Carl Sys

Realization and characterization of 8/spl times/8 resonant cavity LED arrays mounted onto CMOS drivers for POF-based interchip interconnections

An 8/spl times/8 array of resonant-cavity light emitting diodes (RCLEDs) emitting at 980 nm and flip-chip mounted onto complimentary metal-oxide-semiconductor (CMOS) integrated drivers, is presented. The RCLEDs are optimized for maximal extraction efficiency into the numerical aperture of polymer optical fibers (NA=0.5) and minimal optical crosstalk. Design of the optimal cavity structure is presented, and 8/spl times/8 arrays are realized and mounted directly onto standard CMOS chips using a solder reflow technique. The CMOS integrated drivers are designed for high-speed operation and low-power consumption, and are realized in 0.8 and 0.6-/spl mu/m CMOS technology. The electrooptical modules have been realized and characterized, and over 50-/spl mu/W optical power coupled to POF at 3-mA drive current is reported. Open eye diagrams at operation speed up to 250 Mb/s are presented. These characteristics are compatible with CMOS integrated low-power receivers.

Resonant cavity LED's optimized for coupling to polymer optical fibers

Planar resonant-cavity light-emitting diodes have been optimized to meet optical interconnect requirements. The microcavity effect is exploited to increase the extraction efficiency into a given numerical aperture and to reduce the crosstalk in parallel optical interconnect applications. Devices are fabricated with an overall quantum efficiency of 3.7% into a polymer optical fiber with a numerical aperture of 0.5 and a FWHM beam divergence angle of 105/spl deg/ at a drive current of 1 mA.

Highly uniform AlGaAs/GaAs and InGaAs(P)/InP structures grown in a multiwafer vertical rotating susceptor MOVPE reactor.

Abstract Highly uniform AlGaAs GaAs and InGaAs(P) InP epitaxial layers have been grown in a vertical rotating susceptor MOVPE reactor capable of accommodating three 2′ wafers. The unique water-cooled “showerhead”-type injection distributor which is located 1.5 cm above the substrates ensures a uniform reactant distribution, resulting in uniform growth over a wide range of growth conditions. Periodic multilayer and single layer structures have been used to investigate the thickness and compositional uniformities. The thickness variations over a radial distance of 48 mm for three wafers grown in the same run are within ± 2% for both AlGaAs and InGaAs layers, resulting in a standard deviation of only 0.9%. The gallium concentration of an InGaAs layer varies from 46.88% to 47.01% over the same radial distance with the standard deviation of 0.043%. Measurements of InGaAsP layers grown onto 2′ InP wafers with different alloy compositions show good compositional uniformity yielding standard deviations within 4.4 nm in PL wavelength and 135 ppm in lattice mismatch over a 46 mm radial distance.

Stress-induced effects by the anodic oxide in ridge waveguide laser diodes

This paper studies, both theoretically and experimentally, stress-induced effects on the lateral far-field behavior for ridge-type semiconductor laser diodes where anodic oxide is used for the definition of the stripe width. These effects consist of antiguiding under the stripe region, and of two positive waveguiding features near the stripe edges. For low-threshold devices, these effects may be more important than thermal effects, depending on the stress in the oxide. They put a lower limit on the built-in index guiding to be introduced by lateral etch outside the ridge region in order to maintain fundamental mode operation for wider stripes. The magnitude of these effects may be as large as /spl Delta/n/sub ef/=1/spl times/10/sup -3/. An analytical mathematical model is deduced for computing stresses and strains for a certain ridge-shaped interface which bounds the elastic medium.

Preliminary results on high total dose testing of semiconductor photonic sources : a comparison of VCSELs and Resonant-Cavity LEDs

Low-power consumption, high efficiency and high bandwidth surface emitting semiconductor optical sources are critical elements in the development of future photonic systems for space and civil nuclear applications. In this paper, we report on preliminary high total dose experiments performed on two types of recently developed microcavity emitters: VCSELs and microcavity (or resonant cavity) LEDs. We gamma irradiated a total of twelve commercially available packaged VCSELs and two home-made flip-chipped 2 X 2 microcavity LED arrays. For doses between 5(DOT)106 Gy and 1.3(DOT)107 Gy the VCSELs show a threshold current increase lower than 20% and an output power decrease lower than 10%. These values are even smaller if the VCSEL is operated at a higher temperature. At a dose of 3.14(DOT)107 Gy, one VCSEL still showed satisfactory operation. The microcavity LEDs suffered from a burn-in after radiation but recovered quickly when biased. Their output power decrease is comparable to that of the VCSELs, while their quantum efficiency is not much affected. The specifications of both types of devices are not substantially altered by high gamma doses and can therefore be considered for application in enhanced radiation environments.

