Yohei Sobu

Si-wire grating couplers for integrated optical transceivers based on single-mode fiber connection

Recently, grating couplers (GCs) have been extensively reported as a promising device for optical coupling between Siwire waveguides and standard single mode optical fibers. In this paper, we report the feasibility study of Si-wire type GCs fabricated by the 248-nm KrF lithography process on a 200-mm silicon-on-insulator (SOI) wafer with a 220-nmthick Si layer. We report a 1D-GC for a transmitter that operates only with TE mode and a 2D-GC for a receiver that splits arbitrary polarization from a single mode fiber operating at a wavelength of 1550 nm. We investigated the fundamental feasibility with the simple design. Especially, the wafer uniformity in inter-dies of 1D and 2D-GC is mainly examined on a 200-mm SOI wafer. Additionally, we experimentally clarify the fundamental characteristics of the 1DGC from the viewpoint of an insertion loss and a 1-dB fiber misalignment tolerance. As for the 2D-GC, in addition to the same aspects with the 1D-GC, an optical crosstalk and a polarization dependent loss will also be discussed around 1550 nm wavelength. Also, the center wavelength against a grating period of the 1D-GC and a circular hole diameter of the 2D-GC will be characterized.

Spectral variation analysis for silicon grating couplers fabricated on a 300-mm SOI wafer

Spectral variation behavior for many grating couplers is experimentally investigated. It was found that the coupling wavelength is shifted by fabrication deviations in grating structure, and grating depth variation in 300-mm wafer processes is precisely derived by numerical analysis for coupling wavelength variation.

Demonstration of low polarization dependent loss of 1.3 μm two dimensional grating coupler

Reduction of the polarization dependent loss (PDL) of 1.3 μm two dimensional grating coupler (2D-GC) was demonstrated by using slanted arrays and cross shaped scatterers. The PDL of 2D-GC was measured to be < 0.5 dB over a 40 nm range at 1.3 μm.

Silicon-photonics devices for chip to chip communications

Recent progress of silicon-photonics devices developed for chip-to-chip communications is presented. WDM MUX/DEMUX filters, multi wavelength light sources, 1D and 2D grating couplers and 25 Gbps inter-chip transmission experiment with low driving power are detailed.