J.L. Plaza

Spontaneous Emission and Nonlinear Response Enhancement by Silver Nanoparticles in a Nd3+‐Doped Periodically Poled LiNbO3 Laser Crystal

Plasmonic nanostructures are attracting great interest because they can provide mechanisms for remarkable optical brightness enhancement and sub-wavelength light control, which are crucial features for a broad range of scientifi c and technological applications. [ 1,2 ] An extremely large variety of metal/dielectric combinations (types of materials and confi gurations) are currently the subject of intense studies, revealing new fundamental properties and leading to novel devices with improved performances, which in many cases has been possible owing to advances in complex synthesis and fabrication techniques. [ 3 ]

Plasmon-Assisted Nd3+-Based Solid-State Nanolaser

Solid-state lasers constitute essential tools in a variety of scientific and technological areas, being available in many different designs. However, although nanolasing has been successfully achieved for dyes and semiconductor gain media associated with plasmonic structures, the operation of solid-state lasers beyond the diffraction limit has not been reported yet. Here, we demonstrate room temperature laser action with subwavelength confinement in a Nd(3+)-based solid-state laser by means of the localized surface plasmon resonances supported by chains of metallic nanoparticles. We show a 50% reduction of the pump power at threshold and a remarkable 15-fold improvement of the slope efficiency with respect to the bulk laser operation. The results can be extended to the large diversity of solid-state lasers with the subsequent impact on their applications.

Selective plasmon enhancement of the 1.08 μm Nd3+ laser Stark transition by tailoring Ag nanoparticles chains on a PPLN Y-cut.

Selective photoluminescence enhancement of the specific Nd(3+) Stark transition for which laser gain has been obtained in Nd(3+)/LiNbO3 is demonstrated by means of plasmonic resonances with the appropriate symmetry configuration. By using the nonpolar Y-cut of a periodically poled LiNbO3 crystal as platform for photoreduction of metallic nanostructures, periodically distributed chains of Ag nanoparticles oriented parallel to the ferroelectric c-axis are obtained. This alternative metallic nanostructure configuration supports the resonance between the localized surface plasmon and exclusively the π-polarized Stark laser line of Nd(3+) ions at 1.08 μm, while maintaining the remaining crystal field transitions unchanged. The work provides the experimental proof on how plasmonic-based optical antennas can be used to influence selectively rare earth optical Stark transitions to improve the performance of solid state laser gain media.

Controlling solid state gain media by deposition of silver nanoparticles: from thermally- quenched to plasmon-enhanced Nd 3+ luminescence

We show the possibility of controlling the optical properties of Nd(3+) laser ions by using different configurations of metallic nanoparticles (NPs) deposited on a solid state gain medium. In particular, we analyze the effect of two different silver NP arrangements on the optical properties of Nd(3+) ions in LiNbO(3): a two-dimensional (2D) high density and disordered Ag NP distribution and a one-dimensional (1D) long single chain of Ag NPs. We demonstrate that while the 2D disordered distribution produces a thermal quenching of the Nd(3+) luminescence, the 1D single chain leads to the enhancement of the fluorescence from the (4)F(3/2) metastable state. The experimental data are theoretically interpreted by taking into account the different character, radiative or non-radiative, of the localized surface plasmonic modes supported by the Ag nanoparticle distributions at the excitation wavelength. The results point out the capabilities of rare earth ions as optical tools to probe the local plasmonic fields and are relevant to determine the optimal configuration of metallic arrays to improve the performance of potential rare earth ion based sub-micrometer lasers.

Surface Characterisation and Cathodoluminescent Response of Nanodot-Patterned GaSb Surfaces by Low Energy Ion Sputtering

The scope of this paper is to analyse the effect of Au and Cr impurities, diffused onto GaSb substrates on the formation of nanodots created by LEIS using Ar+ ions It is concluded that oblique incidence in rotating configuration delays the formation of the nanodots compared to previously reported normal incidence experiments. The presence of cracks induced by the sputtering process has been observed both in the Au and Cr diffused samples. Cathodoluminescence (CL) spectra obtained in irradiated samples both pure and Crdiffused have revealed no difference between them, showing the usual three band encountered in this material (Band Gap at 798 meV, A Band at 777 meV and tail-states at 815 meV). However, a fourth band has been detected in the Au sample centered at 769 meV.

