We present an optically controlled terahertz (THz) switch to tune the state of polarization based on single-layer chiral metamaterial. The chiral metamaterial consists of an array of perforated S-shaped slits with incorporated photoactive silicon, which allows us to control dynamically cross-polarization transmission. The switch state can be efficiently controlled by external optical stimuli. The realization of cross-polarization THz switch in a single-layer metamaterial has simple structure design and easy fabrication and therefore the S-shaped metamaterial will be a promising candidate for polarization control devices.
In order to move signal detecting point to the most sensitive position and improve the immunity of the system at the
same time, the scheme named passively demodulated all optical fiber current transformer (AOFCT) inserts a Faraday
rotator of 22.5° rotation angle between fiber λ/4retarder and leading fiber. To improve the performance of this type of all fiber current transformer, after considering the temperature features of a large proportion of Faraday crystals, the
effect of the Faraday rotator’s temperature properties on temperature stability of the passively demodulated AOFCTs are
theoretically analyzed and numerically calculated. The results show that the errors induced by the Faraday rotators are
beyond the requested values in the International Standard IEC 60044-8:2002 of International Electrotechnical
Commission (IEC) and the State Standard of P.R.China GB/T 20840.8-2007. Finally, to solve this problem, some
possible solutions are suggested.
We theoretically investigate electromagnetic responses of a bilayered metamaterial in the optical frequency range. The
metamaterial consists of two stacked split ring resonators with a twist angle spatially separated by a dielectric layer. The
simulated results show that the bilayered metamaterial exhibits multiple transmission windows based on mutually
coupling between two twisted resonators at normal incidence and the manifested transmission properties can be
controlled efficiently by adjusting structural parameters of a unit cell. The coupling in metamaterials offers an effective
way to manipulate the electromagnetic properties of metamaterial-based devices.
We study local field energy density enhancement in planar metamaterials at normal incidence based on the finite element
method. The microwave metamaterials composed of asymmetric resonators with/without quartz substrates are utilized to
investigate the resonant response to incident electromagnetic waves. The trapped-mode resonant feature results from the
excitation of an antisymmetric current mode due to the broken symmetry between two resonators and the quality factor
and local field energy density enhancement strongly depend on the asymmetry. The proposed metamaterial on glass
substrate shows the high possible quality factor of about 1000 and energy density enhance factor of up to 150000. To
reduce losses of metamaterials further, freestanding metallic structure is considered being treated as perfect electric
conductor and real-loss metal respectively. Real metallic metamaterial provides a very sharp trapped-mode resonance
having the quality factor of up to 1500.
We study theoretically that a resonant response with a high quality factor could be achieved in a planar positive or
negative metamaterials by weakly breaking the geometrical symmetry of its unit cells. The trapped mode resulting from
broken structures is investigated using the finite element method and the dependence of the quality factor on structural
parameters is also discussed.
The reflectance and transmittance of thin films at oblique incident angles exhibit strong polarization effects, particularly
for the films inside a glass cube. However, the polarization effects are undesirable in many applications. To solve this
problem, non-polarizing beam splitters with unique optical thin films have been achieved employing a method of
combination of interference and frustrated total internal reflection, the non-polarizing condition expressions based on
frustrated total internal reflection has been derived, and the design examples of non-polarizing beam splitters with an
optimization technique have been also presented. The results of Rp=(50±0.5)%, Rs=(50±0.5)% andΔr=(0±0.3) degree in
the wavelength range of 400-700nm have been obtained. The thickness sensitivity of NPBSs is also analyzed.
When used at oblique angles of incidence, the reflectance and transmittance of thin films exhibit strong polarization
effects, particularly for the films inside a glass cube. However, the polarization effects are undesirable in many
applications. Novel non-polarizing beam splitter designs are shown, non-polarizing beam splitters with unique optical
thin films are achieved through combination of interference and frustrated total internal reflection, the non-polarizing
condition expressions based on frustrated total internal reflection is derived, and applied examples of the non-polarizing
beam splitters are also presented with the optimization technique and the results of Rp=(50±0.4)% and Rs=(50±0.4)% in
the wavelength range of 500-600nm are obtained.
A new design of optical current sensor using a Faraday Mirror directly as the current sensing element is proposed, the optical setup is shown, the mathematical expression of the working principle is derived, the experimental result is given, the advantages and shortcomings of the design are discussed in this paper. This design may be used as the primary current sensing element of an electrical current transformer for high voltages applications.
The joint effects of reciprocal optical parameters of a bulk glass current sensing head upon the polarization state of the output optical beam of a Faraday Mirror-typed Optical Current Transformer (FMOCT) are theoretically analyzed, digitally simulated and compared with that of an optical current transformer with polarization-preserving total reflection coatings in this paper. The results show that the FMOCT design can effectively suppress the polarization state fading of the output optical beam induced by the joint effects of reciprocal optical parameters of the bulk glass current sensing head. The work reported here might have some reference significance to the performance improvement and development of bulk glass optical current transformers for practical applications.
