Design and fabrication of a three-dimensional polymer optical waveguide polarization splitter

We present a design and fabrication of a three-dimensional polymer optical waveguide polarization splitter by taking into consideration of the induced birefringence effect of the polymer. We show that it is not possible to couple TM light from one waveguide to the other but evanescent coupling for TE light is possible. Hence the polarization splitter can be designed by considering TE mode coupling alone. This has an advantage of short interaction length of the device. Based on this consideration, we fabricated a polarization splitter with a TE extinction ratio of 15 dB and TM extinction ratio of 21 dB.     

Polarizing beam splitter based on a double-layer subwavelength grating

A Si–ZnS double-layer subwavelength grating is theoretically used as a high-efficient polarizing beam splitter. To design this structure, the rigorous coupled-wave analysis (RCWA) is applied to study the reflectivity and transmissivity for the TE and TM polarization, respectively. Simulation results show that both the zero-order reflection for TE polarization and the zero-order transmission for TM polarization can exceed 90% in a wide tunable working incident angle range from 48° to 72°. Moreover, the proposed polarizing beam splitter has a working wavelength that is in the range of 1500–1600 nm.     

A polarization splitter based on self-imaging phenomena in an anisotropic photonic crystal with an absolute photonic band gap

In a multi-mode waveguide of an anisotropic photonic crystal with an absolute photonic band gap, self-imaging phenomena are achieved for both TE and TM polarizations. Through careful choice of structure parameters, or the working frequency, the field of TE and TM polarization components can be separated in space after a certain propagating distance, based on which a polarization splitter is designed and numerically simulated. The numerical simulation shows that the polarization extinction ratio of the polarization splitter can reach a value of 22.9 dB and 19.2 dB at its two output ports, respectively.     

Ultra-compact polarization beam splitter based on photonic crystal waveguides

The authors design an ultra-compact all-PC-integrated polarization beam splitter which is only composed of three waveguides: one input waveguide and two output waveguides. The input waveguide can support both TM and TE modes, but one of the two output waveguides can only support TM modes while the other can only support TE modes. So an incident beam will be separated into two different polarization beams which emerge from different output waveguides. By the simulation of finite-difference time-domain method, we know that the polarization beam splitter really works the way as we predict.     

Polarization beam splitter with wide bandwidth in air-hole-based periodic dielectric waveguides

A polarization beam splitter with wide bandwidth and simple structure in air-hole-based periodic dielectric waveguides has been proposed and designed. Operation principle of the device is based on different directional coupling properties of beams in TE and TM polarizations in parallel periodic dielectric waveguides. Performances have been evaluated by a finite-difference time-domain simulation. Results show that the polarization beam splitter provides a wide bandwidth of 113 nm with both a high extinction ratio (higher than 21 dB) and a low insertion loss (less than 1.5 dB) for optical communication wavelengths at ∼1.55 μm. Moreover, the performances of the polarization beam splitter are insensitive to longitudinal alignment errors in the coupling region, which is desirable for device fabrication and practical application.     

T-shaped polarization beam splitter based on two-dimensional photonic crystal waveguide structures

A T-shaped polarization beam splitter based on two-dimensional photonic crystal is proposed, which is composed of three waveguides: one input and two output. Unpolarized beams incident from the input port will be separated into two different polarization modes and outputted individually by two different coupling structures. Simulation results can be obtained by the finite-difference time-domain (FDTD) method. In the normalized frequency range of 0.3456 < \(\omega \alpha /2\pi {}c\) < 0.37, multiple frequencies can obtain high transmission efficiency simultaneously for both TE and TM modes. And the degree of polarization is very closed to 1 for both output ports at this frequency range. When the normalized frequency \(f=0.3534 \omega \alpha /2\pi {}c\), the transmission efficiency, respectively, is 88 % and \(91\) % for TE modes and TM modes. The extinction ratio is all 30dB for both modes. The polarization beam splitter attains the requirement we expected by analyzing simulation results.     

