Experimental control of pattern formation by photonic lattices

We study the control of modulational instability and pattern formation in a nonlinear dissipative feedback system with a periodic modulation of the material refractive index. We use a one-dimensional photonic lattice in a single-mirror feedback configuration and identify three mechanisms for pattern control: bandgap suppression of instability modes, periodicity induced pattern modes, and orientational pattern control.The authors acknowledge the support of the Conseil Régional de Lorraine, the bilateral FrenchAustralian Science and Technology program, and the Australian Research Council through Discovery projects

Roles of resonance and dark irradiance for infrared photorefractive self-focusing and solitons in bi-polar InP:Fe

This paper shows experimental evidence of photorefractive steady state self-focusing in InP:Fe for a wide range of intensities, at both 1.06 and 1.55$\mu$m. To explain those results, it is shown that despite the bi-polar nature of InP:Fe where one photocarrier and one thermal carrier are to be considered, the long standing one photocarrier model for photorefractive solitons can be usefully applied. The relationship between the dark irradiance stemming out of this model and the known resonance intensity is then discussed

Noise-sustained dynamics of drifting patterns in a tilted nonlinear feedback system

We investigate experimentally the dynamics of pattern excitation in presence of an advection-like effect in a nonlinear optical system. This advection effect, created when the angle of incidence of the pump beam is not zero, causes the existence of: (i) a transition from convective to absolute instabilities, (ii) the formation of new pattern geometries, (iii) the seeding of noise-sustained structures. All these phenomena, previously observed in nonlinear Kerr-type systems, are demonstrated in our setup composed by a photorefractive nonlinear medium in a tilted feedback configuration

General properties and analytical approximations of photorefractive solitons

We investigate general properties of spatial 1-dimensional bright photorefractive solitons and suggest various analytical approximations for the soliton profile and the half width, both depending on an intensity parameter r

Determination of the absorption constant in the interband region by photocurrent measurements

We determined high absorption constants of crystals from photocurrent measurements within the interband absorption region (10-104cm-1). The method has been demonstrated in the interband absorption regime near 530nm in Sn2P2S6, a novel infrared sensitive photorefractive material, and in the interband absorption regime near 257nm of near stoichiometric LiTaO3. Besides the verification of older measurements with our new technique, precise absorption data for Sn2P2S6 in the wavelength range 488-514nm are presente

Control of pattern formation in a single feedback system by photonic lattices

We present the observation of the manipulation of modulational instability in a nonlinear dissipative system by a periodic photonic lattice. We use a setup based on a photorefractive BaTiO3 crystal in a single feedback mirror configuration leading to the formation of hexagonal patterns. Additionally, we impose an optical lattice to induce one or two-dimensional photonic band-gap structures with variable parameters. We show that by varying the lattice periodicity, thus adjusting the transverse spatial frequencies associated to the bandgap, we can induce patterns of particular symmetry or suppress the modulational instability when the position of the lattice bandgap coincides with the instability gain

Broadband adiabatic light transfer in optically induced waveguide arrays

We demonstrate experimentally the broadband and adiabatic light transfer in coupled waveguides based on multiple stimulated Raman adiabatic passage. Our experimental platform utilizes planar-type reconfigurable optically induced waveguide arrays and allows for efficient and robust transfer of light from an input waveguide over multiple states (up to nine) to an output waveguide. The same waveguide structures are tested for two propagation wavelengths separated by more than 200 nm, proving the achromaticity of the transfer process

Modulational instability and solitons in a periodic dissipative feedback system

International audienceWe review our recent experimental results on control of the modulational instability, pattern formation, and solitons in a nonlinear discrete dissipative feedback system. We show that the discreetness and bandgap effects can provide efficient control of the nonlinear instability modes of the system. Furthermore, we explore the possibilities for excitation of dissipative discrete solitons in such system through seeding with a narrow addressing beam

An experimental study to discriminate between the validity of diffraction theories for off-Bragg replay

We show that experiments clearly verify the assumptions made by the first-order two-wave coupling theory for one dimensional lossless unslanted planar volume holographic gratings using the beta-value method rather than Kogelnik's K-vector closure method. Apart from the fact that the diffraction process is elastic, a much more striking difference between the theories becomes apparent particularly in the direction of the diffracted beam in off-Bragg replay. We therefore monitored the direction of the diffracted beam as a function of the off-Bragg replay angle in two distinct cases: [a] the diffracted beam lies in the plane of incidence and [b] the sample surface normal, the grating vector and the incoming beam do not form a plane which calls for the vectorial theory and results in conical scattering.Comment: Corrected Eqs. (3) & (6); 14 pages, 8 figure