81 research outputs found
Photon propagation in a discrete fiber network: An interplay of coherence and losses
We study light propagation in a photonic system that shows stepwise evolution
in a discretized environment. It resembles a discrete-time version of photonic
waveguide arrays or quantum walks. By introducing controlled photon losses to
our experimental setup, we observe unexpected effects like sub-exponential
energy decay and formation of complex fractal patterns. This demonstrates that
the interplay of linear losses, discreteness and energy gradients leads to
genuinely new coherent phenomena in classical and quantum optical experiments.
Moreover, the influence of decoherence is investigated.Comment: To appear in PR
Observation of Defect States in PT-Symmetric Optical Lattices
We provide the first experimental demonstration of defect states in
parity-time (PT) symmetric mesh-periodic potentials. Our results indicate that
these localized modes can undergo an abrupt phase transition in spite of the
fact that they remain localized in a PT-symmetric periodic environment. Even
more intriguing is the possibility of observing a linearly growing radiation
emission from such defects provided their eigenvalue is associated with an
exceptional point that resides within the continuum part of the spectrum.
Localized complex modes existing outside the band-gap regions are also reported
along with their evolution dynamics
Anderson localization in synthetic photonic lattices
Synthetic photonic lattices provide unique capabilities to realize theoretical concepts emerging in different fields of wave physics via the utilization of powerful photonic technologies. Here we observe experimentally Anderson localization for optical pulses in time domain, using a photonic mesh lattice composed of coupled fiber loops. We introduce a random potential through programmed electro-optic pulse phase modulation, and identify the localization features associated with varying degree of disorder. Furthermore, we present a practical approach to control the band-gap width in photonic lattices by varying the coupling between the fiber loops, and reveal that the strongest degree of localization is limited and increases in lattices with wider band-gaps. Importantly, this opens a possibility to enhance or reduce the effect of disorder and associated localization of optical pulses
Optical gap solitons and truncated nonlinear Bloch waves in temporal lattices
We experimentally demonstrate the formation and stable propagation of various
types of discrete temporal solitons in an optical fiber system. Pulses
interacting with a time-periodic potential and defocusing nonlinearity are
shown to form gap solitons and nonlinear truncated Bloch waves. Multi-pulse
solitons with defects, as well as novel structures composed of a strong soliton
riding on a weaker truncated nonlinear Bloch wave are shown to propagate over
up to eleven coupling lengths. The nonlinear dynamics of all pulse structures
is monitored over the full propagation distance which provides detailed insight
into the soliton dynamics.Comment: accepted in Phys. Rev. Let
Modulational instability in fiber transmission lines with semiconductor optical amplifiers
Experimental observation of spectral Bloch oscillations
We report on the first, to our knowledge, experimental observation of spectral Bloch oscillations in an optical fiber employing the interaction between a probe signal and a traveling-wave periodic potential. The spectrum of weak probe pulses is shown to oscillate on account of their group-velocity mismatch to the periodic field. The behavior of a cw probe spectrum reveals the actual discrete nature of the effect. Recurrences of the spectrum after one and two Bloch periods are demonstrated. (C) 2009 Optical Society of Americ
Spectral and temporal Bloch oscillations in optical fibres
Inspired by the space-time duality of paraxial beam diffraction and dispersive pulse spreading, the experimental implementation of a temporal equivalent of evanescently coupled waveguide arrays is demonstrated. Pulses interact with a time-periodic potential during their propagation through an optical fibre and the generic effect of discrete diffraction is observed in time. The presented system allows fast and high-resolving measurements of the complete signal evolution. To demonstrate the advanced capabilities, Bloch oscillations of an optical signal in both the time and frequency domains are realised
- …