A study on the three-dimensional optical circuits and technology

该项目的目的是开发三维光学电路和技术，其折射率沿传播轴沿着逐渐变化。所研制的电路具有以下新功能：1.辐射波应用;天线耦合Y结波导; 2.锥度和相干锥度的应用;模式匹配器件; 3.基于上述概念，我们提出、分析并部分制作了以下新器件。天线耦合Y结波导：为了减小Y结的辐射损耗，减小了分支区附近的折射率。实际上获得了宽而低损耗的Y型结.一种异质光波导间的光纤模式匹配装置制作了一端为矩形芯，另一端为圆形芯的单模锥形光纤，并对其基本性能进行了验证.一种新的波导弯曲结构;一种在拐角外侧具有低折射率区域的结构。基本性能得到确认.三维光波导的微加工介绍了一种ECR反应离子刻蚀系统。成功制备了离子刻蚀LiNb<O_3>和Si<O_2>脊形波导.理想速度匹配的LiNb<O_3>行波调制器：由脊波导构成的调制器具有约1 THz的调制带宽和低驱动电压。20 GHz的调制进行了实验验证。光开关：（1）制作了小型化LiNb<O_3>定向耦合器。(2)研究了载流子注入<III><V>型半导体开关.利用自制的液相外延设备，计算了薄膜的折射率变化，并制备了外延薄膜.利用相位板进行光束变换的分支电路设计和基本实验，确定了基本性能。

The purpose of the project is the development of 3-dimensional optical circuits and technology, which have gradual refractive index variations along the propagation-axis. The developed circuits have new functions as follows:1. Application of radiation-wave; antenna coupled Y-junction waveguides,2. Application of taper and coherent taper; mode matching device,3. Application of reflaction and resonance; abrupt-bend waveguides.Following new devices have been proposed, analized and partially fabricated based on the above mentioned concepts.1. Antenna coupled Y-junction waveguides; To reduce radiation losses of Y-junctions refractive index near the branching region was reduced. The wide and low loss Y-junctions were actually obtained.2. A fiber mode matching device between dissimilar optical waveguides; A single-mode tapered fiber with a rectangular core at one end and a circular core at the other was fabricated and basic performance was confirmed.3. New waveguide-bend configuration; A structure has a low refractive-index region at the outside of the corner. Basic performance was confirmed.4. Microfabrication for the 3-D optical waveguides; An ECR (electron cyclotron resonance) reactive ion etching system was introduced. Ion-etched LiNb <O_3> and Si <O_2> ridge waveguides were successively fabricated.5. Perfect velocity matching LiNb <O_3> traveling-wave modulators; The modulator that comprises of a ridge-waveguide has about 1 THz modulation band-width and low driving voltage. 20 GHz modulation was confirmed experimentally.6. Optical switches; (1) Miniaturized LiNb <O_3> directional-coupler was fabricated. (2) Carrier injection type <III> - <V> compound semiconductor switches are investigated. Refractive index changes was calculated and epitaxial growth films were fabricated by using a hand-made LPE equipment.7. Branching circuit by beam transformation using phase plates; Design and fundamental experiments were made, and basic performance was confirmed.