Triple bend semiconductor structure splits light into two

A scanning electron micrograph (right) of the three-waveguide polarization beam splitter, and the light intensity of the two polarization components (TE/TM). Credit: A*STAR Institute of High-Performance Computing

A plan to incorporate a third bent waveguide into a silicon-based light splitter led A*STAR researchers to develop a device capable of a 30-fold improvement in splitting efficiency. The novel on-chip light splitter marks a major breakthrough in improving high-performance data transmission systems, as well as applications in quantum computing.

The manipulation of light in micro-scale devices is a fundamental pillar of high-speed optical circuits underpinning communications and next-generation technologies like quantum computing. Light is fast and low-power and can be encoded to transmit data in a variety of ways. As Thomas Ang from the A*STAR Institute of High-Performance Computing (IHPC) explains, for these manipulations to be reliable and efficient, the light needs to be as ‘pure’ as possible—not just tightly confined around a specific wavelength, but also of a uniform polarization.

“Light consists of a mixture of two polarization components,” Ang says. “Polarization beam splitters are used to separate a mixed-polarization beam into two channels for each polarization.”

When the splitting is imperfect, the two channels can contain small proportions of the opposite polarization, an effect known as crosstalk.

“Polarization beam splitters with low crosstalk are very important for high signal fidelity in high-speed optical interconnect applications,” says Jun Rong Ong, Ang’s partner in the study. “Current technology is limited to a crosstalk level, called the extinction ratio, of around 25 decibels, which is high enough to affect high-speed data transmission.”

Read more: Triple bend structure splits light into two highly pure polarization components

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