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Photonic crystals due to their angular bandgaps and quasi-bandgaps can provide spatial (angular) filtering of light. Two-dimensional photonic crystals (photonic structures modulated along the longitudinal and along one transverse dimension) can provide spatial filtering in one one-dimensional, decreasing the beam divergence in one quadrature. Three-dimensional crystals can provide two-dimensional...
We investigate spatial propagation effect behind the Photonic Crystal under particular dispersion conditions, which lead to a near field focusing. We analyze and experimentally demonstrate full two-dimensional near field focusing of light beams at visible frequencies behind the flat three-dimensional woodpile photonic crystal. Experimental results correspond well with numerical FDTD calculations as...
We show how a periodic modulation of loss on the wavelength scale provides negative diffraction propagation. In particular, we consider a 2D square arrangement of lossy cylinders embedded in air, with no index contrast. The phase-shifts accumulated in propagation trough such a structure, with flat-flat interfaces, are then compensated by normal diffraction in air leading to a substantial focalization...
Photonic crystals (PhCs) are materials with spatially modulated refraction index on a wavelength scale. They are well-known due to their temporal dispersion and photonic band-gaps, but also for the spatial dispersion properties, allowing the management of spatial propagation properties of light. For particular geometries PhCs may provide non-diffractive propagation of light or even negative spatial...
Spatial filtering is broadly used to improve the spatial quality of light beams. The conventional technique of spatial filtering uses a confocal system of lenses. Recently, alternative methods for spatial filtering have been proposed, based on periodically micro-modulated refractive index materials on a wavelength scale - the Photonic Crystals (PhCs).
We investigate different linear effects that appear in the light beam propagation behind a three-dimensional woodpile photonic crystal. On one hand we report and analyse experimental observation of narrow and well collimated laser beam formation behind the photonic crystal. We show that this collimation depends on the input laser beam focusing conditions. On the other hand we also report the first...
Three-dimensional photonic crystals with woodpile structure are demonstrated to exhibit collimation of light beams behind the photonic structure. Woodpile structure photonic crystals with longitudinal modulation periods in a range of 7.4 – 7.8 µm, and transverse periods of 1 µm were fabricated using laser multi-photon polymerization technique in a negative-tone photoresist. As expected from theoretical...
Photonic crystals (PCs), are famous due to their well-known temporal dispersion properties as well as recently discovered spatial dispersion properties, allowing to manage spatial propagation properties of light. The peculiarities of the spatial propagation in PCs consist in vanishing of diffraction (self-collimation [1,2], negative-refraction and super-refraction of light [3]). The above listed effects...
We report first experimental evidences of spatial filtering of light beam in three-dimensional photonic crystals. The photonic crystals were fabricated in a glass bulk, where the refraction index was modified by applying femtosecond laser pulses. We observe the modification of the angular spectra (the far field) in the central maximum of the transmitted radiation in accordance with the theory of spatial...
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