Ruby laser radiation

The formation amd dissociation of K, Rb, amd Cs by ruby laser radiation has been reported. ... 

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]. 

Pumping is with a flashlamp, as in the case of the ruby laser, and a pulse energy of the order 1 J may be achieved. Frequency doubling (second harmonic generation) can provide tunable radiation in the 360-400 nm region. 

A series of papers by. Menichelli Yang (Refs 82, 84 86) showed that Q-switched ruby lasers could initiate steady detonation in PETN (and RDX or Tetryl) in <0.5 psec when a lOOOA-thick Al layer was deposited on the face of the sample, and subsequently exposed to laser radiation of 0.5 to 4.2 J with a pulse width of 25nanosec... 

Figure 15.3. Radiation wavelengths of the sun, an LED, a ruby laser, and a tungsten lamp.

Lasers produce spatially narrow and very intense beams of radiation, and lately have become very important sources for use in the UV/VIS and IR regions of the spectrum. Dye lasers (with a fluorescent organic dye as the active substance) can be tuned over a wavelength range of, for instance, 20-50 nm. Typical solid-state lasers are the ruby laser (0.05% Cr/Al203 694.3 nm) and the Nd YAG laser (Nd3+ in an yttrium aluminium garnet host 1.06 pm). 

Lasers are devices for producing coherent light by way of stimulated emission. (Laser is an acronym for light amplification by stimulated emission of radiation.) In order to impose stimulated emission upon the system, it is necessary to bypass the equilibrium state, characterized by the Boltzmann law (Section 9.6.2), and arrange for more atoms to be in the excited-state E than there are in the ground-state E0. This state of affairs is called a population inversion and it is a necessary precursor to laser action. In addition, it must be possible to overcome the limitation upon the relative rate of spontaneous emission to stimulated emission, given above. Ways in which this can be achieved are described below, using the ruby laser and the neodymium laser as examples. 

The optical features of a center depend on the type of dopant, as well as on the lattice in which it is incorporated. For instance, Cr + ions in AI2O3 crystals (the ruby laser) lead to sharp emission lines at 694.3 nm and 692.8 nm. However, the incorporation of the same ions into BeAl204 (the alexandrite laser) produces a broad emission band centered around 700 nm, which is used to generate tunable laser radiation in a broad red-infrared spectral range. 

Polymerization of styrene and p-isopropylstyrene could be photo-initiated with radiation from the ruby laser in the absence of photosensitizers and oxygen Since ordinarily no unsensitized photoinitiation of styrene is detected for wavelengths longer than 4000 A, the results of this experiments must be due to two-photon processes. 

Using as the background continuum the short-lived spontaneous fluorescence of rhodamine B or 6 G, McLaren and Stoicheff 233) developed this method further to obtain inverse Raman spectra over the range of frequency shifts 300-3500 cm" in liquids and solids in a time of 40 nsec The stimulating monochromatic radiation at 6940 A is provided by a giant-pulse ruby laser. A small part of the main laser beam is frequency-doubled in a KDP-crystal and serves to excite the rhodamine fluorescence, thus ensuring simultaneous irradiation of the sample by both beams. 

Amplification by Stimulated Emission of Radiation . (Similar devices producing coherent beams of microwave radiation are known as masers) A typical arrangement for a pulsed ruby laser is depicted in Figure 8.5. 

In phosphors and in the ruby laser, light was absorbed and emitted by electrons localised on an impurity site, but in other optical devices, delocalised electrons emit the radiation. In the next section, therefore, we shall consider the absorption and emission of radiation in solids with delocalised electrons, particularly in semiconductors. 

A continuous laser operates by continually pumping atoms or moie-cules into the excited state from which induced decay produces a continuous beam of coherent radiation. The He—Ne laser is an example of continuous system. Another mode of operation is to apply an energy pulse to the system, exciting a considerable fraction into the excited state. When all these molecules or atoms are induced to decay simultaneously, intense but exteremely short pulse of coherent radiation is emitted. The ruby laser falls in this category. 

Three important papers, published at about the same time in 1966, demonstrated very dramatically the usefulness of lasers in the measurement of molecular energy transfer. The first of these, by DeMartini and Ducuing [137], reports a study of vibrational relaxation in normal H2 using stimulated Raman scattering. The experimental arrangement is shown in Figure 3.16. Radiation from a -switched ruby laser was focused onto a pressure cell of H2 gas at room temperature to produce about IO16 vibrationally excited H2 molecules in a period of about 20 nsec. This excess population distribution... 

Ruby laser A pulsed source of coherent radiation emitting mainly at 694.3 nm from chromium ions (Cr ) in aluminum oxide. 

However, sapphire may contain chromium as an impurity (from earlier production of ruby laser material at the same place). The sapphire spectrum in Fig. 3.5-17c shows such a continuum it is not displayed by extremely pure sapphire. Sapphire which is contaminated with chromium shows - when irradiated by the radiation of an argon ion la.ser at 488 or 515 nm - the typical ruby lines at 694 nm. 

Figure 6.8-9 Schematic representation of the Stokes-/anti-Stokes rotational line intensities of N2 at different temperatures generated by radiating a ruby laser with Ap = 694.3 nm.

---