Abstract
The traditional ways of tuning a silicon photonic network are mainly based on the thermo-optic effect or the free carrier dispersion. The drawbacks of these methods are the volatile nature and the extremely small change in the complex refractive index (Δn<0.001). In order to achieve low energy consumption and smaller footprint for applications such as photonic memories, optical computing, programmable gate array, and optical neural network, it is essential that the two optical states of the system exhibit high optical contrast and remain non-volatile. Phase change materials (PCMs) such as Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Sb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> provide an excellent solution, thanks to the drastic contrast in refractive index between two states which can be switched reversibly and in a non-volatile fashion. Here, we review the recent progress in the field of non-volatile reconfigurable silicon photonics based on PCMs. We start with a general introduction to the material properties of PCMs that have been exploited in integrated photonics and discuss their operating wavelengths. The various photonic switches that are built upon these PCMs are reviewed. Lastly, we review the recent applications of PCM-based photonic integrated circuits and discuss the potential future directions of this field.
Highlights
T RADITIONAL means of tuning silicon photonic integrated circuits (PICs) primarily relies on thermo-optic or free carrier dispersion effect
Part of this work was conducted at the Washington Nanofabrication Facility Molecular Analysis Facility, in part by the National Nanotechnology Coordinated Infrastructure (NNCI) site at the University of Washington, which is supported in part by funds from the National Science Foundation Awards NNCI-1542101, 1337840, and 0335765, and in part by the National Institutes of Health, the Molecular Engineering & Sciences Institute, the Clean Energy Institute, the Washington Research Foundation, the M
The silicon photonics community has started to head toward a hybrid approach where foreign materials are integrated on SOI waveguides to act as a tunable medium [4]
Summary
T RADITIONAL means of tuning silicon photonic integrated circuits (PICs) primarily relies on thermo-optic or free carrier dispersion effect. To overcome these limitations, the silicon photonics community has started to head toward a hybrid approach where foreign materials are integrated on SOI waveguides to act as a tunable medium [4]. We would like to point out that several review papers on similar topics have been published and the readers are encouraged to explore further [41]–[45]
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