M. Peckus

Flat lensing in the visible frequency range by woodpile photonic crystals

We experimentally demonstrate full two-dimensional focalization of light beams at visible frequencies by a three-dimensional woodpile photonic crystal. The focalization (the flat lensing) with focal distances of the order of 50-70 μm is experimentally demonstrated. Experimental results are compared with numerical calculations and interpreted by harmonic expansion studies.

Spatial filtering by axisymmetric photonic microstructures.

We propose and show experimentally axisymmetric spatial (angular) filtering of two-dimensional light beams by axisymmetric photonic microstructures. Such three-dimensional microstructures (similar to photonic crystals), in gapless configuration, were recorded in bulk of glass, where the refractive index has been point-by-point modulated using tightly focused femtosecond laser pulses. Axisymmetric angular filtering of approximately 25 mrad is demonstrated experimentally.

Flat Focusing Mirror

The control of spatial propagation properties of narrow light beams such as divergence, focusing or imaging are main objectives in optics and photonics. In this letter, we propose and demonstrate experimentally a flat focusing mirror, based on an especially designed dielectric structure without any optical axis. More generally, it also enables imaging any light pattern in reflection. The flat focusing mirror with a transversal invariance can largely increase the applicability of structured photonic materials for light beam propagation control in small-dimension photonic circuits.

Photonic Crystal Microchip Laser

Microchip lasers are very efficient, compact and convenient sources of coherent light. However they have a serious disadvantage that, especially in high power operation regimes, the emitted beam structure is relatively bad (with large angular divergence). We show that the intracavity photonic crystals with spatial filtering functionality, can strongly improve the spatial characteristics of the microchip laser. The angular divergence of the emitted beam is strongly reduced, and the radiation brightness is significantly increased due to the intracavity photonic crystal filter.

Chirped axisymmetric photonic microstructures for spatial filtering

Abstract. We explore, theoretically and experimentally, the spatial (angular) filtering of two-dimensional light beams by longitudinally chirped axisymmetric photonic microstructures. The structures comprise a set of planes of concentric rings with the separation between the plates smoothly varying along the propagation direction. Axisymmetric structures were recorded in a bulk of glass, in which the refractive index has been modulated using tightly focused femtosecond laser pulses. We show that the spatial filtering recently shown in nonchirped axisymmetric structures can be substantially improved by the chirp: the angular range of filtering was increased approximately two times. The numerical study reveals that the filtering efficiency can be strongly increased using the longer and larger index contrast axisymmetric photonic structures.

Super-collimation by axisymmetric photonic crystals

We propose and experimentally show the mechanism of beam super-collimation by axisymmetric photonic crystals, specifically by periodic (in propagation direction) structure of layers of concentric rings. The physical mechanism behind the effect is an inverse scattering cascade of diffracted wave components back into on- and near-axis angular field components, resulting in substantial enhancement of intensity of these components. We explore the super-collimation by numerical calculations and prove it experimentally. We demonstrate experimentally the axial field enhancement up to 7 times in terms of field intensity.

Sub-and superdiffractive resonators with intracavity photonic crystals

We investigate experimentally and theoretically plane-mirror Fabry-Perot resonators filled by photonic crystals, i.e., with periodic intracavity refraction index modulation. We show that the diffraction properties of such resonators can be manipulated, resulting in sub- and superdiffractive dynamics of light in the resonator, and in hyperbolic angular transmission profiles.

Stripe patterns in degenerate optical parametric oscillators

We experimentally demonstrate the stripe (or roll) patterns in a broad-aperture degenerate optical parametric oscillator in a plane-mirror minicavity. The stabilization of stripes is achieved by seed injection at a subharmonic frequency. We measure the temporal spectra of the stripe pattern and obtain the 1/f-like noise spectra.

Focussing by a flat woodpile 3D photonic crystal

This paper reports on numerical and experimental observation of a beam focusing behind a flat 3D woodpile PhC. The work demonstrates this idea using paraxial approximation model, as well as using a conventional Finite-Difference Time-Domain (FDTD) method.

Focusing by a flat woodpile 3D photonic crystal

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 well as with the mode expansion studies. The focusing distance of 50 - 70 μm behind the crystal is obtained.