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Tunable Nanophotonic Interface Simplifies PIC Integration

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A chiral nanophotonic interface developed by a research team at the University of Chicago could make photonic integrated circuits (PICs) easier to integrate into mapping systems, biosensors, and other technologies. The interface provides a way for PICs to direct light at the nanoscale.

PICs typically use optical isolators to control the direction of light. These devices prevent light from reentering and destabilizing a system, but they often require large components that make it challenging to create small-scale PICs.

The researchers fabricated titanium dioxide (TiO2) waveguides directly onto the surface of boron nitride (BN)-encapsulated tungsten diselenide (WSe2), integrating light confined in a nanophotonic waveguide with the atomically thin, 2D semiconductor material. The band structure of WSe2 contains properties that enable it to interact with light in various ways, depending on the helicity of the light’s polarization.

In nanophotonic structures, where light is confined below its wavelength, circular polarization arises naturally, and the tracking of the polarization is based on the direction of the propagating light. Consequently, the light emitted from the WSe2 can be guided through the photonic waveguide in a preferred direction.

“We’ve figured out a scalable method for putting photonics and 2D semiconductors together in a way that adds new control knobs and preserves the high quality of the sensitive material,” researcher Robert Shreiner said. “This interface opens new doors for designing ultracompact, one-way photonic devices.”

The researchers can switch the biased coupling of the photonic interface on and off by adding electrons to create a tunable emission router on a micron-size scale.

After the WSe2 is coupled with the photonic waveguide, the photoluminescence from excitonic states going into the waveguide can be electrically switched between balanced and directionally biased emission. This capability leverages the doping-dependent valley polarization of excitonic states in WSe2. The nanophotonic waveguide can also function as a near-field source for diffusive exciton fluxes that display valley and spin polarizations derived from the interface chirality.

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Researchers at the University of Chicago have developed a way to guide light in one direction on a small scale. This could allow for smaller photonic integrated circuits, which could be more easily integrated into modern technologies. Courtesy of istockphoto.com.
Researchers at the University of Chicago have developed a way to guide light in one direction on a small scale. This would allow for smaller photonic integrated circuits that could be more easily integrated into modern technologies. Courtesy of istockphoto.com.
The nanoscale design of the interface and its tunability leads to smaller PICs that could be integrated more easily into optoelectronic technologies, such as computing systems and self-driving cars. Potentially, the photonic interface could be used to develop on-chip lasers for the lidar navigation systems in autonomous vehicles. In this case, the photonic element would be configured as a compact, on-chip optical isolator that would protect the laser system without the need for bulky components.

“We see this research as paving the way towards a whole new class of integrated photonic circuits,” said professor Alex High, who led the research.

Ultimately, the interface could make it easier to integrate PICs into optical computers that operate with light instead of electricity, thereby using less energy and creating less heat than conventional computers.

“We already use photonics to carry information throughout the country in fiber optic networks, but advancements like this could help fully control the flow of light on the nanoscale, thus realizing on-chip optical networks,” researcher Kai Hao said.

The research was published in Nature Photonics (www.doi.org/10.1038/s41566-022-00971-7).

Published: March 2022
Glossary
integrated photonics
Integrated photonics is a field of study and technology that involves the integration of optical components, such as lasers, modulators, detectors, and waveguides, on a single chip or substrate. The goal of integrated photonics is to miniaturize and consolidate optical elements in a manner similar to the integration of electronic components on a microchip in traditional integrated circuits. Key aspects of integrated photonics include: Miniaturization: Integrated photonics aims to reduce the...
nano
An SI prefix meaning one billionth (10-9). Nano can also be used to indicate the study of atoms, molecules and other structures and particles on the nanometer scale. Nano-optics (also referred to as nanophotonics), for example, is the study of how light and light-matter interactions behave on the nanometer scale. See nanophotonics.
nanophotonics
Nanophotonics is a branch of science and technology that explores the behavior of light on the nanometer scale, typically at dimensions smaller than the wavelength of light. It involves the study and manipulation of light using nanoscale structures and materials, often at dimensions comparable to or smaller than the wavelength of the light being manipulated. Aspects and applications of nanophotonics include: Nanoscale optical components: Nanophotonics involves the design and fabrication of...
chirality
Chirality is a property of certain molecules and objects in which they are non-superimposable on their mirror images. In other words, a chiral object or molecule cannot be exactly superimposed onto its mirror image, much like a left and right hand. The term "chirality" comes from the Greek word cheir, meaning hand, emphasizing the handedness or asymmetry of the object or molecule. A molecule or an object with this property is said to be chiral, while its non-superimposable mirror image is...
polarization
Polarization refers to the orientation of oscillations in a transverse wave, such as light waves, radio waves, or other electromagnetic waves. In simpler terms, it describes the direction in which the electric field vector of a wave vibrates. Understanding polarization is important in various fields, including optics, telecommunications, and physics. Key points about polarization: Transverse waves: Polarization is a concept associated with transverse waves, where the oscillations occur...
integrated photonicsphotonics integrationnanonanophotonicsdevicesOpticsoptical computingResearch & TechnologyeducationAmericasUniversity of Chicagocommunicationoptical chiralitychiralitydatacompolarizationlight manipulationTechnology News

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