| dc.description.abstract | Silicon-on-insulator (SOI) waveguides have received much attention as a platform for planar lightwave circuits (PLCs) due to their compatibility with complementary metal oxide semiconductor (CMOS) technologies. Light in the silicon layer of SOI is naturally confined in the vertical direction because of the high index contrast between the bottom oxide layer, Si layer, and air. However, owing to the inherently large index contrast between si and air, the core size of a single-mode SOI waveguide is generally less than sub-micro size, resulting in a very serious coupling problem.
Rib waveguide with specific structure can provide a core width with large cross-section, but still maintain in single-mode operation. In this paper, a large single-mode rib waveguide is designed and demonstrated. For easily coupling to SMF, the upper silicon layer is chosen to 10 μm, and the corresponding width of core is 6 μm with etching depth equal to 3.5 μm. On the basis of the above design, a calculation results of a butt-joint interconnect from SMF can be as high as -1.25 dB. The polarization-dependence loss is less than 0.01 dB, and wavelength- dependent loss preserves 1 dB variation within 100 nm.
E-beam lithography is employed in this fabrication process due to obtain a waveguide sidewall with optical performance. By ICP-RIE dry etching process, the side-wall angle is very close to 90°, which maintains the designed eigen-mode correctly. The smooth side-wall roughness results in the low propagation loss of 0.9 dB/cm. Moreover, the near-field mode pattern is also measured by IR-camera, and it shows highly coincident to the designed eigen mode.
For the purpose of high-density integration in PLC, a phase- compensated air-based microprism is introduced to a wide-angle bending rib waveguide. An air microprism, which can be made by directly dry etching up to oxide layer, compensates the phase difference in this rib waveguide bend, and then properly tilts the planar wavefront to the designed bending angle. A 10° bending waveguide with radius of curvature of only 27.1 μm is designed and fabricated. | en_US |