Total Reflector Research Articles

Switchable quadruple narrowband to broadband terahertz perfect absorber based on graphene and VO2 metamaterials

The article describes a switchable and adjustable terahertz perfect absorber to achieve quadruple narrowband absorption and broadband perfect absorption, consisting of graphene and VO2. Two operating modes can be toggled on account of the electrical tunability of graphene and the reversible insulating property-metallic property transformation of VO2. If VO2 displays as the insulating property, our proposed terahertz absorber manifests as quadruple narrowband perfect absorption mode. Four absorption formants can be altered effectively via adjusting the graphene Fermi energy. And then VO2 is adjusted to the metallic property, the proposed terahertz absorber possesses over 99 % absorption in 6.71–9.75 THz as broadband perfect absorption mode. A variation in the conductance of VO2 can regulate broadband absorption efficiency from 0 % to nearly 100 %. And under this condition, if the conductance of VO2 maintains in 200 S/m, it is possible to utilize broadband perfect absorber as a total reflector. Moreover, the absorption performances of both quadruple narrowband perfect absorption mode and broadband perfect absorption mode are rather polarisation-insensitive and wide-incident-angle tolerant. Generally speaking, the proposed meta-device possesses a better absorption performance, accomplishing the switch of different absorption modes and dynamic regulation of absorption performances under different modes, which can satisfy the function needs under different situations. It is believed that our design can facilitate the development of potential applications of terahertz technology in the field of filters, optical switches and sensors.

A tri-functional, independently tunable terahertz absorber based on a vanadium dioxide-graphene hybrid structure.

This paper proposes a simulated design for a versatile terahertz absorber that can be actively tuned. The absorber utilizes the unique tuning capabilities of graphene and vanadium dioxide, enabling it to alternate between ultra-broadband absorption, broadband absorption, and almost complete reflection. In the metallic phase of vanadium dioxide, coupled with a graphene Fermi level at 0 eV, the absorber achieves ultra-broadband absorption. This spans an extensive frequency range from 3.85 THz to 9.73 THz, exhibiting an absorption rate surpassing 90%. As we shift to the insulating phase of vanadium dioxide and adjust the graphene Fermi level to 1 eV, the absorber operates in a broadband absorption mode. This mode spans 2.98 THz to 4.63 THz, demonstrating an absorption rate exceeding 90%. In the insulating state of vanadium dioxide with a graphene Fermi level at 0 eV, the absorber metamorphoses into a nearly total reflector. Its maximum absorption rate is a mere 0.52%. The unique adjustability of vanadium dioxide and graphene independently enables the fine-tuning of absorption rates for both ultra-broadband and broadband absorption without encountering interference. Additionally, thanks to the central symmetry inherent in the proposed structure, the absorber exhibits insensitivity to alterations in polarization angles and remains stable under a broad range of incident angles. With these benefits, the absorber shows promising potential for applications in electromagnetic stealth, wireless communication, and so on.

Determination of permanent corrections of ball reflectors

Today, there are many manufacturers of triple-prism, spherical reflectors with different mechanical characteristics. That is why there is a problem of matching the signal reflection center with the geometric one. The purpose of this work is to evaluate the methods of determining permanent corrections of electronic tacheometers, ball reflectors and to develop recommendations for their use. Method. To determine the instrument correction, a displacement interferometer is used. It contains a two-frequency He-Ne laser with a wavelength of l = 0.63 μm (red range). The study compared the results of length measurements by an interferometer and an electronic total station with a ball reflector. This allowed determining the instrument correction. The research defined the constant correction of reflectors and total stations on the phase section of the field base using the method of created linear observations. Results. Experimental studies of ball reflectors of various manufacturers and Leica electronic tacheometers were conducted. The determination of constant instrument corrections of the total station and reflector using the displacement interferometer can be performed with an accuracy of 0.1 mm. This significantly depends on the accuracy of measuring lines with the total station. The use of ball reflectors with a built-in triple prism allows significant increase of distance measurement accuracy by reducing centering errors, considering the constant instrument correction (up to 0.4 mm for Leica 1201 total stations). Scientific novelty. The methods of determining permanent corrections of ball reflectors and total stations were investigated. The proposed method determines the measurement interval length with the exception of systematic constant correction of the electronic total station and reflector. Practical relevance. The use of ball reflectors is recommended for quick and unambiguous installation at points, convenience of their use for monitoring observations, as well as for increasing the accuracy of linear measurements due to the reduction of centering errors. In order to achieve high-precision measurements of short lines, it is recommended, according to the performed studies, to carefully determine the constant correction of the total station and ball prisms. This makes it possible to increase the accuracy of line measurements at least three times compared to the declared accuracy of the total station manufacturer.

