We have experimentally demonstrated the ability to couple an arbitrary polarization state from a fiber to the TE-mode of a single waveguide in an integrated silicon photonics circuit with an extinction ratio larger than 31 dB, measured between the output ports of the integrated photonic circuit. To achieve this we combined a 2D- grating coupler and a Mach-Zehnder Interferometer (MZI). After accounting for setup and coupling losses, for a 1 mW input into the 2D coupler, we obtain an average output power of 0.98 mW at the desired waveguide, with less than 1.2 dB variation across all input polarization states. The experiments were performed at a wavelength of 1.55 μm.
A fully-etched grating coupler with improved back re ection and bandwidth is demonstrated in this paper. It can also be made in compact patterns with much smaller footprints than conventional, fully-etched grating couplers with long adiabatic tapers. Sub-wavelength gratings were employed to form the e ective index areas between the major gratings. Our grating has a measured 3-dB bandwidth of 64.37 nm with a back re ection of -14 dB.
A universal design methodology for grating couplers based on the silicon-on-insultator platform is presented in this paper. Our design methodology accomodates various etch depths, silicon thickness (e.g., 220 nm, 300 nm), incident angles, and cladding materials (e.g., silicon oxide or air), and has been verified by simulations and measurement results. Further more, the design methodology presented can be applied to a wide range, from 1260 nm to 1675 nm, of wavelengths.
We demonstrated 2×2 broadband adiabatic 3-dB couplers based on silicon rib waveguides. Functioning as
50/50 optical power splitters, these devices can be used in optoelectronic applications. Fabricated using siliconon-insulator technology, we demonstrated the performance of the adiabatic 3-dB couplers by integrating two couplers into an unbalanced Mach-Zehnder Interferometer (MZI). Measurements of the MZI were made over a 100 nm wavelength range. Extinction ratios in excess of 33.4 dB were obtained over the wavelength range from 1520 nm to 1600 nm, for light injected into Input Port1 and measured at Output Port2, i.e., the cross port response.
Development of large-scale photonic integrated circuits requires an accurate, simple, and space-efficient method for characterizing the optical losses of integrated optical components. Here we present a ring-resonator-based technique for transmission-loss measurement of integrated optical components. Y-branch splitters are used to demonstrate the concept. This measurement techique is based on characterizing the spectral response of a waveguide ring resonator with a number of Y-branches inserted inside the cavity. The measurement accuracy is intrinsically limited by the optical loss of the ring waveguide and is independent of fiber-to-waveguide coupling losses. The devices were fabricated using a CMOS-compatible silicon-on-insulator technology. Our results show that the proposed technique is promising for high-accuracy, high-efficiency characterization of optical losses. Limitations of and potential improvements to the technique are also discussed.