An angular blinking jamming method based on electronically controlled corner reflectors

Passive jamming is believed to have very good potential in countermeasure community.In this paper,a passive angular blinking jamming method based on electronically controlled corner reflectors is proposed.The amplitude of the incident wave can be modulated by switching the corner reflector between the penetration state and the reflection state,and the ensemble of multiple corner reflectors with towing rope can result in complex angle decoying effects.Dependency of the decoying effect on corner reflectors’radar cross section and positions are analyzed and simulated.Results show that the angle measured by a monopulse radar can be significantly interfered by this method while the automatic tracking is employed.

Geological Interpretation and Hydrocarbon Exploration Potential of Three Types of Mound-shaped Reflectors in the Meishan Formation,Southern Qiongdongnan Basin

Many mound-shaped reflectors with different features and shapes are evident in the Upper Member of the Meishan Formation from seismic profiles taken in the deep-water area of the Southern Qiongdongnan Basin.Based on the drilling,2 D and 3 D seismic data from the study area,descriptions of the seismic reflection characteristics as well as the geometric shape,wave impedance inversion,analogy and comparative analyses are carried out.Taken in conjunction with research on the paleo structure and paleo sedimentary background,we consider that the mound-shaped seismic reflectors are distributed in the Southern Slop belt and the Southern High-rise of the Qiongdongnan Basin,which can be subdivided into three types:reefs,contourite mounds and magmatic diapirs.The first type,reefs,includes patch reefs,platform marginal reefs and pinnacle reefs.Patch reefs present mound-shaped seismic facies with medium frequency and a moderately strong amplitude,being distributed at the uplift of the fault control platform on the Southern Slop belt.The platform marginal reefs have flat mound-shaped seismic facies with strong amplitude and medium frequency,developing at the margin of the carbonate platform in the Southern High-rise.The pinnacle reefs have mound-shaped seismic facies with strong amplitude and medium frequency and are developed on an isolated volcanic cone.The boundaries between individual reefs are clear on the seismic section,with reef ridge and reef ditch developed,the phenomenon of’front product’being visible within,two-way superelevation between wings is developed and they exist visibly as mounds in any viewed direction of the crosssection.They are slightly asymmetrical in the direction perpendicular to the paleodepth the reef body being steep near the deep-water side,while being gentle near the shallow water side.The wave impedance of a patch reef is about 7 kg/m^(3)×m/s,while the wave impedance of a platform marginal reef is about 7.5 kg/m^(3)×m/s.The second type-contourite moundsare mainly developed under the slope break of the southern slope fault control platform’s edge.They are subdivided into two types:conical and flat.The former has mound-shaped seismic facies with medium-strong amplitude and low frequency,the latter having mound-shaped seismic facies with medium amplitude and low frequency.The internal texture of the mounds is not clear on the seismic section,with the boundaries between contourite mounds being blurred.They are mound-shaped only in cross-section,being banded in the extending direction.The upper surface of a single contourite mound is relatively gentle near the deep-water side,while being steep near the shallow water area.The wave impedance of contourite mounds is about 5.8 kg/m^(3)×m/s,which is speculated to represent a marly to calcareous clastic deposit.The third type is the magmatic diapir,which has’roots’.They have a dome-shaped upper boundary,are bottomless,with a chaotic interior.They penetrated multiple formations,opening towards the base.There are two major accumulation assemblages of reefs,one is the platform margin reef accumulation assemblage with distant source rocks and long-distance migration through an unconformity surface in the Southern High-rise,the other is the patch reef accumulation assemblage with twin sources and short distance migration through faults in the Southern Slop belt near the Central Depression zone.The latter is the main exploration targets at present.There are contourite mound accumulation assemblages with nearby source rocks and short distance vertical migration through faults,which are potentially important targets.The magmatic diapirs pierce the overlying strata and form good hydrocarbon traps and migration pathways,thus representing potential prospecting targets.