Vanadium dioxide-assisted switchable multifunctional metamaterial structure.

A multifunctional design based on vanadium dioxide (VO2) metamaterial structure is proposed. Broadband absorption, linear-to-linear (LTL) polarization conversion, linear-to-circular (LTC) polarization conversion, and total reflection can be achieved based on the insulator-to-metal transition (IMT) of VO2. When the VO2 is in the metallic state, the multifunctional structure can be used as a broadband absorber. The results show that the absorption rate exceeds 90% in the frequency band of 2.17 - 4.94 THz, and the bandwidth ratio is 77.8%. When VO2 is in the insulator state, for the incident terahertz waves with a polarization angle of 45°, the structure works as a polarization converter. In this case, LTC polarization conversion can be obtained in the frequency band of 0.1 - 3.5 THz, and LTL polarization conversion also can be obtained in the frequency band of 3.5 - 6 THz, especially in the 3.755 - 4.856 THz band that the polarization conversion rate is over 90%. For the incident terahertz waves with a polarization angle of 0°, the metamaterial structure can be used as a total reflector. Additionally, impacts of geometrical parameters, incidence angle and polarization angle on the operating characteristics have also been investigated. The designed switchable multifunctional metasurfaces are promising for a wide range of applications in advanced terahertz research and smart applications.

STUDY OF THE LED REMOVABLE NOZZLE ON THE REFLECTOR OF AN ELECTRON TOTAL STATION

The article presents the results of a study of a removable LED nozzle on the reflector of an electronic total station. A description of the LED removable nozzle on the reflector of the electronic total station is made. The results of measurements of the runtime of pointing the device at the reflector at night, at various distances and in bad weather conditions (snowfall) are presented. A comparison between the results of studies with different backlight modes of the total station reflector is made. Models of reflectors with pulsed illumination manufactured by various instrument-making enterprises and their cost are given. Based on the results of the studies and analysis, conclusions on the use of a removable LED nozzle for performing geodetic measurements in the production of engineering and geodetic surveys and other types of geodetic works are drawn. The advantages and disadvantages of the LED removable nozzle are given.

ВИЗНАЧЕННЯ ВЕЛИЧИНИ Й ТОЧНОСТІ СТАЛОЇ ВІДДАЛЕМІРА ЕЛЕКТРОННОГО ТАХЕОМЕТРА ЗА РЕЗУЛЬТАТАМИ ПРИВ’ЯЗКИ ДО ПОДВІЙНОГО СТІННОГО ГЕОДЕЗИЧНОГО ЗНАКУ

