Hung Hing Ying Distinguished Colloquia Series: Two Frontiers in Photonics

Physics Colloquium: Topological Photonics
 

Date:                    September 22, 2026 (Tuesday)

Times:                 17:30-18:30

Venue:                 Wang Gungwu Lecture Hall, P4, Graduate House (Map)

Moderator:         Professor Shuang Zhang (Department of Physics, Faculty of Science, The University of Hong Kong)

Registration:      https://forms.cloud.microsoft/r/0vYrBn0KRZ?origin=lprLink

Abstract:

The research field now known as Topological Photonics began in 2013, with the first experimental observation of a Photonic Topological Insulator. The field introduced fundamental concepts from solid-state physics into photonics, including the profound discovery that light-wave transport can be protected from scattering by disorder, defects, and imperfections. Over the years, this field has given rise to new fundamental ideas of its own, offering exciting applications that could become real technologies in the near future, including topological lasers and topological protection of quantum light. It is currently one of the most active research areas in optics and undoubtedly one of the spearheads of research in topological physics at large. We are now more than a decade in, and it is time to ask: Where do we go from here?

This talk will review the fundamentals of topological photonics, highlight several key discoveries, and attempt to address the intriguing question of where the field is evolving.

Physics Colloquium: Photonic Time-Crystals and Light-Matter Interactions Therein

Date:                   September 24, 2026 (Thursday)

Times:                16:30-17:30

Venue:                CYPP3, LG1, Chong Yuet Ming Physics Building (Map)

Moderator:        Professor Yi Yang (Department of Physics, Faculty of Science, The University of Hong Kong)

Registration:     https://forms.cloud.microsoft/r/5cD0kyB3Br?origin=lprLink

Abstract:

Photonic Time Crystals (PTCs) are dielectric media whose refractive index is strongly modulated periodically in time, at timescales shorter than a single optical cycle. These systems conserve momentum but not energy. Momentum bands are separated by bandgaps in which the amplitudes of eigenmodes can increase or decay exponentially.

The lecture will introduce the fundamentals of PTCs and the classical and quantum features of light–matter interactions. Most notably, light emission in PTCs enables widely tunable lasers that do not rely on atomic resonance and draw energy from temporal modulation of the medium. Another important feature is the quantum aspects, which yield a plethora of fundamental features, ranging from generating pairs of entangled photons to controlling spontaneous emission through temporal modulation and creating 2D cluster states.

The talk will also cover experimental progress towards order-unity modulation of the refractive index faster than a single cycle, including the observation of time reflection at optical frequencies, and discuss nonlinear optics and new mechanisms for high-harmonic generation in solids.

ALL are welcome.

Enquiry: pearllyw@hku.hk