J. Cross

Thin-film multimaterial optoelectronic integrated circuits

The multimaterial integration of thin-film optoelectronic devices with host substrates ranging from silicon circuits to glass waveguides to polymer micromachines offers to the system designer the freedom to choose the optimal materials for each component to achieve performance and cost objectives. Thin-film compound semiconductor optoelectronic devices are comparable to, and, in some cases, better than, their on-wafer counterparts. Thin-film detectors have been integrated with receiver circuits and movable micromachines, thin-film emitters with drive circuitry, and both have been used to demonstrate three-dimensionally interconnected systems. Vertical electrical integration of detector arrays on top of circuits is examined for massively parallel processing of images. Vertical optical interconnections of stacked silicon circuits (which are transparent to the wavelength of light used) are explored, and are used to develop a massively parallel processing architecture based upon low memory, high throughput, and high input/output.

A single-fiber bidirectional optical link using colocated emitters and detectors

This letter reports the bonding of a small, thin-film GaAs-based emitter onto a larger silicon detector to realize spatial colocation of the emitter and detector. These colocated devices enable single fiber bidirectional communication between the two analog/digital silicon circuits that contain the emitter/detector pairs. Bidirectional communication between two of these circuits is demonstrated with a single plastic optical fiber.

Coupling efficiency of an alignment-tolerant, single fiber, bi-directional link

In this paper, we present a novel Fourier technique to calculate the emitter-to-fiber coupling efficiency between an incoherent source of arbitrary directivity and a multimode fiber. The technique expresses the 4-D integral that describes the coupling as a 2-D sum, and along with Fourier series expansion, the technique increases greatly the computational speed of emitter-to-fiber coupling calculations. We have simulation results of the emitter-to-fiber coupling analysis and coupling analysis for a single-fiber bi-directional link total using the Fourier technique. The results show that the large core plastic optical fiber gives rise to good emitter-to-fiber coupling alignment tolerance, but tends to overfill the detector and cause degradation in fiber-to-detector alignment tolerance. We find that a more directive resonant-cavity light emitting diode only improves emitter-to-fiber alignment tolerance slightly, though it can couple more light into the fiber.

Improvement in bit-error rate for optoelectronic multicomputer interconnection networks using cyclic redundancy code error detection

This letter presents testing results of an integrated optoelectronic (OE) channel employing hop-by-hop error control circuitry based on cyclic redundancy codes (CRC) to improve the effective bit-error rate (BER). The use of OE interconnect in place of wires in multicomputer networks becomes more attractive as channel bandwidth and power efficiency are increased. But these improvements must be accomplished while maintaining an acceptable channel BER. Test results of an integrated OE channel incorporating CRC-based error control circuitry demonstrate a BER reduction of two orders of magnitude while incurring a 20% bandwidth overhead. This may lead to higher bandwidth and higher efficiency OE interconnects.

Bidirectional single fiber low-cost optoelectronic interconnect for automotive applications

Current trends in vehicular technology reflect an increase in the number of electronic modules, leading to more complicated and expensive wiring. The use of optic fibers offers a low-cost alternative to traditional copper-wire harnesses. This paper presents a bidirectional, alignment-tolerant optoelectronic interconnect for automotive applications. The proposed interconnect offers a low manufacturing potential cost because it uses inexpensive alignment tolerant large core plastic fiber for ease of connector alignment. The optoelectronic interface chip uses time-division multiplexing to combine several information sources into a serial data stream that can be easily decoded by a microcontroller. By using a colocated small emitter in the middle of a large detector, the system achieves both bidirectional communication on a single fiber and alignment tolerant capabilities. Results show that this optoelectronic interconnect is a feasible replacement for wire harnesses in automobiles.

Smart photonics: optoelectronics integrated with Si CMOS VLSI circuits

Smart photonics, the integration of optoelectronic devices with electronic circuits and systems, has growing applications in many fields, one of which is computing. An exploration of the opportunities, integration technologies, and some recent results using thin film optoelectronic and electronic device integration with Si CMOS VLSI and GaAs MESFET technologies are presented herein. Applications explored herein include low cost alignment tolerant optoelectronic interconnection links for network inerconnections, smart focal plane array processing through the integration of imaging arrays with sigma delta analog to digital converters underneath each pixel, and three dimensional computational systems using vertical through-Si optical interconnections.

A smart pixel bi-directional optical link using co-located emitters and detectors

A single fiber bi-directional smart pixel link is reported in this paper, which uses the co-location of an emitter and detector at each end of the fiber. To realize a fully functional communications link, CMOS analog optoelectronic receiver and transmitter circuits which had digital input/output were fabricated adjacent to the silicon detector. Digital circuitry for multiplexing, data sampling and encoding, and microprocessor interfacing were also included in this silicon integrated circuit.