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     

Polarization mode converter with polyimide half waveplate insilica-based planar lightwave circuits

A TE/TM polarization mode converter, with an excess loss of 0.26 dB, is constructed by inserting a polyimide half waveplate into a groove formed in a silica-based single mode waveguide. The polarization dependence of an arrayed-waveguide grating multiplexer is completely eliminated with this mode converter     

Embedded channel polyimide waveguide fabrication by direct electronbeam writing method

A new embedded channel polyimide waveguide fabrication process by a direct electron beam writing method (DEBWM) is described. The new technique uses an electron-beam induced effect to directly alter the refractive indices of the two-layer polyimide. Both the core and the lower cladding have been fabricated at the same time in two-layer polyimides using electron beam with 25 keV energy. The obtained embedded channel waveguide was made of two kinds of polyimides, one for lower cladding and one for core and other claddings. Guide losses are 0.3 dB/cm for both TE and TM polarized incident lights and guiding mode is single-mode for TE. The optical properties of the waveguide and a relationship between the doses of electron beam and optical losses or loss dependence on wavelength are also mentioned     

Hybrid polyimide/Ta2O5/polyimide antiresonantreflecting optical waveguides

A hybrid polyimide/Ta₂O₅/polyimide antiresonant reflecting optical waveguide (ARROW) is presented. The ARROW consists of fluorinated polyimide and tantalum pentoxide hybrid layers deposited on Si substrates. The propagation losses of the device are 0.6 and 2.6 dB/cm at 1.3 μm for TE and TM polarised lights, respectively     

Improved 8×8 integrated optical matrix switch usingsilica-based planar lightwave circuits

An improved 8×8 optical matrix switch was fabricated using silica-based planar lightwave circuits (PLCs) on a silicon substrate. Three improvements were made. First, the waveguide material was changed from titanium-doped silica (SiO₂₂-TiO₂) to germanium-doped silica (SiO₂₂-GeO₂) to reduce propagation loss. Second, offset driving powers were supplied to every switch unit to realize high extinction ratios. Third, the dummy switch units were modified to suppress the crosstalk through these units. The average insertion loss of the fabricated device was 3.81 db in the TE mode and 3.82 dB in the TM mode. The average extinction ratio of the switch units was 25.3 dB in the TE mode and 22.3 dB in the TM mode. The accumulated crosstalk was estimated to be less than -14 dB in the TE mode and -11 dB in the TM mode. The average driving power of the phase shifter in the on-state was 0.54 W in the TE mode and 0.52 W in the TM mode. The switching response time was 1.3 ms. The packaged 8×8 matrix switch with additional fiber-waveguide coupling loss of 2.7 dB was successfully employed in photonic multimedia switching and photonic inter-module connector system experiments     

ARROW-B type polarization splitter with asymmetric Y-branchfabricated by a self-alignment process

We have proposed and demonstrated a polarization splitter based on an ARROW-B type waveguide. This device has an asymmetric Y-branch configuration, connecting a waveguide with a large modal birefringence to a low-birefringent waveguide which is channeled by a stripe lateral confinement structure. The device can achieve a high extinction ratio without precise mask alignment, since these two waveguides are connected by a self-alignment process. In addition, a low insertion loss is achieved because of adiabatic Y-branching. We designed this device at the wavelength of 1.55 μm and fabricated it using RF sputtering. As a result, high extinction ratios of -19.4 dB for TE mode and -19.0 dB for TM mode were achieved     

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     

Integrated-Optic Polarization Controlling Devices Using Electro-Optic Polymers

Integrated-optic polarization controlling devices such as polarizers, polarization splitters, and polarization converters, are proposed and demonstrated in nonlinear optic polymers. Poling-induced birefringence in electro-optic polymers is exploited to fabricate the devices. The polymeric waveguide polarizers show low excess losses, and extinction ratios of 20.7 dB and 17.1 dB for TM-pass and TE-pass polarizers, respectively. The polymeric waveguide polarization splitters exhibit TE-TM mode splittings with crosstalk of 14.2 dB and 10.1 dB for TM and TE mode splittings, respectively. The polymeric waveguide polarization converters show successful TE/TM polarization mode conversion with conversion efficiencies of higher than 30 dB. The device employs poling-induced waveguides which have slowly rotating azimuth angle of optic axis along the light propagation direction. The novel polarization converter is insensitive to wavelength and easier to fabricate than the other polarization converters containing periodic structures.     

