K.D. Djordjev

High-Speed 985 nm Bottom-Emitting VCSEL Arrays for Chip-to-Chip Parallel Optical Interconnects

For chip-scale interconnection, 4 times 12 vertical-cavity surface-emitting laser (VCSEL) arrays have been optimized. Each flip-chip bondable bottom-emitting oxide-confined 985 nm VCSEL have integrated backside lenses, and is capable of modulation at >20 Gb/s with a low current density of only 9.9 kA/cm2. An aggregate data rate of 960 Gb/s was obtained from a chip area of only 1.4 mm times 3.75 mm, or 18.3 Tb/(sldrcm2).

Demonstration of a compact low-power 250-Gb/s parallel-WDM optical interconnect

In this letter, we demonstrate error-free operation of a 12-fiber /spl times/4-wavelength /spl times/5.21-Gb/s parallel-wavelength-division-multiplexed (PWDM) optical link. The 250-Gb/s transmitter and receiver assemblies each have a 5/spl times/8-mm footprint and consume a combined power of 1.5 W. To our knowledge, this is the first publication of a fully functional PWDM optical interconnect as well as the highest demonstrated bandwidth per unit area and bandwidth per unit power consumption for any multiple-channel fiber-optic interconnect. This technology is intended for short-distance high-bandwidth-density applications such as multiprocessor computer backplanes.

500-Gbps Parallel-WDM Optical Interconnect

This paper describes a 500-Gbps parallel wavelength-division multiplexed (PWDM) optical interconnect where 48 channels of 10.42-Gbps data are transmitted over a parallel 12-fiber ribbon with 4 wavelengths per fiber. The transmitter and receiver are each chip-scale packages with a footprint of 5 mm times 8 mm and a combined power consumption of 3 W. This work is motivated by the continually increasing bandwidth needs of short-distance computer processor interconnects, which are demanding optical solutions that maximize bandwidth per unit area, power consumption, and cost

Parallel-WDM for multi-Tb/s optical interconnects

This article presents a promising approach for multi-Tb/s optical interconnects. This approach is contained in the MAUI project, which develops a parallel multiwavelength optical subassembly (PMOSA) that uses PWDM to gain the component-density advantages of two-dimensional parallel optics and the connector and cabling density advantages of CWDM. In the MAUI approach, a standard multimode 12-fiber ribbon is used with 4 wavelengths transmitted through each fiber, for a total of 48 optical channels.

Direct integration of dense parallel optical interconnects on a first level package for high-end servers

The direct integration of dense 48-channel parallel multiwavelength optical transmitter and receiver subassemblies directly onto a first level package using a flex lead attach has been demonstrated. Such an approach, at 10 Gb/s/channel would provide a linear edge bandwidth density of 300 Gb/s/cm. By attaching dense multichannel optical subassemblies directly onto an MCM, the performance limitations of the connectors and node card wiring can be avoided and the total bandwidth off the MCM can be increased while also enabling longer distance and higher speed signaling. This approach involves only a modest modification to the bent-flex approach commonly used for parallel optical modules intended for board mounting but enables a significant density and performance improvement for this application.

Folded-cavity resonators as key elements for optical filtering and low-voltage electroabsorption modulation

Folded-cavity (FC) resonators, which are based on shallow-etched ridge waveguides combined with four deeply etched turning mirrors, are designed and fabricated. The device consists of a resonant FC and a bus waveguide coupled to it through a directional coupler. Optical passive filters, based on this technology, exhibit quality factors in the excess of 5000, with a low insertion loss of 5 dB (including the input coupling loss to a fiber) and more than 15-dB extinction at resonance. When the filter is combined with an electroabsorption active region and is designed to operate in the overcoupled regime, a low-voltage/high-extinction-ratio resonant modulation becomes feasible. The resonant modulator exhibits a low insertion loss (greater than 22-dB extinction at resonance) and offers a low-voltage operation. A change in the applied voltage by 0.7 V (close to the critically coupled conditions) leads to a transmission change of more than 16 dB. Open eye diagrams at 12 Gb/s are presented. To decrease the insertion loss, multiple material bangaps are further monolithically integrated across the wafer by utilizing the quantum-well-intermixing techniques

Demonstration of a high-density parallel-WDM optical interconnect

This work presents the first fully-functional 48-channel parallel-wavelength-division-multiplexed (PWDM) transmitter, receiver and link results at a per-channel data rate of 5.21-Gb/s. This high-density PWDM optical interconnect gives an aggregate link bandwidth of a quarter terabit per second.

Ultra-compact, 0.5-Tb/s parallel-WDM optical interconnect

We discuss a 12-fiber /spl times/ 4-wavelength /spl times/ 10.4-Gbit/s short-distance parallel-wavelength-division-multiplexed optical interconnect. The 0.5-Tbit/s transmitter and receiver assemblies each have a 5 /spl times/ 8-mm footprint and together consume 2.95 W.

High-speed 2D VCSEL arrays at 990nm for short reach interconnects

We have demonstrated high density, 2D (4x12) VCSEL arrays operating at an aggregate data rate of over 480Gb/s in an aerial density of 1400x3750 μm2, or 9.14 Tbs/cm2. These flip-chip, bottom-emitting 990nm VCSELs have low drive voltage, low electrical parasitics, improved thermal impedance and 2D scalability over their wire-bonded top emitting counterparts. Excellent high speed performance was obtained through the use of 1) compressively strained InGaAs MQW active region 2) low parasitic capacitance oxide-confined VCSEL structures and 3) low series resistance, high index contrast AlGaAs/GaAs mirrors. 10Gb/s operation was obtained with low operating current density of ~6kA/cm2 at 70C. Our best results to date have achieved data rates greater than 12.5Gb/s @70C at a current density less than 10kA/cm2. The device results show good agreement with theoretically calculated/simulated values. This work was partially supported by DARPA under contract MDA972-03-3-0004.

Demonstration of a low-voltage resonant modulator based on the folded cavity design

A low-voltage folded cavity resonant modulator, based on shallow-etched ridge waveguides combined with four deeply etched turning mirrors is demonstrated. The resonant modulator exhibit a high quality factor in the excess of 5000, low insertion loss, greater than 22 dB extinction at resonance and offers low-voltage operation. A change in the applied voltage by 0.7 V leads to transmission change of more than 16 dB. The DC performance of the modulator is presented