Integrated optical waveguide polarizer based on photobleaching-induced birefringence in an electrooptic polymer

A TE-pass waveguide polarizer is fabricated by utilizing the photobleaching-induced birefringence at room temperature in an electrooptic polymer. The polarizer consists of the photobleached waveguide supporting only TE mode, which is integrated in the middle of the etched rib waveguide supporting both TE and TM modes. It has a simple structure and requires no high temperature process like poling. The measured polarization extinction ratio is about 21 dB at the wavelengths of 1.3 and 1.55 /spl mu/m, and the estimated excess loss is about 0.4 dB.     

基于Bragg光栅的超高消光比SOI波导偏振器设计

波导偏振器是片上集成相干光学系统中的关键器件之一,超高消光比、低损耗、紧凑型波导偏振器的设计一直是研究的热点。基于绝缘体上硅平台的倾斜Bragg光栅被用于实现超高消光比波导偏振器结构。利用一维光子晶体能带理论分别计算TE和TM模式光的能带结构分布,选择TE模式禁带与TM导带重叠带隙设计光栅,可实现TM模式低损传输,而TE模式被Bragg光栅高效反射,从而产生超高偏振消光比。3D FDTD仿真表明:16 μm倾斜Bragg光栅波导偏振器可在中心波长1550 nm附近70 nm的带宽内,实现大于37 dB的超高消光比,器件的损耗小于0.64 dB;进一步增加光栅周期数,当长度为25 μm时,消光比可提高至46 dB。Bragg光栅倾斜角与刻蚀宽度偏差仿真表明:设计的结构加工误差容限较大,同时该结构仅需一次曝光刻蚀,工艺流程简单。     

Design of finite-length metal-clad optical waveguide polarizer

The performance of optical metal-clad waveguide polarizers is analyzed in this paper with a view to optimizing the extinction ratio, a condition for which power of the TM mode is completely attenuated is identified here. In general, such a condition corresponding to an infinitely high extinction ratio can be met for a wide range of buffer layer thicknesses by selection of metal film thickness and polarizer length. When a very thick (e.g., semi-infinitely thick) metal film is used, the aforementioned condition can be met with a properly chosen buffer layer thickness and polarizer length. The numerical results show that all the polarizers designed here for realization of infinitely high extinction ratios have either quite low or reasonably acceptable attenuations for the TE mode     

Silica-based 8×8 optical matrix switch integrating newswitching units with large fabrication tolerance

An 8×8 optical matrix switch consisting of asymmetric Mach-Zehnder (MZ) interferometer switching units with a waveguide intersection was fabricated using silica-based planar lightwave circuits (PLC's) on a silicon substrate. This switching unit can realize a high extinction ratio and a wide operation wavelength range even if the coupling ratios of the directional couplers (DC's) consisting the switching unit, deviate greatly from the ideal value of 50%. A matrix switch with a DC-coupling ratio of 30% was fabricated to test the validity of the proposed geometry. The average insertion loss was 7.3 dB in the transverse electric (TE) mode and 7.5 dB in the transverse magnetic (TM) mode. The average extinction ratio was 31.2 dB in the TE mode and 31.3 dB in the TM mode. The wavelength range with an extinction ratio greater than 20 dB was over 100 nm     

In-line optical fiber polarizer and modulator coated withLangmuir-Blodgett films

In-line optical fiber polarizer and modulator were fabricated by depositing Langmuir-Blodgett (LB) films on polished fiber surface with gold layer. The thickness of LB film was adjusted by changing the number of monolayers, which then optimized the performance of the fiber polarizer. Good agreement was observed between the theoretically predicted conditions for efficient coupling and the experimentally determined conditions for high TM/TE extinction ratio of the optical field. By applying an electric field between the LB film, the polarization state of the lightwave in the optical fiber can be modulated     

Integrated optical waveguide polarizer on glass with a birefringentpolymer overlay

An integrated optical waveguide polarizer on glass is described. It is based on a filtering zone propagating only TE mode whereas the TM mode leaks out into a birefringent polymer simply deposited on the glass. The polymer is poled by a corona process. The measured polarization extinction ratio between TE and TM modes is better than 39 dB and the excess loss due to the filtering zone is less than 4 dB. The total loss is in the order of 7 dB     

TM-pass polarizer based on multilayer graphene polymer waveguide

A TM-pass polarizer based on multilayer graphene polymer waveguide is proposed and theoretically analyzed. The mode properties, the extinction ratio, the insertion loss and the bandwidth are also discussed. The results show that a TM-pass polarizer, which only guides the TM mode, can be achieved by multilayer graphene polymer waveguide. With length of 150 μm, the proposed polarizer can achieve extinction ratio of 33 dB and insertion loss of 0.5 dB at optical wavelength of 1.55 μm. This device has an excellent performance, including large extinction ratio and low insertion loss within the spectral range from 1.45 μm to 1.6 μm.     

