327 research outputs found
Enhanced soliton interactions by inhomogeneous nonlocality and nonlinearity
We address the interactions between optical solitons in the system with
longitudinally varying nonlocality degree and nonlinearity strength. We
consider a physical model describing light propagation in nematic liquid
crystals featuring a strongly nonlocal nonlinear response. We reveal that the
variation of the nonlocality and nonlinearity along the propagation direction
can substantially enhance or weaken the interaction between out-of-phase
solitons. This phenomenon manifests itself as a slowdown or acceleration of the
soliton collision dynamics in one-dimensional geometries or of the soliton
spiraling rate in bulk media. Therefore, one finds that by engineering the
nonlocality and nonlinearity variation rate one can control the output soliton
location.Comment: 22 pages, 5 figures, to appear in Physical Review
Route to nonlocality and observation of accessible solitons
We develop a general theory of spatial solitons in a liquid crystalline
medium exhibiting a nonlinearity with an arbitrary degree of effective
nonlocality. The model accounts the observability of "accessible solitons" and
establishes an important link with parametric solitons.Comment: 4 pages, 2 figure
High-energy terahertz surface optical rectification
The interest in surface terahertz emitters lies in their extremely thin active region, typically hundreds of atomic layers, and the agile surface scalability. The ultimate limit in the achievable emission is determined by the saturation of the several different mechanisms concurring to the THz frequency conversion. Although there is a very prolific debate about the contribution of each process, surface optical rectification has been highlighted as the dominant process at high excitation, but the effective limits in the conversion are largely unknown.
The current state of the art suggests that in field-induced optical rectification a maximum limit of the emission may exist and it is ruled by the photocarrier induced neutralisation of the medium's surface field. This would represent the most important impediment to the application of surface optical rectification in high-energy THz emitters.
We experimentally unveil novel physical insights in the THz conversion at high excitation energies mediated by the ultrafast surface optical rectification process. The main finding is that the expected total saturation of the Terahertz emission vs pump energy does not actually occur. At high energy, the surface field region contracts towards the surface. We argue that this mechanism weakens the main saturation process, re-establishing a clearly observable quadratic dependence between the emitted THz energy and the excitation. This is relevant in enabling access to intense generation at high fluences
Spatially incoherent modulational instability in a non local medium
We investigate one-dimensional transverse modulational instability in a non
local medium excited with a spatially incoherent source. Employing undoped
nematic liquid crystals in a planar pre-tilted configuration, we investigate
the role of the spectral broadening induced by incoherence in conjunction with
the spatially non local molecular reorientation. The phenomenon is modeled
using the Wigner transform.Comment: 13 pages with 4 figures included. To be published in Laser Physics
Letter
Soliton mobility in nonlocal optical lattices
We address the impact of nonlocality in the physical features exhibited by
solitons supported by Kerr-type nonlinear media with an imprinted optical
lattice. We discover that nonlocality of nonlinear response can profoundly
affect the soliton mobility, hence all the related phenomena. Such behavior
manifests itself in significant reductions of the Peierls-Nabarro potential
with increase of the degree of nonlocality, a result that opens the rare
possibility in nature of almost radiationless propagation of highly localized
solitons across the lattice.Comment: 16 pages, 4 figure
Hydex Glass: a New CMOS Compatible Platform for All-Optical Photonic Chips
We demonstrate a range of novel functions based on a high index doped silica
glass CMOS compatible platform. This platform has promise for
telecommunications and on-chip WDM optical interconnects for computing.Comment: 6 pages, 7 figures, 67 references, 1 table. arXiv admin note: text
overlap with arXiv:1404.536
Temporal and spectral shaping of broadband terahertz pulses in a photoexcited semiconductor
Transmission through a photoexcited semiconductor is used to temporally and spectrally shape a terahertz (THz) pulse. By adjusting the optical pump-THz probe delay, we experimentally introduce a polar asymmetry in the pulse profile as large as 92%. To shape the spectrum, we apply the same technique after strongly chirping the terahertz pulse. This leads to significant reshaping of the spectrum resulting in a 52% upshift of its median value. The pulse shaping techniques introduced here are of particular importance for temporal and spectral shape-sensitive THz nonlinear experiment
Curved optical solitons subject to transverse acceleration in reorientational soft matter
We demonstrate that optical spatial solitons with non-rectilinear trajectories can be made to propagate in a uniaxial dielectric with a transversely modulated orientation of the optic axis. Exploiting the reorientational nonlinearity of nematic liquid crystals and imposing a linear variation of the background alignment of the molecular director, we observe solitons whose trajectories have either a monotonic or a non-monotonic curvature in the observation plane of propagation, depending on either the synergistic or counteracting roles of wavefront distortion and birefringent walk-off, respectively. The observed effect is well modelled in the weakly nonlinear regime using momentum conservation of the self-collimated beams in the presence of the spatial nonlocality of the medium response. Since reorientational solitons can act as passive waveguides for other weak optical signals, these results introduce a wealth of possibilities for all-optical signal routing and light-induced photonic interconnects
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