Bengtssonbooker2243

Two diffractive optical elements are used to create a compact raster THz scanning setup in reflective configuration. The first one focuses the radiation into the small focal spot on the sample, while the second one collects reflected radiation and focuses it on the detector. NSC 640488 molecular weight To assure small size of the setup and large apertures of optical elements, structures work in the off-axis geometry. Thus, the focal spot is formed 100 mm after and 60 mm below the optical axis of the element, which measures 75 mm in diameter. The designed iterative algorithm allows further minimization of these values.Photonic topological transitions (PTTs) in metamaterials open up a novel approach to design a variety of high-performance optical devices and provide a flexible platform for manipulating light-matter interactions at nanoscale. Here, we present a wideband spectral-selective solar absorber based on multilayered hyperbolic metamaterial (HMM). Absorptivity of higher than 90% at normal incidence is supported over a wide wavelength range from 300 to 2215 nm, due to the topological change in the isofrequency surface (IFS). The operating bandwidth can be flexibly tailored by adjusting the thicknesses of the metal and dielectric layers. Moreover, the near-ideal absorption performance can be retained well at a wide angular range regardless of the incident light polarization. These features make the proposed design hold great promise for practical applications in energy harvesting.In this paper, we introduce a novel method for the fabrication of self-assembly plasmonic metamaterials by exploiting fluid instabilities of optical thin films. link2 Due to interplay between template reflow and spinodal dewetting, two metal nanoparticles of different sizes are generated on the top mesas of free-standing porous anodic aluminum oxide (AAO) template, which results in the apprearance of double resonant peaks in the extinction spectrum. These two resonant peaks possess refractive index resolution 3.27 × 10-4 and 2.53 × 10-4 RIU, respectively. This optical intensity modulation based plasmonic nanoplatform shows a dramatically surface sensing performance with outstanding detection capacity of biomolecules, because of the very small decay length of electric field at dual-modes. The detection ability for concanavalin A (Con A) demonstrats that the limit of detection of dual-modes reaches as small as 68 and 79 nM, respectively.A novel approach for the production of both amorphous and crystalline selenium nanoparticles (SeNPs) using femtosecond laser-induced plasma shock wave on the surface of Bi2Se3 topological insulators at room temperature and ambient pressure is demonstrated. The shape and size of SeNPs can be reliably controlled via the kinetic energy obtained from laser pulses, so these are applicable as active components in nanoscale applications. Importantly, the rapid, low-cost and eco-friendly synthesis strategy developed in this study could also be extendable to other systems.A novel combined laser pulses (CLPs) consisting of a millisecond (ms) pulse and an assisted nanosecond (ns) pulse train was proposed for drilling alumina ceramic. The processing efficiency and quality were well improved by spatially and temporally superposing the ms and ns laser beams. As a result, due to the multi-reflection of keyhole and ejection of melt, the temporally superposed CLPs could decrease the energy consumption of the drilling by an order of magnitude compared with the conventional ms pulse. link3 On the other hand, the spatial distribution of the ns laser on the focal plane was elliptical due to the off-axis distortion of the optical system. However, since the reflection of the laser in the keyhole was non-uniform, the spatially superposed CLPs showed no dependence on the shape of the focused elliptical ns laser spot in terms of the drilling quality. The research results have an important guiding for improving the efficiency and quality of laser processing, especially for the alumina ceramic laser processing.We investigated the effect of coupled quantum wells to reduce electron overflow in InGaN/GaN dot-in-a-wire phosphor-free white color light-emitting diodes (white LEDs) and to improve the device performance. The light output power and external quantum efficiency (EQE) of the white LEDs with coupled quantum wells were increased and indicated that the efficiency droop was reduced. The improved output power and EQE of LEDs with the coupled quantum wells were attributed to the significant reduction of electron overflow primarily responsible for efficiency degradation through the near-surface GaN region. Compared to the commonly used AlGaN electron blocking layer between the device active region and p-GaN, the incorporation of a suitable InGaN quantum well between the n-GaN and the active region does not adversely affect the hole injection process. Moreover, the electron transport to the device active region can be further controlled by optimizing the thickness and bandgap energy of this InGaN quantum well. In addition, a blue-emitting InGaN quantum well is incorporated between the quantum dot active region and the p-GaN, wherein electrons escaping from the device active region can recombine with holes and contribute to white-light emission. The resulting device exhibits high internal quantum efficiency of 58.5% with highly stable emission characteristics and virtually no efficiency droop.We study the effect of homodyne detector visibility on the measurement of quadrature squeezing for a spatially multi-mode source of two-mode squeezed light. Sources like optical parametric oscillators (OPO) typically produce squeezing in a single spatial mode because the nonlinear medium is within a mode-selective optical cavity. For such a source, imperfect interference visibility in the homodyne detector couples in additional vacuum noise, which can be