Modeling the Solute Segregation in Vertical Bridgman Growth by Using Free-Surface Technique

In this paper, the solute segregation in vertical Bridgman growth of semiconductor diluted alloys is studied by using numerical simulation. The purpose of this work is the 2D axi-symmetric modeling of the transient solidification process of these crystals. The full problem of heat transfer, hydrodynamics and solute conservation is studied with the finite element software FIDAP . To get a more realistic description of time-dependent solidification process we employ the free-surface model for the solid/liquid interface. The dimensionless forms of the governing equations are used in order to avoid the difficulties related to numerical convergence. We discuss the compatibility between the two forms of non-dimensional equations implemented in the software, in the conditions of using the free-surface enhancements introduced by the new version of FIDAP 8.5. The results of our simulation for axial and radial segregation are compared to the experimental data and to the predictions of analytical models. The difficulties related to modeling the solute segregation in the transient process are discussed.

Polishing, chemical etching and thermal treatment effects on surface and electrical properties of Er and Nd-doped GaSb substrates

Abstract In this work several changes induced by polishing, chemical etching and thermal treatment in the properties of Er- and Nd-doped GaSb substrates with different doping levels grown by the vertical Bridgman method have been studied. The analysis has revealed the formation of precipitates at the highest doping levels for both Er- and Nd-doped GaSb. Cathodoluminescence analysis shows the reduction of the defect band induced by the rare earth (RE) elements. For high dopant concentrations the precipitation phenomena reduce this effect. Thermal treatments have produced an enhancement of the p-type properties of the samples. For a dopant density of 2×10 19 cm −3 this effect is more pronounced.

Effect of Er dopant in GaSb bulk crystals grown by vertical Bridgman technique

The distribution of Er in bulk GaSb ingots grown by vertical Bridgman technique has been investigated for different concentrations. The resistivity, mobility and carrier density were analysed. The formation of Er-Sb compounds and the incorporation of Er at subgrain boundaries has been shown by cathodoluminescence studies.

Modification of the optical and structural properties of ZnO nanowires by low-energy Ar + ion sputtering

The effects of low-energy (≤2 kV) Ar+ irradiation on the optical and structural properties of zinc oxide (ZnO) nanowires (NWs) grown by a simple and cost-effective low-temperature technique were investigated. Both photoluminescence spectra from ZnO NW-coated films and cathodoluminescence analysis of individual ZnO NWs demonstrated obvious evidences of ultraviolet/visible luminescent enhancement with respect to irradiation fluence. Annihilation of the thinner ZnO NWs after the ion bombardment was appreciated by means of high-resolution scanning electron microscopy and transmission electron microscopy (TEM), which results in an increasing NW mean diameter for increasing irradiation fluences. Corresponding structural analysis by TEM pointed out not only significant changes in the morphology but also in the microstructure of these NWs, revealing certain radiation-sensitive behavior. The possible mechanisms accounting for the decrease of the deep-level emissions in the NWs with the increasing irradiation fluences are discussed according to their structural modifications.

Effect of low energy ion irradiation on CdTe crystals: Luminescence enhancement

In this work we show that low energy ion sputtering is a very efficient technique as a cleaning process for CdTe substrates. We demonstrate, by using several techniques like grazing-angle x-ray diffraction, cathodoluminescence, microluminescence, and micro-Raman spectroscopy that the luminescent properties of CdTe substrates can be very much increased when CdTe surfaces are irradiated with low energy Argon ions. We postulate that this enhancement is mainly due to the removal of surface damage induced by the cutting and polishing processes. The formation of a low density of nonluminescent aggregates after the sputtering process has also been observed.