Microwave Photonic Filters Reconfigured Without an External Device

LAUSANNE, Switzerland, Sept. 14, 2020 — Researchers from École Polytechnique Fédérale de Lausanne (EPFL) have developed a method of reconfiguring microwave photonic filters without the need for an external device. The research may enable more compact, environmentally friendly filters at lower cost. Potential applications include those involving detection and communication systems.

By establishing interference between two pulses within a microcomb, the researchers were able to accurately control the pulses in order to reconfigure the outgoing radio frequency. The effort generated different types of microcombs on a silicon nitride chip, to produce high-quality soliton pulse signals.

The wavelength of the signal generated can be modified either by varying the light source or by changing the shape or material of the optical channel it passes through.

“Using a light source that can combine several wavelengths means that we can keep the filter’s structure quite simple,” said Camille Brès, who leads the Photonic Systems Laboratory. “If we can reconfigure the frequency by altering the light pulse, we don’t need to change the physical support.”

Researchers from EPFL's Photonics Systems Lab, led by Camille Brès (front) have reconfigured microwave photonic filters without an external device. Potential applications include detection and communications systems. Courtesy of EPFL.

Researchers from EPFL's Photonic Systems Laboratory, led by Camille Brès (left), have reconfigured microwave photonic filters without an external device. Potential applications include detection and communications systems. Courtesy of EPFL.

For the filters to be used in various applications, they also need to be capable of altering the outgoing radio frequency.

“Current filters require programmable pulse shapes to set the outgoing frequency and improve the wave quality, which makes the systems complex and hard to market,” said Jianqi Hu, a Ph.D. student in the Photonic Systems Laboratory and lead author on the study.

To overcome this obstacle, the researchers generated on-chip interference between two solitons. By modifying the angle between them, they were able to reconfigure the filter frequency. The development means that the systems can be made fully portable and used with 5G and terahertz waves.

The research was published in Nature Communications (www.doi.org/10.1038/s41467-020-18215-z).

Published: September 2020

Glossary

microwave: An electromagnetic wave lying within the region of the frequency spectrum that is between about 1000 MHz (1 GHz) and 100,000 MHz (100 GHz). This is equivalent to the wavelength spectrum that is between one millimeter and one meter, and is also referred to as the infrared and short wave spectrum.
microcomb: A microcomb, short for microresonator frequency comb, is a novel photonic device that generates a precise series of evenly spaced optical frequencies, akin to the teeth of a comb, across a broad spectrum of wavelengths. It operates based on the phenomenon of Kerr frequency comb generation, which occurs in certain nonlinear optical resonators. Microcombs are typically fabricated from high-quality optical materials, such as silicon nitride or silicon dioxide, and have dimensions on the order of...
light source: The generic term applied to all sources of visible radiation from burning matter to ionized vapors and lasers, regardless of the degree of excitation.
terahertz: Terahertz (THz) refers to a unit of frequency in the electromagnetic spectrum, denoting waves with frequencies between 0.1 and 10 terahertz. One terahertz is equivalent to one trillion hertz, or cycles per second. The terahertz frequency range falls between the microwave and infrared regions of the electromagnetic spectrum. Key points about terahertz include: Frequency range: The terahertz range spans from approximately 0.1 terahertz (100 gigahertz) to 10 terahertz. This corresponds to...
chip: 1. A localized fracture at the end of a cleaved optical fiber or on a glass surface. 2. An integrated circuit.

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