Pedro Vynck

Low-cost microoptical modules for MCM level optical interconnections

A multichannel free-space microoptical module for dense MCM-level optical interconnections has been designed and fabricated. Extensive modeling proves that the module is scalable with a potential for multi-Tb/s/spl middot/cm/sup 2/ aggregate bit rate capacity while alignment and fabrication tolerances are compatible with present-day mass replication techniques. The microoptical module is an assembly of refractive lenslet-arrays and a high-quality microprism. Both components are prototyped using deep lithography with protons and are monolithically integrated using a vacuum casting replication technique. The resulting 16-channel high optical-grade plastic module shows optical transfer efficiencies of 46% and inter-channel cross talks as low as -22 dB, sufficient to establish workable multichannel MCM-level interconnections. This microoptical module was used in a feasibility demonstrator to establish intra-chip optical interconnections on a 0.6 /spl mu/m CMOS optoelectronic field programmable gate array. This optoelectronic chip combines fully functional digital logic, driver and receiver circuitry and flip-chipped VCSEL and detector arrays. With this test-vehicle multichannel on-chip data-communication has been achieved for the first time to our knowledge. The bit rate per channel was limited to 10 Mb/s because of the limited speed of the chip tester.

High-precision 2-D SM fiber connectors fabricated through deep proton writing

High-precision two-dimensional (2-D) fiber alignment modules would offer great benefits for high-density photonic interconnects at the multichip-module level, where parallel light signals have to be transferred between integrated dense 2-D emitter and detector arrays, or for massive parallel sensing applications. In telecom, the availability of highly accurate low-cost field installable 2-D fiber couplers would boost the further integration of fiber optics in future fiber-to-the-home networks. We present deep proton writing as a prototyping technology for the mastering of small-form-factor 2-D fiber connector components. The alignment components, which we present here, consist of 4 times 8 arrays of circular conically shaped holes for single-mode fibers and feature average insertion losses of 0.062 dB and a maximum loss of 0.15 dB, when used in a fiber butt-coupling configuration

Mass Manufacturable 180

High-efficiency low-cost field-installable 180deg-bend single-mode fiber (SMF) sockets are promising new fiber connector components that can facilitate network element footprint reduction and allow for more comfortable connector handling in the field. We present a novel type of small-form-factor 180deg coupling SMF socket component, yielding coupling losses between two side-by-side positioned fibers as low as 0.5 dB, making use of specially designed low bending loss hole-assisted fiber. The components are prototyped in a polymer using deep proton writing and show all the potentialities for low-cost fabrication in different types of plastics.

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SINPHOS is a monolithic micro-device, able to measure simultaneously time distribution and spectrum of photons coming from a weak source like Delayed Luminescence of biological systems. In order to achieve this challenging goal, we use: Deep Lithography with Ions (DLI) and microelectronic technologies for the fabrication of dedicated passive micro-optical elements and for the realization of Single Photon Avalanche Diode (SPAD) detectors, respectively

-Bend Single-Mode Fiber Socket Using Hole-Assisted Low Bending Loss Fiber

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.

A single photon spectrometer for biomedical applications

We design and realize a scalable multi-channel free-space interconnection prototype with the potential for Tb/s.cm2 aggregate bit rate capacity over inter- and intra-MCM interconnection distances. The component is prototyped in a high quality optical plastic, PMMA, using deep lithography with protons. At present data communication is achieved at 622 Mb/s per channel with a BER smaller than 10-13 for the 16 channels with inter-channel cross-talks as low as -22dB. We perform a sensitivity analysis for misalignments and study the impact of fabrication errors on the performance of the interconnection module in case injection moulding would be the preferred mass-fabrication technique. We provide evidence that these modules can be mass-fabricated with the required precision in optical plastics suited for heterogeneous integration with semiconductor materials.

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

The strength of todays deep lithographic micro-machining technologies is their ability to fabricate monolithic building-blocks including optical and mechanical functionalities that can be precisely integrated in more complex photonic systems. In this contribution we present the physical aspects of Deep Lithography with ion Particles (DLP). We investigate the impact of the ion mass, energy and fluence on the developed surface profile to find the optimized irradiation conditions for different types of high aspect ratio micro-optical structures. To this aim, we develop a software program that combines the atomic interaction effects with the macroscopic beam specifications. We illustrate the correctness of our simulations with experimental data that we obtained in a collaboration established between the accelerator facilities at TUM, LNS and VUB. Finally, we review our findings and discuss the strengths and weaknesses of DLP with respect to Deep Lithography with X-rays (LIGA).

Free-space micro-optical intra-MCM interconnection modules: performances, potentialities and limitations

One of the grand challenges in solving the interconnection bottlenecks at the Printed Circuit Board (PCB) and Multi-Chip-Module (MCM) level, is to adequately replace the PCB and intra-MCM galvanic interconnects with high-performance, low-cost, compact and reliable micro-photonic alternatives. Therefore we address the following components in this paper: 1) out-of-plane couplers for optical waveguides embedded in PCB, 2) peripheral fiber ribbons and two-dimensional single- and multimode fiber connectors for high-speed parallel optical connections, and 3) intra-MCM level optical interconnections via free-space optical modules. For the fabrication of these micro-optical interconnect modules, we are focusing at the Vrije Universiteit Brussel on the continuous development of a rapid prototyping technology, which we call Deep Proton Writing (DPW). The special feature of this prototyping technology is that it is compatible with commercial low-cost mass replication techniques such as micro injection moulding and hot embossing. Laser ablation is used at Ghent University for the fabrication of PCB-embedded waveguides and integrated micro-mirrors. The main advantage of this technology is that it is compatible with present-day PCB manufacturing. For the free-space MCM-level optical interconnect module, we furthermore give special attention to the optical tolerancing and the opto-mechanical integration of the components. We use both a sensitivity analysis to misalignment errors and Monte Carlo simulations. It is our aim to investigate the whole component integration chain from the optoelectronic device to the micro-opto-mechanical components constituting the interconnect module.

Basic aspects of deep lithography with particles for the fabrication of micro-optical and micromechanical structures

Deep Lithography with Protons (DLP) is a rapid prototyping technology for the fabrication of 3D micro-optical precision components. In this paper we will demonstrate how we made this DLP technology compatible with commercially available injection-molding and vacuum casting techniques, allowing to mass-replicate high-quality micro-optical modules at low cost. We will illustrate our technology by presenting optical characteristics of different refractive components made in optical-grade plastics such as polymethyl-methacrylate (PMMA), polycarbonate (PC) and semiconductor compatible plastics with high glass-transition temperatures such as COC.

Low-cost micro-optics for PCB-level photonic interconnects

In this paper we present Deep Lithography with Protons (DLP) as a promising technology for the fabrication of mechanical fiber alignment structures accurately ordered in massive 2D arrays. The fabrication process consists of irradiating PMMA-resist layers with high-energetic proton beams through a lithographic mask with a well-defined circular shape, followed by a selective development of these irradiated zones. To increase the coupling efficiency, we can additionally integrate uniform spherical micro-lenses created by swelling the proton-bombarded zones in a monomer vapor. We highlight the influence of the etching time, the proton beam intensity and the absorbed doses in the PMMA layers on the diameters of the finally developed alignment holes. While selecting the correct process parameters, we prove DLP to be a suitable technology for the fabrication of circular micro-holes with diameters of 125&mum and 155&mum at the front and the back side of a 500&mum thick PMMA plate respectively. We finally illustrate the potentialities of these type of fiber holding plates to realize a user-friendly and accurate 2D fibre positioning component.