Researchers create the first supermode resonator

Experimental validation of cascaded mode resonators in integrated photonics. a SEM images of the cascade-mode resonator show two converters connected by a wide multimode waveguide. wwg and height Lwg. Multimode waveguides located before and after the resonator guide the telecom light into and out of the resonator. Mode converters are realized by combining a silicon waveguide with a grating structure with a single periodicity Λ and width. wg. Scale = 5 mm and 2 mm (included). The periodicity Λ is chosen so that the phase matching condition is satisfied for contra-directional synchronization. The entire photonic circuit is covered with a layer of silicon. b The schematic of the device shows three different parts: 1. two input waveguides (on the left) that allow scanning the resonator with TE.0 (above) or TE2 (bottom), 2. the resonator area with multiple frequencies closed by two mode converters, and 3. two analyzer waveguides that transmit the resonator output to the areas two separate, depending on its different position TE.0 (above) or TE2 (below). Probe 1 excites TE0 mode above the waveguide. Probe 2 excites TE0 in the lower part of the waves. This method is translated into TE2 The above method is a multimode waveguide before the resonator with a first-mode coupler, which works according to the principle that the effective TE index0 mode of the nano-waveguide corresponds to the effective TE index2 mode in a multimode waveguide. In the same way analyzer 1 and analyzer 2 measure TE0 and TE2 methods, respectively. Locally, the coupling occurs in the region where the nanowaveguide is located in the vicinity of the multimode wave. c Detailed simulations of the mobile fields in a cascaded-mode resonator loudspeaker show that independent round-trip mode solutions occur at the same wavelength for modes two different TE.0 (above) and TE2 (below). d Zooming in on the white-marked area inside the resonator reveals a hybrid type of broadband that appears as a high-level TE that resists propagating.0 or TE2 methods with a stroke length independent of input location. Credit: Nature Communication (2023). DOI: 10.1038/s41467-023-35956-9

What does it take for scientists to go beyond the current limits of knowledge? Researchers in Federico Capasso’s group at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed an effective formula.

“Dream big, ask everything we know, ask the books,” says Vincent Ginis, visiting professor at SEAS and first author on the new paper.Nature Communication reports the success of optical resonator technology.”That’s how Federico asks our lab team to work together. He challenges us to rethink all the old rules to see if we can make devices do things better. and in new ways.”

That approach led to the team’s latest result, a telescope that can manipulate light in ways never seen before. The success could affect the way resonators are understood and open the door to new possibilities.

“This is a breakthrough that fundamentally changes the design of resonators by using resonators that convert light from one pattern to another as it rises,” says Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior. Research Work in Electrical Engineering at SEAS.

Optical resonators play an important role in many aspects of modern life.

“Resonators are central components in many applications in optics, lasers, microscopy, sensing—they appear in all of these technologies as important building blocks,” says Ginis, who is also an assistant professor of mathematics and physics Vrije Universiteit Brussel. “They have two devices that beam light back and forth, directing light into lasers for example, or filtering light waves like fiber optics and telecommunications.”

Optical resonators are the key to the transmission of telephone lines, coding images and sound with light waves.

“Each message, to keep itself separate from the other, has been added over and over again,” Ginis says. “Resonators allow us to ‘tap’ specific, unique frequencies to allow many different messages to be transmitted simultaneously.”

Until now, the resonators and the two mirrors that illuminate them controlled the intensity and frequency of the light, but not the direction of the light, which determines the shape and pattern in which the photons flow in space and time. We often think that light travels in a straight line, but light rays can also travel in other directions, like spirals. The new optical resonator developed by Capasso’s team is the first such device that gives scientists precise control over the direction of light, and more importantly, enables multi-spectral light to be synthesized. be present in the resonator.

The team achieved this by installing a new type of pattern on the resonators at each end of the resonator device.

“We realized that we could test our resonator concept on an integrated photonics platform, and chose silicon-on-insulator, which is used by many scientists and companies for applications such as hearing or communicating,” says Cristina Benea-Chelmus, researcher. member of Capasso’s group and assistant professor of microengineering at the EPFL Institute of Electro and Microengineering, who led the experimental part of the work.

The etchings, about 300-600 nanometers in size, gave the team control over the shape of the light rays inside the resonator. Using resonators with different patterns on either end of the resonator unlocks their ability to change the shape of light as it travels.

“We can make these light patterns play, change from one pattern to another, and then go back to the original pattern, creating loops of different light patterns moving through the same area,” Ginis says. “When we saw this, we realized that we are ‘terra incognita’ here.”

Combining more than one mode of light creates what researchers call a “supermode.”

“In traditional resonators, as the light travels back and forth, the pattern stays the same – the properties of the light stay the same,” he says. “For us, when the light goes from left to right, or right to left, the processes are different. We found a way to break the symmetry inside the resonator.”

“Having multimode light control will have a huge impact on the bandwidth of information that can be transmitted through light,” he says. “It opens up multiple channels of transmission that we haven’t been able to access simultaneously until now.”

The Capasso group’s optical resonator provides a new tool for conducting fundamental experiments in physics, including optomechanics, using light to make objects move.

“By putting an object in a resonator, you can manipulate materials like tiny atoms, molecules and DNA strands,” says Ginis. The new device, with supermode capability, could unlock new degrees of freedom for researchers to use small devices with different light beam shapes.

“By questioning the theoretical foundations of the book’s resonator, we discovered new and contradictory light sources not found in traditional resonators,” Capasso says. These properties, including “independent resonances and direction-dependent propagation,” add unprecedented possibilities to photonics, acoustics and more.

Additional information:
Vincent Ginis et al, Resonators with a structured optical path in cascaded mode changes,Nature Communication (2023). DOI: 10.1038/s41467-023-35956-9

Presented by Harvard University

Excerpt: Researchers create first supermode optical resonator (2023, February 2) Retrieved February 2, 2023 from

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