloro-aluminum phthalocyanine" (sic) solution. Tunable dye lasers operating throughout the visible spectrum were soon produced, using dyes such as coumarins, fluorescein, rhodamines, etc. Each dye will emit laser radiation which is continuously tunable over approximately the fluorescence wavelength range of the dye. 

Enhancement of x2 will lead to improvement (in terms of efficiency per interaction volume) in the following applications up-conversion in the visible or near U.V. of powerful I.R. laser radiation, frequency modulation of a laser carrier beam, optical parametric oscillation and amplification for solid state infrared tunable coherent devices. 

Frequency Doubling. As the name implies, in frequency doubling a substance doubles the frequency of the incident laser radiation. This effect is important in telecommunications and optical data storage. For example, in telecommunications the most efficient way to transmit data is by using infrared radiation, e g., 1200 nm radiation from an indium phosphide laser [60], Detection of infrared radiation is inefficient. In contrast, visible radiation is much easier to detect but is an inefficient transmitter of data. Consequently, an important application of nonlinear optical (NLO) materials is to convert infrared radiation into visible and thus enable easier detection of the signal. 

Pulsed lasers such as Nd YAG and excimer lasers are commonly used for the pump-probe experiment just mentioned. Some characteristics of these lasers are listed in Table 3-1. Although the fundamental of the Nd YAG laser is at 1,064 nm, this frequency can be multiplied by using nonlinear crystals, such as KDP (potassium dideuterium phosphate), to obtain the second (532 nm), third (355 nm) and fourth (266 nm) harmonics. Furthermore, a wide range of UV-visible pulsed radiation can be generated from th se harmonics by pumping a dye laser or using a Raman shifter (Sectior 2.2.5). 

Karu TI, Tiphlova OA, Matveyets YA, Yartsev AP, Letokhov VS. Comparison of the effects of visible femtosecond laser pulses and continuous wave laser radiation of low average intensity on the clonogenicity of Escherichia coli. J Photochem Photobiol B Biol 1991 10 339. 

The laser radiates various kinds of radiations from infrared to visible and ultraviolet. These are coherent rays with very high, focused energy. This power can be very dangerous to the human eye or skin if not used properly. 

Effects of CO2 laser radiation on CH4-SFg mixtures. 596 Visible luminescence observed characteristic of fluorine-supported flames... 

GW cm ) pulsed CO2 laser radiation shown to result in broad u.v.-visible chemiluminescence Measurement of time-resolved emission spectra in the 618 2—5 p,m region following CO2 laser irradiation of CDF, and mixtures of CDF3-CHF,. Emission from vibrationally excited CDF, and DF observed, the latter being produced in the IRMPD of CDF,... 

Fig. 11. Experimental setup for the in situ detection of chemisorbed CO during catalytic combustion of CO on Pt using optical infrared-visible sum frequency generation (SFG) and mass spectrometry. A mode-locked Nd YAG laser system is used to provide the visible laser beam (second harmonic 532 nm) and to pump an optical parametric system to generate infrared radiation (wir) tunable with a pulse duration of 25 ps. MC monochromator, PMT Photomultiplier, AES Auger Electron Spectrometer, LEED Low Energy Electron Diffraction Spectrometer, QMS Quadrupole Mass Spectrometers for CO Thermal Desorption (TD) and CO2 production rate measurements.

---