Microcavity LED-based parallel data link using small-diameter (125 m) plastic optical fibres

Parallel optical data links using high-efficiency microcavity LEDs (MCLEDs) and small-diameter plastic optical fibre ribbons are proposed. MCLED performance, coupling efficiencies, alignment tolerances, plastic optical fibre end-facet termination techniques and first link experiments are studied.

Electrically pumped grating-assisted resonant-cavity Light-Emitting Diodes

The Grating -Assisted Light-Emitting Diode, an LED design for high brightness based on a resonant cavity containing 1D or 2D periodically corrugated layers (grating), is subject of this presentation. The diffractive properties of the wavelength scaled periodic grating integrated in one or both of the interfaces of the resonant-cavity, can redirect the laterally propagating resonant guided mode to an extractable direction. Because of the high power fraction in these guided modes, the use of such gratings can result in a higher extraction efficiency than a homogeneously layered RCLED, in which the trapped guided mode is a loss of power. In this scope, a generally applicable rigorous electromagnetic analysis based on the Coupled Wave Theory for diffractive gratings, has been developed to calculate the extraction efficiency of spontaneous emission in a periodically corrugated layer structure. This general model has been applied to a GA-RCLED emitting at 980 nm. The structure consisting of a hybrid bottom-emitting cavity with metallic grating and bottom DBR mirror, shows simulated efficiencies of over 40%. Electrically pumped devices have been processed. Experimental data and simulation results, such as polarization selective emission, spectral behavior and efficiency are compared and discussed.

Microcavity LEDs with an overall efficiency of 4% into a numerical aperture of 0.5

Summary form only given. Microcavity LEDs were optimised for optical interconnect requirements. Overall quantum efficiency of up to 4.3% into a numerical aperture of 0.5 and a FWHM beam divergence angle of 105 degrees at a drive current of 1 mA was achieved. Microcavity LEDs with one gold and one GaAs-AlAs DBR-mirror have been optimized for efficiency into a limited NA of 0.5. Simulations indicate that an efficiency of 8% can be achieved. Experimental devices give a best value of 3.7%.

Microcavity LEDs coupled to POF arrays for parallel optical interconnects

A low cost approach for realising parallel optical interconnects, based on the use of micro-cavity LEDs and polymer optical fibres (POFs) has been proposed. LEDs were optimised for coupling to POF, yielding 3% external quantum efficiency into POF. Optimisation of the POF-termination procedure has led to interface losses of 0.3 dB. An alignment scheme, avoiding active alignment, has been discussed offering lateral misalignment tolerances in the 10 - 15 /spl mu/m range, which is compatible with the use of 125 /spl mu/m POF.

A reservation-based scheduling mechanism for fair QoS provisioning in packet-based networks

In this paper, we present a mechanism for scheduling multi-class traffic in a node of a packet-based communication network. We focus in particular on the output queues used for contention resolution at the output links of a network node. The mechanism, referred to as R-scheduling, is based on the use of in-queue reservations for future arriving data packets. Each traffic class has a given number of class-dedicated reservations at its disposal. If a data packet is enqueued, it seizes its reservation which is closest to the head of the queue by taking its place in the queue, after which a new reservation belonging to the same traffic class as the enqueued packet is created at the tail of the queue. The performance of the R-scheduling mechanism is investigated by means of extensive simulations for a wide parameter space. Based on these simulations, a meta-model is constructed that allows to translate given QoS (Quality of Service) targets into working parameters for the R-scheduling mechanism. We show that R-scheduling offers unique properties in terms of the QoS delivered to each of the traffic classes. In particular, it allows shaping the distributions of the queueing delay perceived by each traffic class in order to achieve a target spacing of their delay quantiles. Other important features that can be effectuated by R-scheduling are: isolation of traffic classes through temporal priority, mitigation of packet starvation for lower-priority traffic classes and early provision of tight delay bounds. The mechanism has low complexity and is suitable for dynamic applications.