Single-mode optical isolator at 1.3 ?m using all-fibre components

An optical isolator for use at 1.32 ?m has been fabricated using standard communication-grade single-mode fibre as an optical rotator fitted with high-birefringence fibre pigtails containing an in-line tapered fibre polariser. A novel adjustment procedure ensures isolation levels are limited only by the polariser extinction ratio. Isolation levels in excess of 21 dB have been recorded with an insertion loss of less than 3 dB.     

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.     

全保偏光纤迈克尔逊干涉仪

报道了全保偏光纤迈克尔逊干涉仪的研究结果.实验中采用熊猫保偏光纤、磨抛型保偏光纤偏振器(消光比为35dB.损耗相似文献   

Fabrication of 2×2 tapered multimode interference coupler

The authors demonstrate a 3 dB 2×2 parabolically tapered multimode interference (MMI) coupler with a large cross-section and space between the different ports using silicon-on-insulator technology. The device exhibits a uniformity of <0.8 dB and can be used in the realisation of an MMI-based optical switch with a high extinction ratio     

High modulation efficiency and high power 1060 nm tapered lasers with separate contacts

A high direct optical modulation amplitude of more than 1.6 W, modulation efficiencies of 20 W/A at 700 Mbit/s and 50 W/A for quasistatic modulation, and a very high optical extinction ratio of 19 dB have been demonstrated in custom-designed gain guided tapered lasers emitting at 1060 nm. The devices were fabricated with split contacts, allowing the separate injection of the ridge waveguide and tapered sections. The modulation of a large output power with low modulating current was achieved by modulating the current injected into the ridge waveguide section of the device.     

Polarisation splitter based on beam steering in periodic planaroptical waveguides

A novel planar optical polarisation splitter for simultaneous extraction of both TE and TM modes is proposed and demonstrated. The device, designed according to the principle of the polarisation-dependent direction of energy flow near Bragg incidence, consists of a periodic waveguide section joined by straight tapered transitions to smooth regions. Experimentally, a minimum extinction ratio of 17 dB was achieved     

Low-loss TM-pass polariser fabricated by proton exchange for z-cut ti:LiNbO3 waveguides

We fabricated a low-loss TM-pass polariser at ? = 1.32 ?m integrated with low-loss titanium waveguides in Z-cut LiNbO3. The polariser, fabricated by proton exchange, had an excess insertion loss of 0.3 dB and a polarisation extinction ratio of > 40dB.     

Polarising fibre coupler with high extinction ratio

Fused polarising fibre couplers have been fabricated using single-polarisation single-mode fibres. When circularly polarised light is fed into the coupler, one of the two orthogonal polarisation modes suffers strong attenuation, and only one polarisation mode couples in the fused biconical taper region. The extinction ratio of the coupler is 41 dB at a wavelength ? = 1.3 ?m with a coupling ratio of 48:52.     

Low switching threshold using nonlinearities in stopband-tapered waveguide Bragg gratings

We numerically study the nonlinear switching characteristics in a waveguide grating with a linearly tapered stopband. This type of design shows promising results in decreasing the threshold switching power, while simultaneously preserving a significant extinction ratio. We find that the switching threshold changes linearly with the tapering coefficient. The physical explanation for these phenomena is discussed. Potential applications for this type of device include all-optical switches and isolators.     

Thin-film polariser for Ti:LiNbO3 waveguides at ?=1.3?m

Thin-film polarisers using a dielectric buffer layer and a metallic overlay on Ti:LiNbO3 channel waveguides for ? = 1.3 ?m have been designed and fabricated. The TM mode extinction ratio better than 35 dB and negligible TE mode excess losses have been measured with Si3N4/Al polarisers 2 mm long.     

Fiber-Optic Polarizer Using Resonant Tunneling through a Multilayer Overlay

We demonstrate an in-line fiber-optic polarizer using resonant tunneling through a leaky multilayer overlay for the first time. Polarization extinction ratio (PER) ? 27 dB with an insertion loss (IL) ? 3 dB has been demonstrated experimentally with scope of further improvement. A simple planar waveguide model is developed to analyze the device whose predictions match very well with the experimental results. It is further shown that by properly selecting the device parameters one can achieve PER ? 68 dB with IL ? 0.2 dB for λ = 0.6328 μm and PER ? 80 dB with IL ? 1.2 dB for λ = 1.3 μm.     

高功率980nm锥形增益区脊形波导量子阱激光器的优化

利用MOCVD生长980nm InGaAs-AlGaAs渐变折射率分别限制异质结单量子阱激光器外延片,采用锥形增益区脊形波导结构制备器件.保持总腔长1850μm不变,改变脊形区的长度分别为450,700和950μm,对比三种情况的P-I特性和光束质量.发现LRW＝450μm时,器件特性参数和远场光束质量最优,斜率效率达0.83W/A,饱和功率为4.28W.输出功率为1W时,远场发散角为7.5°×30.6°,M2因子为3.79.     

关于单块双45°LN电光Q开关消光比的讨论

给出了单块双45°LN电光Q开关消光比的定义,并讨论了这种Q开关的性能与最佳运转.介绍了这类开关的一种结构,它有理想的消光比,并具有校准方便,对沿Z轴长度无严格限制等特点.     