Calculation of thermal neutron albedo for mono-material and bi-material reflectors

Thermal neutron albedo has been investigated for different thicknesses of mono-material and bi-material reflectors. An equation has been obtained for a bi-material reflector by considering the neutron diffusion equation. The bi-material reflector consists of binary combinations of water, graphite, lead, and polyethylene. An experimental measurement of thermal neutron albedo has also been conducted for mono-material and bi-material reflectors by using a^(241) Am–Be(5.2 Ci) neutron source and a BF3 detector. The maximum value of thermal neutron albedo was obtained for a polyethylene–water combination(0.95 ± 0.02).

Influence of light absorption on the metallic nanotextured reflectors of GaN-based light emitting diodes

Metallic nanotextured reflectors have been widely used in light emitting diodes(LEDs) to enhance the light extraction efficiency. However, the light absorption loss for the metallic reflectors with nanotexture structure is often neglected. Here, the influence of absorption loss of metallic nanotextured reflectors on the LED optoelectronic properties were studied. Two commonly used metal reflectors Ag and Al were applied to green GaN-based LEDs. By applying a Ag nanotextured reflector, the light output power of the LEDs was enhanced by 78% due to the improved light extraction. For an Al nanotextured reflector, however,only a 6% enhancement of the light output power was achieved. By analyzing the metal absorption using finite-difference timedomain(FDTD) and the metal reflectivity spectrum, it is shown that the surface plasmon(SP) intrinsic absorption of metallic reflectors with nanotexture structure play an important role. This finding will aid the design of the high-performance metal nanotextured reflectors and optoelectronics devices.

Penumbra lunar eclipse observations reveal anomalous thermal performance of Lunakhod 2 reflectors

As the signal reflected by the corner-cube reflector arrays is very weak and easily submerged during the full moon,we analyze the influence of the thermal effect of corner-cube reflector arrays on the intensity of lunar laser ranging echo.Laser ranging measurements during the penumbra lunar eclipse verify suspected thermal deformation in the Lunakhod 2 reflectors.Signal levels vary over two orders of magnitude as the penumbra eclipse progresses.This can be explained by the change in the dihedral angle of the corner-cube reflectors caused by the temperature.The results show that when the dihedral angle errors reach 1,the energy is reduced by 100 times compared with the ideal corner-cube reflector.In the experiment,our findings suggest that when the corner-cube reflector arrays enter the penumbra of the earth,the effective echo signal level which reaches 0.18 photons/s far exceeds the historical level of the full moon.However,11 minutes after the penumbra lunar eclipse,the effective echo rate of Lunakhod 2 will drop two orders of magnitude.The mechanism can explain the acute signal deficit observed at full moon.

The investigation of ZnO:Al_2O_3/metal composite back reflectors in amorphous silicon germanium thin film solar cells

Different aluminum-doped ZnO （AZO）/metal composite thin films, including AZO/Ag/Al, AZO/Ag/nickelchromium alloy （NiCr）, and AZO/Ag/NiCr/Al, are utilized as the back reflectors of p-i-n amorphous silicon germanium thin film solar cells. NiCr is used as diffusion barrier layer between Ag and Al to prevent mutual diffusion, which increases the short circuit current density of solar cell. NiCr and NiCr/AI layers are used as protective layers of Ag layer against oxidation and sulfurization, the higher efficiency of solar cell is achieved. The experimental results show that the performance of a-SiGe solar cell with AZO/Ag/NiCr/Al back reflector is best. The initial conversion efficiency is achieved to be 8.05%.

Tunable Ba_(0.5) Sr_(0.5) TiO_3 film bulk acoustic resonators using SiO_2 /Mo Bragg reflectors

Tunable and switchable Ba 0.5 Sr 0.5 TiO 3 film bulk acoustic resonators（FBARs） based on SiO 2 /Mo Bragg reflectors are explored,which can withstand high temperature for the deposition of Ba x Sr 1 x TiO 3（BST） films at 800 C.The dc bias-dependent resonance may be attributed to the piezoelectricity of the BST film induced by an electrostrictive effect.The series resonant frequency is strongly dc bias-dependent and shifts downwards with dc bias increasing,while the parallel resonant frequency is only weakly dc bias-dependent and slightly shifts upwards at low dc bias（ 45 V） while downwards at higher dc bias.The calculated relative tunability of shifts at series resonance frequency is around 2.3% and the electromechanical coupling coefficient is up to approximately 8.09% at 60-V dc bias,which can be comparable to AlN FBARs.This suggests that a high-quality tunable BST FBAR device can be achieved through the use of molybdenum（Mo） as the high acoustic impedance layer in a Bragg reflector,which not only provides excellent acoustic isolation from the substrate,but also improves the crystallinity of BST films withstanding higher deposition temperature.

