非均匀扰动结构TE0n模式变换器研究

本文提出一种半径和周期双重扰动的非均匀圆波导TE_0n模式变换器. 通过耦合波理论(CWT)和数值优化方法对该模式变换器进行研究, 计算结果与电磁仿真软件基本一致. 与传统的均匀结构半径微扰模式变换器比较, 非均匀扰动结构TE_0n模式变换器可以在更少的波纹周期内实现高于均匀结构的模式转换效率, 95%功率转换绝对带宽增加150%, 器件长度减小接近一半. 本文的研究工作为设计轴向尺寸短、工作带宽大、 转换效率高的高功率回旋管外接模式变换器提供了重要参考.     

宽带非均匀半径渐变TE0n-TE0(n+1)模式转换器的设计研究

基于耦合波理论,对两类半径渐变圆波导TE_0n-TE_0(n+1)模式转换器进行理论分析、数值计算和仿真模拟.均匀半径渐变波导高功率模式转换器,采用中心频率为17.14GHz、六周期TE₀₂-TE₀₃模式和中心频率为34.30GHz、六周期TE₀₁-TE₀₂模式两种设计参数.非均匀半径渐变波导高功率模式转换器,采用中心频率为34.30GHz、六周期TE 关键词： 模式转换器 耦合波理论 非均匀半径渐变 转换带宽     

A novel Y-branch waveguide for power dividing and mode splitting

A novel Y-branch waveguide for variable-ratio power dividing and transverse electrical-transverse magnetic (TE-TM) mode splitting depending on the applied voltage is presented. The Y-branch waveguide is formed by two closely coupled waveguides tabricated by nickel indiffusion (NI) and by magnesium-oxide induced lithium outdiffusion (MILO) in a y-cut lithium niobate (LiNbO₃) substrate. The TE component of the randomly polarized light is tuned between these two waveguides, such that the device can be either a power divider or a mode splitter depending on the applied voltage. The measured TE mode extinction ratio is about 20 dB.     

Micro-optical 3-dB mode converters

We present a detailed design of a 3-dB TE₀-TE₁ micro-optical mode converter using a chirped grating to phase-match the two propagation modes in an optical waveguide. Devices were fabricated in titanium in-diffused lithium niobate by ion-beam etching the tapered grating pattern into the waveguide surface. The power transfer between the two coupled modes was observed experimentally by varying the angle between the light beam and the normal grating wave-vector. Insertion loss of the TE₀-TE₁ mode converter due to spurious scattering was estimated at 1.5 dB.     

Collinear light scattering on dipole-exchange spin waves in inhomogeneous ferromagnetic films

A theory is developed for the collinear TE-TM scattering of optical waveguide modes on dipoleexchange spin waves in perpendicularly magnetized ferromagnetic films that are inhomogeneous across their thickness. It is found in homogeneous ferromagnetic films and in films with small deviations from homogeneity that the TE-TM scattering on higher spinwave modes is strongest when the synchronism conditions for the transverse phases and for the longitudinal and transverse wave vectors are satisfied. When the thickness of the planar optical waveguide does not match the thickness of the ferromagnetic film, the phase synchronism condition is violated with the resultant appearance of an oscillating type of dependence of the TE-TM scattering on the spin-wave mode number. The scattering of light on spin-wave modes in films with a magnetization gradient is investigated in the presence of turning points for the magnetostatic potential. It is found that the existence of a turning point in the region of the antinode for the optical modes leads to an increase in the scattering amplitude. The formation of inhomogeneous magnetooptical structures and superlattices based on (Lu,Y,Bi)₃(Fe,Ga)₅O₁₂ is discussed. Zh. Tekh. Fiz. 68, 78–84 (June 1998)     

Acoustooptic collinear TE-TM mode conversion in a two-layer Ti-indiffused and proton-exchanged waveguide structure in LiNbO3

Acoustooptic collinear TE-TM mode conversion was investigated in a two-layer Ti-indiffused and proton-exchanged waveguide structure in LiNbO₃. A very narrowband interaction of only 130 kHz (0.31 nm optical bandwidth) was achieved with about 25 mW acoustic power for 96% conversion efficiency. This structure is especially suitable for constructing novel-type acoustooptical gas sensors.     

An improved optical TE-TM mode splitter and modulator using a Ti-LiNbO3 Y-junction waveguide

An optical TE-TM mode splitter and modulator with an improved design using a Y-junction waveguide by Ti-diffusion in a Y-cut LiNbO₃ substrate has been fabricated and characterized. Improvements in fabrication and measurement techniques are discussed. Experimental results on the device characteristics are presented.     

