We demonstrate that photonic crystals can be used to generate powerful and highly coherent Cerenkov radiation that is excited by the injection of a beam of free electrons. Using theoretical and numerical investigations we present the startup dynamics and coherence properties of such laser, in which gain is provided by matching the optical phase velocity in the photonic crystal to the velocity of the electron beam. The operating frequency can be varied by changing the electron beam energy and scaled to different ranges by varying the lattice constant of the photonic crystal. arXiv:1608.06502v2 [physics.optics]

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We present a method to map the absolute electromagnetic field strength inside photonic crystals. We apply the method to map the dominant electric field component Ez of a two-dimensional photonic crystal slab at microwave frequencies. The slab is placed between two mirrors to select Bloch standing waves and a subwavelength spherical scatterer is scanned inside the resulting resonator. The resonant Bloch frequencies shift depending on the electric field at the position of the scatterer. To map the electric field component Ez we measure the frequency shift in the reflection and transmission spectrum of the slab versus the scatterer position. Very good agreement is found between measurements and calculations without any adjustable parameters.

We present a method to map the absolute electromagnetic field strength inside photonic crystals. We demonstrate our method by applying it to map the electric field component E z of a two-dimensional photonic crystal slab at microwave frequencies. The slab is placed between two mirrors to create a resonator and a subwavelength spherical scatterer is scanned inside the resonator. The resonant Bloch frequencies shift depending on the electric field at the scatterer position. By measuring the frequency shift in the reflection and transmission spectrum versus the scatterer position we determine the field strength. Excellent agreement is found between measurements and calculations without any adjustable parameters and a possible realization is suggested for measurements at optical frequencies.