Zero-broadening slow light from photorefractive two-wave mixing.

The ability to delay short light pulses is a promising solution for all-optical telecommunications, but suffers from a large distortion of the delayed pulse as a consequence of the high material dispersion. In this Letter, we demonstrate the possibility to all-optically control the group delay in a photorefractive (PR) crystal by the use of the two-wave mixing (TWM) effect in the pulse regime at room temperature. Most importantly, we show that a proper choice of the pump pulse width in the TWM process enables us to slow down shorter or longer signal pulses without distortion.

Wideband chaos induced by the optical injection of a frequency comb.

In this Letter, we experimentally demonstrate a method to improve the bandwidth and flatness of chaos from a laser diode using the optical injection of a frequency comb. Our results show that the injection of an optical frequency comb into a laser diode extends the area of chaotic dynamics to much broader injection parameters (injected power and detuning frequency). The increased number of injected lines and the injected comb spacing are used to control and significantly improve the chaos properties.

Fully controllable multichannel waveguides induced by counterpropagating Bessel beams.

We theoretically analyze the waveguiding structures photo-induced by two incoherent counter-propagating Bessel beams (BBs) in a biased photorefractive crystal. We demonstrate that the cross-coupling of two BBs enables adressable channels and tunability of the forming guiding structures. The truncation parameter of the BBs, their Bessel orders and the misalignment between the two beams are all key parameters for tailoring the characteristics of the photo-induced waveguides such as the number of outputs, the output intensity levels and the distance between each output channel.

Two dimensional Airy beam soliton.

We demonstrate the formation of a two dimensional Airy beam soliton in a photorefractive crystal. By simply varying the nonlinearity strength we identify several scenarios showing the coexistence between an Airy beam and the emerging soliton. The soliton output profile behaves according to the theoretical soliton existence curve and can be tailored by the nonlinearity strength even without modifying the input Airy beam shape.

Multiple input/output waveguides light-induced by a single Bessel beam for all-optical interconnects.

We numerically study photo-induced waveguides using a single Bessel beam in a photorefractive (PR) medium. Under self-focusing nonlinearity, we demonstrate the possibility for creating complex waveguiding structures with multiple input/output channels. The truncation of the incoming Bessel beam, the nonlinearity of the PR medium, the light intensity, and the order and the size of the Bessel beam are the key parameters for achieving different configurations with high guiding efficiencies.

Tailoring frequency combs through VCSEL polarization dynamics.

We investigate experimentally the nonlinear polarization dynamics of a VCSEL subject to optical injection of a frequency comb. By tuning the polarization of the injected comb to be orthogonal to that of the VCSEL, we demonstrate the generation of either a single polarization or a dual polarization frequency comb. The injection parameters (injected power and detuning frequency) are then used either to generate harmonics of the initial comb spacing or to increase the number of total output frequency lines up to 15 times the number of injected comb lines.

Optimized properties of chaos from a laser diode.

We perform an experimental parametric study of the chaos generated by a laser diode subjected to phase-conjugate feedback. In addition to the typical figure of merit, i.e.

Nonlinear dynamics of a laser diode with an injection of an optical frequency comb.

We experimentally and theoretically demonstrate the variety of the nonlinear dynamics exhibited by a single frequency semiconductor laser subjected to optical injection from a frequency comb. The injection parameters (the detuning and the injection strength) and the comb properties (comb spacing and the amplitude of the injected comb lines) are varied to unveil several dynamics such as injection locking, wave-mixing, chaotic dynamics, and unlocked time-periodic dynamics corresponding to new comb solutions. The asymmetry of the injected comb is shown to modify the size of the injection locking region in the parameter space, as well as the common properties between the new comb solutions observed and the injected comb.

Slow light with photorefractive beam fanning.

The beam fanning naturally occurring in a photorefractive crystal is shown to slow down a single light pulse at room temperature. Slow light is demonstrated for both visible and infrared wavelength light pulses as short as the response time of the photorefractive crystal and with fractional delay- i.e ratio of delay to output pulse duration- up to 0.

Spatiotemporal complexity of chaos in a phase-conjugate feedback laser system.

An 852 nm semiconductor laser is experimentally subjected to phase-conjugate time-delayed feedback achieved through four-wave mixing in a photorefractive ($ {{\rm BaTiO}_{3}} $BaTiO) crystal. Permutation entropy (PE) is used to uncover distinctive temporal signatures corresponding to the sub-harmonics of the round-trip time and the relaxation oscillations. Complex spatiotemporal outputs with high PE mostly upwards of $ \sim 0.

Counterpropagating interactions of self-focusing Airy beams.

We study the first experimental collisions of two incoherent self-focused counterpropagating Airy beams in a nonlinear crystal. Their interactions demonstrate that the self-focusing dynamics of the Airy beams can be spatially controlled by the counterpropagating Airy beam. By tuning the misalignment and the size of the beams, we can control the output position of the self-focused Airy beam and switch to multiple outputs.

Improved slow light performances using photorefractive two-wave mixing.

We experimentally observe an ultralow effective group velocity of 0.9 cm/s of light pulses using the two-wave mixing process in an SnPS (SPS):Te crystal at a visible wavelength. The time delay can be controlled through the nonlinear photorefractive gain and the input pulse duration.