Quansi-optical mode converter for Ka-band application on a gyrotron

A series of electron cyclotron masers (ECMs) has been designed and successfully operated in the frequency range of 6 to 200 GHz over the past 10 years at Strathclyde University. The current Mk. VI ECM operated between 35–200 GHz, the TE _{0 1} ⁰ mode (35.2 GHz) being the lowest order cavity mode excited. Investigation of this ECM and quasi-optical converter combination was made to establish to what extent a Gaussian beam could be produced from the TE _{0 1} ⁰ gyrotron cavity mode.An antenna of the Vlasov (step-cut radiator) configuration was chosen and successfully developed in a series of low-power experiments up to the W-band frequency regime. The low-power experiments demonstrated that such an antenna system could be constructed and operated in the K_a-band frequency region without resorting to high precision quasi-optical components. The final version of the quasi-optical antenna was externally coupled to the output window of the maser and a plane polarized pencil beam was successfully obtained from the combined maser/Vlasov antenna mode converter.A theoretical model involving a single TE _0n ⁰ input mode was chosen to analyse the output beam characteristics from the Vlasov antenna system. Comparison was made between the single mode theoretical model and the experimental results obtained from the maser.     

X波段过模弯曲圆波导TM01-HE11模式变换器研究

在波束波导和反射面天线的馈源应用中, 为了产生低副瓣且方向图等化的高斯波束, 需要将高功率微波转换为准高斯模HE₁₁模辐射. 本文利用弯曲圆波导可同时从TM₀₁模产生TE₁₁模和TM₁₁模的原理, 提出了采用双弯曲过模圆波导结构直接将TM₀₁转换为HE₁₁的模式变换器, 避免了常规微波领域中首先将TM₀₁转换为TE₁₁再用波纹式或半径渐变式TE₁₁-HE₁₁转换器转换为准高斯波束功率容量不足或尺寸过长的不足. 基于模式耦合理论和Taguchi优化算法对模式变换器的弯曲半径、相移直端长度及引入位置进行了优化, 使输出的TE₁₁和TM₁₁成一定比率, 以组成HE₁₁模式, 并对设计的模式变换器进行了全电磁波仿真分析, 结果表明输出波束的标量高斯含量在9.05–9.8 GHz范围内均高于99%, 理论功率容量可达4.5 GW. 关键词： 高功率微波 模式耦合理论 Taguchi优化算法 模式变换器     

Spectral Polarimeters Based on Integrated Acousto-Optical Ti:LiNbO3 TE-TM Converters

An integrated Ti:LiNbO3 acousto-optical TE-TM converter followed by a polarizer was used to realize a wavelength-selective polarimeter. The stop-band attenuation was shown to increase to > 28 dB when more mode converters were integrated on a chip. Based on this experience, a four-stage demonstration unit was built, and polarimetric spectra as well as the time evolution of the state of polarization were measured. Finally, a simple optical spectrum analyzer is proposed.     

Determination of phase mismatch in a Z-propagating LiNbO3 TE-TM convertor

We describe a method suitable for the measurement of phase mismatch in a LiNbO₃ Z-propagating TE-TM convertor. The method is based on the measurement of the transmission peaks produced by a mode coupling voltage applied to the electrodes. A major advantage of the method is that it allows phase mismatch measurements to be performed with quite a few parameters easily assessable experimentally (operating wavelength and electrode length).     

Refined relationship between extended Rydberg and generalized Morse functions for a special class of diatoms

In line with the development of a potential function converter software, numerous relationships among parameters of interatomic potentials have been established in recent years. In the recently developed relationship between the extended Rydberg and the generalized Morse parameters an excellent agreement was found for a ₂ > 0, but an inaccurate one for a ₂ < 0. To address the inaccuracy of the latter case, a refined relationship is developed herein by recasting the generalized Morse potential in a form that more closely resembles the extended Rydberg function by using series approximation. Results show that, for the special case of a ₂ < 0, the refined relationships give better agreement as compared to the previously developed one. Consequently, the developed relationship will be incorporated into the proposed potential function converter software.     

Broadband mode converter and multiplexer based on dielectric-loaded plasmonic waveguides

We theoretically demonstrate a broadband mode converter and multiplexer based on plasmonic waveguides loaded with structured dielectrics. The proposed device can realize conversions between a fundamental TM₀ mode and a first order TM₁ mode, as well as (de)multiplex them with another TM₀ mode. Our design exhibits as wide as 400 nm bandwidth and as short as 6~7 μm coupling length. This work has potential application in high density photonic integrated devices for both computing and communication applications.     

