Ruby lasers

pp 40-2 Chemical Laser Efforts Broaden Scope of Laser Research  

An experimental Laser-pump usin g a ball of light to bathe a Laser rod from all directions has been developed at the Westinghouse Research Laboratories. In this device the Laser rod and lamp are placed along the center of a hollow spherical reflector, the entire inside surface of which is reflecting 

A portable neodymium Laser has been produced by the Photon Systems Department of Space Ordnance Systems, Inc, El Segundo, California. This device named Macro-Pak is claimed by the Co as a break-through in both size and simplicity and provides a truly portable working Laser-head and power supply. The device is only 140 cu inches in size and weighs 6 lbs. It emits a wave length of 1.06 microns, producing a maximum output of 5 joules] 

9) American Optical Co, Space-Defense Division, Laser Products Department, South-bridge, Mass, 01550, announced in their News Release , published in 1968, the development of UNI-LASER , claimed to be the lowest cost - longest operating 

The gain (Ref 1, pp 12-13) is a function of the frequency corresponding to the interlevel energy difference, and increases exponentially with lengthening of the cavity, with increase in the number of active atoms (density) in it, and with decrease in the temperature 

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An interferometric method was first used by Porter and Topp [1, 92] to perfonn a time-resolved absorption experiment with a -switched ruby laser in the 1960s. The nonlinear crystal in the autocorrelation apparatus shown in figure B2.T2 is replaced by an absorbing sample, and then tlie transmission of the variably delayed pulse of light is measured as a fiinction of the delay This approach is known today as a pump-probe experiment the first pulse to arrive at the sample transfers (pumps) molecules to an excited energy level and the delayed pulse probes the population (and, possibly, the coherence) so prepared as a fiinction of time. 

Ruby Laser. Ruby (essentially alumina) owes its well-known color to the presence of very small proportions of chromium ions (Cr +) distributed through it. Ruby lasers do not use natural rubies because of the imperfections they contain. Instead, synthetic single crystals of chromium... 

Neodymium and YAG Lasers. The principle of neodymium and YAG lasers is very similar to that of the ruby laser. Neodymium ions (Nd +) are used in place of Cr + and are often distributed in glass rather than in alumina. The light from the neodymium laser has a wavelength of 1060 nm (1.06 xm) it emits in the infrared region of the electromagnetic spectrum. Yttrium (Y) ions in alumina (A) compose a form of the naturally occurring garnet (G), hence the name, YAG laser. Like the ruby laser, the Nd and YAG lasers operate from three- and four-level excited-state processes. 

Figure 9.6 (a) Low-lying energy levels of in ruby, (b) Design for a ruby laser... 

The efficiency of a ruby laser is less than 0.1 per cent, typically low for a three-level laser. 

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. 

Despite the fact that the first laser to be produced (the ruby laser. Section 9.2.1) has the remarkable property of having all its power concentrated into one or two wavelengths, a property possessed by most lasers, it was soon realized that the inability to change these wavelengths appreciably, that is to tune the laser, is a serious drawback which limits the range of possible applications. 

Laser action involves mainly the 3/2 hi/i transition at about 1.06 pm. Since is not the ground state, the laser operates on a four-level system (see Figure 9.2c) and consequently is much more efficient than the ruby laser. 

AI2O3 (aluminium oxide) in ruby laser, 346 in titanium-sapphire laser, 348 3142 (cyclic) interstellar, 120 3142 (linear) interstellar, 120... 

CH3I (methyl iodide) principal axes, 103 If rotation, 113 CH2NH (methanimine) interstellar, 120 Cr203 (chromium trioxide) in alexandrite laser, 347ff in ruby laser, 346ff HC3N (cyanoacetylene) interstellar, 120 HCOOH (formic acid) interstellar, 120 NH2CN (cyanamide) interstellar, 120... 

Ruby laser Ruby red glass Ruetschi vacancy model... 

Ruby lasers are frequently operated in the normal pulse mode, ie, pulse durations are around 1 ms and pulse energy up to tens of joules, or in the... 

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... 

Capellos and Suryanarayanan (Ref 28) described a ruby laser nanosecond flash photolysis system to study the chemical reactivity of electrically excited state of aromatic nitrocompds. The system was capable of recording absorption spectra of transient species with half-lives in the range of 20 nanoseconds (20 x lO sec) to 1 millisecond (1 O 3sec). Kinetic data pertaining to the lifetime of electronically excited states could be recorded by following the transient absorption as a function of time. Preliminary data on the spectroscopic and kinetic behavior of 1,4-dinitronaphthalene triplet excited state were obtained with this equipment... 

CA 73,100610 (1970) A pulsed ruby laser-mass spectrometry technique was developed and applied, wherein granular mixts of AP and lightabsorbing substrate materials were rapidly flash py roly zed (0.8 msec) within the low-pressure lon-source chamber of a Bendix TOF mass... 

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

Ruby lasers use crystals of AI2O3. The crystals contain small amounts of Cr ions, which absorb light... 

A surprising observation was made in the first experiments on the flash photolysis of CdS and CdS/ZnS co-colloids Immediately after the flash from, a frequency doubled ruby laser (X = 347.2 nm photon energy, = 3.57 eV) the absorption spectrum of the hydrated electron was recorded. This species disappeared within 5 to 10 microseconds. More recent studies showed that the quantum yield increased... 

Transient signals are not observed when a pure Ti02 sol is illuminated with a flash from a frequency doubled ruby laser (A, = 347,1 nm). The charge carriers seem to... 

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). 

But the next year, in 1960, Ted Maiman built the first laser, the ruby laser. He did that work at Hughes, and I ll ask you to note, now, as we moved from the ideas to its being a hot field with everybody interested, that... 

The first laser Raman spectra were inherently time-resolved (although no dynamical processes were actually studied) by virtue of the pulsed excitation source (ruby laser) and the simultaneous detection of all Raman frequencies by photographic spectroscopy. The advent of the scanning double monochromator, while a great advance for c.w. spectroscopy, spelled the temporary end of time resolution in Raman spectroscopy. The time-resolved techniques began to be revitalized in 1968 when Bridoux and Delhaye (16) adapted television detectors (analogous to, but faster, more convenient, and more sensitive than, photographic film) to Raman spectroscopy. The advent of the resonance Raman effect provided the sensitivity required to detect the Raman spectra of intrinsically dilute, short-lived chemical species. The development of time-resolved resonance Raman (TR ) techniques (17) in our laboratories and by others (18) has led to the routine TR observation of nanosecond-lived transients (19) and isolated observations of picosecond-timescale events by TR (20-22). A specific example of a TR study will be discussed in a later section. 

A rather specialized emission source, which is applicable to the study of small samples or localized areas on a larger one, is the laser microprobe. A pulsed ruby laser beam is focused onto the surface of the sample to produce a signal from a localized area ca. 50 pm in diameter. The spectrum produced is similar to that produced by arc/spark sources and is processed by similar optical systems. 

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 first laser produced was the ruby laser, invented in 1960. Rubies are crystals of aluminum oxide (corundum, AI2O3), containing about 0.5% chromium ions Cr3+, as substitution impurities, CrA, and laser action, as well as color, is entirely due to these... 

Figure 9.21 Ruby laser (a) main transitions responsible for the color of ruby and (b) the main transitions responsible for laser action.

Double-pulse ruby laser, 14 697-698 Double refraction, 14 675 Double salts, lanthanide, 14 633-634 Double-stranded DNA viruses, 3 135... 

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