A Numerical Simulation of a Stationary Solar Field Augmented by Plane Reflectors: Optimum Design Parameters

In this study, a theoretical analysis of a solar field augmented by a fixed reflector placed in the front between the top of the preceding row and the bottom of the succeeding row is presented. An analytical model has been developed and used to estimate the solar irradiation. The analytical model is based on the anisotropic sky model, assuming an infinite length of collector and reflector rows. A simulation has been carried out in order to figure out the behavior of the solar field and to find the optimum design parameters of the solar field leading to a maximum solar energy augmentation. The results obtained are depicted synoptically as a relationship between the solar field design parameters and the latitude angle, and this presentation enables us to determine the optimum design parameters in order to achieve the intended percentage improvement of solar radiation incident on the solar field rows at any location on the Northern hemisphere, which presents the novelty of this research. Also we have introduced a new parameter named “the effective height of the collector”, which presents the portion of the collector’s height illuminated by the reflector. This parameter is very important especially in case of PV solar fields, because it determines the domain of the concentrated solar energy over the surface of the PV panel.

Migrated Exploding Reflectors in Evaluation of Finite Difference Solution for Inhomogeneous Seismic Models

Earth is inhomogeneous, which means its elastic characteristics change with depth. The seismic method employs the propagation of waves throughout the earth to locate different structures and stratigraphy. Understanding the wave propagation is an important matter in exploration seismology;therefore modeling of seismic wave is an important tool. To validate the interpreted earth model out of the seismic data, seismic synthetic seismograms should be generated in a process named “seismic forward modeling”. Finite difference method is used as one of the most common numerical modeling techniques. In this paper the accuracy of finite difference method in seismic section modeling is explored on different modeled data set of heterogeneous earth. It is shown that finite difference method completes with migration to reposition the events in their correct location. Two different migration methods are used and various velocities are also tested to determine an appropriate migration velocity. Finally the validly of finite difference modeling is examined using a 2D structural similarity index technique.

Monitoring nonlinear and fast deformation caused byunderground mining exploitation using multi-temporal Sentinel-1 radar interferometry and corner reflectors: application,validation and processing obstacles

In this study,Differential Interferometric Synthetic Aperture Radar Interferometry(DInSAR)of artificial Corner Reflectors(CRs)were validated in the area of fast and nonlinear deformation gradient caused by active coal longwall exploitation.Three Sentinel-1 datasets were processed using conventional DInSAR,Persistent Scatterer Interferometry(PSI),and Small BAseline Subset methods implemented in ENVI SARscape™.For evaluation,leveling and Global Navigation Satellite System(GNSS)measurements were used.Considering the challenge of snow cover,the removal of all winter images was not a successful strategy due to the long temporal baseline and strong movement,which cause phase unwrapping problems and underestimate the real deformation.The results indicate that only conventional DInSAR and SBAS with low network redundancy allow us to capture maximal deformation gradient and the root mean square error calculated between the CRs and the ground truth is on the level of 2–3 cm for the vertical and easting deformation component,respectively.For the small deformation gradient represented by the permanent GNSS station(4 cm/year),all SBAS techniques appeared to be more accurate than DInSAR,which corresponds to higher redundancy and better removal of the atmospheric signal.In contrast,DInSAR results allowed to capture information about two subsidence basins,which was not possible with SBAS and PSI approaches.

