Amplified spontaneous emission

A low-threshold, blue amplified spontaneous emission (ASE) in a statistical copolymer from 9,9-dihexylfluorene-2,7-divinylene-m-phenylene vin-ylene and p-phenylene vinylene) and its blend with PVK has been re-ported. PVK and CPDHFPV act as donor and as acceptor of the Forster-type excitation energy transfer, respectively. 

ASE around 400 nm was observed in polymer films of PS and PVK doped up to 20% with the hole-transporting organic molecule TPD. Therefore, these films are promising materials for blue-emitting organic diode lasers. 

Low-dimensional crystals such as epitaxial needles and solution-grown platelets of TPCOs act as a microscale gain medium. The self-cavity and self-waveguiding effects of these crystals result in ASE in the wavelength region of the fluorescence band where the self-absorption loss is minimized. Furthermore, the uniaxial orientation of the TPCO molecules in these low-dimensional crystals promotes the stimulated emission process and enhances the polarized ASE. 

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The chapter is organized as follows in Section 8.2 a brief overview of ultrafast optical dynamics in polymers is given in Section 8.3 we present m-LPPP and give a summary of optical properties in Section 8.4 the laser source and the measuring techniques are described in Section 8.5 we discuss the fundamental photoexcitations of m-LPPP Section 8.6 is dedicated to radiative recombination under several excitation conditions and describes in some detail amplified spontaneous emission (ASE) Section 8.7 discusses the charge generation process and the photoexcitation dynamics in the presence of an external electric field conclusions are reported in the last section. 

Nonpolymeric amorphous dyes for electron transport, some of them containing an oxadiazole ring, were prepared and theoretically studied. It was concluded that reversible electron injections and ejection properties without impurity effects could be obtained for the symmetric and globular amorphous molecules <1997PCA2350>. Amplified spontaneous emission laser spikes were observed for some simple 2,5-diaryl oxadiazoles <1997PCA3260>. 

An alternative way to preform a channeled plasma consists in exploiting the nanosecond precursor that usually precedes a short femtosecond pulse in the output of a multi-terawatt laser system. In fact, the amplified spontaneous emission (ASE) pedestal has typically an intensity 106-1010 times lower than the main pulse, which, however, can be sufficient to ionize a gas-jet or a solid target. This drawback can be turned into a benefit assuming that this long precursor can prepare the plasma channel for the short pulse propagation. 

Figure 3.21. Effective index of TE and TM optical modes in a thin film of spiro-sexiphenyl on a glass substrate at the amplified spontaneous emission (ASE) wavelength. Note the different cutoff thicknesses that determine the number of possible modes for a certain film thickness. 

Films of this material can be optically pumped to induce amplified spontaneous emission at 535 nm, as shown in Figure 14. The lasing threshold (Eth) h the pump energy at which amplified spontaneous emission is observable, and depends strongly, among other factors, upon the lifetime of the polymer excited state. A longer excited state lifetime allows more emissive excitons to build up in... 

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