Event
Ph.D. Dissertation Defense: Yuqi Zhao
Monday, September 30, 2024
10:00 a.m.
ERF 1207
Maria Hoo
301 405 3681
mch@umd.edu
ANNOUNCEMENT: Ph.D. Dissertation Defense
Name: Yuqi Zhao
Committee:
Prof. Edo Waks, Chair/Advisor
Prof. Thomas Murphy
Prof. Avik Dutt
Prof. Julius Goldhar
Prof. Victor Yakovenko, Dean's Representative
Date/Time: Monday, Sep 30th, 2024 at 10:00 AM - 12:00 PM
Location: ERF 1207
Title: Integration of Atomic Emitters in Photonic Platforms for Classical and Quantum Information Applications
Abstract:
Integrated photonics provides a powerful toolbox for a wide range of classical and nonclassical applications. In addition to their scalability and significantly lower power consumption, integrated photonic structures enable new design knobs and functionalities that are inaccessible in their bulk counterparts.
Solid-state atomic emitters, such as rare-earth ions (REIs) and quantum dots, serve as excellent candidates for scalable quantum memories and exhibit strong nonlinear resonant absorption. Integrating these atomic emitters with photonic devices enhances light-matter interactions, unlocking new opportunities for advanced optoelectronic systems across both classical and quantum regimes.
This thesis tackles two main challenges through the integration of photonic devices and atomic emitters: (1) developing scalable quantum network components, and (2) creating low-power nonlinear components for classical on-chip optical signal processing. Specifically, we focus on a platform of rare-earth ion doped thin-film lithium niobate (TFLN), leveraging the stable optical transitions of REIs and TFLN’s rich toolbox of high-performance photonics.
We first demonstrate an integrated atomic frequency comb (AFC) memory in this platform, an essential component for quantum networks. This memory exhibits a broad storage bandwidth exceeding 100 MHz and optical storage time as long as 250 ns. As the first demonstrated integrated AFC memory, it features a significantly enhanced optical confinement compared to previous REI memories based on ion-diffused waveguides, leading to a three orders of magnitude reduction in optical power required for a coherent control.
Next, we develop reconfigurable narrowband spectral filters using ring resonators in the REI:TFLN platform. These on-chip optical filters, with linewidths in the MHz and kHz range and extinction ratios of 13 dB - 20 dB, are crucial for reducing background noise in quantum frequency conversion. By spectral hole burning at 100 mK temperature in a critical-coupled resonance mode, we achieve bandpass filters with a linewidth as narrow as 681 kHz. Moreover, the cavity enables reconfigurable filtering by tuning the cavity coupling rate. Such versatile integrated spectral filters with high extinction ratio and narrow linewidth could serve as a fundamental component for optical signal processing and optical memories on-a-chip.
We also demonstrate picowatt-threshold nonlinearity in TFLN, utilizing the strong resonant nonlinear absorption induced by three-level REIs and enhanced by TFLN ring resonators. This work presents three distinct nonlinear transmission functions by adjusting the ring’s coupling strength. The lifetime of the nonlinear transmission is measured to be ~3 ms, determined by the ion’s third-level lifetime.
Finally, we propose a novel nonlinear device design based on a different material system and mechanism - an ultrathin optical limiter with low threshold intensity (0.45 kW/cm2 ), utilizing a 500 nm-thick GaAs zone plate embedded with InAs quantum dots. The optical limiting performance, enabled by the zone plate’s nonlinear focusing behavior, is investigated using FDTD simulations. We also explore the effects of the zone plate’s thickness and radius on its optical limiting performance.
