Photonic time crystals – materials whose dielectric permittivity is modulated periodically in time – offer new concepts in light manipulation. We study theoretically the emission of light from a radiation source placed inside a photonic time crystal, and find that radiation corresponding to the momentum band gap is exponentially amplified, whether initiated by a macroscopic source, an atom, or by vacuum fluctuations, drawing the amplification energy from the modulation. The radiation linewidth becomes narrower with time, eventually shrinking to the middle of the bandgap, which enables to propose the concept of non-resonant tunable photonic time-crystal laser. Finally, we find that the spontaneous decay rate of an atom embedded in a photonic time-crystal vanishes at the band edge due to low density of photonic states.

中文翻译：

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光子时间晶体中的放大发射和激光

光子时间晶体——介电常数随时间周期性调制的材料——为光操纵提供了新概念。我们从理论上研究了放置在光子时间晶体内的辐射源发出的光，发现对应于动量带隙的辐射呈指数放大，无论是由宏观源、原子还是真空涨落引发，都可以得到放大。来自调制的能量。辐射线宽随时间变窄，最终缩小到带隙中间，这使得提出非谐振可调谐光子时间晶体激光器的概念成为可能。最后，我们发现嵌入光子时间晶体中的原子的自发衰减率由于光子态的低密度而在能带边缘消失。