SBIR Phase II: Development of Chiral Fiber Polarizer

这一小型企业创新研究(SBIR)第二阶段项目将开发一种基于手性光纤光栅的新型光纤内手性偏振器。有效折射率的双螺旋变化将由具有非圆形纤芯的光纤在通过微型烤箱时扭曲而成。这些手性光纤偏振器将由专门准备的玻璃预制件以低成本、多功能、连续的工艺制造，这将不需要对通常用于生产光纤布拉格光栅的光敏玻璃进行相干照射。手性偏振器是真正的光纤器件，不需要任何衬底、散体组件或刚性封装。它们的螺距分布将被设计成最大限度地减少通过偏振的插入损耗，并在广泛的光谱范围内最大限度地提高正交偏振的消光效果。该设计将实现一种多芯光纤，使标准光纤的低数值孔径与手性偏振器的数值孔径在其输入和输出端匹配，同时在偏振区保持高的数值孔径。手性偏振器在单偏振传输、偏振模色散补偿、测试仪器等领域具有广阔的应用前景。偏振器也是依赖光学干涉的传感器的关键元件，如陀螺仪和电流传感器。偏振和频率选择性手性光纤的应用范围从电信到传感。在高带宽光纤通信中使用外部调制器要求入射光波被线偏振。这就需要使用偏振器，因为电信中使用的激光光源通常具有随机偏振。此外，任何偏振保持光纤的使用都需要将偏振光发射到光纤中。偏振器也是偏振模色散补偿系统中的关键部件。由于手性偏振器可以由耐火或耐辐射玻璃制成，并且只涉及玻璃的机械变形，因此它们可以在高辐射、高温或腐蚀性化学物质的恶劣环境中发挥作用。手性光纤偏振器的制备技术的发展将促进基于手性光纤光栅的其他器件的发展。这些设备，从传感器和过滤器到光纤内激光器，将成为无源和有源光纤设备的新平台的构建块。对玻璃在极端剪应力作用下行为的了解将推动玻璃成型技术的前沿，并促进新的应用。了解非共振波段内的偏振选择光散射将为基于微结构光纤的新型器件开辟道路。

This Small Business Innovation Research (SBIR) Phase II project will develop a new class of in-fiber chiral polarizers based upon chiral fiber gratings. A double helix variation of the effective refractive index will be formed by twisting fibers with a noncircular core as they pass through a miniature oven. These chiral fiber polarizers will be created from specially prepared glass performs in a low-cost, versatile, continuous process, which will not require coherent irradiation of photosensitive glass commonly used to produce fiber Bragg gratings. Chiral polarizers are true fiber devices and do not require any substrates, bulk components, or rigid package. Their pitch profile will be engineered to minimize insertion loss for the passing polarization and maximize the extinction of the orthogonal polarization over a broad spectral range. The design will implement a multi-core optical fiber to match the low numerical aperture of standard fiber with the numerical aperture of the chiral polarizer at its input and output while maintaining a high numerical aperture in the polarizing zone. Chiral polarizers will have broad application in single polarization transmission, polarization mode dispersion compensation, and test and measurement instrumentation. Polarizers are also key elements in sensors relying on optical interference such as gyroscopes and current sensors.Polarization and frequency selective chiral fibers have applications ranging from telecommunications to sensing. The use of external modulators for high bandwidth fiber telecommunication requires that the incident wave be linearly polarized. This necessitates use of a polarizer since laser sources used in telecommunications generally have random polarization. Further, any use of polarization maintaining fiber requires that polarized light be launched into the fiber. Polarizers are also key components in polarization mode dispersion compensation systems. Since chiral polarizers may be fabricated from refractory or radiation resistive glasses and involve only mechanical deformation of glass they may function in harsh environments with high levels of radiation, high temperature, or corrosive chemicals. The fabrication techniques developed for chiral fiber polarizers will spur the development of other devices based on chiral fiber gratings. These devices, ranging from sensors and filters to in-fiber lasers will become building blocks for a new platform for passive and active in-fiber devices. The understanding of glass behavior under extreme shear stress will push the frontier of glass forming technology and stimulate new applications. Understanding polarization-selective light scattering within the nonresonant band will open the way for new devices based upon microstructured fibers.