Excessive-Effectivity Frequency Comb Invitations Vary of Optical Endeavors | Analysis & Know-how | Sep 2022

CAMBRIDGE, Mass., Sept. 16, 2022 — On-chip laser frequency combs are a promising know-how for purposes together with environmental monitoring, optical computing, astronomy, and metrology. Nevertheless, the shortcoming to design an on-chip laser frequency comb that’s each environment friendly and broad has stymied researchers for years and hindered the widespread commercialization of those gadgets.

Now, a workforce from the Harvard John A. Paulson College of Engineering and Utilized Sciences (SEAS) has developed an electro-optic frequency comb that’s 100× extra environment friendly and has greater than twice the bandwidth of earlier variations. The analysis integrates the ideas of excessive effectivity and broad bandwidth to deal with the efficiency-bandwidth trade-off that at the moment exists in resonator-based electro-optic frequency combs.

A new on-chip frequency comb combines a coupled resonator with an electro-optical frequency comb to improve the efficiency of frequency combs and improve the bandwidth. Courtesy of Yiqing Pei/Harvard SEAS.

An on-chip frequency comb combines a coupled resonator with an electro-optical frequency comb to enhance the effectivity of frequency combs and enhance the bandwidth. Probably supported purposes span optical communications and computing to optical metrology. Courtesy of Yiqing Pei/Harvard SEAS.

The high-efficiency, broadband electro-optic frequency comb builds on earlier work by the SEAS workforce; in 2019, the workforce demonstrated what it reported to be the primary secure, on-chip frequency comb that might be managed with microwaves. This electro-optical frequency comb, constructed on a lithium niobate platform, spanned all the telecommunications bandwidth however had restricted effectivity. In 2021, the workforce developed a coupled resonators gadget to regulate the movement of sunshine. The researchers used the gadget to display on-chip frequency shifters that would change the colour of sunshine with practically 100% effectivity.

The not too long ago developed on-chip frequency comb from the SEAS workforce integrates a coupled resonator with an electro-optical frequency comb to enhance each effectivity and bandwidth. In experiments, it demonstrated a conversion effectivity of 30% and an optical span of 132 nm, based mostly on a coupled-resonator platform on thin-film lithium niobate.

In keeping with researcher Yaowen Hu, the demonstrated comb improved effectivity with out sacrificing bandwidth. “The truth is, we truly improved bandwidth,” Hu stated.

The researchers additionally confirmed that the electro-optic frequency comb might function an built-in femtosecond pulse supply. For instance, within the ultrafast and high-power regime, the workforce demonstrated a frequency comb with simultaneous electro-optic and third-order nonlinearity results. The power to generate on-chip femtosecond pulses is necessary for nonlinear photonics, optical atomic clocks, optical sensing, and time-bin-encoded optical computing.

“We discovered that while you enhance the efficiency of the comb supply to this degree, the gadget begins working in a wholly new regime that mixes the method of electro-optic frequency comb technology with the extra conventional method of a Kerr frequency comb,” former SEAS postdoctoral fellow Mengjie Yu stated. 

An on-chip frequency comb that concurrently achieves a excessive effectivity and large span might have significance for a variety of optical purposes. For instance, a hundredfold enchancment in comb effectivity might result in a 20-dB enhance within the signal-to-noise ratio of frequency-multiplexed purposes akin to optical communications. The superior on-chip frequency comb might additionally scale back the optical pump energy wanted to function optical neural networks. As well as, microwave-power consumption might be decreased by integrating on-chip microwave resonators with the high-efficiency, broadband, on-chip, electro-optic frequency comb supply. The excessive conversion effectivity of the on-chip frequency comb might result in a brand new technology of broad electro-optic combs for entangled photons, broadly enabling frequency-domain quantum info processing.

The analysis was revealed in Nature Photonics (www.doi.org/10.1038/s41566-022-01059-y).

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