Switchable Electromagnetic Absorber/Reflectors Using Back-Loaded Active Radio Frequency Circuits

In this paper,three switchable electromagnetic absorbers/reflectors using back-loaded active radio frequency circuits are presented.In the first design,the incident waves are received by an antenna array,transmitted to the back-loaded active circuits and then reflected into the free space when the PIN diode in series in the circuit is off.When the diode is on,the incident waves can be absorbed by a matching load.In the second design,the phase of the reflected waves in the unit cell can be manipulated by adjusting the length of the microstrip lines,allowing the reflection polarization to be tuned.In the third design,by integrating RF switching chips into the back-loaded circuits,a switchable absorber/reflector with a switching polarization state is presented.The first design is fabricated and measured.The profile of the switchable absorber/reflector is approximately 0.14.A total of 2 PIN diodes are used per unit cell for both TE and TM polarizations.By using active circuits,flat in-band reflection performance and stable absorption performance can be achieved in the frequency band of 7 to 18.5 GHz(FBW of 90%)for normal incidence,and an angular stability of 45°for TE and TM polarizations is realized.

The Novel Y-Branch With Two Reflectors

A novel Y-branch waveguide with two reflectors is proposed. The normalized transmitted power for the branching angle of 50?is greater than 70%, which is higher than conventional Y-branch with such wide angle.

Genetically optimized on-chip wideband ultracompact reflectors and Fabry–Perot cavities

Reflectors are an essential component for on-chip integrated photonics. Here, we propose a new method for designing reflectors on the prevalent thin-film-on-insulator platform by using genetic-algorithm optimization.In simulation, the designed reflector with a footprint of only 2.16 μm× 2.16 μm can achieve ~97% reflectivity and 1 dB bandwidth as wide as 220 nm. The structure is composed of randomly distributed pixels and is highly robust against the inevitable corner rounding effect in device fabrication. In experiment, we fabricated on-chip Fabry–Perot(FP) cavities constructed from optimized reflectors. Those FP cavities have intrinsic quality factors of>2000 with the highest value beyond 4000 in a spectral width of 200 nm. The reflectivity fitted from the FP cavity resonances is >85% in the entire wavelength range of 1440–1640 nm and is beyond 95% at some wavelengths.The fabrication processes are CMOS compatible and require only one step of lithography and etch. The devices can be used as a standard module in integrated photonic circuitry for wide applications in on-chip semiconductorlaser structures and optical signal processing.

Room temperature Ⅲ–Ⅴ nanolasers with distributed Bragg reflectors epitaxially grown on(001) silicon-on-insulators

Efficient, scalable, bufferless, and compact Ⅲ–V lasers directly grown on(001)-oriented silicon-on-insulators(SOIs) are preferred light sources in Si-photonics. In this article, we present the design and operation of Ⅲ–V telecom nanolaser arrays with integrated distributed Bragg reflectors(DBRs) epitaxially grown on industry-standard(001) SOI wafers. We simulated the mirror reflectance of different guided modes under various mirror architectures, and accordingly devised nanoscale DBR gratings to support high reflectivity around1500 nm for the doughnut-shaped TE01 mode. Building from InP/InGaAs nanoridges grown on SOI, we fabricated subwavelength DBR mirrors at both ends of the nanoridge laser cavities and thus demonstrated room-temperature low-threshold InP/InGaAs nanolasers with a 0.28 μm^2 cross-section and a 20 μm effective cavity length. The direct growth of these bufferless nanoscale Ⅲ–V light emitters on Si-photonics standard(001) SOI wafers opens future options of fully integrated Si-based nanophotonic integrated circuits in the telecom wavelength regime.

Damage characteristics of dual-band high reflectors affected by nodule defects in the femtosecond regime

The influence of nodule defects on the characteristics of femtosecond laser-induced damage has not been fully investigated.In this study,two types of 800 nm/1064 nm dual-band HfO_(2)=Si O_(2) high-reflection films with different configurations were analyzed.Combined with finite-difference time-domain electric field simulation and focused ion beam analysis,the initial state and growth process of femtosecond laser damage of nodules were explored.In particular,the sequence of blister damage determined by the film design and the inner damage caused by nodules were clarified.The rule of the laser-induced damage threshold of different size nodules was obtained.The difference in the damage behavior of nodules in the two types of films was elucidated.

