Laser-like emissions

One of the practical advantages of ASE and quasi-laser-like emissions of powders is that such an emission has been shown to be spatially incoherent while it is still temporally coherent (coherence time 8 ps) this is due to the macroscopic diffiise nature of the powder medium (Gouedard et al. 1993). Figure 14 shows streak camera spatio-temporal pictures of powder emission, and of a YAG Nd laser for comparison. We cleariy see temporal modulations of the emission that are due to the beating of modes the spatial speckle pattern does not change with time. This stationary pattern is the signature of the temporal space i... 

The above discussion allows concluding that that the remarkable improvement observed in the laser performance of dye-doped POSS systems is a direct consequence of scattering processes. Under defined experimental conditions, the dye-laser action is enhanced by stimulated emission build up in the gain direction by the elongated photon path length inside the gain media with scatterers. The laser-like emission adds up... 

Similar mirrorless laser-like emission was observed for silica inverse opals infiltrated with rhodamine 6G [105]. Figure 30.15 shows the latex opal obtained... 

A locally resolved detection of radioactive samples after chromatographic separation can be performed by imaging techniques which work either indirectly with Eu3+- or P-doped sensor plates and laser activated emission or directly by a micro channel array detector which works like an open Geiger-Muller counter. 

The time-resolved fluorescence spectroscopic approach is very fruitful in elucidating electronic and molecular aspects of laser ablation of fluorescent polymers. While a plasma-like emission and fluorescence behavior of ablated radicals have been reported (21,... 

Only excimer emissions were observed during laser pulse, a broad plasma-like emission was detected later, and fragmented radicals became distinct. Ablation behavior can be interpreted in terms of photophysical and photochemical processes, including Si - Si annihilation. 

There exists a large variety of spectroscopic techniques that employ ultra-short laser pulses. These methods may differ, for example, in the detection mechanism and in the number and properties of laser fields, and will in general monitor different aspects of the dynamics of the molecular system. Most of these experiments are of the pump-probe (PP) type, that is, the molecular system is prepared by a first laser pulse (the pump ) into a nonstationary state, the time evolution of which is interrogated by a time-delayed second laser pulse (the probe ). It is important to distinguish between resonant and nonresonant electronic excitation of the system. In the latter case, it is not possible to establish a population in the excited electronic state which survives the duration of the pump field. As a consequence, nonresonant excitation gives only rise to Raman-like emission, which is known... 

---