Backscattering for circular polarisation

Equations are given that express scattering for transmitting and receiving circularly polarised waves in terms of the characteristics for linear polarisation. Special cases are discussed, for which it is possible to estimate the radar cross-section for one polarisation based on data for other polarisations. Knowledge of polarisation characteristics is sometimes helpful for acquiring insight into the scattering mechanisms of complex surfaces.     

Wideband trapezoidal strip grating for elimination of specularreflection

A trapezoidal strip grating surface that eliminates specular reflections almost over the entire X-band frequency range for TM polarisation is reported. This new grating structure overcomes the bandwidth limitation of conventional rectangular strip grating surfaces     

Axial ratio improvement in aperture antennas using high-impedance ground plane

High-impedance surfaces are studied as a means of improving the radiation pattern symmetry in aperture antennas. Compared to a solid metal ground plane, the results suggest that high-impedance surfaces can significantly improve the axial ratio of circularly polarised antennas. This can be used to reduce interference between left and right polarisation components.     

Reflection circular polarisers

Conducting surfaces corrugated with rectangular grooves which convert linearly polarised incident waves to circular polarisation are described. Design data for normal incidence and for incidence at 45° to the normal are given.     

Frequency selective surface design based on genetic algorithm

An optimisation procedure based on the genetic algorithm is applied to the design of frequency selective surfaces (FSSs) fabricated by printed circuit technology. The inclusion of the shape of the mask in the set of parameters controlling the optimisation scheme enables the requisite frequency and polarisation performance to be obtained     

New simulated corrugated scattering surface giving wideband characteristics

Simultaneous elimination of specular reflection and backscattered power from a plane metallic surface by simulated corrugated surfaces of constant period and variable strip width for TM polarisation is reported. This new configuration offers almost a ten-fold frequency bandwidth compared with a regularly spaced strip grating of the same size.<>     

Variable polarisation compensator using artificial dielectrics formillimetre and submillimetre waves

A variable polarisation compensator has been designed and demonstrated experimentally at 100 GHz. The device uses two silicon plates with interlocking artificial dielectric surfaces to produce a birefringence that varies with the separation distance. The experimental results indicate a maximum differential phase-shift of 74°, and show good agreement with computer simulations     

Cross-polarisation and astigmatism in matching grooves

Circular grooves are frequently cut in dielectric lenses and windows to form antireflection layers. These induce a phase difference between polarisation components, with consequent loss of power into cross-polarisation and a phase error similar to astigmatism. Expressions derived for these losses show that the losses are generally small compared to the insertion losses of an unmatched surface. For several consecutive surfaces the effects may be quite significant.     

Cross-shaped dielectric resonator antenna analysis using conformalfinite difference time domain method

A cross-shaped dielectric resonator antenna, designed for circular polarisation, is analysed via the conformal finite difference time domain technique. The conformal technique, which can handle canted surfaces that do not conform to the Cartesian system of co-ordinates, is used to generate accurate results with a relatively coarse mesh, e.g. it is shown that the conformal FDTD offers a 2:1 advantage over staircasing, without compromising accuracy     

四通道多模光纤旋转连接器的相关问题及措施

提出了多通道光纤旋转连接器的全新级联方式，对出现的一些问题进行了分析并采取了相应的解决措施，最后给出了四通道光纤旋转连接器的一些实验结果。     

光偏振的微小旋转角的测量技术

本实验提供一种对光偏振的微小旋转角的测量技术、实验采用法拉第调制方法,分别用６３２．８ｎｍ的Ｈｅ－Ｎｅ激光器和５３２ｎｍ的ＬＤ泵浦固体激光器做测量光源,对乙醇水溶液（浓度５０％）的磁光法拉第偏振角进行测量,当改变外加磁场的磁感应哟度时,可使偏转角在亚毫度范围内取值,采用这一技术,对蔗糖水溶液的旋光角进行测量,浓度低达每毫升１０＾４克,为具有小的常德常数的化学物质或生命物质地旋光测量提供了很好的手段     

透明液晶薄膜旋光色散特性研究

以透明塑料为基板,将液晶薄膜均匀涂于其上制成透明的具有旋光性的薄片,并用自行研制的旋光色散装置,对所制薄片的旋光色散特性进行了研究,测试结果显示其具有很大的旋光性.同时,用玻尔兹曼方程进行了理论拟合,发现拟合结果与实验结果有着极好的符合。     

Polarisation conservation in single-mode fibres

There exist proper orthogonal elliptical polarisation states, which are maintained over long fibre length without converting. When one of the proper polarisation states is excited, orthogonal polarisation less than ?40 dB is confirmed after 5 km single-mode fibre transmission. It is also proposed that twisted single-mode fibres show a high degree of polarisation for any incident polarisation state. The polarisation characteristics are hardly affected by external perturbations.     

Spin controlled optically pumped vertical cavity surface emitting laser

It is shown that the output polarisation of optically pumped vertical cavity surface emitting lasers (VCSELs) can be unambiguously controlled by the pump polarisation. The degree of the output polarisation is higher than that of the pump polarisation. It is concluded that the polarisation of VCSELs with spin polarised electrical pumping can be controlled even with low spin injection efficiencies.     

Polarisation-scrambled Er-doped superfluorescent fibre source with improved mean-wavelength stability

A polarisation scrambling scheme is employed to reduce the pump-polarisation-dependent mean-wavelength change in the Er-doped superfluorescent fibre source for gyroscope application. A PZT-based fibre-optic polarisation modulation is used at the pump port for polarisation scrambling. Changes of mean wavelength owing to pump polarisation variation are suppressed below 1 ppm.     

Active stabilisation of polarisation on a single-mode fibre

We report on a practical method for stabilising the state of polarisation on a single-mode fibre exhibiting a 100% degree of polarisation. The principle of operation is reviewed, as are the practical implementation aspects and experimental results for polarisation stabilisation with a 1.3 ?m-wavelength laser diode.     

New fabrication technique for high performance polarisationmaintaining optical fibre couplers

A simple and novel technique for fabricating polarisation maintaining optical fibre couplers is reported. This technique is different from existing approaches of polarisation coupler fabrication, in that it avoids the need to align the polarisation axis during each coupler fabrication. Both low loss and low polarisation crosstalk have been achieved     

Quadrature phase sampling of a fibre interferometer by input-polarisation switching

A technique for the generation of quadrature phase components at the output of a fibre interferometer using input polarisation modulation is described. This approach allows a passive path-balanced sensor interferometer to be remotely interrogated using a simple concept based on polarisation switching of the input state of polarisation coupled to the interferometer.<>     

Impact of polarisation mode dispersion on 10 Gbit/s terrestrialsystems over non-dispersion-shifted fibre

Depending on the launched state of polarisation 10 Gbit/s system impairments are investigated experimentally in the presence of chromatic dispersion and variable differential group delay caused by polarisation mode dispersion. In addition an actual fibre cable, not an optical simulator was used to bring polarisation mode dispersion     

Stress effect for polarisation control of surface emitting lasers

To control the electric polarisation of output light in surface emitting (SE) lasers, the stress effect on the resonance model of SE lasers with an elliptical holed region is investigated. For the first time, polarisation switching by external stress has been observed and the relation between the polarisation characteristics and the structural dependence on stress clarified.<>