Silicon is the dominant material for the fabrication of integrated circuits and is also becoming a popular material for making photonics circuits—miniaturized circuits that use light instead of electronic signals for processing information. One of the challenges in the field, however, has been silicon’s intrinsic sensitivity to the polarization of light, which can limit the rate of information transmission. Jing Zhang, Tsung-Yang Liow and co-workers at the A*STAR Institute of Microelectronics have now developed a novel solution to this problem.
Light of different polarizations, which normally travel at the same speed in air, travel at different speeds in silicon waveguides due to random imperfections and asymmetries in the silicon itself. To overcome this problem, the researchers turned to a scheme known as ‘polarization diversity’, by which incoming light is split into two perpendicular modes of polarization, called the transverse electric (TE) and transverse magnetic (TM) modes. They then rotated the TM mode by 90° so that both of the modes propagate in parallel at the same speed inside the photonic circuit.
Zhang, Liow and their co-workers had previously demonstrated a silicon-based device, called a polarization rotator, which comprises the first half of the diversity scheme (see image). The rotator transforms TM light into TE light by passing the light through a horizontal waveguide and then rotating it into a vertical waveguide. In their present work, they designed, built and characterized a device that completes the second half of the scheme. Called a polarization mode converter, it transforms TE light in the vertical waveguide into TE light in a horizontal waveguide. By connecting their mode converter to their rotator, the researchers were able to construct a polarization diversity scheme that provides mode conversion to reduce propagation loss in the waveguide while retaining the original polarization state.
Both halves of the polarization rotation device work by gradually changing the geometry of the waveguide, which in turn changes the polarization mode of the light it is guiding. The Singapore research team characterized their devices by studying the signal loss introduced over the transition length between polarization modes, as well as the propagation loss in the rest of the device. They found that the device efficiencies would need to be improved to be practical, for example by reducing the roughness of the waveguide walls through thermal oxidation, and by improving the coupling between the waveguide and the fiber optic cable connected to it.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Microelectronics
 Zhang, J., Liow, T.-Y., Yu, M., Lo, G.-Q. & Kwong, D.-L. Silicon waveguide based TE mode converter. Optics Express 18, 25264–25270 (2010).
A two-atom quantum duet
12.11.2018 | Institute for Basic Science
Improving understanding of how the Solar System is formed
12.11.2018 | Goethe-Universität Frankfurt am Main
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly
The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...
Scientists developed specially coated nanometer-sized vehicles that can be actively moved through dense tissue like the vitreous of the eye. So far, the transport of nano-vehicles has only been demonstrated in model systems or biological fluids, but not in real tissue. The work was published in the journal Science Advances and constitutes one step further towards nanorobots becoming minimally-invasive tools for precisely delivering medicine to where it is needed.
Researchers of the “Micro, Nano and Molecular Systems” Lab at the Max Planck Institute for Intelligent Systems in Stuttgart, together with an international...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
12.11.2018 | Life Sciences
12.11.2018 | Materials Sciences
12.11.2018 | Physics and Astronomy