电极分离的980nm锥形激光器的研制

对脊形波导区和锥形区电极分离的980nm锥形激光器(简称电极分离的980nm锥形激光器)改变脊形波导区所加电流,测试激光器的P-I特性和光束质量因子,与脊形波导区和锥形区共用电极的980nm锥形激光器(简称电极共用的980nm锥形激光器)的测量参数进行对比.发现电极分离的980nm锥形激光器的P-I特性曲线比较光滑,没有明显的扭折.随着脊形波导区的电流逐渐超过150mA以后,器件的最大输出功率逐渐达到4.28W,与电极共用的980nm锥形激光器相同并趋于饱和,光束质量因子从3.79降到2.45(输出功率为1W).     

电极分离的980nm锥形激光器的研制

对脊形波导区和锥形区电极分离的980nm锥形激光器(简称电极分离的980nm锥形激光器)改变脊形波导区所加电流,测试激光器的P-I特性和光束质量因子,与脊形波导区和锥形区共用电极的980nm锥形激光器(简称电极共用的980nm锥形激光器)的测量参数进行对比.发现电极分离的980nm锥形激光器的P-I特性曲线比较光滑,没有明显的扭折.随着脊形波导区的电流逐渐超过150mA以后,器件的最大输出功率逐渐达到4.28W,与电极共用的980nm锥形激光器相同并趋于饱和,光束质量因子从3.79降到2.45(输出功率为1W).     

基于拉锥单模-多模-单模光纤结构的高灵敏折射率传感器

文章介绍基于拉锥单模-多模-单模(SMS)光纤结构的模间干涉仪,当拉伸长度为35mm时形成自由光谱区(FSR)为1.3nm的干涉透射谱,消光比达到10dB。此时拉锥多模光纤的腰椎平坦区直径约为3.85μm,具有较强的倏逝场,可用作高灵敏折射率传感器。实验证明,此拉锥SMS结构在折射率范围1.35-1.36内的灵敏度高达771nm/RIU,能精密监测溶液溶质扩散现象。     

Optical losses in metal/SiO2-clad Ti:LiNbO3 waveguides

We present measured excess loss resulting from electrode overlays for both TE and TM polarisations as a function of SiO2 buffer layer thickness for Ti:LiNbO3 strip waveguides at ? = 1.32 ?m. We find there is negligible excess loss to the TE mode with no buffer layer and that the excess loss to the TM mode can be essentially eliminated with a SiO2 layer only 700 ? thick. A passive polariser with ? 1.5 dB fibre-waveguide-fibre insertion loss and > 13 dB extinction ratio is also demonstrated.     

Optical properties of electrochemically synthesized polypyrrole thin films:the electrolyte effect

Polypyrrole thin films are prepared by the potentiostatic mode of electrodeposition at ＋0.7 V versus a saturated calomel electrode （SCE）. The polypyrrole films are prepared in the presence of different electrolytes such as： p-toluene sulphonic acid （PTS）, oxalic acid and H2SO4. The prepared films are characterized by UV- vis absorption spectroscopy and normal reflectance measurements. The electrochemically synthesized films are semiconductor in nature. The band gap energy ofpolypyrrole thin films is found to be 1.95, 1.92 and 1.79 eV for H2 SO4, oxalic acid and p-toluene sulphonic acid, respectively. The normal reflectance spectroscopy of polypyrrole films shows that the maximum reflectance is in the presence of p-toluene sulphonic acid; this is may be due to a more distinct microstructure than the others. The optical constants such as the extinction coefficient, refractive index, optical conductivity, etc. are calculated and studied with various electrolytes.     

Electrooptic polymer modulators operating in both TE and TM modes incorporating a vertically tapered cladding

We propose a modified electrooptic (EO) PMMA polymer waveguide structure supporting both TE and TM modes in spite of the large birefringence induced by the poling. A vertically tapered structure is employed to connect a single-mode rib waveguide and a confinement-enhanced rectangular buried waveguide. This waveguide structure can be easily fabricated by a two-step reactive ion etching (RIE) process with a shadow mask. To demonstrate TE/TM confinement and single-mode operation, Mach-Zehnder intensity modulators are fabricated by incorporating the proposed waveguide structure. The extinction ratio is better than -15 dB, which proves the single-mode operation. Half-wave voltages for TM and TE modes are 6 and 24 V, respectively.     

Spot-size converted polarization-insensitive SOA gate with avertical tapered submicrometer stripe structure

To develop polarization-insensitive semiconductor optical amplifier (SOA) gates into more efficient and functional optical components by using hybrid integration with a planer lightwave circuit (PLC) platform, vertical tapered spot-size converters were integrated into a SOA gate with a narrow mesa-stripe structure of submicrometer width leading to low coupling loss (2.6 dB). Very-low polarization dependence of gain (<0.2 dB) and high extinction ratio (>30 dB) were achieved in a wide wavelength range (40 nm). High-speed (<1 us) gate operation was also demonstrated. These results indicate that the spot-size converted SOA integrated on a PLC platform will perform well in wavelength-division-multiplexing (WDM) applications