Kotura creates WDM compatible silicon photonics detector

MONTEREY PARK, USA: Kotura Inc., a leading provider of Silicon Photonics products, today announced that it has demonstrated a high-speed horizontal p-i-n germanium photo detector integrated with silicon waveguides on a single chip.

“The previous research has focused on vertical detectors within sub-micron scale waveguides to achieve high speed operation. 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,” reported Mehdi Asghari, CTO of Kotura.

“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. 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. We have demonstrated devices with more than 32 GHz optical bandwidth @1V bias, a responsivity of 1.1 A/W, a dark current <300nA and a fiber coupling loss of less than 1.2dB.”

“A low-loss, high-speed, easy-to-manufacture detector is a key component for optical interconnects. When we evaluated these devices we were impressed by their performance,” commented Dr. Ashok Krishnamoorthy, Principal Investigator on this 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.”

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

The Kotura’s horizontal detector was developed as part of the Defense Advanced Research Project Agency’s Ultra-performance Nano-photonic Intrachip Communications (UNIC) program in conjunction with Oracle America, Inc., under the leadership of Dr. Jagdeep Shah, DARPA Program Manager. An article, “High-speed Ge photo-detector monolithically integrated with large cross-section silicon-on-insulator waveguide,” by Dazeng Feng et al. was recently published in Applied Physics Letters.