F. Van Laere

Compact and Highly Efficient Grating Couplers Between Optical Fiber and Nanophotonic Waveguides

We present high-efficiency grating couplers for coupling between a single-mode fiber and nanophotonic waveguides, fabricated both in silicon-on-insulator (SOI) and InP membranes using BenzoCycloButene wafer bonding. The coupling efficiency is substantially increased by adding a gold bottom mirror to the structures. The measured coupling efficiency to fiber is 69% for SOI grating couplers and 56% for bonded InP membrane grating couplers

Compact Focusing Grating Couplers for Silicon-on-Insulator Integrated Circuits

We report experimental results on compact and broadband focusing grating couplers, both in silicon-on-insulator (SOI) and gold on SOI. An eight-fold length reduction of the coupling structure from fiber to photonic wire in SOI, as compared to a linear grating and adiabatic taper, is obtained, without performance penalty. A proof of principle is given for a focusing grating coupler in gold on SOI, with 20% fiber-to-focus efficiency.

Focusing Polarization Diversity Grating Couplers in Silicon-on-Insulator

We report on compact focusing polarization diversity grating couplers in silicon-on-insulator, which can be used to overcome the polarization dependence of nanophotonic integrated circuits. The minimum fiber-to-fiber polarization dependent loss is 0.4 dB and the focusing grating couplers are as performant as standard 2-D-grating couplers without focusing. In addition, the focusing property of the gratings results in an 8-fold length reduction of the coupling structure as compared to standard nonfocusing 2-D-grating versions.

Heterogeneous integration and precise alignment of InP-based photonic crystal lasers to complementary metal-oxide semiconductor fabricated silicon-on-insulator wire waveguides

The integration of two-dimensional III-V InP-based photonic crystal and silicon wire waveguides is achieved through an accurate alignment of the two optical levels using mix-and-match deep ultraviolet (DUV)/electron beam lithography. The adhesively bonded structures exhibit an enhancement of light emission at frequencies where low group velocity modes of the photonic crystal line defect waveguides occur. Pulsed laser operation is obtained from these modes at room temperature under optical pumping. The laser light is coupled out of the Si waveguide via grating couplers directly to single mode fiber.

Nanophotonic Polarization Diversity Demultiplexer Chip

We demonstrate a very compact multifunctional photonic-crystal demultiplexer on high index contrast InP-membrane for coarse WDM applications. Polarization diversity is implemented using 2D-grating couplers. The performance of the device is evaluated using integrated p-i-n photodetectors. Polarization diversity from fiber to detector-without intermediate functional device-results in a minimal polarization dependent loss (PDL) of 0.2 dB. This value increases to 1.1 dB when including the photonic-crystal demultiplexer.

Focused-Ion-Beam Fabrication of Slanted Grating Couplers in Silicon-on-Insulator Waveguides

We have designed and fabricated an efficient grating coupler for coupling light between optical fibers and silicon-on-insulator waveguides. The coupler consists of 88-nm-wide slits, etched at an angle of 58deg to the surface normal. They are defined by direct etching with a focused ion beam, using iodine gas and an alumina hard mask. The measured efficiency is 46%

Compact grating couplers between optical fibers and Silicon-on-Insulator photonic wire waveguides with 69% coupling efficiency

We present efficient, compact and broadband grating couplers in Silicon-on-Insulator, for coupling between single mode fiber and nanophotonic waveguides. By adding a gold bottom mirror, the coupling efficiency is increased to 69%.

Compact Slanted Grating Couplers Between Optical Fiber and InP–InGaAsP Waveguides

We present theoretical and experimental results for compact slanted gratings for vertical coupling between single-mode fiber and InP-InGaAsP waveguides. The maximum calculated coupling efficiency is 59%. We have measured a coupling efficiency of 16% for a 10-mum-long slanted grating

Photonic-Crystal Demultiplexer With Improved Crosstalk by Second-Order Cavity Filtering

In this paper, we implement on a silicon-on-insulator (SoI) platform a photonic-crystal demultiplexer that operates on the principle of mini-stopbands of broader waveguides. Previous InP-based membrane versions showed modest crosstalk at 10 nm spacing. Here, we implement a second cavity in the form of a second parallel waveguide almost identical to the core one. Simulations employing three-modes coupled-mode theory and finite-difference time-domain help optimizing the coupling. The experimental realization with deep ultraviolet exposure and grating couplers is the first of this demux strategy on SoI. It successfully shows crosstalk in the 15-20 dB range on a very small footprint.

Focusing polarization diversity gratings for Silicon-on-Insulator integrated circuits

We present experimental results for focusing grating couplers for coupling between optical fiber and nanophotonic silicon-on-insulator waveguides in polarization diversity configuration. The footprint is reduced by a factor of 8 compared to standard grating couplers.