Hensler D H, Cuthbert J D, Martin R J, Tien P K
Appl Opt. 1971 May 1;10(5):1037-42. doi: 10.1364/AO.10.001037.
Attention is drawn to the properties of Ta(2)O(5) film which make it attractive as a new dielectric medium for use in integrated optical circuitry. The Ta(2)O(5) film discussed was formed by thermally oxidizing sputtered , beta-tantalum films in an oxygen atmosphere. Measurements showed that these films will support propagation of coherent red (6328-A.) light with a loss of 0.9 dB cm(-1) and coherent blue (4880-A) light with a somewhat higher loss of 4.1 dB cm(-1). From measurements of the coupling angle at which propagation of the various modes takes place, refractive indices for the TE and TM modes at 6328 A, 5145 A, and 4880 A were obtained. The loss mechanisms are discussed, and it is shown that most of the loss is due to scattering during the internal reflections at the air-oxide and oxide-substrate film surfaces. A small fraction of the loss appears to occur in the interior of the film. With Ta(2)O(5) it is demonstrated for the first time that optical circuit components can be formed for use in integrated optics by employing existing thin-film technology. The basic process steps include the pattern generation of the beta-Ta followed by thermal oxidation of the pattern. Experimental studies of propagation in straight and curved waveguides are described. It was found that the losses in pattern generated waveguides are of the order of 5 dB cm(-1) to 7 dB cm(-1), with the excess loss due to scattering from the waveguide edges. It is concluded that improvements in the smoothness of the boundaries of circuit elements are desirable to reduce transmission losses in pattern generated film.
人们注意到Ta₂O₅薄膜的特性，这使其作为一种用于集成光学电路的新型介电介质具有吸引力。所讨论的Ta₂O₅薄膜是通过在氧气气氛中对溅射的β - 钽薄膜进行热氧化形成的。测量结果表明，这些薄膜能够支持相干红光（6328 Å）的传播，损耗为0.9 dB cm⁻¹，以及相干蓝光（4880 Å）的传播，损耗稍高，为4.1 dB cm⁻¹。通过测量各种模式传播时的耦合角，获得了6328 Å、5145 Å和4880 Å处TE和TM模式的折射率。讨论了损耗机制，结果表明大部分损耗是由于在空气 - 氧化物和氧化物 - 衬底薄膜表面的内反射过程中的散射造成的。一小部分损耗似乎发生在薄膜内部。使用Ta₂O₅首次证明，可以通过采用现有的薄膜技术来形成用于集成光学的光学电路元件。基本工艺步骤包括β - Ta的图案生成，然后对图案进行热氧化。描述了在直波导和弯曲波导中传播的实验研究。发现图案化波导中的损耗约为5 dB cm⁻¹至7 dB cm⁻¹，额外损耗是由于波导边缘的散射造成的。得出的结论是，改善电路元件边界的光滑度对于减少图案化薄膜中的传输损耗是可取的。