基于Ti扩散铌酸锂偏振分束器的研制

对定向耦合型偏振分束器的原理进行了分析。设计了一种零间距定向耦合器,在空间上实现TE/TM模式分束;用BPM软件对所设计的器件进行仿真模拟,对于TE/TM模的消光比分别可以达到21.2dB和19.5dB;该器件在X切Y传的LiNbO3晶片上采用Ti扩散技术制作完成。实验样品消光比测试结果TE/TM模分别为11.5dB和19.1dB,对于消光比不够理想的原因进行了初步的分析。     

A polarization splitter based on slow light effect in a left-handed material waveguide

We propose a polarization splitter (PS) based on the slow light effect in a three-layer waveguide that consists of left-handed material (LHM) and dielectric layers with no birefringence. Transverse electric (TE) and transverse magnetic (TM) waves can be split by the intrinsic configuration of permittivity and permeability of LHM and dielectric layers. Simulation results are given to discuss the influence of electromagnetic parameters on the properties of our PS, and the capture and release of TE or TM waves are also realized in our PS which provides a flexible method to modulate the switching of different polarization waves.     

Detailed investigation of self-imaging in multimode photonic crystal waveguides for applications in power and polarization beam splitters

Properties of the self-imaging effect based on multimode interference (MMI) in multimode photonic crystal waveguides (PCWs) are investigated and analyzed in detail. By combining photonic band gap (PBG) and total internal reflection (TIR) effects in PCWs, self-imaging phenomena are achieved for both TE and TM polarizations. To observe the images reproduced by this self-imaging phenomenon, finite-difference time-domain (FDTD) simulations are performed on a multi-mode PCW. From these numerical simulations the reproduced images are identified and their positions along the propagation axis are described. We also, present the design and simulation of novel polarization-insensitive power splitter and polarization splitter. The simulation results show that the optimized devices have excellent transmission efficiencies as well as wide operating frequency bandwidths and small structure size. So, the proposed devices are promising and may play an important role in high-density photonic integrated circuits in the future.     

Optimal design of sub-wavelength metal rectangular gratings for polarizing beam splitter based on effective medium theory

A novel optimal design of sub-wavelength metal rectangular gratings for the polarizing beam splitter (PBS) is proposed. The method is based on effective medium theory and the method of designing single layer antireflection coating. The polarization performance of PBS is discussed by rigorous couple-wave analysis (RCWA) method at a wavelength of 1550~nm. The result shows that sub-wavelength metal rectangular grating is characterized by a high reflectivity, like metal films for TE polarization, and high transmissivity, like dielectric films for TM polarization. The optimal design accords well with the results simulated by RCWA method.     

Design of a compact polarization beam splitter based on a deformed photonic crystal directional coupler

In this paper a compact polarization beam splitter based on a deformed photonic crystal directional coupler is designed and simulated. The transverse-electric （TE） guided mode and transverse-magnetic （TM） guided mode are split due to different guiding mechanisms. The effect of the shape deformation of the air holes on the coupler is studied. It discovered that the coupling strength of the coupled waveguldes is strongly enhanced by introducing elliptical airholes, which reduce the device length to less than 18.Sttm. A finite-difference tlme-domain simulation is performed to evaluate the performance of the device, and the extinction ratios for both TE and TM polarized light are higher than 20 dB.     

Connecting-layer-based polarizing beam splitter grating with high efficiency for both TE and TM polarizations

We describe a novel polarizing beam splitter (PBS) of transmission connecting-layer-based grating, which can show high efficiency for TE polarization in the ?1st order and TM polarization in the 0th order. According to the modal method, grating duty cycle and period are prescribed to obtain high efficiency for TM polarization. Using the rigorous coupled-wave analysis, grating depth and thickness of the connecting layer are optimized to achieve high efficiency for TE polarization. The presented PBS has advantages of wideband properties for incident wavelength and angle. Most importantly, the efficiency is improved greatly for TE polarization compared with the reported PBS based on fused-silica grating.     

基于一维金属-介质周期结构的偏振分束

分析了一维金属一介质周期结构的能带特性,根据一定频率范围内TM波(磁场方向与界面平行)在结构中的负折射以及TE波的正常折射,提出了一种偏振分束器件.利用传输矩阵法(TMM)模拟了该结构对入射高斯光束的偏振分束作用,讨论了不同入射角度下的偏振分束能力,并结合实际金属参量,分析了金属层吸收对结构特性的影响.结果表明该结构在55°附近入射时有最好的性能;在吸收作用下结构偏振分束能力有一定的减小,TM波透射比发生了较大变化,TE波效果较好;随着周期数增加,结构透射比下降,但分光能力显著提高;在工作波段上随着波长增大,金属层吸收对器件的影响减弱.该结构能实现宽波段、宽角度、较高透射比的偏振分束.     