Analysis of the ${rm TE}$ -Pass or ${rm TM}$-Pass Metal-Clad Polarizer With a Resonant Buffer Layer

A metal-clad optical polarizer with a resonant buffer layer has been investigated by the finite-element method in this paper. Important waveguide design parameters, such as the refractive index, thickness, interaction length, fabrication tolerance, and band-stop characteristics, have been analyzed in detail. Mode coupling within the polarizer and the losses due to coupling between the polarizer and the input and output waveguides are considered using the normal mode analysis. The loss behaviors of and modes are explained and the roles of the resonant buffer layer are interpreted. By using ultralow index layers, resonance, as well as its phase-matching conditions and excellent performance, has also been presented and discussed for this structure for the first time. Simulations show that high performance can be achieved in a wide range of the cladding thicknesses (ges 2 mum) and interaction length for both TE-pass and TM-pass polarizers. With optimized parameters under 3-mm length, it is possible to obtain a broadband TE-pass polarizer with an extinction ratio of more than 40 dB and insertion loss below 0.2 dB over 200 nm, and a TM-pass polarizer with an extinction ratio of more than 30 dB and insertion loss below 0.4 dB over 28 nm.     

Design of three-dimensional silica on a silicon single-mode single-polarization waveguide

We present a design of three-dimensional(3D) silica on a silicon single-mode single-polarization waveguide (SMSPW) by taking into consideration the induced birefringence effect of the silica.This can cut off the TM mode and transmit the TE mode.The characteristics of the light propagating across the polarization maintaining waveguide were simulated by 3D beam propagation methods(3D-BPM).The result showed that the SMSPW has a high extinction ratio over 50 dB for the TM mode.Without increasing the complexi...     

硅基二氧化硅单模单偏振光波导的设计

在不增加工艺难度的前提下,利用硅基二氧化硅光波导的双折射效应并结合有效折射率方法, 设计了一种新型单模单偏振波导, 使得两个正交偏振模式中的TM 模式被截止, TE 模式可以通过. 利用三维有限差分光束传输法(3D -BPM ) 进行数值模拟,结果显示,对于TM 模式消光比可高达到50dB 以上.此种结构的光波导可以直接制作偏振器, 同时还易与其他波导器件集成.     

Waveguide polarizer based on resonant tunneling

A novel and highly efficient waveguide polarizer which is based on the phenomenon of resonant tunneling is proposed. Designs for both transverse-electric (TE) and transverse-magnetic (TM) pass polarizers based on this principle are suggested, and it is shown that with such a device it is possible to achieve TM mode loss greater than 80 dB/mm and TE mode loss less than 0.5 dB/mm for the TE pass polarizer, and TE mode loss of 24 dB/mm with a TM mode loss less than 0.8 dB/mm for the TM pass polarizer     

Poling-induced waveguide polarizers in electrooptic polymers

In order to demonstrate polymeric waveguide polarizers, photobleached polymer waveguides supporting both TE and TM modes are integrated with poling induced polymer waveguides that support either TE or TM modes. Fabrication parameters like UV exposures and poling voltages are controlled to reduce excess losses due to the mode profile mismatch between the connected waveguides. A TM-pass polarizer is realized by poling the polymer in the vertical direction. For TE-pass polarizer the polymer is poled horizontally by using four poling electrodes which enhance the uniformity of the poling field direction. The measured excess loss is less than 0.5 dB, and polarization extinction ratios for TM-pass and TE-pass polarizers are 20.7 dB and 17.1 dB, respectively.     

LiNbO3TE-TM mode converter using collinear acoustooptic interaction

A highly efficient TE-TM mode conversion device utilizing the acoustooptic effect has been demonstrated. Mode conversion has been made by an acoustic surface wave propagating collinearly with an optical guided wave. The maximum mode conversion, although the fraction was restricted to 70 percent, has been obtained with an acoustic power of only 55 mW (electrical input 0.55 W). Effective interaction length of the present device is limited to 5 mm due to optical and/or acoustic inhomogeneity of the waveguides. For selecting TE and TM waves, a polarizer is constructed monolithically and the extinction ratio is improved by up to 21 dB. Performance characteristics of a tunable optical filter of this type of the mode conversion are also discussed.     

基于两次衰减全反射结构的激光偏振控制器

为了实现激光偏振态的控制和提高两偏振态消光比,用由各向异性材料加工而成的耦合棱镜并采用两次衰减全反射方法,使具有相同入射角的TE和TM偏振态的共振激发条件不同,即当TE偏振态满足共振激发条件能量耦合进波导时,TM偏振态却不满足共振激发条件而被反射来实现其在空间上的分离.同时将电光系数较大、光学性能和热稳定性好的聚合物材料作为波导层,利用其电光效应来改变共振条件来实现输出光束偏振态的调谐.结果表明,反射型结构插入损耗小于0.2dB,器件的消光比高达27dB,驱动电压为19V.该方案预计在光信息存储、光路由、光开光以及图像处理等光学系统里有着极其广泛的应用.     

