2024-03-23 09:10:00
The miniaturization of technologies remains a major issue of our time, affecting many areas, from communication to navigation. Progress in this area has just been made by researchers from theColumbia Universitywho designed a photonic chip capable of generating high-quality microwave signals with extremely low noise.
A major innovation in integrated photonics
Columbia School of Engineering researchers have developed a photonic chip that, using a single laser, produces microwave signals of exceptional quality and ultra-low noise. . This chip, so small that it could fit on the tip of a well-sharpened pencil, made it possible to achieve the lowest level of microwave noise ever observed on an integrated photonics platform.
The compact device offers a promising path toward generating ultra-low-noise microwaves for applications such as high-speed communications, atomic clocks and autonomous vehicles.
The technological challenge met
Electronic devices used for global navigation, wireless communications, radar, and precision timing require stable microwave sources to serve as clocks and information carriers. A key aspect to improving the performance of these devices is the reduction of noise, or random phase fluctuations, present in the microwave signal.
« Over the past decade, a technique known as optical frequency division has generated the quietest microwave signals to date. “, explains Alexander Gaeta, professor of applied physics and materials science, as well as professor of electrical engineering at Columbia University. “ Usually, such a system requires several lasers and a relatively large volume to contain all the components. »
Optical frequency division, a method of converting a high frequency signal to a lower frequency, is a recent innovation for microwave generation where noise has been greatly suppressed. The bulk of these systems prevents them from being used for miniaturized sensing and communications applications that require more compact microwave sources.
« We have realized a device capable of performing optical frequency division entirely on a chip in an area as small as 1 mm² using only a laser », adds Alexander Gaeta. “ We demonstrate for the first time the process of optical frequency division without the need for electronics, greatly simplifying device design. »
The innovative approach
The Gaeta’s group specializes in quantum and nonlinear photonics, or how laser light interacts with matter. Areas of interest include nonlinear nanophotonicsgeneration of frequency combs, intense ultrafast pulse interactions, and generation and processing of quantum states of light.
In this study, his group designed and fabricated an all-optical device-on-chip that generates a 16 GHz microwave signal with the lowest frequency noise ever achieved on an integrated chip platform. The device uses two silicon nitride micro-resonators that are photonically coupled.
A single frequency laser powers the two micro-resonators. One is used to create an optical parametric oscillator, which converts the input wave into two output waves – one of higher frequency and the other lower. The frequency spacing of the two new waves is adjusted to be in the terahertz regime. Due to the quantum correlations of the oscillator, the noise of this frequency difference can be thousands of times lower than the noise of the input laser wave.
The second micro-resonator is adjusted to generate an optical frequency comb with microwave spacing. A small amount of light from the oscillator is then coupled to the comb generator, leading to synchronization of the frequency of the microwave comb with the terahertz oscillator which automatically results in optical frequency division.
The potential impact
The work of Gaeta’s group represents a simple and effective approach to achieving optical frequency division in a small, robust, and highly portable package. The results open the door to chip-scale devices that can generate stable, pure microwave signals comparable to those produced in laboratories performing precision measurements.
« Ultimately, this type of all-optical frequency division will lead to new designs for future telecommunications devices “, did he declare. “ It could also improve the accuracy of microwave radars used for autonomous vehicles. »
Illustration caption: High-level schematic of the integrated photonic chip, developed by the Gaeta lab, for all-optical optical frequency division, or OFD – a method of converting a high-frequency signal to a lower frequency. Credit: Yun Zhao/Columbia Engineering
Article : “All-optical frequency division on-chip using a single laser” – DOI: https://www.nature.com/articles/s41586-024-07136-2
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