With detectors licked, Luxtera claims CMOS-based transceivers are at hand

MARCH 14, 2007 By Stephen Hardy -- Luxtera (search for Luxtera) announced today that it had developed a way to integrate germanium around silicon waveguides to create monolithically integrated photodetectors. This advancement represents the last step toward the ability to create a monolithic optical transceiver using CMOS processes, according to company sources.

In a visit to Lightwave's office Friday, Marek Tlalka, Luxtera's vice president of marketing, said the advance enables Luxtera to create all the elements of an optical transceiver, except the laser, on the same wafer using CMOS processes. Tlalka minimized the fact that the laser would have to be integrated into the package in a hybrid fashion, likening the laser to the external power sources common for ICs. In fact, he said Luxtera plans to use a single CW light source to power multiple transceivers, thus reducing overall costs and power consumption. Tlalka predicted Luxtera's first 10-Gbit/sec device will operate at less than 1 W.

He also said that the company's first product, which will be a multichannel transceiver aimed at four-lane InfiniBand requirements, is expected to debut during the second half of this year. The product will not take advantage of the newly announced photodetector capabilities; the design will feature separate photodetectors mounted on the transceiver die. While the company envisions that its technology will enable systems houses to place transceivers on boards much they way they do ICs, Tlalka admitted that the first product will be packaged to look like a conventional transceiver. While he did not describe the package in detail, a QSFP form factor would be a reasonable expectation.

The photodetector hurdle proved somewhat tricky because germanium doesn't bond well with silicon, Tlalka said. Having overcome this problem, Luxtera can create very low cost (less than a penny) photodetectors in a very small size -- 40 sq. microns. Tlalka says the capability could spur the inclusion of more photodetectors than are found in applications using conventionally constructed devices. The extra photodetectors could be used for improved monitoring, for example.

The company also will be able to place photodetectors immediately adjacent to the receiver electronics. The arrangement will reduce electronic noise and enable the photodetector to detect signals at lower power levels. The company asserts its design will improve receiver performance by a factor of four and enable the use of less expensive low-power lasers to be used on the transmit side.

Luxtera is using Freescale Semiconductor's CMOS processes. Tlalka said the company can derive approximately 300 chips per wafer.

While the telecom space will represent Luxtera's initial focus, Tlalka said the company also envisions offering products for consumer electronics and digital signage, particularly driving optical interconnect. Optical busses and chip-to-chip communications to create optically interconnected multi-core processors also offers a target, he said.

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