Search results for "Optoelectronics"

The effect of high-In content capping layers on low-density bimodal-sized InAs quantum dots

2013

[EN] The structural and morphological features of bimodal-sized InAs/(In) GaAs quantum dots with density in the low 10(9) cm(-2) range were analyzed with transmission electron microscopy and atomic force microscopy and were related to their optical properties, investigated with photoluminescence and time-resolved photoluminescence. We show that only the family of small quantum dots (QDs) is able to emit narrow photoluminescence peaks characteristic of single-QD spectra; while the behavior of large QDs is attributed to large strain fields that may induce defects affecting their optical properties, decreasing the optical intensity and broadening the homogeneous linewidth. Then, by using a rat…

Tunable light emission by exciplex state formation between hybrid halide perovskite and core/shell quantum dots: Implications in advanced LEDs and ph…

2016

A perovskite–quantum dot exciplex has been detected, opening a broad range of possibilities for advanced optoelectronic devices.

WAVEFRONT TESTER: Un nuevo laboratorio virtual para el estudio de los sensores frente de onda.

2016

[EN] We present a new virtual laboratory developed with MatlabcGUI (Graphical User Interface) used toteach di erent aberration eff ects in the "Tecnologi a de Sensores Optoelectr onicos" at "Escuela T ecnicaSuperior de Ingenier a del Diseño" of the Universitat Polit ecnica de Val encia. The objective of this lab is to provide a computer tool to study the working principle of a Shack Hartman sensor and the parameters that determine the dynamic range of the same. Some examples made with di fferent aberrations (defocus,astigmatism, coma) and for diff erent sensor con gurations are presented.

Solution nuclear magnetic resonance spectroscopy on a nanostructured diamond chip

2017

We demonstrate nuclear magnetic resonance (NMR) spectroscopy of picoliter-volume solutions with a nanostructured diamond chip. Using optical interferometric lithography, diamond surfaces were nanostructured with dense, high-aspect-ratio nanogratings, enhancing the surface area by more than a factor of 15 over mm^2 regions of the chip. The nanograting sidewalls were doped with nitrogen-vacancy (NV) centers so that more than 10 million NV centers in a (25 micrometer)^2 laser spot are located close enough to the diamond surface (5 nm) to detect the NMR spectrum of 1 pL of fluid lying within adjacent nanograting grooves. The platform was used to perform 1H and 19F NMR spectroscopy at room tempe…

Direct imaging of high frequency multimode spin wave propagation in cobalt iron waveguides using X ray microscopy beyond 10 GHz

2020

Fabrication and characterization of tuned Gaussian mirrors for the visible and the near infrared

1988

A thin-film technique has been developed for vacuum fabrication of mirrors with Gaussian reflectivity profiles. Samples with diameters from 2 to 8 mm and assigned maximum reflectivities for visible or near-IR wavelengths have been made and their optical properties evaluated. By properly choosing both the geometry of the evaporation source and the masking system, one can obtain quasi-Gaussian or super-Gaussian reflectivity profiles.

Photoinduced mass transport in amorphous As‐S‐Se films

2012

Direct surface patterning due to photoinduced mass transport in amorphous As-S-Se films has been studied. Illumination of the films with two orthogonally (±45°) polarized beam interference pattern causes the formation of surface relief gratings on the films due to lateral mass transport regarding to light propagation direction. The obtained experimental results showed the dependence of photoinduced surface relief depth (Δh) on film thickness during holographic recording from film side as well as from glass substrate side. After constant exposure doses for the films with a thickness d 1 μm values of Δh do not depend significantly on the film thickness for recording from film side but decreas…

Photoinduced mass transfer in amorphous As 2 S 3 films

2011

The surface relief grating formation in amorphous As2S3 films strongly depends on the polarization state of recording beams. The surface relief grating formation efficiency of s-s and p-p recording beam combination can be essentially enhanced by additional illumination with orthogonal polarization. It is shown that the direction of mass transport on the film surface is determined by the direction of light electric vector (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The Amorphous Semiconductor Schottky Barrier Approach to Study the Electronic Properties of Anodic Films on Ti

2017

A detailed study of the electronic properties of thin (>20 nm) anodic TiO2 potentiostatically grown on titanium in two different solutions is presented. The results show that the nature of the anodizing solution affects the electronic properties of the anodic film and, more specifically, the density of electronic states (DOS) distribution. Different DOS were derived from the experimental data analyzed according to the theory of amorphous semiconductor (a-SC) Schottky barrier. It is shown that the usual non-linear and frequency dependent Mott-Schottky plots are in agreement with expected theoretical behavior of a-SC Schottky barrier.

Low-temperature growth of n ++-GaN by metalorganic chemical vapor deposition to achieve low-resistivity tunnel junctions on blue light emitting diodes

2018

We report on low-resistivity GaN tunnel junctions (TJ) on blue light-emitting diodes (LEDs). Si-doped n ++-GaN layers are grown by metalorganic chemical vapor deposition directly on LED epiwafers. Low growth temperature (<800 °C) was used to hinder Mg-passivation by hydrogen in the p ++-GaN top surface. This allows achieving low-resistivity TJs without the need for post-growth Mg activation. TJs are further improved by inserting a 5 nm thick In0.15Ga0.85N interlayer (IL) within the GaN TJ thanks to piezoelectric polarization induced band bending. Eventually, the impact of InGaN IL on the internal quantum efficiency of blue LEDs is discussed.