Orr Beer | Searcharxiv

arXiv2023

Purcell-enhanced X-ray scintillation

Scintillation materials convert high-energy radiation to optical light through a complex multi-stage process. The last stage of the process is light emission via spontaneous emission, which usually governs and limits the scintillator emission rate and light yield. For decades, the quest for faster emission rate and greater light yield motivated the frontier of scintillators research to focus on developing better materials and dopants. Here, we experimentally demonstrate a fundamentally different, recently proposed concept for enhancing the scintillation rate and yield: the Purcell effect. The Purcell effect is a universal enhancement mechanism for spontaneous emission by engineering the optical environment. In scintillators, such an enhancement arises from engineering the nanoscale geometry within the scintillation bulk, which thus applies universally to any scintillating material and dopant. We design and fabricate a thin multilayer nanophotonic scintillator, demonstrating Purcell-enhanced scintillation, achieving a 50% enhancement in emission-rate and an 80% enhancement in light yield. We demonstrate the potential of our device for realizing these enhancements in real-life settings for X-ray applications, also due to the robustness of the nanophotonic design to fabrication disorder. Our results show the bright prospects of bridging nanophotonics and scintillators science, toward reduced radiation dosage and increased resolution for high-energy particles detection.

physics.app-ph↗

arXiv2019

Observation of the Stimulated Quantum Cherenkov Effect

As charged particles surpass the speed of light in an optical medium they produce radiation - analogously to the way jet planes surpass the speed of sound and produce a sonic boom. This radiation emission, known as the Cherenkov effect, is among the most fundamental processes in electrodynamics. As such, it is used in numerous applications of particle detectors, particle accelerators, light sources, and medical imaging. Surprisingly, all Cherenkov-based applications and experiments thus far were fully described by classical electrodynamics even though theoretical work predicts new Cherenkov phenomena coming from quantum electrodynamics. The quantum description could provide new possibilities for the design of highly controllable light sources and more efficient accelerators and detectors. Here, we provide a direct evidence of the quantum nature of the Cherenkov effect and reveal its intrinsic quantum features. By satisfying the Cherenkov condition for relativistic electron wavefunctions and maintaining it over hundreds of microns, each electron simultaneously accelerates and decelerates by absorbing and emitting hundreds of photons in a coherent manner. We observe this strong interaction in an ultrafast transmission electron microscope, achieving for the first time a phase-matching between a relativistic electron wavefunction and a propagating light wave. Consequently, the quantum wavefunction of each electron evolves into a coherent plateau, analogous to a frequency comb in ultrashort laser pulses, containing hundreds of quantized energy peaks. Our findings prove that the delocalized wave nature of electrons can become dominant in stimulated interactions. In addition to prospects for known applications of the Cherenkov effect, our work provides a platform for utilizing quantum electrodynamics for applications in electron microscopy and in free-electron pump-probe spectroscopy.

physics.optics↗