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  1. Free, publicly-accessible full text available December 1, 2022
  2. https://www.thearcticinstitute.org/infrastructure-community-resilience-changing-arctic-status-challenges-research-needs/
  3. In review.
    Free, publicly-accessible full text available August 1, 2022
  4. https://www.thearcticinstitute.org/infrastructure-community-resilience-changing-arctic-status-challenges-research-needs/
  5. Realization of chip‐scale nonreciprocal optics such as isolators and circulators is highly demanding for all‐optical signal routing and protection with standard photonics foundry process. Owing to the significant challenge for incorporating magneto‐optical materials on chip, the exploration of magnetic‐free alternatives has become exceedingly imperative in integrated photonics. Here, a chip‐based, tunable all‐optical isolator at the telecommunication band is demonstrated, which is based upon bulk stimulated Brillouin scattering (SBS) in a high‐Q silica microtoroid resonator. This device exhibits remarkable characteristics over most state‐of‐the‐art implements, including high isolation ratio, no insertion loss, and large working power range. Thanks to the guided acousticmore »wave and accompanying momentum‐conservation condition, bulk SBS also assist in realizing the nonreciprocal parity‐time symmetry in two directly coupled microresonators. The breach of time‐reversal symmetry further makes the design a versatile arena for developing many formidable ultra‐compact devices such as unidirectional single‐mode Brillouin lasers and supersensitive photonic sensors.« less
  6. Free, publicly-accessible full text available July 1, 2022
  7. Whispering-gallery-mode optical microresonators have found impactful applications in various areas due to their remarkable properties such as ultra-high quality factor (Q-factor), small mode volume, and strong evanescent field. Among these applications, controllable tuning of the optical Q-factor is vital for on-chip optical modulation and various opto-electronic devices. Here, we report an experimental demonstration with a hybrid structure formed by an ultra-high-Q microtoroid cavity and a graphene monolayer. Thanks to the strong interaction of the evanescent wave with the graphene, the structure allows the Q-factor to be controllably varied in the range of 3.9 × 105 ∼ 6.2 × 107 bymore »engineering optical absorption via changing the gap distance in between. At the same time, a resonant wavelength shift of 32 pm was also observed. Besides, the scheme enables us to approach the critical coupling with a coupling depth of 99.6%. As potential applications in integrated opto-electronic devices, we further use the system to realize a tunable optical filter with tunable bandwidth from 116.5 MHz to 2.2 GHz as well as an optical switch with a maximal extinction ratio of 31 dB and response time of 21 ms.« less
  8. Atmospheric new-particle formation (NPF) affects climate by contributing to a large fraction of the cloud condensation nuclei (CCN). Highly oxygenated organic molecules (HOMs) drive the early particle growth and therefore substantially influence the survival of newly formed particles to CCN. Nitrogen oxide (NO x ) is known to suppress the NPF driven by HOMs, but the underlying mechanism remains largely unclear. Here, we examine the response of particle growth to the changes of HOM formation caused by NO x . We show that NO x suppresses particle growth in general, but the suppression is rather nonuniform and size dependent, whichmore »can be quantitatively explained by the shifted HOM volatility after adding NO x . By illustrating how NO x affects the early growth of new particles, a critical step of CCN formation, our results help provide a refined assessment of the potential climatic effects caused by the diverse changes of NO x level in forest regions around the globe.« less
  9. Free, publicly-accessible full text available March 1, 2023
  10. Free, publicly-accessible full text available January 1, 2023