Design of broadband subwavelength grating couplers with low back reflection.

We present a methodology to design broadband grating couplers using one-dimensional subwavelength gratings. Using the presented method, we design subwavelength grating couplers (SWGCs) with 1-dB bandwidths ranging from 50 to 90 nm. Our designed SWGCs have competitive coupling efficiency, as high as -3.

Precise control of the coupling coefficient through destructive interference in silicon waveguide Bragg gratings.

We present waveguide Bragg gratings with misaligned sidewall corrugations on a silicon-on-insulator platform. The grating strength can be tuned by varying the misalignment between the corrugations on the two sidewalls. This approach allows for a wide range of grating coupling coefficients to be achieved with precise control, and substantially reduces the effects of quantization error due to the finite mask grid size.

Focusing sub-wavelength grating couplers with low back reflections for rapid prototyping of silicon photonic circuits.

We demonstrate fully-etched fiber-waveguide grating couplers with sub-wavelength gratings showing high coupling efficiency as well as low back reflections for both transverse electric (TE) and transverse magnetic (TM) modes. The power reflection coefficients for the TE and TM modes have been significantly suppressed to -16.2 dB and -20.

Focusing-curved subwavelength grating couplers for ultra-broadband silicon photonics optical interfaces.

We report on the design and characterization of focusing-curved subwavelength grating couplers for ultra-broadband silicon photonics optical interfaces. With implementation of waveguide dispersion engineered subwavelength structures, an ultra-wide 1-dB bandwidth of over 100 nm (largest reported to date) near 1550 nm is experimentally achieved for transverse-electric polarized light. By tapering the subwavelength structures, back reflection is effectively suppressed and grating coupling efficiency is increased to -4.

Photolithographically fabricated low-loss asymmetric silicon slot waveguides.

We demonstrate low-loss asymmetric slot waveguides in silicon-on-insulator (SOI). 130 and 180 nm wide slots were fabricated with a 248 nm stepper, in 200 nm thick silicon. An asymmetric waveguide design is shown to expand the range in which the TE0 mode is guided and suppress the TE1 mode, while still maintaining a sharp concentration of electric field in the center of the slot.

Low-loss strip-loaded slot waveguides in silicon-on-insulator.

Electro-optic polymer-clad silicon slot waveguides have recently been used to build a new class of modulators, that exhibit very high bandwidths and extremely low drive voltages. A key step towards making these devices practical will be lowering optical insertion losses. We report on the first measurements of low-loss waveguides that are geometrically suitable for high bandwidth slot waveguide modulators: a strip-loaded slot waveguide.