Urgency of the research. Now manufacturers of geodetic instruments supply a variety of geodetic equipment to the market. An important place in this assortment belongs to electronic range finders. They combine in their design a goniometer, an electronic rangefinder and a processor that allows to solve various geodetic tasks based on the measurements. Target setting. To ensure reliable data on the measured distance, it is necessary to periodically determine the constant correction of the range finder of the electronic total station. This is especially true in the case of measuring distance using a reflector from an electronic total station of a different brand. Actual scientific researches and issues analysis. The method for determining the constant correction of the range finder of an electronic total station based on the results of binding to a double geodetic wall sign is described in [1]. The technology of measurements and the formula for determining the constant are shown. An unexplored parts of a common problem. In continuation of the topics given in [1], it is advisable to carry out a practical implementation of the method for determining the constant correction and establish its accuracy. The research objective. The main goal of this article is to determine the constant correction of the range finder of an electronic total station based on the data obtained from the results of binding to a double geodetic wall sign, and also to calculate its accuracy. The statement of basic materials. The approbation of the technology for determining the constant correction of the range finder of an electronic total station for the results of measurements made during binding to the double wall sign of the city polygonometry of Chernihiv is presented. The Trimble 3305 DR total station and reflector for binding to wall signs, developed at the Department of Geodesy, Cartography and Land Management of the Chernihiv Polytechnic National University, were used. As a result, a constant correction value of +22.6 mm was obtained. Formulas for calculating the mean square error of the constant correction for various options for binding to a double wall sign are derived and calculations are performed using these formulas. Conclusions. The developed technology was tested for determining the constant correction of the range finder of an electronic total station according to the measurement results obtained during binding to a double wall sign. Formulas are obtained and calculations are performed to determine the mean square error of the constant correction of the range finder of an electronic total station

Development of a standoff terahertz imaging system for concealed weapon detection

AbstractIn this article, terahertz imaging system based on a single‐channel 360 GHz transceiver front‐end and optical‐machine scanning platform, is studied. The transmitting antenna is irradiated by a wide beam of a small aperture antenna to reduce the “angular glint” effect caused by high frequency electromagnetic radiation. The receiving antenna is of a large aperture to ensure high resolution. Beam scanning is achieved through a fast conical scanning method using a total reflector to achieve fast real‐time imaging.

Computational investigation of Tehran research reactor graphite reflector replacement with Be, BeO or D<SUB align=right>2O and its impacts on thermal neutron flux enhancement

Thermal neutron flux enhancement is an essential objective to achieve more radioisotope production in the research reactors. Here, the effect of graphite reflector replacement with other customary reflectors on thermal neutron flux enhancement of Tehran Research Reactor (TRR) core has been investigated. The core is modelled using Monte Carlo-based code with the graphite routine reflector and with Be, BeO, and D2O reflectors. The calculations showed that the reflector replacement could result in a little enhancement of thermal neutron flux while beryllium oxide is suggested as the most efficient material (about 2.78% on average per channel). In addition, instead of total reflector conversion, application of some dimensionally optimised BeO blocks located around the irradiation boxes increases the thermal neutron flux up to 2.62%. Moreover, this study demonstrates that compacting the core could significantly enhance the thermal neutron flux up to 58% that is noticeably more than the reflector conversion effect.

Optical Assembling of Micro-Particles at a Glass–Water Interface with Diffraction Patterns Caused by the Limited Aperture of Objective

Optical tweezers can manipulate micro-particles, which have been widely used in various applications. Here, we experimentally demonstrate that optical tweezers can assemble the micro-particles to form stable structures at the glass–solution interface in this paper. Firstly, the particles are driven by the optical forces originated from the diffraction fringes, which of the trapping beam passing through an objective with limited aperture. The particles form stable ring structures when the trapping beam is a linearly polarized beam. The particle distributions in the transverse plane are affected by the particle size and concentration. Secondly, the particles form an incompact structure as two fan-shaped after the azimuthally polarized beam passing through a linear polarizer. Furthermore, the particles form a compact structure when a radially polarized beam is used for trapping. Thirdly, the particle patterns can be printed steady at the glass surface in the salt solution. At last, the disadvantage of diffraction traps is discussed in application of optical tweezers. The aggregation of particles at the interfaces seriously affects the flowing of particles in microfluidic channels, and a total reflector as the bottom surface of sample cell can avoid the optical tweezers induced particle patterns at the interface. The optical trapping study utilizing the diffraction gives an interesting method for binding and assembling microparticles, which is helpful to understand the principle of optical tweezers.

