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Silicon Photonics

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Definition: photonic technology based on silicon chips

German: Silizium-Photonik

Category: photonic devices

How to cite the article; suggest additional literature

For applications in microelectronics, an extremely powerful technology platform based on silicon chips has been developed in the recent decades. This is now the basis of complex microprocessors, large memory circuits, and other digital and analog electronics. With the introduction of the silicon-on-insulator technology [3] it has been demonstrated that photonic functions can be integrated into this technology platform, so that silicon-based photonic integrated circuits became possible. Here, different kinds of optical components can be connected with each other using silicon waveguides [1]. Such circuits could be used e.g. to establish very fast communication between circuit boards, between chips on a board, or even within single chips, e.g. connecting different cores of a microprocessor. There is a strong need for such fast communication links, because the rapid progress of microprocessors may soon be severely limited by the transmission bandwidth capabilities of electronic connections, made e.g. of copper. Optical data transmission allows for much higher data rates and would at the same time eliminate problems resulting from electromagnetic interference. The technology may also be useful for other areas of optical communications, such as fiber to the home.

Silicon photonics can also be considered from the viewpoint of photonics, which is so far normally based on other materials. (Silica = amorphous SiO2 is common in photonics, e.g. in silica fibers, but not elementary silicon.) The implementation of silicon-based photonic devices, maybe even electrically pumped silicon lasers and silicon amplifiers, could possibly lead to much smaller and much cheaper photonic devices, making accessible a range of applications which so far have been impossible already for reasons of too high cost.

Technological Challenges

Although the possible merits of silicon-based photonics are huge, there are also very substantial challenges for such a technology:

It is possible to fabricate hybrid devices where the photonic functions are provided by structures made of III–V semiconductors (with a direct bandgap and electro-optic properties), such as indium phosphide, and these are placed on a silicon chip containing the bulk of the electronic components. One class of techniques is based on epitaxial regrowth procedures, which are complicated and often greatly reduce the yield. For that reason, hybrid devices tend to be expensive and are strongly limited in complexity. Another approach is to apply a sophisticated bonding process to combine a silicon chip containing waveguides with an indium phosphide chip providing the optical gain [17]. Still, all-silicon solutions, arising from the “siliconization of photonics”, would probably be more suitable for widespread application.

State of Research

The following paragraphs briefly describe the current state of research concerning basic building blocks of silicon photonics:

It is clear that an enormous amount of work, corresponding to huge capital investments, is still required before silicon photonics can be established as a key technology. However, the potential merits motivate big players such as Intel to pursue this development seriously. If it is successful, it can lead to a very powerful technology with huge benefits for photonics and microelectronics and their applications.


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[27]A. Rickman, “The commercialization of silicon photonics”, Nature Photon. 8, 579 (2014)
[28]SiCoud, a silicon photonics calculator developed at UCLA, http://www.sicloud.org/

(Suggest additional literature!)

See also: photonics, photonic integrated circuits, integrated optics, optoelectronics, Raman lasers, amplifiers, optical modulators
and other articles in the category photonic devices

Dr. R. Paschotta

This encyclopedia is authored by Dr. Rüdiger Paschotta, the founder and executive of RP Photonics Consulting GmbH. Contact this distinguished expert in laser technology, nonlinear optics and fiber optics, and find out how his technical consulting services (e.g. product designs, problem solving, independent evaluations, or staff training) and software could become very valuable for your business!

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