Getting in gear: Researchers create a slow light device with high
optical quality

Date:
January 26, 2022
Source:
University of Massachusetts Amherst
Summary:
Researchers have created a gear-shaped photonic crystal microring
that increases the strength of light-matter interactions without
sacrificing optical quality. The result is an on-chip microresonator
with an optical quality factor 50 times better than the previous
record in slow light devices that could improve microresonators
used in a range of photonics applications, including sensing and
metrology, nonlinear optics and cavity quantum electrodynamics.



FULL STORY ========================================================================== Researchers including a postdoc at the University of Massachusetts
Amherst have created a gear-shaped photonic crystal microring that
increases the strength of light-matter interactions without sacrificing
optical quality. The result is an on-chip microresonator with an optical quality factor 50 times better than the previous record in slow light
devices that could improve microresonators used in a range of photonics applications, including sensing and metrology, nonlinear optics and
cavity quantum electrodynamics.


========================================================================== Optical microresonators are structures that enhance light-matter
interactions through a combination of long temporal confinement (i.e.,
high quality factor) and strong spatial confinement of an electromagnetic
wave. The device the authors have developed in many ways integrates the
best attributes of two types of optical microresonators -- a photonic
crystal and a whispering gallery mode resonator -- in one device. While combining the two has been attempted in the past, previous microring
devices that have succeeded in slowing light to increase interactions
(a consequence of the photonic crystal) have had to sacrifice quality
factor. In this new "microgear" photonic crystal ring, researchers
observed modes with group velocity slowed down by 10 times relative to conventional microring modes without any degradation in quality factor.

The study, led by first author Xiyuan Lu and principal investigator
Kartik Srinivasan, both from the National Institute of Standards and
Technology (NIST) and the University of Maryland, appears in the January
2022 issue of Nature Photonics. UMass Amherst's Andrew McClung, a postdoc
in the photonics lab of Amir Arbabi and a former NIST colleague of Lu,
provided modeling and computer simulations for the work.

"We show that the optical modes in these structures can show a much lower
group velocity than the modes in standard integrated photonic waveguides ('slow- light') while maintaining low loss (high quality factor), and
that we can further localize these modes spatially by introducing a
'defect' region within the resonator," Srinivasan says. "Due to its
unique combination of features, the overall system is appealing for
many applications of microresonators, which in general are used to
enhance light-matter interactions in a wide range of contexts, from single-photon sources to single-photon gates to nonlinear optics."
"What differentiates this work," McClung says, "is the geometry of
their microring." "In the past, people have put holes in the center
of these rings to introduce the photonic crystal," he says. "Instead
of punching a hole, we created little bumps along the inside of the
ring. This introduces the modulation you need and it perturbs the mode
less aggressively." In the defect version of the device, instead of
the bumps being perfectly periodic along the circumference of the ring,
some number of bumps have a slightly different amplitude, forming a way
to localize light within just a small fraction of the ring.

"Devices like ours can be used to enhance light-matter interaction,
and we are currently working on using our microgear photonic crystal
ring to increase the strength of interaction between light and a vapor
of rubidium atoms for applications in quantum networking," added Lu.

This research is supported by the DARPA Science of Atomic Vapors for
New Technologies (SAVaNT) and NIST on a chip programs.

========================================================================== Story Source: Materials provided by
University_of_Massachusetts_Amherst. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Xiyuan Lu, Andrew McClung, Kartik Srinivasan. High-Q slow light
and its
localization in a photonic crystal microring. Nature Photonics,
2021; 16 (1): 66 DOI: 10.1038/s41566-021-00912-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220126165524.htm

--- up 7 weeks, 4 days, 7 hours, 13 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)