Biomedical subjects
Publications and source records attributed to D N Christodoulides.
We demonstrate all-optical switching at 1550 nm between two weakly coupled cores in a photonic crystal fiber for intensities up to 0.5 TW/cm2. Spectrum analysis at higher intensities reveals that the output was dominated by continuum generation primarily towards shorter wavelengths.
We report the first observation of discrete optical surface solitons at the interface between a nonlinear self-focusing waveguide lattice and a continuous medium. The effect of power on the localization process of these optical self-trapped states at the edge of an AlGaAs waveguide array is investigated in detail. Our experimental results are in good agreement with theoretical predictions.
We have observed the incoherent interaction between a highly confined (blocker) soliton and wide, moving signal beams of a different wavelength in a one-dimensional discrete Kerr medium. Digital switching of the blocker solitons to successive adjacent channels was measured with increasing signal power via both one and two cascaded interactions in an AlGaAs waveguide array, operations equivalent to a reconfigurable three-output router.
We investigate experimentally and numerically the interaction of a highly localized, single-channel discrete soliton (blocker) with a wide, tilted beam in a one-dimensional AlGaAs array. In agreement with theory the blocker is observed to discretely shift its position by multiple channels, depending on the intensity and relative phase of the tilted beam.
We predict the existence of random phase solitons in nonlinear periodic lattices. These solitons exist when the nonlinear response time is much longer than the characteristic time of random phase fluctuations. The intensity profiles, power spectra, and statistical (coherence) properties of these stationary waves conform to the periodicity of the lattice. The general phenomenon of such solitons is analyzed in the context of nonlinear photonic lattices.
We report the first experimental observation of modulation instability in a discrete optical nonlinear array.
We analytically demonstrate the existence of white light solitons in logarithmically saturable noninstantaneous nonlinear media. This incoherent soliton has elliptic Gaussian intensity profile, and elliptic Gaussian spatial correlation statistics. The existence curve of the soliton connects the strength of the nonlinearity, the spatial correlation distance as a function of frequency, and the characteristic width of the soliton. For this soliton to exist, the spatial correlation distance must be smaller for larger temporal frequency constituents of the beam.
We identify and investigate bimodal (vector) solitons in models of square-lattice arrays of nonlinear optical waveguides. These vector self-localized states are, in fact, self-induced channels in a nonlinear photonic-crystal matrix. Such two-dimensional discrete vector solitons are possible in waveguide arrays in which each element carries two light beams that are either orthogonally polarized or have different carrier wavelengths. Estimates of the physical parameters necessary to support such soliton solutions in waveguide arrays are given. Using Newton relaxation methods, we obtain stationary vector-soliton solutions, and examine their stability through the computation of linearized eigenvalues for small perturbations. Our results may also be applicable to other systems such as two-component Bose-Einstein condensates trapped in a two-dimensional optical lattice.
It is shown that discrete solitons can be navigated in two-dimensional networks of nonlinear waveguide arrays. This can be accomplished via vector interactions between two classes of discrete solitons: signals and blockers. Discrete solitons in such two-dimensional networks can exhibit a rich variety of functional operations, e.g., blocking, routing, logic functions, and time gating.
We present a comprehensive study of interactions (collisions) between two-dimensional composite vector solitons carrying topological charges in isotropic saturable nonlinear media. We numerically study interactions between such composite solitons for different regimes of collision angle and report numerous effects which are caused solely by the "spin" (topological charge) carried by the second excited mode. The most intriguing phenomenon we find is the delayed-action interaction between interacting composite solitons carrying opposite spins. In this case, two colliding solitons undergo a fusion process and form a metastable bound state that decays after long propagation distances into two or three new solitons. Another noticeable effect is spin-orbit coupling in which angular momentum is being transferred from "spin" to orbital angular momentum. This phenomenon occurs at angles below the critical angle, including the case when the initial soliton trajectories are in parallel to one another and lie in the same plane. Finally, we report on shape transformation of vortex component into a rotating dipole-mode solitons that occurs at large collision angles, i.e., at angles for which scalar solitons of all types simply go through one another unaffected.
We show that three approaches previously developed to describe partially incoherent wave propagation in inertial nonlinear media are in fact equivalent. This equivalence is formally established through the evolution of the mutual coherence function and by means of Karhunen-Loeve expansions.
We report on new fundamental phenomena in soliton interactions: delayed-action interaction and "spin"-orbit coupling upon collision between two-dimensional composite solitons carrying topological charges.
We report on the experimental observation of modulation instability of partially spatially incoherent light beams in noninstantaneous nonlinear media and show that in such systems patterns can form spontaneously from noise. Incoherent modulation instability occurs above a specific threshold that depends on the coherence properties (correlation distance) of the wave packet and leads to a periodic train of one-dimensional filaments. At a higher value of nonlinearity, the incoherent one-dimensional filaments display a two-dimensional instability and break up into self-ordered arrays of light spots. This discovery of incoherent pattern formation reflects on many other nonlinear systems beyond optics. It implies that patterns can form spontaneously (from noise) in diverse nonlinear many-body systems involving weakly correlated particles, such as atomic gases at (or near) Bose-Einstein condensation temperatures and electrons in semiconductors at the vicinity of the quantum Hall regime.
We report on an experimental observation of dark incoherent soliton Y splitting. The effects of incoherence on the evolution of incoherent dark soliton doublets are investigated both theoretically and experimentally. We show that the dynamics of these incoherent self-trapped entities are associated with strong "phase-memory" effects that are otherwise absent in the linear regime.