Omnidirectional Reflector based on Transparent Oxide Materials for Light Extraction Enhancement of Organic and Inorganic Solid-state Light Emitting Devices

High performance reflector is significant structure for efficiency improvement of organic and inorganic solid-state light emitting devices because a large difference in the refractive index between the light source and air leads to multiple internal reflections at the reflector. Then we focused on wide angular light incidence and designed a total internal omnidirectional reflector (TI-ODR) based on transparent oxide layers. The simulation results showed that light extraction structure with TI-ODR gives 17% and 4% efficiency enhancement compared to typical Ag based mirror for organic LED (n=1.8) and inorganic LED (n=2.4), respectively. Then the TI-ODR on blue LED structure was fabricated and that showed enhancement effect of about 8%. The layers are composed of conductive layer for current distribution, low-index thick layer for total internal reflection (TIR) of wide angular light, and high-index layer for the reinforcement of adhesion of layers.

Thermoeconomic analysis of an integrated solar combined cycle power plant

In this work, a dynamic model of a high-temperature integrated solar combined cycle power plant is presented. The system includes a three-pressure combined cycle power plant coupled to parabolic trough solar collectors. Thermal storage, a heat solar steam generator, pumps, heat exchangers, and several controllers are also included in the system. Solar energy is used to produce additional steam to be supplied to the steam turbine of the combined cycle power plant. The integrated solar combined cycle system is based on the heat transfer fluid arrangement, exploiting solar energy to produce steam. The analysis is developed by a dynamic simulation model including detailed algorithms for the calculation of the performances of system components. Special control strategies are included in the model in order to accurately manage the steam production of the heat solar steam generator. The paper presents a thermo-economic and environmental comparison between the integrated solar combined cycle and a conventional combined cycle, powered by fossil fuels, based on dynamic simulations. A case study, referred to a plant with a maximum power of around 100 MW, located in Almeria (Southern Spain), is presented and discussed. A parametric analysis was also performed to show the effect of the variation of total solar field reflector area on the system performance. For the case under evaluation, a simple pay-back of 15 years was found, for a solar field aperture area of 80 000 m2; however, the parametric analysis suggests that a smallest solar field area should be used under the hypotheses of the case study.

Analysis of photonic spectra in Thue-Morse, double-period and Rudin-Shapiro quasiregular structures made of high temperature superconductors in visible range

The present paper attempts to determine the properties of photonic spectra of Thue-Morse, double-period and Rudin-Shapiro one-dimensional quasiperiodic multilayers. The supposed structures are constituted by high temperature HgBa2Ca2Cu3O10 and YBa2Cu3O7 superconductors. Our investigation is restricted to the visible wavelength domain. The results are demonstrated by the calculation of transmittance using transfer matrix method together with Gorter-Casimir two-fluid model. It is found that by manipulating the parameters such as incident angle, polarization, the thickness of each layer and operation temperature of superconductors the transmission spectra exhibit some interesting features. This paper, provides us a pathway to design tunable total reflector, optical filters and optical switching based on superconductor quasiregular photonic crystals.

Precise Spatial-Color Optical Modeling in Phosphor-Converted White LEDs

White light LEDs are playing a more and more important role in display in various structures. Here, a new modeling algorithm is proposed for use in phosphor-converted white light-emitting diodes (pcW-LEDs); the algorithm can be used to accurately simulate color appearances, potentially enabling optical designers to remove yellowish/bluish spots in LED lighting. The proposed modeling method was applied to simulate a pcW-LED without an encapsulation lens, and subsequently, a pcW-LED with a hemispherical lens. Both simulations accurately predicted the blue and yellow light distribution. The model was further verified by applying a total internal reflector lens to the pcW-LED. In the midfield region, the blue and yellow light distribution exhibited large variations as the observation distance changed; this varying light pattern for both the blue and yellow lights can be accurately predicted using the proposed model. The developed optical model should facilitate designing a pcW-LED that features high-quality illumination and increased color uniformity.

