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Home > News Room > NEC Develops Silicon MOS Optical Modulator with a Leading Power-Consumption Efficiency

NEC Develops Silicon MOS Optical Modulator with a Leading Power-Consumption Efficiency

*** For immediate use March 23, 2010

Silicon MOS Optical Modulator Consisting of a Mach-Zehnder Interferometer Structure

Silicon MOS Optical Modulator Consisting of a Mach-Zehnder Interferometer Structure

Tokyo, March 23, 2010 - NEC Corporation (NEC; TSE: 6701), a leading network, communications and information technology company, announced today the successful development of a silicon MOS (metal-oxide-semiconductor) optical modulator that boasts a leading power-consumption efficiency of less than 1mW/Gbps, a compact size of 120- m in length and high-speed operation of 25Gbps. The silicon optical modulator consists of a Mach-Zehnder interferometer structure based on a rib optical waveguide with a MOS junction structure. Its exceptional efficiency of less than 1mW/Gbps with 25Gbps modulation was demonstrated using a newly developed MOS junction structure and an improved electrode that feature higher optical modulation efficiency with low optical loss and low electrical resistivity. The silicon optical modulator also achieves more than 10 km of optical transmission which is applicable with a standardized 100GbE optical interconnection and an optical network transceiver.

The silicon optical modulator is one of the most important optical components for achieving optical network transceivers and optical interconnections that are compact, high-speed and consume low levels of power. It is also critical for enabling platform technology to integrate the opto-electronic functions for optical networks and optical interconnections. The newly developed silicon optical modulator holds great potential for the field of optical network transceivers and is a catalyst for next-generation optical networks and optical interconnections. This is due to both optical and electrical functions that can be integrated, as well as the cost, size and power-consumption that can be reduced by using CMOS-compatible technology.

Features of the newly developed power-efficient optical modulator are as follows:

  1. Power-consumption efficiency and a compact size are achieved by adapting a newly-developed projection MOS junction structure.
    A conventional planar MOS junction structure features little overlap between its optical fields and carrier modulation regions, therefore the size of an optical modulator needs to be at least several mm long in order for the necessary modulation to take place. NEC's new MOS junction structure features a great deal of overlap between the optical fields and the carrier modulation regions by application of a projection MOS junction structure. The newly-developed optical modulator, which is 120- m long, is one-tenth the size of conventional silicon optical modulators. It also demonstrated more than ten times the modulation efficiency, and one-tenth the power consumption when compared to conventional PN-type silicon optical modulators.

  2. High-speed operation of 25Gbps is enabled by an improved electrode structure with both low resistivity and low optical loss.
    The development of an improved electrode structure with low resistivity and low optical loss has enabled silicon modulators to achieve high-speed operation of 25Gbps. Low resistivity electrodes are 100-nm thin and feature an extended structure with a poly-crystalline silicon layer on a rib waveguide and locally-high-doping concentration, which is formed without affecting the low optical loss of the modulator.

The silicon optical modulator also achieved high speed optical signal transmission of more than 10-km. This long distance transmission requires low transmission loss in the optical modulator, which is accomplished through NEC's development of a low loss spot-size-converting waveguide between the optical modulator of a rib waveguide and the silicon optical wire of a channel waveguide.

NEC will continue to carry out extensive research on this innovative new optical interconnection technology towards the realization of world-class high-density/high-speed optical transmission technology.

This research is in collaboration with the Institute of Microelectronics (IME), a research institute of the Agency for Science, Technology and Research (A*STAR). The results of this research will be presented at Optical Fiber Communication 2010, held in San Diego, California, U.S.A. from March 21 to 25, 2010.

About NEC Corporation
NEC Corporation is a leading provider of Internet, broadband network and enterprise business solutions dedicated to meeting the specialized needs of a diversified global base of customers. NEC delivers tailored solutions in the key fields of computer, networking and electron devices, by integrating its technical strengths in IT and Networks, and by providing advanced semiconductor solutions through NEC Electronics Corporation. The NEC Group employs more than 140,000 people worldwide. For additional information, please visit the NEC website at:

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NEC Press Contact (Japan):

Joseph Jasper
NEC Corporation

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