Search results for "Optoelectronics"
showing 10 items of 2306 documents
Optical determination of the oxygen content of YBa2Cu3O6+x thin films by IR reflectance and transmittance measurements
2001
Abstract Recent studies of the optical properties of YBa2Cu3O6+x (YBCO) single crystals by several authors have shown that the optical conductivity in the infrared spectral region is a sensitive function of the oxygen content of the samples. Infrared spectroscopy thus offers a possibility for oxygen concentration analysis and is an alternative to other methods such as (i) the X-ray determination of the length of the c-axis and (ii) spectroscopic ellipsometry at an electronic transition band centered around 4.1 eV whose strength decreases with increasing oxygen content. We explore the applicability of the IR optical method for the case of YBCO thin films of about 300 nm thickness which are e…
Anti-recombination organic dyes containing dendritic triphenylamine moieties for high open-circuit voltage of DSSCs
2013
Abstract Three novel sensitizers with dendritic triphenylamine moieties were synthesized and used for dye-sensitized solar cells (DSSCs). Their absorption spectra, electrochemical and photovoltaic properties were extensively investigated. All three DSSCs exhibit high open-circuit voltage over 0.8 V. The photovoltaic results indicate that the dendritic triphenylamine units improve the open-circuit voltage, which is attributed to the retardation of charge recombination, demonstrating that non-planar and larger molecules exert better blocking function. Under standard global AM 1.5 solar conditions, the best performance of the DSSCs exhibits a short-circuit current density of 10.35 mA cm−2, an …
Filament-induced visible-to-mid-IR supercontinuum in a ZnSe crystal: Towards multi-octave supercontinuum absorption spectroscopy
2016
Abstract We report on the generation of multiple-octave supercontinuum laser source spanning from 0.5 μm to 11 μm induced by multi-filamentation in a ZnSe crystal. The generated supercontinuum is both spatially and spectrally characterized. It is then exploited in a proof-of-principle experiment for methane spectroscopy measurements by means of the supercontinuum absorption spectroscopy technique. The entire absorption spectrum is successfully recorded within the whole spectral bandwidth of the supercontinuum. Experimental results are in fairly good agreement with the HITRAN database, confirming the reliability and stability over several hours of the generated supercontinuum.
Dual-Comb Spectroscopy With Frequency-Agile Lasers
2015
Multiheterodyne frequency comb spectroscopy without mode-locked lasers is reported in the near-infrared C and L telecommunication bands. The system without active stabilization combines high signal-to-noise ratio, rapid tuning and moderate multiplex spectral span.
Terahertz spectroscopy for all-optical spintronic characterization of the spin-Hall-effect metals Pt, W and Cu80Ir20
2018
Identifying materials with an efficient spin-to-charge conversion is crucial for future spintronic applications. In this respect, the spin Hall effect is a central mechanism as it allows for the interconversion of spin and charge currents. Spintronic material research aims at maximizing its efficiency, quantified by the spin Hall angle and the spin-current relaxation length . We develop an all-optical contact-free method with large sample throughput that allows us to extract and . Employing terahertz spectroscopy and an analytical model, magnetic metallic heterostructures involving Pt, W and Cu80Ir20 are characterized in terms of their optical and spintronic properties. The validity of our …
Low-frequency band gap in cross-like holey phononic crystal strip
2018
International audience; A silicon-based cross-like holey phononic crystal (PnC) strip is proposed for the control of elastic waves in the field of micro-electro-mechanical systems (MEMS). The goal is to obtain a broad bandgap at low frequencies with a lightweight structure. In this respect, the effects of varying the in-plane and the out-of-plane geometry parameters are discussed. After design, a gap-to-midgap ratio of 47% is obtained with an intermediate filling fraction of the solid material and a small thickness of the strip. The band gap can be moved to an extremely low frequency range while keeping the strip significantly smaller than previously reported PnC strips. The transmission pr…
Effects of 5 MeV electron irradiation on deep traps and electroluminescence from near-UV InGaN/GaN single quantum well light-emitting diodes with and…
2020
The electrical properties, electroluminescence (EL) power output and deep trap spectra were studied before and after 5 MeV electron irradiation of near-UV single-quantum-well (SQW) light-emitting diodes (LED) structures differing by the presence or absence of InAlN superlattice underlayers (InAlN SL UL). The presence of the underlayer is found to remarkably increase the EL output power and the radiation tolerance of LEDs, which correlates with a much lower and more slowly changing density of deep traps in the QW region with radiation dose, and the higher lifetime of charge carriers, manifested by higher short-circuit current and open-circuit voltage in current–voltage characteristics under …
Non-radiative recombination centres in catalyst-free ZnO nanorods grown by atmospheric-metal organic chemical vapour deposition
2013
We have investigated the cathodoluminescence (CL) emission and the Raman spectra along individual ZnO nanorods grown by a catalyst-free method. The spatial correlation between the CL emission and the defect related Raman modes permits establishing a correspondence between the non-radiative recombination centres (NRRCs) and the defects responsible for the 275 cm−1 Raman band. According to this relation, the NRRCs in these nanorods are tentatively associated with complexes of zinc interstitials.
Cladding-Pumped Erbium/Ytterbium Co-Doped Fiber Amplifier for C-Band Operation in Optical Networks
2021
Space-division multiplexing (SDM) attracts attention to cladding-pumped optical amplifiers, but they suffer from a low pump power conversion efficiency. To address this issue, ytterbium (Yb3+) and erbium (Er3+) co-doping is considered as an effective approach. However, it changes the gain profile of Er3+-doped fiber amplifiers and induces the gain difference between optical wavelengths in the C-band, significantly limiting the effective band of the dense wavelength-division multiplexed (DWDM) system. This paper is devoted to a detailed study of a cladding-pumped Er3+/Yb3+ co-doped fiber amplifier (EYDFA) through numerical simulations aiming to identify a configuration, before assembling a s…
Investigating the mechanical properties of GeSn nanowires.
2019
Germanium tin (GeSn) has been proposed as a promising material for electronic and optical applications due to the formation of a direct band-gap at a Sn content >7 at%. Furthermore, the ability to manipulate the properties of GeSn at the nanoscale will further permit the realisation of advanced mechanical devices. Here we report for the first time the mechanical properties of GeSn nanowires (7.1-9.7 at% Sn) and assess their suitability as nanoelectromechanical (NEM) switches. Electron microscopy analysis showed the nanowires to be single crystalline, with surfaces covered by a thin native amorphous oxide layer. Mechanical resonance and bending tests at different boundary conditions were use…