The effects of linear birefringence (LB) upon Bulk Glass Optical Current Sensors (BGOCSs) with return-back optical path designs, such as the Orthoconjugate Reflection (OCR)-typed, the Direct Reflection (DR)-typed and the Roof-prism Reflection (RPR)-typed BGOCS design, are theoretically analyzed and compared with that of the BGOCS with a single-loop optical path in this paper. The results show that the return-back dual-loop current sensing designs with conventional signal processing scheme of "-/+" cannot eliminate the harmful effects of the LB thoroughly, if suitable signal processing schemes which can separate the LB from Faraday effect are not used.
A method is proposed for smooth surface roughness measurement. Two standard reference surfaces and two polaroids are employed to realize the measurement. The reversibility of the optical beam is overcome by using two quarter-wave plates. Measuring optical set-up is shown. The mathematical expression of the working principle of the method is derived. The uncertainty of the method is theoretically calculated and digitally simulated. Finally, the feasibility of this method is verified by measuring a standard roughness sample. The measurement result is in accordance with the standard value of the sample roughness provided by the manufacturer.
A novel method based on interferometry for measurement of fine surface roughness is proposed, designed and
completed. The polarization state of the optical beam in one path is changed utilizing a half wave-plate in this design,
avoiding the reversibility of the beam in similar systems previously reported, so that the stability of the system is
ensured. A quarter-wave plate is used to make the consistency of the polarization states of the coherent light to obtain the
better visibility. The absolute measurement values of the surface roughness are achieved using two concentrical beams
scanning the surface. The set-up is simple and easy to be realized. Experiment results show that roughness of
Ra=0.012&mgr;m is achieved.
Based on the mode equations of the core mode LP01 and the cladding mode LP0M, combining with the phase matching condition, a method for simultaneous measurement of liquid refractive index and temperature using a single resonance
peak of long-period fiber grating's transmission spectrum is proposed. The operational principle is analyzed; experiments
are conducted. The theoretical results are compared with those of the experiments. The results show that they are in accordance with each other.
The dispersion properties of the reflection-induced retardance of the polarization- preserving reflecting medium layer
and its effect upon the sensitivity of an optical current sensor are theoretically analyzed taking the Jones' Matrix as a
mathematical tool and simulated with a computer. The investigation results show that the dispersion will obviously affect
the scale factor of the system. Therefore, it is necessary to stabilize the driving current and the ambient temperature of
the optical source by some technical means. These results might be useful for the researchers and designers working in
the optical current sensing techniques area.
The effect of the dispersion of Verdet constant of ZF-7 optical glass upon the sensitivity of a bulk-glass optical current
sensor are theoretically analyzed taking the Jones' Matrix as a mathematical tool and simulated with a computer. The
investigation results show that the dispersion will obviously affect the scale factor of the current sensor. Therefore, it is
necessary to stabilize the driving current and the ambient temperature of the optical source by some technical means. These
results might be useful for the researchers and designers working in the optical current transforming techniques area.
The effects of reciprocal optical parameters of a bulk glass current sensing head upon the polarization state of the output
optical beam of a Faraday Mirror-typed Optical Current Transformer (FMOCT) are theoretically analyzed, digitally
simulated and compared with that of an optical current transformer with polarization-preserving total reflection coatings
in this paper. The results show that the FMOCT design can effectively suppress the polarization state fading of the output
optical beam induced by the reciprocal optical parameters of the bulk glass current sensing head. The work reported here
might have some reference significance to the performance improvement and development of bulk glass optical current transformers for practical applications.
When used at oblique angles of incidence, the reflectance and transmittance of thin films exhibit strong polarization effects, particularly for the films inside a glass cube, which result from the fact that the tangential components of the electric and magnetic fields are continuous across each layer interface. However, for many applications, the polarization effects are undesirable and should be reduced. Therefore, the concept of non-polarizing beam splitter is proposed. Up to now, however, most of the reports of non-polarizing beam splitters are suitable for visible light. Therefore, it is necessary to find out some methods to reduce the polarization effects for infrared applications. A design method of infrared non-polarizing beam splitter in a cube is proposed, the theoretical analysis is given, designs for different substrates are demonstrated and the simulations of their optical properties are presented in this paper.
The effects of linear birefringence (LB) upon Bulk Glass Optical Current Transformers (BGOCTs) with return-back optical path designs, such as the Orthoconjugate Reflection (OCR)-typed, the Direct Reflection (DR)-typed and the Roof-prism Reflection (RPR)-typed BGOCT design, are theoretically analyzed and compared with that of the BGOCT with a single-loop optical path in this paper. The results show that the return-back dual-loop current sensing designs with conventional signal processing scheme of "-/+" cannot eliminate the harmful effects of the LB thoroughly, if suitable signal processing schemes which can separate the LB from Faraday effect are not used.