accounted for by introducing an equivalent loss term. In a free-space multi-spatial-mode system imperfect homodyne detector visibility can couple in uncorrelated squeezed modes, and hence can cause faster degradation of the measured squeezing. We show experimentally the dependence of the measured squeezing level on the visibility of homodyne detectors used to probe two-mode squeezed states produced by a free space four-wave mixing process in 85Rb vapor, and also demonstrate that a simple theoretical model agrees closely with the experimental data.We present the first demonstration of visible emission from highly doped silica glass micro-ring resonators (MRRs) through a third-harmonic generation (THG) nonlinear process. We obtain green light conversion efficiency of 2.7×10-5 W-2 in a MRR with loaded Q-factor of 1.4×106 pumped in the telecom band. A thermal nonlinear model is developed to account for the in-cavity power dependence of the resonance detuning. Using the extracted thermal nonlinear coefficients, the measured TH resonance shift is calibrated by subtracting the thermal nonlinear-induced phase mismatch to obtain the theoretical threefold wavelength relationship along with the measured cubic power relationship.Viscoelastic properties of glass within molding temperatures, such as shear relaxation modulus and bulk relaxation modulus, are key factors to build successful numerical model, predict forming process, and determine optimal process parameters for precision glass molding. However, traditional uniaxial compression creep tests with large strains are very limited in obtaining high-accuracy viscoelastic data of glass, due to the declining compressive stress caused by the increasing cross-sectional area of specimen in testing process. Besides, existing calculation method has limitation in transforming creep data to viscoelasticity data, especially when Poisson's ratio is unknown at molding temperature, which further induces a block to characterize viscoelastic parameter. This study proposes a systematic acquisition method for high-precision viscoelastic data, including creep testing, viscoelasticity calculation, and finite element verification. A minimal uniaxial creep testing (MUCT) method based on thermo-mechanical analysis (TMA) instrument is first built to obtain ideal and accurate creep data, by keeping compressive stress as a constant. A new calculation method on viscoelasticity determination is then proposed to derive shear relaxation modulus without the need of knowing bulk modulus or Poisson's ratio, which, compared with traditional method, extends the application range of viscoelasticity calculation. After determination, the obtained viscoelastic data are further incorporated into a numerical simulation model of MUCT to verify the accuracy of the determined viscoelasticity. Base on the great consistence between simulated and measured results (uniaxial creep displacement), the proposed systematic acquisition method can be used as a high accuracy viscoelasticity determination method.In this work, shape-dependent mid-infrared properties of novel split ring resonator (SRR) metamaterials composed of single-walled carbon nanotube (CNT) forest are investigated. The introduction of the gap and dip shape to the closed ring geometry reduced the total reflectance by 15%, due to the generation of circular currents and LC resonances in SRRs. The increase of the SRR height reduced the total IR reflectance by 25%. Unique one-dimensional anisotropic electric and photonic properties of CNTs, combined with an artificial refractive index induced in SRR circuits, will stimulate the development of new optoelectronics applications.In this work, we derive and present the coupled amplitude equations to describe the evolutions of different spectral components in different transverse modes for Raman fiber amplifiers (RFAs). Both the effects of the four-wave-mixing in the fundamental mode (FM FWM) and the inter-modal four-wave-mixing (IM FWM) on high-power RFAs are demonstrated through numerical simulations. Specifically, effective FM FWM interaction could occur and lead to a drop of the 2nd order Raman limit for RFAs by over 50%, despite that the corresponding wave-vector mismatch is rather big. In addition, the IM FWM could also impact the 2nd order Raman limit for RFAs with additional generation of the first order Raman Stokes light in the higher-order mode. We also investigate the effects of the intensity fluctuations in the initial inserted pump and seed lasers on high-power RFAs. It reveals that the temporal stability of the initial inserted pump laser has much more significant impacts on high-power RFAs than that of the initial inserted seed laser. Notably, through applying temporal stable laser as the initial inserted pump laser, both the FM FWM and IM FWM effects could be effectively suppressed, and the 2nd order Raman limit for high-power RFAs could be increased by over twice.We theoretically study the optomechanically induced transparency (OMIT) and absorption (OMIA) phenomena in a single microcavity optomechanical system, assisted by an indirectly coupled auxiliary cavity mode. We show that the interference effect between the two optical modes plays an important role and can be used to control the multiple-pathway induced destructive or constructive interference effect. The three-pathway interference could induce an absorption dip within the transparent window in the red sideband driving regime, while we can switch back and forth between OMIT and OMIA with the four-pathway interference. The conversion between the transparency peak and absorption dip can be achieved by tuning the relative amplitude and phase of the multiple light paths interference. Our system proposes a new platform to realize multiple pathways induced transparency and absorption in a single microcavity and a feasible way for realizing all-optical information processing.