Search results for " Optics"
showing 10 items of 5880 documents
Window-Based Energy Selecting X-ray Imaging and Charge Sharing in Cadmium Zinc Telluride Linear Array Detectors for Contaminant Detection
2023
The spectroscopic and imaging performance of energy-resolved photon counting detectors, based on new sub-millimetre boron oxide encapsulated vertical Bridgman cadmium zinc telluride linear arrays, are presented in this work. The activities are in the framework of the AVATAR X project, planning the development of X-ray scanners for contaminant detection in food industry. The detectors, characterized by high spatial (250 µm) and energy (<3 keV) resolution, allow spectral X-ray imaging with interesting image quality improvements. The effects of charge sharing and energy-resolved techniques on contrast-to-noise ratio (CNR) enhancements are investigated. The benefits of a new energy-resolved …
Improving nanoscale terahertz field localization by means of sharply tapered resonant nanoantennas
2020
Abstract Terahertz resonant nanoantennas have recently become a key tool to investigate otherwise inaccessible interactions of such long-wavelength radiation with nano-matter. Because of their high-aspect-ratio rod-shaped geometry, resonant nanoantennas suffer from severe loss, which ultimately limits their field localization performance. Here we show, via a quasi-analytical model, numerical simulations, and experimental evidence, that a proper tapering of such nanostructures relaxes their overall loss, leading to an augmented local field enhancement and a significantly reduced resonator mode volume. Our findings, which can also be extended to more complex geometries and higher frequencies,…
Non-linear interactions of femtosecond laser pulses with graphene : photo-oxidation, imaging and photodynamics
2017
This thesis presents a study focused on interactions of femtosecond laser pulses with graphene, a one atom thick carbon membrane. Graphene, which exhibits exceptional electronic and optoelectronic properties, could provide considerable advantage over current silicon-based electronics. Graphene alone, being semi-metal, is not sufficient for electronic applications, but requires modification. For this, a set of methods for modifying and measuring the properties of graphene was developed. With the perspective of making graphene a suitable component for electronics, optoelectronics or photonics, ultrashort laser pulses were used for drawing patterns on graphene. The procedure modifies graphene …
Cladding-Pumped Er/Yb-Co-Doped Fiber Amplifier for Multi-Channel Operation
2022
The Institute of Solid State Physics, University of Latvia, as a Center of Excellence, has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2. We express our gratitude to rer. nat. Nicoletta Haarlammert from Fraunhofer Institute for Applied Optics and Precision Engineering IOF for the refractive index measurements of ytterbium/erbium-co-doped fibers. This work is supported by the European Regional Development Fund project No. 1.1.1.1/18/A/068.
Performance analysis of dual-pump nonlinear amplifying loop mirror mode-locked all-fibre laser
2019
We numerically characterise, in the three-dimensional space of adjustable cavity parameters, the performance of a recently reported layout of a flexible figure-8 laser having two independently pumped segments of active fibre in its bidirectional ring (Smirnov et al 2017 Opt. Lett. 42 1732–5). We show that this optimisation problem can be efficiently addressed by applying a regression model based on a neural-network algorithm.
Flat bands and strongly correlated Fermi systems
2019
Many strongly correlated Fermi systems including heavy-fermion (HF) metals and high-Tc superconductors belong to that class of quantum many-body systems for which Landau Fermiliquid (LFL) theory fails. Instead, these systems exhibit non-Fermi-liquid properties that arise from violation of time-reversal (T) and particle-hole (C) invariance. Measurements of tunneling conductance provide a powerful experimental tool for detecting violations of these basic symmetries inherent to LFLs, which guarantee that the measured differential conductivity dI/dV, where I is the current and V the bias voltage, is a symmetric function of V. Thus, it has been predicted that the conductivity becomes asymmetric …
Two-step cross correlation-based algorithm for motion estimation applied to fertilizer granules' motion during centrifugal spreading
2011
Imaging systems are progressing in both accuracy and ro- bustness, and their use in precision agriculture is increasing accordingly. One application of imaging systems is to understand and control the cen- trifugal fertilizing spreading process. Predicting the spreading pattern on the ground relies on an estimation of the trajectories and velocities of ejected granules. The algorithms proposed to date have shown low ac- curacy, with an error rate of a few pixels. But a more accurate estimation of the motion of the granules can be achieved. Our new two-step cross- correlation-based algorithm is based on the technique used in particle image velocimetry (PIV), which has yielded highly accurate…
Observational Results On The Influence Of Surface Layer Stability And Inversion Entrainment On Surface Layer Marine Aerosol Number Density (1 Microme…
1983
Wind speed and relative humidity have been the physical variables used in empirical expressions for equilibrium marine aerosol distributions. Recent formulations, which include the role of hydrostatic stability because it influences turbulent transport and entrainment of clear air from aloft, are examined on the basis of 1 um radius aerosol number density values. The aerosol data were collected along with a quite complete meteorological data set in the Northeast Atlantic during the international Joint Air Sea Interaction Experiment (JASIN-78). The 1 um number density values are normalized for generation and relative humidity influences, and analyses are performed to gain reasonable assuranc…
On the discreet spectrum of fractional quantum hydrogen atom in two dimensions
2019
We consider a fractional generalization of two-dimensional (2D) quantum-mechanical Kepler problem corresponding to 2D hydrogen atom. Our main finding is that the solution for discreet spectrum exists only for $\mu>1$ (more specifically $1 < \mu \leq 2$, where $\mu=2$ corresponds to "ordinary" 2D hydrogenic problem), where $\mu$ is the L\'evy index. We show also that in fractional 2D hydrogen atom, the orbital momentum degeneracy is lifted so that its energy starts to depend not only on principal quantum number $n$ but also on orbital $m$. To solve the spectral problem, we pass to the momentum representation, where we apply the variational method. This permits to obtain approximate analytica…
Design and simulation of efficient combinational circuits based on a new XOR structure in QCA technology
2021
AbstractQuantum-dot cellular automata (QCA), due to its unique characteristics like low power consumption, nanoscale design, and high computing speed is considered as an emerging technology, and it can be used as an alternative for CMOS technology in circuit design for quantum computers in the near future. XOR gate has many applications in the design of digital circuits in QCA. In this paper, an efficient novel structure of XOR gate is proposed in QCA. Also, a novel 1-bit comparator circuit, 1-bit full adder, binary to gray and gray to binary convertor code based on the proposed XOR is designed and simulated using QCADesigner 2.0.3. The simulation results demonstrated that the proposed stru…