R Vounckx

Mushroom microlenses: optimized microlenses by reflow of multiple layers of photoresist

A novel type of photoresist microlenses is conceived. The characteristic of these lenses is their mushroom shape: the lens dome is located at a certain controllable distance from the substrate, and the curvature of the lens is larger than that of traditional truncated-sphere lenses. These mushroom microlenses are equilibrium-state, stable products of reflow that are obtained when starting from a multilayer photoresist stack. Integration on light-emitting diodes results in enhanced output efficiency and directivity: a vertical-to-surface emission enhancement of up to a factor of 8 has been achieved.

A monolithic optoelectronic receiver in standard 0.7-μm CMOS operating at 180 MHz and 176-fJ light input energy

A novel monolithic optoelectronic receiver/converter system is presented in standard 0.7-/spl mu/m N-well CMOS technology. Differential light input incident on enlarged drains of two MOS transistors of a sense amplifier induces latching in either the digital HIGH state or the digital LOW state. The enlarged drains serve as photodiodes, circumventing hybridization techniques like flip-chip and/or solderbumping necessary when using III-V photodiodes. The first receivers of this type have photodetector areas of 15/spl times/15 /spl mu/m/sup 2/ and demonstrate bitrates of 180 Mb/s with a differential light input of 176 fJ. The electrical power dissipation is of the order of the dissipation of one CMOS logic gate. The very small total receiver area makes the receiver further perfectly suited for use in massive parallel optical interconnects between VLSI chips.

Receiver with optical thyristors operating at 155 Mbit/s with 3 femto-Joule optical inputs

A receiver for digital optical inputs is presented which is based on a differential pair of optical thyristors. Modification of the conventional differential pair allows the electrical readout of its ON and OFF states. Optical input pulses with an energy of about 3 femto-Joule (at a wavelength of 830 nm) are sufficiently large for detection. In its present size, the receiver works up to 155 Mbit/s.

Image transcription between arrays of N-p-n-P optoelectronic switches

Double-heterojunction optical thyristors with a low holding current (0.2 mu A/6*10/sup -4/ cm/sup 2/) and a low breakover current (70 nA/6*10/sup -4/ cm/sup 2/) have been fabricated. Such thyristors can be made to switch when receiving an optical input signal from a twin device. Excellent uniformity and stability of the characteristics are obtained in arrays of such thyristors. Monolithic arrays of 25 thyristors connected in parallel have been processed. Winner-takes-all operation can be achieved in such arrays: when applying a bias to the array, only the one thyristor receiving maximum input light switches on, while all others are inhibited from reaching the on-state. With this system, the maximum of a light input pattern can be detected with a resolution of 0.3 nW-or 30 pJ for pulsed input light signals. Image transcription between thyristor arrays is demonstrated: the on-state of more than one thyristor can be copied with a single electrical pulse to the corresponding thyristors of a twin array. >

Demonstration of a monolithic multichannel module for multi-Gb/s intra-MCM optical interconnects

In this letter, we report on the demonstration of a 2.48-Gb/s multichannel optical data-link for intramultichip module interconnects. The optical module was fabricated in polymethylmethacrylate (PMMA) by deep proton lithography and monolithically integrates micromirrors and cylindrical lenses. With the same technology, we have also fabricated a single-channel optical bridge and used this component to demonstrate a proof-of-principle optical intrachip interconnect by establishing a digital data-link between optoelectronic transceivers integrated on the same chip.

Parallel optoelectronic data transcription with fan-out between planes of PnpN optical thyristors

Optical data transcription is implemented between differential pairs of PnpN optical thyristors. A minimum input pulse length of 500 ns is achieved, demonstrating a thyristor switching energy of 11 fJ. Parallel data transcription with fan-out over three cascaded thyristor arrays is also demonstrated, using a compact and modular optical system.

Maximum optical dose detection with a 16*16 monolithic thyristor array

The authors report on the fabrication of a 2-D array (16*16) of optical thyristors connected into a winner-takes-all network with capability of spatially resolved maximum optical dose detection. In every pixel of the network, optical energy is integrated in time (during up to 1 ms) by means of precharging of the optoelectronic thyristors. At the moment of verdict, a voltage step is applied to the whole 256 element array. Only the element with the highest stored charge then switches on and holds off all other thyristors. A differential resolution of 80 pJ optical energy has been measured, while the time to take the appropriate decision is less than 150 ns.<<ETX>>

8/spl times/8 array of cascadable differential pairs of optical thyristors for parallel optical interconnects

We report on the fabrication of the first monolithic array of 8/spl times/8 differential pairs of optical thyristors. The 64 thyristor pairs have a common anode and a common cathode, such that the complete array has only 2 electrical contact pads for the electrical power supply. Each differential pair of the array is an optoelectronic switch which can emit and receive dual-rail code binary optical data perpendicular to the chip surface. The required optical input energy for switching is only 50 fJ, and the bit rate is at present 25 Mbit/sec.

Generation of four negative differential resistance regions using two resonant tunnelling diodes

In this paper we report on the experimental observation of four negative differential resistance regions in the current-voltage characteristic of a monolithically integrated seriesconnection of two resonant tunneling diodes at room temperature. An equivalent circuit of the seriesconnection is proposed which gives an explanation of the experimental results. The required current-voltage characteristics of the two resonant tunneling diodes in the seriesconnection, to generate the multiple negative resistance regions, are discussed. Simulations based on the equivalent circuit, show the possibility of five negative differential resistance regions with a monolithically integrated seriesconnection of two resonant tunneling diodes.

Determination of the band line-up for strained InGaAs/AlAs heterojunctions using resonant tunnelling diodes

Abstract Conduction band offsets for strained InGaAs/AlAs heterointerfaces have been deduced from a great number of current-voltage measurements on GaAs/AlAs/InGaAs resonant tunnelling diodes with different In concentrations, at room temperature and liquid nitrogen temperature. The method is based on the determination of the peak voltage of the resonant tunnelling diodes. Simple analytical techniques, using the well known GaAs/AlAs/GaAs resonant tunnelling diodes as a reference system, give us the conduction band offsets of the measured system. A profound error analysis showed an accuracy comparable to other techniques. This quite simple method offers great potential to determine the band offsets of strained layer heterointerfaces.