交叉型TE/TM模分离器的研制

采用光束传播法（ＢＰＭ）计算了交叉型ＴＥ／ＴＭ模分离器的偏振串音（ｃｒｏｓｔａｌｋ）。通过结构参数的优化，理论计算的偏振串音为－２３．７ｄＢ（ＴＭ）和－２２．８ｄＢ（ＴＥ）。同时制成相应的器件，测试结果表明，理论计算与实验是一致的     

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。     

Polyimide/Ta2O5/polyimide antiresonantreflecting optical waveguides

A novel antiresonant reflecting optical waveguide (ARROW) fabricated using both the organic and dielectric thin film technologies is presented for the first time. The ARROW consisted of the fluorinated polyimide and tantalum pentoxide (Ta₂O₅) hybrid layers deposited on a Si substrate. For TE polarized light, the propagation loss of the waveguide as low as 0.8 dB/cm is obtained at 632.8 nm. The propagation loss for TM polarized light is 2.7 dB/cm. Some design considerations of the hybrid ARROW are also discussed in this work     

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.     

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     

指向耦合器型TE/TM模分离器结构参数优化设计

采用简单的理论模型 ,对折射率呈渐变分布的钛扩散LiNbO3 波导进行结构优化 ,得到模式分离的最佳结构参数 ,用光束传播方法 (BPM法 )设计了有金属覆盖层的指向耦合器型TE/TM模分离器 ,偏振串音分别达到 -2 0 8dB(TE模 )和 - 2 1 3dB(TM模 )。     

Four-channel integrated-optic wavelength demultiplexer with weakpolarization dependence

A planar four-channel wavelength demultiplexer with weak polarization dependence is proposed and demonstrated. This demultiplexer is based on an optical-phased array. An experimental device with dimensions 4.5×3.2 mm² was designed and fabricated, using conventional (high-quality) optical lithography. The demultiplexer operates in the wavelength range 776.5-781.2 nm, with a channel spacing of 1.55 nm. Insertion loss was 0.6 dB for the central channels and 1.2 dB for the outer channels for transverse-electric (TE) polarization, excluding 1.3-dB waveguide propagation loss. Crosstalk values measured 15.4-29.7 dB for the TE and 13.4-22.2 dB for the transverse-magnetic (TM) polarization     

First heterodyne receiver frontend module including a polarizationdiversity receiver OEIC on InP

For the first time a packaged polarization diversity coherent receiver OEIC including detector units (photodetectors, JFET, load resistor) has been fabricated with the following data: waveguide loss 2 dB, 3 dB balance within 0.4 dB, polarization extinction >30 dB (TM) and >17 dB (TE), 3 dB cutoff frequency of 0.9 GHz, common mode rejection ratio 30 dB     

Passive mode converter with a periodically tilted InP/GaInAsP ribwaveguide

TE to TM converters with constant 45° operation are a key component in OEICs for coherent optical system applications. A passive TE/TM-mode converter with a laterally tilted rib waveguide fabricated on a stepped substrate is proposed and investigated. The conversion effect has been simulated using scalar and vectorial two-dimensional finite difference methods. The device fabricated on (001)-InP/GaInAsP yields 45° conversion with two subsequent elements of half the TE/TM-beatlength at an excess loss of 3 dB     

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.     

Tunable Mach-Zehnder polarization splitter using height-tapered Y-branches

A tunable TE/TM polarization splitter, based on a Mach-Zehnder interferometer with an electrooptic switch, is demonstrated in GaAs-AlGaAs. Symmetric and asymmetric Y-branches employing height-tapered waveguides are used to achieve power splitting and mode sorting, respectively, in the interferometer. The device has an extinction ratio of /spl sim/20 dB and an excess loss less than 1.5 dB for both TE and TM polarized light. The device can be reconfigured by tuning the switching voltage for operation at both 1.3- and 1.55-pm wavelengths.     

Directional couplers using fluorinated polyimide waveguides

Optical properties of directional couplers using a fluorinated polyimide waveguide were demonstrated. At a wavelength of 1.3 μm, directional couplers with the refractive index difference of 0.3% between the core and cladding have a maximum power coupling ratio of more than 97 and 96% for TE and TM polarisations, respectively. The excess loss for a 3-dB coupler was as low as 0.3 dB. Moreover, the change in the coupling ratio of the 3-dB couplers remained within 0.5% between 25 and 100°C