Roger Vounckx

Slab plasmon polaritons and waveguide modes in four-layer resonant semiconductor waveguides

This paper presents a detailed study of the waveguide and plasmon polariton properties of four-layer systems involving highly doped semiconductor material. The dispersion relations of waveguide and plasmon polariton modes are calculated for different geometrical parameters and material properties. Special attention is paid to the transition region between the latter modes, which exhibits a complex behavior. Slab plasmon polaritons at wavelengths slightly larger than the plasma wavelength, yielding a positive real part of the permittivity, have been found. Finally, applications at wavelengths near the transition region and near the plasma wavelength are proposed and discussed.

Spatially modulated light detector in CMOS with sense-amplifier receiver operating at 180 Mb/s for optical data link applications and parallel optical interconnects between chips

We present a first realization of a detector receiver combination based on the spatially modulated light detector (SML-detector). The SML-detector gives an output signal that has a shorter falling edge than that of a conventional CMOS detector. It is combined with a sense-amplifier in a standard 0.8-/spl mu/m CMOS technology, allowing one to receive over 155-Mb/s of light pulses at 5.6-/spl mu/W average light input power for /spl lambda/=860 nm. The detector 3-dB bit-rate is 300 Mb/s for this wavelength and for the used spatial topology. For /spl lambda/=635 nm the detector 3-dB bitrate is 510 Mb/s. Apart from monolithic integration of detector and receiver, further signal processing circuitry (including digital signal processing functions) can be integrated on the same chip. The compact system allows conceiving low cost densely packed optoelectronic receivers for parallel optical interconnects and for wavelength division multiplexing applications in the visible and the near-infrared wavelength range.

Differential optical PnpN switch operating at 16 MHz with 250‐fJ optical input energy

We present an optoelectronic switch with exceptional optical sensitivity (250 fJ) operating at high speed (16 MHz). The switch consists of a differential pair of optical PnpN devices. Its excellent optical sensitivity directly ensues from the differential switching principle. The operation speed results from the use of a specially conceived PnpN layer structure, called the depleted optical thyristor, in combination with a particular operation cycle. The performance of our switch corresponds to an improvement of about five orders of magnitude in speed for comparable sensitivity, and of two orders of magnitude in optical sensitivity for the given speed as compared to that of conventional PnpN switches.

Depleted double-heterojunction optical thyristor

A novel double‐heterojunction PnpN optical thyristor is presented in which both the center n‐layer and the center p‐layer are completely depleted at equilibrium. This structure is an extremely attractive optoelectronic switch, because it allows the marriage of two usually incompatible features: speed and optical sensitivity. The speed results from the fact that our PnpN‐structure can be reset to equilibrium, from any point on the current‐voltage characteristics, in less than 10 ns by means of a simple negative anode‐to‐cathode voltage pulse. The optical sensitivity is a direct consequence of the center n‐ and p‐layers being completely depleted of free carriers at equilibrium. We show experimental evidence of this reset operation by studying the dynamics of the free‐carrier extraction from the center n‐ and p‐layers.

A GaAs pressure sensor based on resonant tunnelling diodes

A GaAs-AlAs resonant tunnelling diode (RTD) is incorporated in a 1 mu m thick membrane and used as a pressure sensor. The fabrication technology of the membrane is based upon the selective etch of GaAs with AlAs as an etch stop layer. An external pressure introduces stress in the layers of the RTD and modifies the position of the conduction band, the value of the effective mass and the Fermi level. These variations will change the peak current and voltage of the RTD. Measurements at room temperature show that the effect of an applied pressure on a symmetric RTD is asymmetric. This asymmetric is explained theoretically by the difference in the sign of the stress between the top and bottom layers of the RTD.

Integrated Waveguide Structure for Highly Sensitive THz Spectroscopy of Nano-Liter Liquids in Capillary Tubes

Terahertz dielectric spectroscopy permits the study of biomolecular interactions. However, water induces high attenuation of electromagnetic waves in the THz frequency range, obscuring the response of biomolecules. The developed sensor overcomes this problem by concentrating the THz wave propagating in an integrated waveguide on a small liquid volume contained within a capillary tube. Detailed electromagnetic modeling shows efiective interaction between the THz waves and liquids. Transmission measurement results for capillary tubes fllled with water and methanol mixtures demonstrate a substantial increase in sensitivity to changes of liquid permittivity. The current integrated sensor facilitates THz spectroscopy of biological liquids: a case study on bufiered human serum albumin solution demonstrates a great potential to complement biochemical analytical tools.