On-chip mode-locked laser diode structure using multimode interference reflectors

We report, for the first time to our knowledge, an on-chip mode-locked laser diode(OCMLLD) that employs multimode interference reflectors to eliminate the need of facet mirrors to form the cavity. The result is an OCMLLD that does not require cleaved facets to operate, enabling us to locate this OCMLLD at any location within the photonic chip. This OCMLLD provides a simple source of optical pulses that can be inserted within a photonic integrated circuit chip for subsequent photonic signal processing operations within the chip(modulation, optical filtering, pulse rate multiplication, and so on). The device was designed using standardized building blocks of a generic active/passive In P technology platform, fabricated in a multi-project wafer run, and achieved mode-locking operation at its fundamental frequency, given the uncertainty at the design step of the optical length of these mirrors, critical to achieve colliding pulse mode-locked operation.

975 nm multimode semiconductor lasers with high-order Bragg diffraction gratings

The 975 nm multimode diode lasers with high-order surface Bragg diffraction gratings have been simulated and calcu-lated using the 2D finite difference time domain(FDTD)algorithm and the scattering matrix method(SMM).The periods and etch depth of the grating parameters have been optimized.A board area laser diode(BA-LD)with high-order diffraction grat-ings has been designed and fabricated.At output powers up to 10.5 W,the measured spectral width of full width at half maxi-mum(FWHM)is less than 0.5 nm.The results demonstrate that the designed high-order surface gratings can effectively nar-row the spectral width of multimode semiconductor lasers at high output power.

A nonlinear equivalent circuit method for analysis of passive intermodulation of mesh reflectors

Passive intermodulation（PIM） has gradually become a serious electromagnetic interference due to the development of high-power and high-sensitivity RF/microwave communication systems, especially large deployable mesh reflector antennas. This paper proposes a field-circuit coupling method to analyze the PIM level of mesh reflectors. With the existence of many metal–metal（MM） contacts in mesh reflectors, the contact nonlinearity becomes the main reason for PIM generation. To analyze these potential PIM sources, an equivalent circuit model including nonlinear components is constructed to model a single MM contact so that the transient current through the MM contact point induced by incident electromagnetic waves can be calculated. Taking the electric current as a new electromagnetic wave source, the far-field scattering can be obtained by the use of electromagnetic numerical methods or the communication link method. Finally, a comparison between simulation and experimental results is illustrated to verify the validity of the proposed method.

Crustal and Upper-Mantle Seismic Reflectors beneath the Three Gorges Reservoir Region

Seismic studies of the crustal structure beneath the Three Gorges Reservoir（TGR） region in Central China have been limited by the sparse and uneven distribution of seismic stations.To in-crease the station coverage,we made three deployments of a mobile seismologic array in the TGR re-gion during the three summers from 2008 to 2010.Here we present interpretations along a west-east profile through the central TGR region based on new seismic waveform data and a velocity model con-strained by regional earthquake data.Two strong mid-crustal reflection interfaces at depths around 10 and 20 km are seen under the TGR.The shallow reflector defines the bottom of the Zigui（秭归） basin.The new waveform data show that the amplitude of the Moho reflection is quite weak,and beneath the Moho,there is a strong reflector around 54-km depth.It is likely that in the TGR region,the Moho is a gradient rather than a sharp boundary.We speculate that the gradient Moho and the 54-km-deep re-flector in the upper mantle in the TGR region may be by-products of the Qinling（秦岭）-Dabie（大别） orogen.

In situ growth monitoring of AlGaN/GaN distributed Bragg reflectors at 530 nm using a 633 nm laser

The metal-organic chemical vapor deposition（MOCVD） growth of AlGaN/GaN distributed Bragg reflectors （DBR） with a reflection peak at 530 nm was in situ monitored using 633 nm laser reflectometry.Evolutions of in situ reflected reflectivity for different kinds of AlGaN/GaN DBR were simulated by the classical transfer matrix method.Two DBR samples,which have the same parameters as the simulated structures,were grown by MOCVD.The simulated and experimental results show that it is possible to evaluate the DBR parameters from the envelope shape of the in situ reflectivity spectrum.With the help of the 633 nm laser reflectometry,a DBR light emitting diode（LED） was grown.The room temperature photoluminescence spectra show that the reflection peak of the DBR in the LED is within the design region.