Ultra-High-Capacity Optical Communications and Networking: High-Performance Electrooptic Tunable Filters for Dense Wavelength Division Multiplexing

该提案是根据NSF 01-65“超高容量光通信和网络”招标提交的。该项目的目标是利用最近开发的设计原理和制造方法，展示用于密集波分复用（WDM）的电光可调谐滤波器的前所未有的调谐范围和速度。该滤波器将在LiNb03衬底上生产，预计将提供比以往任何可调谐滤波器技术更快的调谐（50纳秒）和更宽的调谐范围（10太赫兹）。该滤波器的光频率选择基于单模光波导中空间周期性应变扰动的相位匹配偏振模式转换。调谐是通过外加电场来完成的，电场改变了波导的双折射，从而改变了发生几乎完全偏振转换的相位匹配频率。由于TE - TM和TM - TE耦合是互反过程，因此器件具有固有的极化无关性。德克萨斯A&amp；M研究的创新将被纳入这些设备中，包括：(1)使用空间周期性SiO2条带通过应变光学效应诱导光的偏振耦合。在LiNb03衬底上高温沉积SiO2，并在室温下进行图案化，使纵向应变由热膨胀失配引起。(2)一种新的滤波器设计，消除了对偏振分束器的需要，从而在制造过程中提供了额外的自由度。(3)采用稀疏化应变光栅实现偏振耦合。这使得滤波器响应具有类似于标准龙的周期性，其空值在频率上几乎是均匀间隔的。这种设计技术可以使光谱范围比以前的etf设计扩大一个数量级。针对LiNb03电路元件优化的初步实验室工作为拟议的研究准备了道路。在1537 nm的直波导中，实现了以99.3%的效率进行TE TM和TM TE转换的相位匹配偏振耦合，并在15 nm（2太赫兹）范围内实现了峰值转换波长的电光调谐。测得偏振转换响应速度为52 ns。制备了分光比为25 dB的偏振分束器和适合于EOTF应用的非偏振分束器，并对其进行了表征。在该项目下，将在LiNb03基板上制造具有50 GHz和100 GHz通道间距的四端口频谱切片滤波器、两端口带通滤波器和四端口加降滤波器。滤波器的光谱和时间响应及其调谐范围将被表征。

0123367EknoyanThis proposal was submitted in response to the solicitation NSF 01-65 on "Ultra-High Capacity Optical Communications and Networking." The goal of this project is to demonstrate unprecedented tuning range and speed in electrooptic tunable filters for dense wavelength division multiplexing (WDM) using recently developed design principles and fabrication methods. The filters, which will be produced on LiNb03 substrates, are expected to provide a combination of faster tuning ( 50 ns) and wider tuning range ( 10 THz) than has previously been achieved in any tunable filter technology.Optical frequency selection in the proposed filters is based upon phase-matched polarization mode conversion by a spatially periodic strain perturbation in a single mode optical waveguide. Tuning is accomplished by an applied electric field which alters the waveguide birefringence, and hence the phase-match frequency at which near-complete polarization conversion occurs. The devices are inherently polarization independent because the TE TM and TM TE coupling are reciprocal processes.Innovations from the research at Texas A&M which will be incorporated into these devices include: (1) The use of spatially periodic strips of SiO2 to induce polarization coupling of light via the strain-optic effect. The SiO2 is deposited at an elevated temperature on the LiNb03 substrates and patterned at room temperature, so that longitudinal strain results from thermal expansion mismatch. (2) A new filter design which eliminates the need for polarizing beam splitters and thus gives an extra degree of freedom in the fabrication process. (3) The use of a sparse, apodized strain grating to achieve polarization coupling. This gives an etalon-like periodicity to the filter response, with nulls which are almost evenly spaced in frequency. This design technique should make it possible to extend the spectral range by an order of magnitude over previous EOTF designs.Preliminary laboratory work directed towards the optimization of LiNb03 circuit elements has prepared the way for the proposed research. Phase-matched polarization coupling with 99.3% efficiency for both TE TM and TM TE conversion has been achieved in straight waveguides at a wavelength of 1537 nm, and electrooptic tuning of the peak conversion wavelength over a range 15 nm (2 THz) was also demonstrated. Response speed for polarization conversion was measured to be 52 ns. Both polarizing beam splitters with splitting ratios 25 dB and non-polarizing beam splitters suitable for EOTF application have been produced and characterized.Under this project, four-port spectral slicing filters, two-port bandpass filters, and four-port add-drop filters with 50 GHz and 100 GHz channel spacing will be fabricated on LiNb03 substrates. Spectral and temporal response of the filters and their tuning range will be characterized.