Multiple folded resonator for LD pulse end pumped Q-switched Yb:YAG slab laser

In this paper, a multiple folded resonator is presented which consists of a multiple optical folding setup, a flat total reflector, a flat output coupler, a Q-switch crystal and a polarizer. By this technique, the output energy of 32.6mJ and pulse width of 13.4ns with a repetition rate of 5Hz was obtained, which is three times higher than that reported in the past publications by the use of the currently existing technique of the Q-switched slab gain lasers with the unstable resonator. The output beam with a quality of M² = 1.55 in the slow axis and M² = 1.40 in the fast axis was also obtained.

Integral freeform illumination lens design of LED based pico-projector

In this paper, an illumination lens design for a LED-based pico-projector is presented. Different from the traditional illumination systems composed by lens group, the integral illumination lens consists of a total internal reflector (TIR) and a freeform surface. TIR acts as collimation lens and its top surface formed by a freeform surface reshapes the nonuniform circular light pattern generated by TIR to be rectangular and uniform. Diameter and height of the lens are 16 and 10mm, respectively. An optimization method to deal with the problem of extended light source is also presented in detail in this paper. According to the simulation results of the final optimized lens, 77% (neglecting the effect of polarization) of the power of light source is collected on liquid crystal on silicon panel with a 16∶9 ratio and illumination uniformity achieves 92%.

Echelle grating silicon multi/demultiplexers with single-reflection total internal reflectors

We present a silicon-on-insulator Echelle grating 8-channel demutiplexer showing characteristic features, average insertion loss 2.4 dB measured at 1520~1570 nm, adjacent channel crosstalk 15-18 dB, and channel spacing 11.9 nm. Our Echelle grating is remarked by a total internal reflector (TIR) which reflects incident light by a single reflection in contrast to the double reflections of retro-reflector TIR Echelle gratings.

Tunable Omnidirectional Total Reflection Frequency Range in One-Dimensional Photonic Crystals Based on the Faraday Effect

We report that tunable omnidirectional total reflector can be realized theoretically with one-dimensional (1D) photonic crystals (PCs) by adding external magnetic fields. The 1D PCs consist of two alternating layers with SiO2 and InSb. We show that the 1D PCs have rather large omnidirectional photonic band gaps (omni-PBGs). After being added external magnetic fields the omni-PBGs will be tuned accordingly. The shift ranges of left and right circular polarizations are different. As a result, the omnidirectional reflector and omnidirectional circular polarizer can be realized.

10 GHz high-speed optical interconnection

An AlGaAs/GaAs waveguide is coupled to an InGaAs pin photodetector by a total internal reflector, polyimide process, and a microwave ground-signal-ground coplanar waveguide. This monolithic module achieved 10 GHz 3 dB bandwidth and is suitable for 10 Gbit/s data transmission of optical interconnections.

利用一维电介质-磁光子晶体设计宽带全方向全反镜

The omnidirectional total reflectors based on one-dimensional dielectric and magnetic photonic crystals were investigated in this paper.The transmission matrix method was adopted to analyze the transmission properties of such reflectors.In order to obtain broad omnidirectional total reflection bandwidth,the decimal Genetic algorithm was used to optimize their structural parameters including the thickness ratios of the layers and the numbers of periods.The calculation results show that,with the more parameters(including the number of periods and the thickness ratios of the layers) participating in the optimization,the omnidirectional total reflection band becomes wider,the number of the layers becomes less,and the total thickness of the whole structure becomes thinner.Finally,an optimal design described as(0.255A0.255B)5(0.169A0.066B)8 is obtained.The omnidirectional total reflection bandwidth can reach to 1.34ω0,the number of the layers is just 26,and the whole thickness is just 1.8634λ0.The whole structure is very simple.

基于光子晶体异质结的高效太阳能电池反射器研究

A two-dimensional triangular lattice photonic crystal heterostructure is designed for solar reflector.The reflectivity of the incident electromagnetic wave in the visible to near infrared wavelength range is simulated by the transfer matrix method and the variation of reflectivity with different incident angle is studied.The results shows that the structure displays perfect reflection for the near-infrared incident light at normal incidence.As the deflection angle increases,it shows high reflectance in visible-near infrared wavelength range.The structure should enable new application for omnidirectional total reflector for the visible to near infrared light.