Polymer laser diodes

Polymer laser diodes have been an attractive topic after the discovery of EL in conjugated polymers. Optical lasing in semiconducting luminescent polymer solutions was first... 

The use of conjugated light emitting polymers in the construction and commercialisation of organic LEDs is described in the section 3.8.6 on electroluminescence phenomena of Chapter 3. The rapid expansion of the development work on LEDs has inevitably led to the examination of luminescent conjugated polymers as materials for constructing laser diodes. 

Reviews addressing specifically poled polymers for frequency doubling of a laser diode have been published emphasizing the different material aspects and potential phase matching techniques [9]. The best materials available at that time were also reviewed. There has also been a more general, recent review specifically concerned with the work performed in Japan and addressing the question of materials and phase-matching techniques [10]. 

A more direct route to making polymer lasers would be to excite the polymers electrically in a diode structure. Although polymer LEDs have been made in which the injected carrier density matches the threshold excitation density of the best photopumped polymer lasers, a polymer diode laser has not yet been made. The threshold for diode lasers is higher because the electrodes that must be incorporated to the structure increase the waveguiding loss. In addition, for some... 

After these initial and promising lateral-force results, the friction force microscopy (FFM) was introduced. The FFM is a modified SFM with a four-quadrant photodiode, based on the laser beam deflection technique (Meyer Amer 1988) (Fig. 2.17). The beam is emitted by a low-voltage laser diode and reflected from the rear side of the cantilever to the four-quadrant photodiode. With this detection scheme, normal and torsional forces can be measured simultaneously. The torsional forces correspond to the lateral forces measured with the instrument of Mate et al. (1987). In 1993, Ovemey introduced the threefold measurement of topography, friction and elasticity on a polymer sample using an ITM. With this latest achievement, a wide spectram of tribological information was opened up, limited only by the lattice parameters of the sample. 

Phenylene-based polymers are one of the most important classes of conjugated polymers, and have been the subject of extensive research, in particular as the active materials in light-emitting diodes (LEDs) [1,2] and polymer lasers [3]. These materials have been of particular interest as potential blue emitters in such devices [4], The discovery of stable blue-light emitting materials is a major goal of research into luminescent polymers [5]. Poly(para-phenylene) (PPP, Scheme 1, 1) is a blue emitter [6], but it is insoluble and so films of PPP have to be prepared via precursor routes [7]. Substitution with long alkyl... 

The near-infrared laser diode has a maximum laser output of 100 mW. The short laser pulse widths utilized, the low laser power levels required, the absorption of the laser pulse by the polymer and dye, and the long elapsed time between laser pulses combine to prevent the experimenter from depositing any significant amount of heat at the tissue surface, which may affect later laboratory analysis. The Class IV UV cutting laser, on the contrary, ablates the cells in the vicinity of the laser pulse. The UV cutting tool is designed for microdissection of larger... 

One of the most fascinating developments in recent times concerns the generation of light with the aid of polymers. This development is characterized by two inventions, which are described in the following subsections the polymeric light-emitting diode and the polymer laser. 

A potential application of polymer laser ablation concerns the propulsion of small satellites (1-10 kg) used in space science [86]. Laser plasma thrusters, LPTs, operating with small, powerful diode lasers emitting in the near-infrared wavelength range (930-980 nm) have been proposed. Polymers intended to serve as fuel for a thruster are required to possess a large momentum coupling coefficient, C, defined by Eq. (9-3) ... 

In materials science we often divide materials into distinct classes. The primary classes of solid materials are ceramics, metals, and polymers. This classification is based on the types of atoms involved and the bonding between them. The other widely recognized classes are semiconductors and composites. Composites are combinations of more than one material and often involve ceramics, such as fiberglass. Semiconductors are materials with electrical conductivities that are very sensitive to minute amounts of impurities. As we will see later, most materials that are semiconductors are actually ceramics, for example, gallium nitride, the blue-green laser diode material. 

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