Photonic integrated circuits (PICs) integrate optical components onto a single chip, drastically reducing device size and boosting performance, akin to electronic circuits. This enables faster, more efficient data handling for optical interconnects, artificial intelligence, and sensing, vital given the growth of data centers and AI. At the core of advanced PICs are ultra-high-Q (UHQ) on-chip micro-resonators, boasting Q factors exceeding 10 million (indicative of ultra-low-loss). Achieving these is a monumental feat, demanding meticulous fabrication and exquisite design, making each chip a true masterpiece. This superior Q factor minimizes light loss, enabling ultra-low power operation and powerful light-matter interactions crucial for nonlinear phenomena like Kerr solitons and Brillouin lasers. UHQ resonators are also vital for quantum applications, facilitating on-chip single-photon sources and robust light-matter coupling for quantum memory and logic gates.

My expertise encompasses creating UHQ on-chip photonics using diverse materials. This includes fabricating world-class silica-based on-chip cavities with Q factors over 100 million. Furthermore, I've developed chalcogenide glass-based on-chip optical devices that hold world-record Q factors in both the near-infrared (Q>10 million) and mid-infrared (Q>60 million) spectral regions. Notably, these Q factors are over 60 times higher than previous research, with optical losses comparable to commercial optical fibers. These foundational achievements pave the way for a wide array of advanced research initiatives.

Nonlinear optics investigates how light interacts with matter non-proportionally at high intensities, enabling light manipulation. Key phenomena include Kerr nonlinearity, where light intensity alters a material's refractive index, crucial for generating Kerr frequency combs used in precision metrology and high-capacity communications. Brillouin scattering, involving light-sound interactions, creates Brillouin lasers having ultra-narrow linewidth with ultra-low noise, essential for high-resolution and coherent communication systems. In addition, nonlinear optics is fundamental for quantum technologies, facilitating the generation of quantum light states for quantum computing and communication. 

Building upon ultra-high-Q (UHQ) on-chip platforms, my research has made significant strides in these areas. In the near-infrared, exploration of Kerr soliton dynamics, including their phase noise and potential for time crystals, has been conducted, alongside studies of spontaneous soliton locking via Brillouin/Raman scattering. Crucially, the first mid-infrared Brillouin laser on a chip was demonstrated, achieving ultra-low power (<100 uW) and an unprecedented sub-100 Hz linewidth for highly accurate mid-infrared applications.

Mid-infrared (MIR) optics explores the 2 to 20 micrometer wavelength range, crucial for applications like trace gas sensing, medical diagnostics, and environmental monitoring due to unique molecular absorption fingerprints. While on-chip MIR photonics holds great promise for compact, sensitive systems, its full potential has been limited by the historical lack of ultra-high-Q (UHQ) resonators in this region.

 My recent breakthroughs have addressed these limitations by developing chalcogenide glass-based on-chip optical devices with world-record UHQ factors in MIR. A key achievement was the first quantitative optical loss analysis of on-chip MIR devices, confirming material purity limits via the first observation of internal impurity absorption peaks and a similar loss floor of fiber. Leveraging these advanced MIR UHQ resonators, the first mid-infrared Brillouin laser on a chip was demonstrated, showcasing an ultra-narrow linewidth laser critical for high-accuracy MIR applications. Building on this, ongoing research includes Kerr frequency comb-based molecular spectroscopy and cavity-enhanced light-molecule interactions.