Spectral Polarimeters Based on Integrated Acousto-Optical Ti:LiNbO3 TE-TM Converters

An integrated Ti:LiNbO3 acousto-optical TE-TM converter followed by a polarizer was used to realize a wavelength-selective polarimeter. The stop-band attenuation was shown to increase to > 28 dB when more mode converters were integrated on a chip. Based on this experience, a four-stage demonstration unit was built, and polarimetric spectra as well as the time evolution of the state of polarization were measured. Finally, a simple optical spectrum analyzer is proposed.     

Method for synthesis of wideband multimode waveguide elements

We propose a modification of the iterative method for synthesis of waveguide mode converters, which allows obtaining various elements of microwave transmission lines with a wide operating frequency band. The efficiency of the synthesis is illustrated by the calculated waveguide components. This method makes it possible to synthesize converters with significantly improved characteristics, e.g., a converter of the TM_0,1 mode to the rotating TE_3,1 mode, a converter of the TM_0,1 to the TE_1,1 mode, a converter of the TE_1,1 mode of a smooth waveguide to the HE_1,1 mode of a corrugated waveguide, and a waveguide 90° bend for the TE_1,1 mode. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 9, pp. 793–799, September 2007.     

Efficient and compact TE-TM polarization converter built on silicon-on-insulator platform with a simple fabrication process

An efficient TE-TM polarization converter built on a silicon-on-insulator nanophotonic platform is demonstrated. The strong cross-polarization coupling effect in air-cladded photonic-wire waveguides is employed to realize the conversion. A peak TE-TM coupling efficiency of 87% (-0.6 dB insertion loss) is measured experimentally. A polarization conversion efficiency of >92% with an overall insertion loss of <-1.6 dB is obtained in a wavelength range of 40 nm. The proposed device is compact, with a total length of 44 μm and can be fabricated with one lithography and etching step.     

Numerical modelling of 8mm TM01-TE11 mode converter

A numerical study of TM₀₁-TE₁₁ circular waveguide mode converter, with its optimized size and structure, is presented in this paper. Many factors such as spurious modes, backward wave, perturbation functions of waveguide axis or radius, phase-rematching techniques and ohmic losses are taken into account for the influence to mode converter's efficiency and bandwidth. And the dimensions of an optimized model (f₀=35GHz. with input and output radius a₀=13.6mm) are given.     

The fabrication of polymer-based evanescent optical waveguide for biosensing

A polymer waveguide was fabricated to amplify the evanescent optical field for biosensing. The structure of waveguide was designed to propagate a normal single mode at the input and output regions for low loss beam coupling and propagation. A sensing region was formed in the middle of the waveguide to activate the evanescent mode and to induce high birefringence by depositing a thin dielectric film with a high refractive index on a single mode waveguide. A polymer waveguide with the dimensions of 7 μm-width and 2.5 μm-thickness was fabricated by photolithography and dry-etching. The active region of the TiO₂ thin film was fabricated with the dimensions of 20 mm-length, 20 nm-thickness and 2 mm-tapered tail. A polarimetric interference technique was used to evaluate the evanescent waveguide biosensor, and biomaterial such as glycerol was tested. The sensitivity of the sensor increased with increasing TiO₂ film thickness. For the fabricated waveguide with a 20 nm-thick TiO₂ film, the measured index change to the lead phase variation of 2π was 1.8 × 10⁻⁴.     

Ka波段高功率斜角弯头的设计

介绍了一种基于准光技术的高功率斜角弯头的设计方法,可实现圆波导TE0m模式的高效转弯传输。使用模式变换器将工作模式TE0m转换成锥形高斯模,经过转弯后,锥形高斯模被重新转换成工作模式。这种锥形高斯模可以减少波束在镜面的衍射,从而实现工作模式的高效率转弯传输。基于这一方法,设计了工作在Ka波段、工作模式TE01的MW级波导斜角弯头。HFSS计算结果表明: 在8%的带宽内,传输效率大于98%。     

Depletion-induced sphere-cylinder transition in C12E5 microemulsion: a small-angle X-ray scattering study

Small-angle X-ray scattering was used to study the mixture of C₁₂E₅ (pentaethylene glycol monododecyl ether)/H₂O/n-decane microemulsion and polyethylene glycol (PEG). The size, shape and the structure factor of the microemulsion were investigated by adding the polymer (PEG) to the mixture. Attractive depletion potential was induced between the microemulsion droplets by the non-adsorb polymer. The range and strength of the attractive potential were changed by varying the molecular weight and concentration of PEG. The forward scattering, S(0), of the spherical microemulsion, declined gradually as the polymer concentration decreased. For PEG with the molecular weight of M_n = 285?315, the microemulsion morphology remained spherical, but the main peak of the structure factor moved towards a bigger q. When PEG with molecular weights of M_n = 2200 and M_n = 6000 were used, a shape transition from spherical to cylindrical was induced in line with increasing polymer concentration.