Ultracompact and silicon-on-insulator-compatible polarization splitter based on asymmetric plasmonic–dielectric coupling

An ultracompact and silicon-on-insulator-compatible polarization splitter (PS) is proposed by utilizing asymmetric directional coupling between a hybrid plasmonic waveguide and a strip dielectric waveguide. Owing to the plasmon-assisted asymmetry, birefringence is highly enhanced. Polarization splitting can be realized by strong coupling of one polarization while the other polarization is phase-mismatched. As an example, a PS based on strong TM coupling is demonstrated at the wavelength of 1.55 μm with a coupling length of 4.13 μm. Extinction ratios are 20.9 and 16.4 dB for TM and TE polarizations, respectively. The device is also broadband and fabrication-tolerant.     

新型高效偏振光分束器的设计

研究及分析了光波在分束结构中的传播行为和特性,发现当增大波导邻近两侧空气孔半径时,能形成完全光子禁带范围内某一频率光波单一偏振态的传播,基于此原理提出了一种全新结构的偏振光分束器,计算与模拟结构表明,该结构可以实现TE模与TM模高效大角度分离. 器件尺寸不超过17.6 μm×9.8 μm,在集成光回路中无疑有着很大的应用潜力. 关键词： 光子晶体 偏振光分束器 时域有限差分法 平面波展开法     

A reflective surface-relief two-layer grating for splitting beams with the polarization-selective property

A polarization-selective beam splitter is presented based on a reflective surface-relief two-layer grating with a metal slab. The grating is composed of two dielectric layers and a metal slab on the substrate. For TE polarization, efficiencies of 97.58% can be diffracted into the reflective −1st order. For TM polarization, two-port output of 47.55% and 47.11% can be split into the 0th order and the −1st order, respectively. Such a polarization-selective beam splitter can be fulfilled by one grating in reflection. The grating depths of two layers are optimized by using rigorous coupled-wave analysis with the given duty cycle of 0.6 and period of 1100 nm. The performance for different incident conditions is investigated when the incident wavelength and angle deviate from the central wavelength and the Bragg angle, respectively. For TM polarization, good uniformity can still be achieved within the given incident wavelength and angle regions. For TE polarization, the reflective polarization-selective beam splitter can have merits of wideband for different incident wavelengths.     

Design of a 50/50 splitting ratio non-polarizing beam splitter based on the modal method with fused-silica transmission gratings

The optical design of a beam splitter that has a 50/50 splitting ratio regardless of the polarization is presented. The non-polarizing beam splitter (NPBS) is based on the fused-silica rectangular transmission gratings with high intensity tolerance. The modal method has been used to estimate the effective index of the modes excited in the grating region for TE and TM polarizations. If a phase difference equals an odd multiples of π/2 for the first two modes (i.e. modes 0 and 1), the incident light will be diffracted into the 0 and ?1 orders with about 50% and 50% diffraction efficiency for TM and TE polarizations, respectively.     

Polarization beam splitters based on a two-dimensional photonic crystal of negative refraction

A two-dimensional metallo-dielectric photonic crystal of negative refraction was designed for the application of polarization beam splitters. To match the refractive index of air, the effective refractive index of the designed photonic crystal is -1 for TE polarization and +1 for TM polarization. Two types of polarization beam splitter are presented.     

Passive broadband silicon-on-insulator polarization splitter

We present the implementation of a novel wavelength independent polarization splitter on a silicon-on-insulator platform. The waveguide splitter is based on a zero-order arrayed waveguide grating (AWG) configuration. The splitting function is realized by employing cladding stress-induced birefringence. The device demonstrated a TE to TM splitting ratio better than -15 dB over a 20 nm tuning range centered around lambda=1550 nm and better than -10 dB over our entire accessible wavelength range from lambda=1465 nm to 1580 nm. The highest splitting extinction ratio achieved was -20 dB. To our knowledge, this is the first reported passive broadband polarization splitter based on AWG.     

Fabrication and performance of a medium-dependent SiO2/Si photonic heterostructure device

An optical device based on a photonic bandgap heterostructure is designed, fabricated, and characterized. The sample contains two sets of Si/SiO2 photonic crystals with different periods. When the device is working in air, it reflects omnidirectionally both TE and TM mode lights at the wavelength near 1.3 microm. The reflectivity measured in the bandgap is higher than 98% in an incident angle range 0 degrees-70 degrees. When the device is surrounded with silica (n > 1.33), it permits the total transmission for the TM mode but prevents the TE mode from propagating, thus behaving as a polarization splitter. The experimental extinction ratio of the reflected TE/TM is approximately 31 dB. The uniformity of the device performance over a large sample area is demonstrated.