Strong Energy Dependent Transition Radiation in a Photonic Crystal

Abstract

Radiation of a charged particle crossing an alternating stack of slabs in the optical region is considered. Both disordered and periodic stacks are investigated. It is shown that for special type of alternating disordered and periodic stacks the radiation problem can be solved exactly for backward and forward Brewster observation angles. Strong $N^2$ dependence of radiation intensity on slab number is re-established in special case of the disordered stack. This leads to strong directivity either on forward or on backward Brewster angles depending on the type of stack randomness. In certain type of periodic photonic crystal, a strong energy dependence $E^4$ for relativistic particles of the radiation intensity, observed at Brewster's angle is found. Further increment of particle energy leads to saturation. The band structure of the corresponding photonic crystal (PhC) has a behavior, analogous to the Dirac cones in graphene. We suggest this special type $1D$ photonic crystal for application as a detector of relativistic particles.

Figures (4)

• Figure 1: Illustration of the problem
• Figure 2: (a) Illustration of the $\sim \gamma^4$ law, (b) demonstration of the saturation law for the forward-propagating radiation. The spectral-angular intensity was integrated over the frequencies, corresponding to $\lambda > 2l$. Here $N_s = 10^3$.
• Figure 3: Band structure of the described PhC for the modes propagating at (a) $\theta = \theta_{Br}$ and (b) $\theta = 1.013\cdot \theta_{Br}$. For labels, the number indicates $n$ for a respective branch, and the symbol following the number indicates the sign of $q_z$
• Figure 4: Differential yield for the photons, radiated along the Brewster's angle in forward direction, integrated over a window $|\delta\theta| < 4 \cdot 10^{-3}$, (a) illustration of $\gamma$-dependence for a fixed wavelength $\lambda = 5l$, (b) illustration of $\lambda$-dependence for various fixed values of $\gamma$. Here $N_s = 10^3$.