Amir Rosen

Critical Behavior of Light in Mode-Locked Lasers

Light is shown to exhibit critical and tricritical behavior in passively mode-locked lasers with externally injected pulses. It is a first and unique example of critical phenomena in a one-dimensional many-body light-mode system. The phase diagrams consist of regimes with continuous wave, driven parapulses, spontaneous pulses via mode condensation, and heterogeneous pulses, separated by phase transition lines that terminate with critical or tricritical points. Enhanced non-Gaussian fluctuations and collective dynamics are present at the critical and tricritical points, showing a mode system analog of the critical opalescence phenomenon. The critical exponents are calculated and shown to comply with the mean field theory, which is rigorous in the light system.

LOCALIZATION IN FREQUENCY FOR PERIODICALLY KICKED LIGHT PROPAGATION IN A DISPERSIVE SINGLE-MODE FIBER

We show a special effect of localization in the temporal frequency domain of light pulses that propagate in a dispersive single-mode fiber in the presence of a time-periodic phase modulation that is repeatedly applied at equally spaced locations along the fiber. The effect is analogous to the dynamical localization that occurs for the quantum kicked rotor, which is similar to Anderson localization in disordered solids. The wave behavior eliminates the diffusive spread of sidebands (harmonics). The light propagation, which is described by a Schrodinger-like propagation equation, can provide a new testing ground for the investigation of localization besides shedding light on technologically important pulse propagation in fibers and mode-locked lasers.

Optical kicked system exhibiting localization in the spatial frequency domain

An optical kicked system with free-space light propagation along a sequence of equally spaced thin phase gratings is presented and investigated. We show, to our knowledge for the first time in optics, the occurrence of the localization effect in the spatial frequency domain, which suppresses the spreading of diffraction orders formed by the repeated modulation by the gratings of the propagating wave. Resonances and antiresonances of the optical system are described and are shown to be related to the Talbot effect. The system is similar in some aspects to the quantum kicked rotor, which is the standard system in the theoretical studies of the suppression of classical (corresponding to Newtonian mechanics) chaos by interference effects. Our experimental verification was done in a specific regime, where the grating spacing was near odd multiples of half the Talbot length. It is shown that this corresponds to the vicinity of antiresonance in the kicked system. The crucial alignment of the gratings in-phase positioning in the experiment was based on a diffraction elimination property at antiresonance. In the present study we obtain new theoretical and experimental results concerning the localization behavior in the vicinity of antiresonance. The behavior in this regime is related to that of electronic motion in incommensurate potentials, a subject that was extensively studied in condensed matter physics.

Evolution of localization in frequency for modulated light pulses in a recirculating fiber loop.

We present an experimental demonstration of the evolution of localization in frequency of light pulses that are repeatedly kicked by phase modulation and then propagated along equally spaced lengths of fiber with weak dispersion. The experiment was performed with a long fiber recirculating loop that allows us to follow the pulses spectral changes after each cycle.

Evolution of localization in frequency for modulated light pulses in a recirculating fiber loop

Summary form only given. We present an experimental demonstration of the evolution of localization in frequency of the optical kicked rotor in dispersive single mode fibers, predicted previously. This localization occurs after propagation in a dispersive fiber of broad light pulses that are repeatedly kicked by a sinusoidal RF phase modulation at equally spaced locations along the fiber. The naive expectation concerning the evolution of the spectrum and the buildup of sidebands (harmonics) is that their number diffusively increases with the number of kicks, so that the spectrum continuously broadens with propagation. However due to localization the spectrum is confined, usually with an exponential signature. The focus of the present paper is the transition between the broadening and the localization regimes, and the number of kicks needed for it. The experimental system to track the evolution of localization consisted of a recirculating fiber loop comprised of a tunable erbium doped fiber amplifier, a LiNbO/sub 3/ phase modulator, a chirped fiber Bragg grating (to minimize lasing of the system), polarization controls, and an electrooptic switch.

Long Range Soliton Interaction Related to Sidebands Generation in Mode-Locked lasers

Soliton formation in passively mode-locked lasers is often accompanied with spectral sidebands. We find how the exact spectral shape of the sidebands affects the long range interaction between pulses in a fiber laser cavity.

Pulse-Quasi-Crystal Formation in Mode-Locked Lasers

Many-pulse formation in passively mode-locked fiber lasers is shown to exhibit self pulse crystallization phenomena. We present experimental demonstrations and theoretical thermodynamic-like modeling.

First experimental observation of critical phenomena in a mode-locked laser

We report on a first experimental observation of critical behavior in a laser system with passive mode-locking and external pulse injection. The critical exponents were found to match the theoretical values of beta = 0.5 and delta = 3 .

Localization in frequency for periodically "kicked" light propagation along a dispersive single mode fiber

We show a special effect of localization in the temporal frequency domain of light pulses that propagate in a dispersive single-mode fiber in the presence of a time-periodic phase modulation that is repeatedly applied at equally spaced locations along the fiber. The effect is analogous to the dynamical localization that occurs for the quantum kicked rotor, which is similar to Anderson localization in disordered solids. The wave behavior eliminates the diffusive spread of sidebands (harmonics). The light propagation, which is described by a Schrödinger-like propagation equation, can provide a new testing ground for the investigation of localization besides shedding light on technologically important pulse propagation in fibers and mode-locked lasers.