ABSTRACT
Rabi oscillation, originally proposed in nuclear magnetic resonance, is a well-known phenomenon associated with a driven two-level system. Although magnetic fields typically can bring about chirality into unusual phenomena such as chiral edge states in the quantum Hall effect, it is not clear if chirality exists in Rabi oscillations. Here we unveil the intrinsic chirality carried by the phase in a Rabi problem. For opposite detuning of the driving field, the phase evolution of the probability amplitude exhibits a mirror symmetry. Consequently, constructive or destructive interference of two off-resonant Rabi processes under different initial conditions is level dependent and symmetry protected. Experimentally, we demonstrate such features in a photonic setting with adjustable detuning, yet our results may prove pertinent to the study of similar phenomena in other driven two-level systems beyond photonics.
ABSTRACT
We demonstrate that a single Gaussian-like beam can self-bend during nonlinear propagation in a uniform photonic lattice. The two components of the beam experiencing normal and anomalous diffractions spontaneously separate and form a pair in a diametric-drive acceleration due to nonlinear action. Such a diametric drive generally describes a jointly accelerating behavior of two beams analogous to positive- and negative-mass objects. The influences of the initial momentum of the input beam and the nonlinear strength are considered in this process. We further realize a self-bending propagation for a partially coherent light beam and discuss the impact of incoherence on the acceleration strength.
ABSTRACT
In this Letter, we demonstrate the first, to the best of our knowledge, coherent propulsion with negative-mass fields in an optical analog. We observe a self-accelerating state, driven by a nonlinear coherent interaction of its two components that are experiencing diffractions of opposite signs in a photonic lattice, which is analogous to the interaction of two objects with opposite mass signs. Surprisingly, the coherent propulsion is highly immune to the initial phase of the two components, which is in sharp contrast with the behavior encountered in traditional coherent wave interactions. Compared to its incoherent counter-part, the coherent propulsion exhibits an enhanced acceleration.
ABSTRACT
We experimentally and theoretically demonstrate a spatial diametric drive acceleration of two mutually incoherent optical beams in 1D optical lattices under a self-defocusing nonlinearity. The two beams, exciting the modes at the top/bottom edges of the first Bloch band and hence experiencing normal/anomalous diffraction, can bind together and bend in the same direction during nonlinear propagation, analogous to the interplay between two objects with opposite signs of mass that breaks Newton's third law. Their spatial spectrum changes associated with the acceleration are analyzed for different lattice modulations. We find that the acceleration limit is determined by the beam exciting the top band edge that reaches a saturated momentum change prior to the other pairing beam.
ABSTRACT
We report the first experimental demonstration of localized flat-band states in optically induced Kagome photonic lattices. Such lattices exhibit a unique band structure with the lowest band being completely flat (diffractionless) in the tight-binding approximation. By taking the advantage of linear superposition of the flat-band eigenmodes of the Kagome lattices, we demonstrate a high-fidelity transmission of complex patterns in such two-dimensional pyrochlore-like photonic structures. Our numerical simulations find good agreement with experimental observations, upholding the belief that flat-band lattices can support distortion-free image transmission.
