Imprinted silicon-based nanophotonics.

We demonstrate and optically characterize silicon-on-insulator based nanophotonic devices fabricated by nanoimprint lithography. In our demonstration, we have realized ordinary and topology-optimized photonic crystal waveguide structures. The topology-optimized structures require lateral pattern definition on a sub 30-nm scale in combination with a deep vertical silicon etch of the order of ~300 nm. The nanoimprint method offers a cost-efficient parallel fabrication process with state-of-the-art replication fidelity, comparable to direct electron beam writing.

Photonic-crystal waveguide biosensor.

A photonic-crystal waveguide sensor is presented for biosensing. The sensor is applied for refractive index measurements and detection of protein-concentrations. Concentrations around 10 mug/ml (0.15muMolar) are measured with excellent signal to noise ratio, and a broad, dynamic refractive index sensing range extending from air to high viscous fluids is presented.

Strained silicon as a new electro-optic material.

For decades, silicon has been the material of choice for mass fabrication of electronics. This is in contrast to photonics, where passive optical components in silicon have only recently been realized. The slow progress within silicon optoelectronics, where electronic and optical functionalities can be integrated into monolithic components based on the versatile silicon platform, is due to the limited active optical properties of silicon. Recently, however, a continuous-wave Raman silicon laser was demonstrated; if an effective modulator could also be realized in silicon, data processing and transmission could potentially be performed by all-silicon electronic and optical components. Here we have discovered that a significant linear electro-optic effect is induced in silicon by breaking the crystal symmetry. The symmetry is broken by depositing a straining layer on top of a silicon waveguide, and the induced nonlinear coefficient, chi(2) approximately 15 pm V(-1), makes it possible to realize a silicon electro-optic modulator. The strain-induced linear electro-optic effect may be used to remove a bottleneck in modern computers by replacing the electronic bus with a much faster optical alternative.

Photonic crystal waveguides with semi-slow light and tailored dispersion properties.

We demonstrate a concept for tailoring the group velocity and dispersion properties for light propagating in a planar photonic crystal waveguide. By perturbing the holes adjacent to the waveguide core it is possible to increase the useful bandwidth below the light-line and obtain a photonic crystal waveguide with either vanishing, positive, or negative group velocity dispersion and semi-slow light. We realize experimentally a silicon-on-insulator photonic crystal waveguide having nearly constant group velocity ~c(0)/34 in an 11-nm bandwidth below the silica-line.

Efficient photonic crystal directional couplers.

We demonstrate highly efficient and spectrally flat broadband coupling in photonic crystal directional couplers. The result is obtained by use of a novel design with smaller holes between coparallel photonic crystal waveguides for efficient channel-to-channel coupling. The system studied is based on a planar hexagonal photonic crystal lattice of holes made in silicon-on-insulator material. Results from three-dimensional finite-difference time domain modeling are shown to closely match results measured on fabricated samples.