Autocreative hierarchy II: dynamics self-organization, emergence and level-changing

Natural systems are characterized more by the way they change than by their appearance at any one moment in time. There is, however, no self-consistent theory capable of ascribing the development of living hierarchical organisms to conventional scientific rationality. We have derived a generic model for the dynamics and evolution of natural hierarchical systems. We present the resultant birational dynamics which may be attributed to a real hierarchy. We describe the nature of self-organization and of emergence in hierarchies, and the rationality which may be employed to move between scalar levels. We propose the use of diffusely-rational recursive Dempster-Shafer-probability to model inter-hierarchical-level complex regions, and consider its implications. The evolution of living from nonliving systems is attributed to a change in the style of emergence which characterizes the appearance of new scalar levels.

A diffuse biosemiotic model for cell-to-tissue computational closure

The adoption of diffuse rationality creates a practical bridge between biosemiotics and computation in formulating local-to-global self-consistent criteria for cellular-to-tissue interfacing and for the emergence of life and consciousness. Nature is always complex, the more so at biological membranic inter-scalar interfaces. We present an evolutionary model of the relationship between autonomy and dependence across scales, and describe the implications of its alternating complex-rational-complex nature.

Two-dimensional optical interconnect between CMOS IC's

The central issue of optically interconnected integrated circuits (OIIC) concerns the area optical interconnect approach to the interconnect bottleneck encountered in advanced VLSI-CMOS designs. The envisaged route to solving this problem offers throughput data interconnects on inter-chip and MCM level, facilitating implementation of new digital architectures and systems. The OIIC project is aimed towards the realisation of three demonstrators: a system demonstrator, implementing state-of-the-art technology, and two link demonstrators, aiming at a high speed approach with 16 channels (Gigalink), and a low power, high density approach on 100 pm pitch with 100 channels (Photonlink). In the paper, progress and results in the project on architecture, components, optical pathways and mounting techniques for the system demonstrator will be highlighted. This system demonstrator aims at using a smart-pixel like interconnect structure to create a logically 3-D architecture, conceptually consisting of a number of electronic planes (electrical FPGAs), that are interconnected bidirectionally along a regular pattern that runs across the chip surface. The full-custom CMOS FPGA circuit is an 8/spl times/8 array of simple configurable logic blocks (a 4-bit function table, one flip-flop), interconnected by a programmable 6-6 switch matrix fabric, including the access to off-chip optical interconnections. The optical components consist of two 8/spl times/8 source arrays (either LEDs or VCSELs) and two 8/spl times/8 InP detector arrays, which are flip-chip bonded to the CMOS circuit and actually overlay part of the CMOS circuits. Electronic driving and receiving circuits are realised in CMOS, and are intermixed with the digital circuits. Each of the 256 optical channels is designed to operate at an information rate of 80 Mbit/s. To ensure reliable communication over so many parallel channels in a noisy digital environment, AC-coupled communication with Manchester coded data is used in the design. The optical pathways between the central chip and its two neighbours consists of removable 8/spl times/16 POF ribbons. Preliminary tests of the CMOS functionality have been completed with good results. A methodology for hybrid assembly, packaging and passive alignment of all components has been implemented. The hybridisation and packaging steps of the CMOS chips and the optical components, final assembly and measurements are discussed.

Fast optical thresholding with an array of optoelectronic transceiver elements

In this letter, we present an optoelectronic system for fast gray-level image decomposition into binary slices. To perform thresholding, we are making use of the differential nature of optical thyristors and compare the light level of the image pixels to that of a reference intensity. As input a gray-level image was generated using a nematic liquid crystal spatial light modulator (SLM) and as a reference intensity a VCSEL light source combined with a diffractive fan-out element was used. We also introduced a compact, large field of view telecentric optical system based on gradient refractive index lenses to image between the SLM and the array. A frame rate decomposition of a six gray-level image has been obtained at 1.8 kHz. Future prospects for system improvements are discussed.