24 June 2010


First WDM-compatible silicon photonics detector operating at 32GHz

Kotura Inc of Monterey Park, CA, USA, which manufactures application-specific silicon photonics components for the communications, computing, sensing and detection markets, has demonstrated a high-speed horizontal p-i-n germanium photo-detector integrated with silicon waveguides on a single chip. The device has been developed as part of the US Defense Advanced Research Project Agency’s Ultra-performance Nano-photonic Intrachip Communications (UNIC) program in conjunction with Oracle America Inc (under the leadership of DARPA program manager Dr Jagdeep Shah).

“Previous research has focused on vertical detectors within sub-micron scale waveguides to achieve high-speed operation,” says chief technical officer Mehdi Asghari. “These typically exhibit high loss and are hard to integrate with waveguide geometries needed for other functionalities such as WDM (wavelength division multiplexing) multiplexer and de-multiplexer devices,” he adds. “Our invention of a horizontal junction detector does away with conventional designs and creates a new structure that supports high-speed operation and yet is compatible with a variety of waveguide heights including the larger waveguides needed for high-performance WDM operation,” Asghari continues. “These structures allow standard silicon processing techniques to be used to couple waveguides and photo-detectors on the same chip with extremely low loss and high performance.” The Kotura-led team has demonstrated devices with more than 32GHz optical bandwidth at 1V bias, a responsivity of 1.1A/W, a dark current of less than 300nA, and fiber coupling loss of less than 1.2dB.

“A low-loss, high-speed, easy-to-manufacture detector is a key component for optical interconnects,” comments Dr Ashok Krishnamoorthy, principal investigator on the project at Sun Labs, Oracle America Inc. “This horizontal junction detector is a huge improvement for several reasons, not the least among which is that it can be readily coupled to single-mode fiber. This opens the door for wavelength-multiplexed silicon-based optical interconnects that will reduce the complexity of connectors and cabling in high-performance systems,” he adds.

“Now we can easily integrate WDM and detection functionality into one chip,” adds Asghari. “A single silicon photonics device can take a single input stream of light with 100 WDM channels, demultiplex the wavelengths and route each wavelength to its own detector,” he adds. “We can envision integrating 100 receiver channels, each operating at 40Gb/s, on a single chip.”

See related item:

Kotura demos first silicon photonics mux/demux for 0.5Tb/s transmission

Search: Kotura Silicon photonics