Integration of polarization converter on the IMOS platform

March 25, 2022

Sander Reniers defended his PhD at the department of Electrical Engineering on March 24th.

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The total bandwidth required for the internet traffic is increasing, and new ways are needed to increase the capacity of optical fiber links. PhD researcher Sander Reniers has integrated a polarization rotation device on a nanophotonic platform. This research paves the way to new modulation formats for optical communication, and hence increased bandwidth capacities.

Nowadays, most people are familiar with electronic chips, which can be found in almost any electronic device. For an increasing number of applications, photonic chips are becoming more popular, where light is used to communicate data instead of electricity.

The indium-phosphide-membrane-on-silicon (IMOS) platform is a photonic integration platform that enables the production of very small optical components. This makes it possible to process signals on tiny optical chips, which is possible by removing materials with high refractive indices above and below the light-guiding layer so that the light is strongly squeezed in the waveguides and leads to several benefits.

Importance of polarization

For his PhD research, Sander Reniers focused on the large difference in properties between horizontally polarized and vertically polarized light. His research covers the full cycle of design, simulations, chip-fabrication, and chip-characterization of a device to convert light from any polarization state to any desired polarization state on a single chip, which also includes optical amplifiers and numerous other components.

Using this approach, a full set of devices to manipulate light becomes available for optical chips. Phase and amplitude are metrics that are widely exploited to increase bandwidth, often by using complex modulation formats. Conversion of light polarization leads to an additional degree of freedom in optical communication systems, which can be utilized with relatively low cost in comparison to complex coherent systems.

IMOS platform

Reniers included such components on an IMOS platform. Among the demonstrated circuits is an on-chip amplifier that can amplify both horizontally and vertically polarized light with almost the same amplification, and a laser that can generate light with both horizontally and vertically polarized light. Furthermore, improvements to traditional methods of characterization of these components are introduced which enhance accuracy significantly.

This research is an important step towards an integrated nanophotonic platform with full functionality with polarization handling. Continued research will include polarization modulated transceivers and sensing applications that can exploit the polarization handling of the platform.

Title of PhD Thesis: Integration of a polarization converter on the active-passive IMOS platform. Supervisors: Jos van der Tol and Yuqing Jiao.

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