Stijn Scheerlinck

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.

Efficient, broadband and compact metal grating couplers for silicon-on-insulator waveguides.

Metal grating couplers for Silicon-on-Insulator waveguides are proposed. A silver grating coupler with 33% coupling efficiency is designed. A gold grating coupler prototype is fabricated using Focused Ion Beams demonstrating over 10% coupling efficiency.

Flexible metal grating based optical fiber probe for photonic integrated circuits

An optical probe for photonic integrated circuits is proposed and demonstrated. The device is based on a single-mode fiber containing a subwavelength period metal grating on the facet. When approaching an integrated waveguide, light can be efficiently coupled between probe and waveguide without the need for integrated coupling structures, paving the way for wafer-scale circuit testing. A nanoimprint-and-transfer process were developed for fabricating this probe in a single step. We report 15% coupling efficiency between a gold grating fiber probe and a 220nm×3μm silicon-on-insulator waveguide and demonstrate testing of an integrated microring resonator using two probes.

Metal Grating Patterning on Fiber Facets by UV-Based Nano Imprint and Transfer Lithography Using Optical Alignment

UV-based nano imprint and transfer lithography (NITL) is proposed as a flexible, low cost and versatile approach for defining sub-micron metal patterns on optical fiber facets in a single-processing step. NITL relies on a specially prepared mold carrying the pattern that is to be transferred to the facet. The fibers light-guiding properties allow control of the position of the metal structures by optical alignment.

Coupling mechanisms for a heterogeneous silicon nanowire platform

We discuss different mechanisms for coupling light from nanophotonic silicon waveguides to different types of materials added on top of these waveguides for enhancing the functionality of these waveguides. We consider diffractive coupling, evanescent coupling, adiabatic coupling and coupling to an overlay and illustrate these with recent experimental and modelling results.

Surface Plasmon Interferometer in Silicon-on-Insulator: Novel Concept for an Integrated Biosensor

We propose a novel configuration for a highly integrated and highly sensitive optical biosensor. The basic element of our sensor is a surface plasmon interferometer consisting of a thin layer of gold embedded in a silicon membrane. We investigate the performance of our sensor by simulation using eigenmode expansion. We calculate that refractive index changes in the order of 10-6 RIU (refractive index unit) are detectable for a component of length 10 mum. Moreover, we illustrate that the operation wavelength of our sensor can be tuned to a desired wavelength for a wide range of environmental refractive indices, making our device suitable for chemo- and biosensing

A PSQ-L Polymer Microring Resonator Fabricated by a Simple UV-Based Soft-Lithography Process

Photonic integrated circuits based on polymer waveguides have great potential as low-cost optical devices. A novel inorganic-organic hybrid polymer polysiloxane-liquid (PSQ-L) is introduced for defining the waveguides and for use as both core and cladding layer for the waveguides. The waveguide circuits are replicated by a simple ultraviolet-based soft lithography method consisting of two steps. All-polymer microring resonators are fabricated by this approach and characterized. About 6-dB extinction ratio at the through port and 18-dB extinction ratio at the drop port is demonstrated. A Q-factor of 4.2 times 104 is obtained. Extracted from the measured spectrum, the scattering loss of the ring waveguides is estimated to be about 1.6 dB/cm. This easy fabrication technique can be easily extended to fabricate other devices.

Efficient, Broadband and Compact Metal Grating Couplers for Silicon-on-Insulator Waveguides

Metal grating couplers for Silicon-on-Insulator waveguides are proposed. A silver grating coupler with 33% coupling efficiency is designed. A gold grating coupler prototype is fabricated using Focused Ion Beams demonstrating over 10% coupling efficiency.

Polymer wedge for perfectly vertical light coupling to silicon

We present the design and fabrication of a refractive polymer wedge that allows perfectly vertical coupling of light into a silicon waveguide, which is of interest for flip-chip bonding of vertical cavity emitting light sources on a silicon integrated circuit. The structure includes a conventional diffractive grating coupler that requires off-normal incidence to avoid second order Bragg reflections. The polymer wedge is thus used to refract vertically impinging light into an off-normal wave that couples into the underlying grating. The fabrication involves two steps: mold fabrication and imprint replication. Firstly negative wedge-shaped craters are etched into a quartz mold by Focused-ion-beam milling. Secondly the mold is used to imprint a UV-curable polymer onto a silicon chip containing waveguides and grating couplers, and so replicating the wedges. The characterization setup consisted of a fiber-to-fiber transmission measurement of a silicon waveguide equipped with a pair of grating couplers and polymer wedges. The obtained fiber coupling efficiency was equal to the efficiency of regular grating couplers and fiber positioned at an off-normal angle. The proposed fabrication method enables low cost integration of vertical cavity emitting light sources on silicon integrated photonic circuits.

Interfacing optical fibers and high refractive index contrast waveguide circuits using diffractive grating couplers

The interfacing of an optical fiber and a photonic integrated circuit becomes more complex on a high refractive index contrast waveguide platform due to the large mismatch in mode size between the optical fiber mode and the waveguide modes in the integrated circuit. In this paper we review our work in the field of diffractive grating structures, in order to realize a high efficiency, polarization independent, large bandwidth optical interface with high index contrast waveguides fabricated on the silicon-on-insulator platform.