Wideband chaos from a laser diode with phase-conjugate feedback.

We analyze experimentally and theoretically the chaotic dynamics generated by a laser diode subjected to phase-conjugate feedback. Phase conjugation is obtained from four-wave mixing in a BaTiO photorefractive crystal. We demonstrate that the chaos bandwidth first increases linearly with feedback ratio but then saturates to relatively high values.

Stability analysis of a quantum cascade laser subject to phase-conjugate feedback.

We investigate the stability boundaries of a quantum cascade laser subject to phase-conjugate optical feedback. From a three-level model, we reduce our set of equations to the usual modified Lang-Kobayashi equations describing a semiconductor laser subject to phase-conjugate feedback. We then determine the Hopf bifurcation conditions, which we explore by using asymptotic methods.

Mapping of external cavity modes for a laser diode subject to phase-conjugate feedback.

We numerically investigate the dynamics of a semiconductor laser subject to phase-conjugate optical feedback. We explore the effects of the laser model and feedback parameters for the generation of time-periodic oscillations of the output power at harmonics of the external cavity frequency, i.e.

Bistability Controlled by Convection in a Pattern-Forming System.

We analyze the transition from convective to absolute dynamical instabilities in a nonlinear optical system forming patterns, i.e., a photorefractive crystal in a single feedback configuration.

High-order external cavity modes and restabilization of a laser diode subject to a phase-conjugate feedback.

We experimentally report the sequence of bifurcations destabilizing and restabilizing a laser diode with phase-conjugate feedback when the feedback rate is increased. Specifically, we successively observe the initial steady state, undamped relaxation oscillations, quasi-periodicity, chaos, and oscillating solutions at harmonics up to 13 times the external cavity frequency but also the restabilization to a steady state. The experimental results are qualitatively well reproduced by a model that accounts for the time the light takes to penetrate the phase-conjugate mirror.

Airy beam self-focusing in a photorefractive medium.

The unique bending and shape-preserving properties of optical Airy beams offer a large range of applications in for example beam routing, optical waveguiding, particle manipulation and plasmonics. In these applications and others, the Airy beam may experience nonlinear light-matter interactions which in turn modify the Airy beam properties and propagation. A well-known example is light self-focusing that leads to the formation of spatial soliton.

High-frequency chaotic dynamics enabled by optical phase-conjugation.

Wideband chaos is of interest for applications such as random number generation or encrypted communications, which typically use optical feedback in a semiconductor laser. Here, we show that replacing conventional optical feedback with phase-conjugate feedback improves the chaos bandwidth. In the range of achievable phase-conjugate mirror reflectivities, the bandwidth increase reaches 27% when compared with feedback from a conventional mirror.

Laser diode nonlinear dynamics from a filtered phase-conjugate optical feedback.

The rate equations for a laser diode subject to a filtered phase-conjugate optical feedback are studied both analytically and numerically. We determine the Hopf bifurcation conditions, which we explore by using asymptotic methods. Numerical simulations of the laser rate equations indicate that different pulsating intensity regimes observed for a wide filter progressively disappear as the filter width increases.

Spatiotemporal dynamics of counterpropagating Airy beams.

We analyse theoretically the spatiotemporal dynamics of two incoherent counterpropagating Airy beams interacting in a photorefractive crystal under focusing conditions. For a large enough nonlinearity strength the interaction between the two Airy beams leads to light-induced waveguiding. The stability of the waveguide is determined by the crystal length, the nonlinearity strength and the beam's intensities and is improved when comparing to the situation using Gaussian beams.

Numerical study of extreme events in a laser diode with phase-conjugate optical feedback.

Extreme intensity pulses sharing statistical properties similar to rogue waves have been recently observed in a laser diode with phase-conjugate feedback [A. Karsaklian Dal Bosco, D. Wolfersberger, and M.

All-optical interconnects using Airy beams.

We analyze numerically optical waveguide structures in photorefractive media induced by one or two incoherent counter-propagating (CP) Airy beams. Under nonlinear focusing conditions, we show that for a single Airy beam or for two CP beams with various input positions, multiple waveguiding structures can be photo-induced in the medium. Optical Gaussian beams can therefore be guided with a deflecting trajectory and/or even split into several output beams.

Bifurcation to chaotic low-frequency fluctuations in a laser diode with phase-conjugate feedback.

We unveil theoretically the bifurcations to chaotic low-frequency fluctuations (LFF) in a laser diode with phase-conjugate feedback (PCF). LFF occur from a chaotic itinerancy among destabilized limit-cycle attractors that correspond to the external-cavity modes (ECMs) of the PCF laser system and with a directional motion toward a self-pulsating dynamics of increasing frequency and larger output power. When increasing the feedback strength, the frequency of the fast-pulsing dynamics changes about a multiple of the external-cavity frequency, which is a unique feature of LFF in a laser diode with PCF.

Extreme events in time-delayed nonlinear optics.

We report experimentally on extreme events in the pulsating dynamics of an optical time-delayed system, i.e., a diode laser subject to a phase-conjugate feedback.