Free-electron Brewster-transition radiation

Abstract

We reveal a mechanism to enhance particle-matter interactions by exploiting the pseudo-Brewster effect of gain materials, presenting an enhancement of at least four orders of magnitude for light emission. This mechanism is enabled by the emergence of an unprecedented phase diagram that maps all phenomena of free-electron transition radiation into three distinct phases in a gain-thickness parameter space, namely, the conventional, intermediate, and Brewster phases, when an electron penetrates a dielectric slab with a modest gain and a finite thickness. Essentially, our revealed mechanism corresponds to the free-electron transition radiation in the Brewster phase, which also features ultrahigh directionality, always at the Brewster angle, regardless of the electron velocity. Counterintuitively, we find that the intensity of this free-electron Brewster-transition radiation is insensitive to the Fabry-Pérot resonance condition and, thus, the variation of slab thickness, and moreover, a weaker gain could lead to a stronger enhancement for light emission.

The design engineering of nanocatalysts for high power redox flow batteries

“…These breakthroughs augur well for the widespread application of aqueous polysulfide RFBs. [77][78][79][80][81] Metal sulfides with controlled chemical compositions and various nanosized morphologies exhibited a wide range of applications in aqueous polysulfide RFBs. 14 Spherical CoS 2 / CoS heterojunction nanoparticles with a size of approximately 100 nm (Fig.…”

Multicolor x-rays from free electron–driven van der Waals heterostructures

“…When the vdW heterostructure is excited by an electron beam, it emits multicolor x-rays via the PCB mechanism. It should be noted that when free electrons penetrate the sample, other types of free electron radiation such as transition radiation are also produced (32)(33)(34). However, the contribution of transition radiation is substantial only at much lower photon energies and is negligible at x-ray photon energies because the refractive indices of target materials are close to unity in the x-ray regime.…”

Free electron emission in vacuum assisted by photonic time crystals

“…To enhance radiation, strategies such as the pseudo-Brewster effect of gain materials [17] and enhancement by surface polaritons excitation [6] have been proposed. Moreover, time-varying media have also been used to increase the intensity of waves in particular modes [18][19][20].…”

“…On the one hand, the frequency conversion characteristics of PTCs are used to convert evanescent waves into propagating ones, and on the other hand, the momentum band gap is utilized for parametric amplification of certain radiation components. Unlike previous methods [17,38], our approach offers the ability to flexibly manipulate the radiation angle and achieves exponential radiation enhancement without relying on any specific structural resonance.…”