Pulsed laser action

In a somewhat similar approach 288, the flash initiated reaction of Cl2 with HI gives pulsed laser action with inversion produced by the reaction... 

In this work we compare the results of investigation of nanosecond pulsed laser action on Ge/Si heterostructures with different depths of QD occurrence. Raman spectroscopy was used to study the nanocluster states before and after laser irradiation. The numerical simulation of laser-induced thermophysical processes in the samples was carried out. 

Pulsed laser action is observed from several fluorescing levels at 300 K and lower temperatures. Absorption bands are intense but few in number for broadband pump sources, hence the thresholds are high. The shortest wavelength rare earth laser demonstrated is the Po-> H4 transition of Pr in PrCb (German et al, 1973). 

Only pulsed laser action at reduced temperatures has been observed from Eu. There are no intense absorption bands in the visible. For efficient utilization of the higher-lying pump bands, a rapid nonradiative cascade through the D levels is necessary to minimize fluorescence losses. Emission cross sections are small. 

Very recently pulsed laser action in the ultraviolet from excimer states of several rare gas monohalides has been reported. Laser wavelengths from 1930 to 3530 A are observed from 1 /2 transitions connecting the lowest... 

In 1991 a remarkable discovery was made, accidentally, with a Tp -sapphire laser pumped with an Ar+ laser. Whereas we would expect this to result in CW laser action, when a sharp jolt was given to the table supporting the laser, mode locking (Section 9.1.5) occurred. This is known as self-locking of modes, and we shall not discuss further the reasons for this and how it can be controlled. One very important property of the resulting pulses is that they are very short. Pulse widths of a few tens of femtoseconds can be produced routinely and with high pulse-to-pulse stability. Further modification to the laser can... 

Compact and stable devices are available that take advantage of the improved quality of the crystal lasers, as well as increased pump efficiencies. Hundreds of different models of Nd + based lasers have demonstrated laser action (Kaminskii, 1981). It is possible to operate these Nd + solid state lasers in the continuous regime, with output powers ranging from 1 W to 1000 W. Pulsed operation is also possible, with a pulse length from the picosecond range, via mode-locking, to tens of nanoseconds by Q-switch operation. 

Examples of the optical pumping of solutions of luminescent conjugated polymers include laser action at 596 nm of poly[2-methoxy-5-(2-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) using excitation with 6 ns Nd YAG third harmonic pulses (354.7 nm). ° Tuning of hexane solutions of the co-polymer poly(2,2, 5,5 -tetraoctyl-p-terphenyl-4,4 -xylene-vinylene-p-phenylenevinylene) (TOP-PPV) was possible between 414 and 456 mn, similar to the classical coumarin laser dyes. ... 

In these new laser materials, unlike all others, there is no upper energy level involved no initial excitation to upper energy levels is required. However, very strong incident or "pumping light is needed to initiate laser action. Such pumping can be provided with a high-power, short-pulse ruby laser (Ref 6)... 

The use of strong fields to drive the dynamics leads to somehow similar effects than those of ultrafast pulses. If the Rabi frequency or energy of the interaction is much larger than the energy spacing between adjacent vibrational states, a wave packet is formed during the laser action. The same laser can prepare and control the dynamics of the wave packet [2]. Both short time widths and large amplitudes can concur in the experiment. However, the precise manipulation of dynamic observables usually becomes more difficult as the duration of the pulses decreases. 

The advent of fs pulse lasers recently opened new perspectives for asymmetric photochemistry. The elaboration of this field still is in the theoretical realm. Pulse sequence [125,126] and coherence [127] scenarios are set up for chiral molecular products from achiral precursors. If, for example, phosphinothiotic acid H2PO(SH) molecules are preoriented, which can be effected by laser action, and a special sequence of cpl pulses is used, then the theoretical prediction is that the l enantiomer is transformed to the r enantiomer, but the reverse process is suppressed and vice versa for a different pulse sequence [125]. Chapter 2 of this book is dedicated to these coherent phenomena controlling asymmetric photoreactions. 

The only nonhydride molecule to have been excited directly to chemical laser action is CO. When mixtures of CS2 + Oa are flash photolyzed [236, 237], or subjected to a pulsed electrical discharge [238], oscillation occurs on vibration-rotation lines in a wide range of CO fundamental bands. Infrared emission experiments [239, 240] have established that the reaction mechanism is... 

When optically pumped with a pulsed Ne laser at 540 nm, the rhodamine exhibited laser action at a wavelength determined by the... 

OPTICAL GAIN SPECTRA AND LASER ACTION OF InGaN/GaN MQWs GROWN ON SILICON AT PUMPING BY FEMTOSECOND PULSES... 

Optical gain spectra and laser action of InGaN/GaN MQWs grown on silicon at pumping by femtosecond pulses. 

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