The effects of the linear birefringence inside a bulk glass current sensing element and the incident polarizing angle upon the performance of a bulk glass optical current sensor are derived and analyzed theoretically. The investigation results show that the linear birefringence will modify the scale factor of the system with a sample function; it can also affect the extent of the influence of the incident polarizing angle, at the same time. When the incident polarizing angle has some special values such as 0, 45, or 90 degree, its effect to the system will be zero. These results might provide some useful reference to the researchers and designers of bulk glass optical current sensors.
The wavelength dependence of the sensitivity of a bulk-glass optical current transformer is theoretically analyzed taking the Jones’ Matrix as a mathematical tool, simulated with a computer and verified with an experiment. The results show that the wavelength dependence will cause obvious sensitivity fluctuation of the system because of the existing of the dispersions of the reflection-induced retardance, Verdet constant and the linear birefringence inside the bulk-glass current transducing head. Therefore, it is necessary to stabilize the driving current and the ambient temperature of the optical source used by some technical means, because these two factors can result in wavelength variation. These results might be useful for the researchers and designers working in the optical current transducing techniques area.
The dispersion properties of the reflection-induced retardance of the polarization-preserving reflecting medium layer and its effect upon the sensitivity of an optical current sensor are theoretically analyzed taking the Jones' Matrix as a mathematical tool and simulated with a computer. The investigation results show that the dispersion will obviously affect the scale factor of the system. Therefore, it is necessary to stabilize the driving current and the ambient temperature of the optical source by some technical means. These results might be useful for the researchers and designers working in the optical current sensing techniques area.
Linear birefringence inside the sensing head can obviously affect the performances of optical (fiber-optic) current transformers. Therefore, it is important to measure the linear birefringence for the design and the property enhancement of optical current transformers. A method employing a retarder to measure the linear birefringence inside the bulk glass current sensing head is reported. The theoretical analyses of the principle and the measurement uncertainty of the method are given using Jones Matrix as a mathematical tool. An applied example is also given. The main advantage of this method is that it can uniquely determine the value of the linear birefringence inside the sensing head, which overcomes the shortcoming of that only a trigonometric function value of the birefringence can be determined by the method reported before. Furthermore, there are some other advantages such as simple structured, practical and that the devices needed are easy to obtain.
A novel method used for the enhancement of the accuracy of the measurement of the retardance of a quarter-wave plate employing two polaroids and a prism is reported under the condition of knowing the direction of the fast axis of the plate. The theoretical analysis of the principle and the uncertainty formula are given. An application example is also demonstrated. The measured result of the example is verified with an experiment. The main advantages of this method include the accuracy enhancement, simple measuring setup and easy operation.
We found a new solid electrolyte K-Cu-I thin film which can transmit the organic group (OG). The film was prepared by depositing a mixture of KI and CuI powders on heated glass substrate in vacuum. Under direct current (DC) electric field, the OGs can migrate toward cathode through the K-Cu-I film and congregated at the edge of the cathode. At room temperature, the film had an OG conductivity that can reach up to 0.15Ω-1cm-1 when the electron conductivity was ignorable (σ≤10-4Ω-1cm-1).
We report a novel application of the solid electrolyte K-Cu-I thin film for preparing copper nanowires. The K-Cu-I film was prepared by depositing a mixture of KI and CuI powders on a heated glass substrate in vacuum and had a copper ion conductivity of 1.5x10-3Ω-1cm-1 at 540K. At 540K, being applied a direct current (DC) electric field of 1.0x104 V/m, the copper ions migrated toward cathode through the K-Cu-I film and congregated to form nanowires at the edge of the cathode. The copper nanowires were about 40~100nm in diameter and several micrometers in length.
The measurement of reflection-induced retardance of optical devices is the usual case encountered in optical research, development and engineering. This kind of measurement usually can be completed using a linear polarizer and a retarder. A novel method used for the measurement of reflection-induced retardance employing a polarizer and an analyzer is proposed in this paper, the theoretical analysis of the method and an application example are given.
In this paper, a novel approach to measure linear birefringence in bulk optical glass sensing heads of current sensors is reported. The theoretical analysis based on Jones matrix, the formula of uncertainty and applied examples are also given. The main advantages of this method are simple structured, practical and that the devices needed are easy to obtain.
Extinction ratio is an important parameter of a polarizer, and the bias angle of the polarizer used in optical current sensing systems is also an important adjustable parameter. Both them can certainly affect the performance of the sensing systems. In this paper, the effects of the extinction ratio and bias angle error of polarizers upon the output characteristics of an optical current sensor are investigated theoretically and experimentally, some useful results are given for the optical current sensor designers.
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