Analysis of optical integration between Si3N4 waveguide and a Ge-based optical modulator using a lateral amorphous GeSi taper at the telecommunication wavelength of 1.55 µm

• Main Authors: Traiwattanapong, Worawat (Author), Wada, Kazumi (Author), Chaisakul, Papichaya (Author)
• Other Authors: Massachusetts Institute of Technology. Department of Materials Science and Engineering (Contributor)
• Format: Article
• Language: English
• Published: Multidisciplinary Digital Publishing Institute, 2020-05-21T19:32:18Z.
• Subjects: Article
• Online Access: Get fulltext

 We report on the theoretical investigation of using an amorphous Ge[subscript 0.83]Si[subscript 0.17] lateral taper to enable a low-loss small-footprint optical coupling between a Si[subscript 3]N[subscript 4] waveguide and a low-voltage Ge-based Franz-Keldysh optical modulator on a bulk Si substrate using 3D Finite-Difference Time-Domain (3D-FDTD) simulation at the optical wavelength of 1550 nm. Despite a large refractive index and optical mode size mismatch between Si[subscript 3]N[subscript 4] and the Ge-based modulator, the coupling structure rendered a good coupling performance within fabrication tolerance of advanced complementary metal-oxide semiconductor (CMOS) processes. For integrated optical modulator performance, the Si[subscript 3]N[subscript 4]-waveguide-integrated Ge-based on Si optical modulators could simultaneously provide workable values of extinction ratio (ER) and insertion loss (IL) for optical interconnect applications with a compact footprint. Keywords: germanium; silicon nitride; optical interconnect; Franz-Keldysh effect