Pronounced 10(4)-fold enhancement of Raman scattering has been obtained for ZnO nanocrystals on substrates coated with 50 nm Ag nanoparticles under nonresonant excitation with a commercial red-emitting laser. This makes feasible beyond 10(-18) mole detection of ZnO nanocrystals with a commercial setup using a 0.1 mW continuous wave laser and can be purposefully used in analytical applications where conjugated nanocrystals serve as Raman markers. For Au-coated surfaces the enhancement is much lower and the heating effects in the course of Raman experiments are pronounced.

Plasmon-exciton coupling is of great importance to many optical devices and applications. One of the coupling manifestations is plasmon-enhanced fluorescence. Although this effect is demonstrated in numerous experimental and theoretical works, there are different particle shapes for which this effect is not fully investigated. In this work electrostatic complexes of gold nanorods and CdSe/CdZnS quantum dots were studied. Double-resonant gold nanorods have an advantage of the simultaneous enhancement of the absorption and emission when the plasmon bands match the excitation and fluorescence wavelengths of an emitter. A relationship between the concentration of quantum dots in the complexes and the enhancement factor was established. It was demonstrated that the enhancement factor is inversely proportional to the concentration of quantum dots. The maximal fluorescence enhancement by 10.8 times was observed in the complex with the smallest relative concentration of 2.5 quantum dots per rod and approximately 5 nm distance between them. Moreover, the influence of quantum dot location on the gold nanorod surface plays an important role. Theoretical study and experimental data indicate that only the position near the nanorod ends provides the enhancement. At the same time, the localization of quantum dots on the sides of the nanorods leads to the fluorescence quenching.

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A system of radiative transfer equations is used to calculate the loss coefficient for amplified luminescence fluxes propagating along and transverse to the cavity axis in the active layer of high-power laser diode arrays taking the spreading of charge carriers in the cladding and contact layers of InGaAs/GaAs/AlGaAs heterostructures into account. It is shown that the spreading of charge carriers leads to a significant change in the amplified luminescence flux which can contribute up to 18% to the lasing threshold of these laser diode arrays. The calculated loss coefficients can greatly simplify the determination of the amplified luminescence fluxes in laser diode arrays with an error of less that 16% and can be used to determine how much the amplified luminescence affects the power and dynamic characteristics of diode arrays.Introduction. High-power laser diode arrays (LDAs) are coming into ever wide use as compact, highly efficient sources of optical excitation for solid state lasers [1][2][3]. Reducing the energy demand by these emitters requires optimization of the parameters of the LDAs, as well as of the solid state lasers. The power of modern LDAs used as pumps is approaching 80-150 W [1, 4]. These relatively high LDA powers have been achieved by substantial increase in the length of the cavities and the total widths of the heterostructure lasing elements. In most cases of practical interest, the LDA is characterized by a relatively high area of the active layer of the laser heterostucture. Thus, it is to be expected that, in accordance with [5-10], intense fluxes of amplified luminescence should develop in the active layers of LDAs; these result in an increase in the threshold and a reduction in the laser output power. It has been shown [5, 6, 8-10] that the AL fluxes for single laser diodes (with a single emitting region, or strip contact) can be analyzed by introducing an AL loss coefficient α lum determined from the balance between emission, amplification, and absorption of spontaneous emission ]11]. The value of α lum depends on many factors, in particular, on the composition of the active layer, the geometry of the laser structure, the excitation conditions, etc. Thus, as opposed to the loss coefficient for the laser emission, finding α lum is a rather complicated task in most cases of practical importance. This paper deals with the determination of the loss coefficient for AL produced in the active layer of highpower LDAs with as many as a few hundred regions. The resulting values of α lum can be used to estimate how much AL affects the threshold, dynamic, and power properties of LDAs and to determine methods for further improvement in the characteristics of LDAs and of diode pumped solid state lasers.Propagation of Fluxes of Amplified Luminescence in LDAs. The AL characteristics of concern for the parameters of LDAs (output wavelengths 940-980 nm) used to pump solid state erbium lasers are studied here. These LDAs are generally based on InGaAs/GaAs/AlGaAs heterostructures with two quantum-dimension...