Superradiant lasers

SuperPro software, 26 1040 Superradiant lasers, 14 690 Supersensitization, 9 510 Supersoft copolymers, 26 538, 540 Super spring copper alloys, 7 723t Superstructure, creating and optimizing, 20 726-728... 

Shamrakov D., Reisfeld R. Superradiant laser operation of red Perylimide Dye doped silica-polymethylmethacrylate composite. Chem. Phys. Lett. 1993 213 47-54 Shamrakov D., Reisfeld R. Super radiant film laser operation of perylimide dyes doped silica-polymethylmethacrylate composite. J. Opt. Mater. 1994 4 103-106 Sorek Y., Reisfeld R., Finkelstein I., Ruschin R. Sol-gel glass wave guides prepared at low temperature. Appl. Phys. Lett. 1993 63 3256-3258... 

Introduction. - Fundamental Physical Applications of Laser Spectroscopy. - Two and Three Level Atoms/High Resolution Spectroscopy. - Rydbeig States. - Multiphoton Dissociation, Multiphoton Excitation. - Nonlinear Processes, Laser Induced Collisions, Multiphoton Ionization. - Coherent Transients, Time Domain Spectroscopy, Optical Bistability, Superradiance. - Laser Spectroscopic Applications. - Laser Sources. - Postdeadline Papers. - Index of Contributors. 

Laser A source of ultraviolet, visible, or infrared radiation which produces light amplification by stimulated emission of radiation from which the acronym is derived. The hght emitted is coherent except for superradiance emission. 

Nitrogen laser A source of pulsed semi-coherent superradiance mainly around 337 nm. The lasing species is molecular nitrogen. 

Superradiance Spontaneous emission amplified by a single pass through a population inverted medium. It is distinguished from trae laser action by its lack of coherence. The term superradiance is frequently used in laser technology. 

It is somewhat difficult to compare these predictions with experimental results since no really systematic experimental study has yet been published. This is due in part to difficulties in preparing mixtures of H2 and Fa of any desired composition and pressure and also to experimental limitations in the sufficiently rapid initiation of the pumping reaction. However, as far as the experimental information goes, it can be concluded that the efficiency is considerably lower than expected. For instance, in flash photolysis-initiated HF lasers a chemical efficiency of below 1% is usually found 101>. Two suggestions may be made to explain this discrepancy. One may look at it as either a chemical rate problem or a laser problem. In the first case, some unknown rate process must be assumed to reduce the build-up of excited HF. Since the formation and deactivation rates are known with some accuracy, this could only be excessive recombination or an unusually high rate of the reverse reaction 102>. Alternatively, parasitic oscillations or superradiance have been claimed to cause radiation losses in off-axis... 

If a second laser pulse that has the proper intensity and duration to invert the phase of the induced polarization (tt-pulse) is applied to the sample at a time = T < Ti, it causes a reversal of the phase development for each dipole (Fig. 7.20d-f). This means that after a time U = 2T all dipoles are again in phase (Fig. 7.20f). As discussed above, while these excited atoms are in phase they emit a superradiant signal at the time t = 2T that is called photon echo (Fig. 7.21). 

Amplified Spontaneous Emission Superradiance and Superfiuorescence Cavity-Based Lasers Random Lasers Experimental Setup for Studying Laser Action... 

Processes 1-3 and 5 occur without the necessity of optical feedback (or mirrors), and thus have been termed as mirrorless lasing [111]. Processes 2—5 are also coherent, whereas ASE is not. In addition, processes 2 and 3 are examples of cooperative emission, whereas ASE is a collective emission process. The superradiance process is very. similar to the SF laser action process, except that in superradiance the system is prepared coherently from t= 0, whereas in SF the system evolves in time to be coherent at t > 0 [111]. 

Amplifier A device used to increase the amplitude of some input signal. The term superradiant amplifier is often used to describe a free-electron laser that is configured to amplify noise (i.e., random fluctuations) in the beam rather than an externally supplied signal. In contrast to oscillator configurations, there is no reflection of the signal, and the superradiant amplifier is a single-pass device. 

So the first example of real superradiance was in fact the free induction decay and die decay of the photon echo observed in ruby by Kumit, Abella and Hartmann (1964). When a pulse from a ruby laser was sent onto a ruby crystal, the free induction decay and the echo decay observed were about 50 ns, when compared to the usual Cr " radiative decay time of 4 ms, showing clearly the radiation emission from the macro-dipole. 

Auzel s chapter on coherent emission is different from many reviews on the subject, which are concerned with the laser effect itself, in that he concentrates on the broader issues. The emphasis of chapter 151 is on superradiance, superfluorescence, amplification of spontaneous emission by other stimulated emission than the laser effect, and coherent spontaneous emission. Also discussed are up-conversion by energy transfer, up-conversion by the avalanche effect, and recent advances in lanthanide lasers and amplifiers. 

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