1,720,972 research outputs found
Using Bessel Beams to Induce Optical Waveguides
No full textOptical fabrication of waveguides in a volume is limited by diffraction in the writing beams. We
demonstrate the use of nondiffracting waves in the form of Bessel beams to fabricate scalable optical wiring through direct writing in a photosensitive volume. Experiments are performed in paraelectric
potassium-lithium-tantalate-niobate (KLTN), where writing occurs through photogenerated space charge
while guiding and electro-optic functionality are supported by the quadratic electro-optic effect. The
method allows components to be integrated sequentially without interfering with each other during fabrication, an intrinsic superposition property that is used to realize single, double, and multiple waveguides,
and 1 × 2, 1 × 3, and 1 × 4 splitters, and electrically controlled optical switching
Observation of diffraction cancellation for nonparaxial beams in the scale-free-optics regime
No full textWe report the observation of diffraction cancellation for visible beams with widths from tens of wavelengths down to fractions of the optical wavelength. The phenomenon is observed at the transition from diffraction- to antidiffraction-dominated beam propagation, triggered by a thermal shock in a photorefractive nanodisordered lithium-enriched potassium-tantalate-niobate (KTN:Li) crystal. Here beams propagate without distortion, independently of intensity and size. Confirming the main prediction of the scale-free-optics model, we find a single unified light behavior that spans across the entire hierarchy of standard optical spatial scales, from wide plane-wave-like beams that obey geometrical optics down to ultranarrow beams with widths of the order of a single wavelength
Volume integrated phase modulator based on funnel waveguides for reconfigurable miniaturized optical circuits
No full textWe demonstrate the integration of a miniaturized 30 μm × 30 μm × 2.7 mm electro-optic phase modulator operating in the near-IR (λ = 980 nm) based on the electro-activation of a funnel waveguide inside a paraelectric
sample of photorefractive potassium lithium tantalate niobate. The modulator forms a basic tassel in the realization
of miniaturized reconfigurable optical circuits embedded in a single solid-state three-dimensional chip
Spatial Rogue Waves in Photorefractive Ferroelectrics
No full textRogue waves are observed as light propagates in the extreme nonlinear regime that occurs when
a photorefractive ferroelectric crystal is undergoing a structural phase transition. The transmitted spatial
light distribution contains bright localized spots of anomalously large intensity that follow a signature
long-tail statistics that disappears as the nonlinearity is weakened. The isolated wave events form as
out-of-equilibrium response and disorder enhance the Kerr-saturated nonlinearity at the critical point.
Self-similarity associable to the individual observed filaments and numerical simulations of the generalized
nonlinear Schrödinger equation suggests that dynamics of soliton fusions and scale invariance can
microscopically play an important role in the observed rogue intensities and statistics
Turbulent Transitions in Optical Wave Propagation
No full textWe report the direct observation of the onset of turbulence in propagating one-dimensional optical waves. The transition occurs as the disordered hosting material passes from being linear to one with extreme nonlinearity. As the response grows, increased wave interaction causes a modulational unstable quasihomogeneous flow to be superseded by a chaotic and spatially incoherent one. Statistical analysis of high-resolution wave behavior in the turbulent regime unveils the emergence of concomitant rogue waves. The transition, observed in a photorefractive ferroelectric crystal, introduces a new and rich experimental setting for the study of optical wave turbulence and information transport in conditions dominated by large fluctuations and extreme nonlinearity
Anti-diffracting beams through the diffusive optical nonlinearity
Full text linkAnti-diffraction is a theoretically predicted nonlinear optical
phenomenon that occurs when a light beam spontaneously focalizes independently of its intensity. We observe anti-diffracting beams supported by the peak-intensity-independent diffusive nonlinearity that are able to shrink below their diffraction-limited size in photorefractive lithium-enriched potassium-tantalate-niobate (KTN:Li)
Aging solitons in photorefractive dipolar glasses
Full text linkWe study experimentally the aging of optical spatial solitons in a dipolar glass hosted by a nanodisordered sample of photorefractive potassium-sodium-tantalate-niobate (KNTN). As the system ages, the waves erratically explore varying strengths of the nonlinear response, causing them to break up and scatter. We show that this process can still lead to solitons, but in a generalized form for which the changing response is compensated by changing the normalized wave size and intensity so as to maintain fixed the optical waveform
Miniaturized electro-optic infrared beammanipulator based on 3D photorefractive funnels
No full textWe demonstrate tunable electro-optic guiding, shaping, and switching of beams in the near
infrared spectrum (λ ≃ 980 nm), typical of VCSEL technology, using biomimetic 3D funnel
waveguides miniaturized into a sample of potassium–lithium–tantalate–niobate. The switchable
waveguides are written using the slow photorefractive build-up of a 3D volume space-charge
field caused by a diffracting continuous wave low intensity λ = 532 nm beam, and electro-optic
functionality is supported by the quadratic electro-optic effect of the high-symmetry paraelectric
phase
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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