Jürgen Bruns

Electro-optic modulation in slotted resonant photonic crystal heterostructures

Two dimensional photonic crystal waveguides in high index materials enable integrated optical devices with an extremely small geometrical footprint on the scale of micrometers. Slotted waveguides are based on the guiding of light in low refractive index materials and a field enhancement in this particular region of the device. In this letter we experimentally demonstrate electro-optic modulation in slotted photonic crystal waveguides based on silicon-on-insulator substrates covered and infiltrated with nonlinear optical polymers. A photonic crystal heterostructure is used to create a cavity, while simultaneously serving as an electrical connection from the slot to the metal electrodes that carry the modulation signal.

Tunable Bragg reflectors on silicon-on-insulator rib waveguides.

We present the design, fabrication and characterization of Bragg reflectors on silicon-on-insulator rib waveguides. The fabrication is based on a new double lithographic process, combining electron-beam lithography for the grating and photolithography for the waveguides. This process allows the realization of low loss reflectors, which were fully characterized. The influence of the etching depth and of the waveguide geometry on the reflector performance is considered. We demonstrate a reflectivity larger than 80% over a bandwidth of 0.8 nm with an insertion loss of only 0.5 dB. A thermal tunability of the device is also considered, showing that a shift of the reflected wavelength of 77 pm/K is possible.

Performance of 40-Gb/s DPSK Demodulator in SOI-Technology

A silicon-on-insulator delay interferometer manufactured in 4-mum rib waveguide technology is presented. The polarization-dependent frequency shift is tuned to a value as low as 0.4 GHz. Continuous-wave device performance and polarization-independent differential phase-shift keying demodulation performance in a 40-Gb/s testbed are demonstrated.

Continuously tunable delay line based on SOI tapered Bragg gratings.

The realization of an integrated delay line using tapered Bragg gratings in a drop-filter configuration is presented. The device is fabricated on silicon-on-insulator (SOI) rib waveguides using a Deep-UV 248 nm lithography. The continuous delay tunability is achieved using the thermo-optical effect, showing experimentally that a tuning range of 450 ps can be obtained with a tuning coefficient of -51 ps/°C. Furthermore the system performance is considered, showing that an operation at a bit rate of 25 Gbit/s can be achieved, and could be extended to 80 Gbit/s with the addition of a proper dispersion compensation.

Deep-UV Technology for the Fabrication of Bragg Gratings on SOI Rib Waveguides

In this letter, we present a wafer level technology based on deep-ultraviolet lithography to fabricate Bragg gratings on silicon-on-insulator rib waveguides. The principle of the used double-patterning technique is presented, as well the influence of the process variation on the device performances. The fabricated Bragg gratings were characterized and compared to analogue structures patterned with electron-beam lithography.

CWDM Transmitter Module Based on Hybrid Integration

A simple concept for hybrid integration and packaging of III/V active devices in a multipurpose optical platform is introduced. The board could be used as a coarse wavelength-division multiplexing transmitter with four lasers or as a receiver with photodiodes, respectively. The assembly ensures ample heat dissipation, so the laser performance does not suffer after the packaging

CMOS-compatible purely capacitive interfaces for high-density in-vivo recording from neural tissue

CMOS-based neural tissue in-vivo recording chips with a purely capacitive interface are presented with 256 sites resp. 256 recording channels. A 3D post-CMOS ALD-based process allows to provide a highly efficient sensor dielectric and to realize a protective insulation layer for the non-active part of the fabricated devices. A simple interconnect-efficient sensor array topology is used. Electrical characterizations and in-vivo measurements with biological content reveal proper operation of the presented approach.

Digital Optical Circuit Switches and Switching Matrices in Polymers

Summary We discuss and compare different designs of digital optical switches (DOS) in polymers utilizing the thermo optical effect (y-branched DOS, three branched DOS, DOS cascade with partially merged switching stages, DOS with integrated attenuators) with respect to their applicability in switching matrices and their crosstalk (CT) performance. The underlying oversized rib waveguide concept is also briefly discussed with emphasis on the integration of absorbers. Finally we present results for an optimized matrix switch design.

Facet preparation of SOI waveguides by etching and cleaving compared to dicing and polishing

We compared two different techniques of facet preparation of silicon-on-insulator (SOI) waveguides: The conventional by dicing and polishing and our proposed by dry etching the facets and cleaving along anisotropically etched cleaving grooves.

Three dimensional ALD of TiO 2 for in-vivo biomedical sensor applications

Titanium dioxide, known as a high-k biocompatible dielectric transducer material, is processed by means of ALD and applied to a 3D structure with dimensions typical for multi-site multi-channel in-vivo neural interfaces. High uniformity, high areal capacitance, and in particular low leakage current densities are achieved within a sufficiently wide operation voltage window. The results demonstrate the suitability of this process to provide dielectric interfaces for 3D biomedical applications.