Single-Mode Fiber-Type Polarizer

The simple and novel fabrication technique of the fiber-type polarizer has been demonstrated and the polarization characteristics of the polarizer have been investigated. The polarizer structure consists of the eccentric core and the metal coat on the thin buffer layer whose thickness is controlled by chemical etching. The maximum extinction ratio of 41 dB (polarizer length L = 40.8 mm) was obtained at Lambda = 1.15 µm when the buffer layer thickness was about 0.3 µm. Although the insertion loss increases with decreasing the buffer layer thickness, the insertion loss of 0.66 dB was obtained with the extinction ratio of 22 dB (polarizer length L = 21.4 mm). An aluminum coat was superior to a gold coat for low propagation loss and a high extinction ratio.     

INPUT COUPLER FOR Ka BAND TE021 CIRCULAR ELECTRIC MODE OPERATION IN A GYROKLYSTRON AMPLIFIER

An input coupler for the TE021 circular electric mode in a gyroklystron amplifier through using TEs11 as a transition coupling mode in a coaxial cavity has been proposed and numerically simulated in a frequency range of Ka-Band with HFSS code. The coupling efficiency of the TE021 mode and the suppression for the TE811 mode in the main cylindrical cavity are deliberately considered by adjusting the position and size of coupling holes as well as the radius of the drift tubes. The numerical results show that the TE021 mode can successfully be excited, and rational coupling efficiency and high mode purity for the TE021 mode in the cylindrical cavity can be reached for the engineering application of gyroklystron amplifier study.     

Polarization-selective mode coupling in two-mode Hi-Bi fibers

We propose and demonstrate a mode coupler which converts either of the LP₀₁ polarization states in a two-mode high-birefringence (Hi-Bi) fiber to the LP₁₁ mode with the same polarization. We use coupled-mode theory to develop design rules based on the polarization splitting of the beat length between the two lower-order modes. The device can be operated either as a narrow-band device in a region with large intermodal group delay difference or as a broadband device in a region with zero group delay difference. We use this novel device as a key component in a two-mode Hi-Bi fiber polarizer. In this configuration either of the polarization eigenstates can be selected and transmitted with an adjustable extinction ratio which can be as large as 30 dB. The coupling loss in the transmitted state of polarization can be less than 0.2 dB. In the broadband polarizer we demonstrate -20 dB extinction over 42 nm with a potential for considerable improvement. We also propose and experimentally investigate an increased differential group delay obtained by propagating one polarization state in the LP₁₁ mode instead of in the LP₀₁ mode. The largest differential group delay measured in this configuration is 14.5 ps/m which is seven times larger than the differential group delay between the polarization modes. We discuss several possible uses in fiber sensors and measure the transmission of a proposed two-coupler configuration     

基于表面等离子波耦合的流体波导光栅耦合器

提出了一种由金属光栅和流体光波导结构组成的,基于表面等离子波耦合的光栅耦合器。利用光栅的衍射效应,将金属光栅与介质分界面之间产生的表面等离子波耦合到流体光波导中,并且能够沿着流体光波导稳定地向前传播。通过采用基于有限时域差分算法的FDTD Solutions软件对光栅耦合器进行了参数优化及特性分析,通过优化使该结构在650 nm波长下的耦合效率达到56%。此外,由于该结构对TE偏振光和TM偏振光的选择比达到70∶1,因此具有偏振器的功能。同时由于TE偏振光耦合频谱的频带宽度仅为20 nm,该结构还具有窄带滤波的作用。此外,还研究了光栅结构参数、入射角以及流体折射率对耦合频谱的影响。     

Polarized Superfluorescent Fiber Sources

We report the theoretical and experimental performance of new, linearly polarized superfluorescent fiber sources (SFS). Internal polarization is produced either by splicing a fiber polarizer at an optimum location along a standard Er-doped SFS or by using a single-polarization Er-doped fiber. Numerical simulations predict that when operated in the backward, forward, or double-pass configuration, these SFSs produce nearly twice the power in the desired linear polarization as a standard, unpolarized SFS. This efficiency figure depends weakly on the polarizer location and extinction ratio, but requires a low polarizer insertion loss ( < 0.5 dB). Laboratory prototypes of a backward and a forward polarized SFS are presented that exhibit a power output in the desired linear polarization about 1.75 times larger than that of an unpolarized SFS, and an extinction ratio in excess of 17.5 dB.     

等离激元微腔耦合长波红外量子阱高消光比偏振探测器（特邀）

长波红外偏振探测器能够大幅提升对热成像目标的识别能力。受制于衍射极限的物理限制,目前的微线栅偏振片型长波红外偏振探测器的偏振消光比基本上只能做到最高10∶1左右。文中采用金属/介质/金属的等离激元微腔结构,将量子阱红外探测激活层相嵌在微腔之中。由于上、下金属之间的近场耦合形成了在双层金属区域的横向法布里-珀罗共振模式,构成等离激元微腔。文中利用微腔的模式选择特性及其与量子阱子带间跃迁的共振耦合,将量子阱子带跃迁不能直接吸收的垂直入射光耦合进入等离激元微腔并转变为横向传播,从而能够被量子阱子带吸收,实现了在长波红外13.5 μm探测波长附近偏振消光比大于100∶1的结果。相关工作为发展我国高消光比长波红外偏振成像焦平面提供了全新的物理基础和技术路径。