糖心视频

A new study reveals that spontaneous emission, a key phenomenon in the interaction between light and atoms, manifests in a new form within a photonic time crystal. This research, led by a KAIST team, not only overturns existing theory but further predicts a novel phenomenon: spontaneous emission excitation. The findings are in the journal 糖心视频ical Review Letters.

Professor Bumki Min's research team from the KAIST Department of 糖心视频ics, in collaboration with Professor Jonghwa Shin of the Department of Materials Science and Engineering, Professor Wonju Jeon of the Department of Mechanical Engineering, Professor Gil Young Cho of the Department of 糖心视频ics, and researchers from IBS, UC Berkeley, and the Hong Kong University of Science and Technology, announced that they have proven that the spontaneous emission decay rate in a photonic time crystal is, on the contrary, enhanced rather than being "extinguished," as suggested by a paper published in Science in 2022. Furthermore, they predicted a new process鈥攕pontaneous emission excitation鈥攚here an atom transitions from its ground state to an excited state while simultaneously emitting a photon.

Spontaneous emission is the process by which an atom intrinsically emits a photon and is fundamental to quantum optics and photonic device research. Until now, control over spontaneous emission has been achieved by designing spatial structures like resonators or photonic crystals. However, the advent of photonic time crystals, which periodically modulate the refractive index of a medium over time, has drawn attention to the potential for control along the time axis.

Previous theory predicted that the spontaneous emission decay rate in a photonic time crystal would completely vanish at a specific frequency. In contrast, this study is the first to prove that the decay rate is significantly enhanced. This is attributed to the non-orthogonal mode effect, highlighting the importance of research into non-Hermitian optics.

The research team also predicted and reported a new process, "spontaneous emission excitation," where an atom gains energy and transitions from its ground state to an excited state while simultaneously emitting a photon. This is a non-equilibrium process made possible by the time-crystal medium supplying external energy, representing a new light-matter interaction phenomenon that cannot be explained by conventional equilibrium optics.

The findings fundamentally shift the paradigm of spontaneous emission research and hold promise for broad applications in fields such as quantum light source design and non-equilibrium quantum optics.

Professor Min stated, "This achievement re-establishes the fundamental theory describing spontaneous emission in a rapidly time-varying environment. The enhancement of spontaneous emission decay and the 'spontaneous emission excitation' phenomenon have the potential to change the paradigm of light-matter interaction research."