121 research outputs found
Mid-Infrared Soliton and Raman Frequency Comb Generation in Silicon Microrings
We numerically study the mechanisms of frequency comb generation in the
mid-infrared spectral region from cw pumped silicon microring resonators.
Coherent soliton comb generation may be obtained even for a pump with zero
linear cavity detuning, through suitable control of the effective lifetime of
free-carriers from multiphoton absorption, which introduces a nonlinear cavity
detuning via free-carrier dispersion. Conditions for optimal octave spanning
Raman comb generation are also described
Ge-Doped microstructured multicorefiber for customizable supercontinuum generation
Supercontinuum generation in a multicore fiber in which several uncoupled cores
were doped with dissimilar concentrations of germanium was studied experimentally.
Germanium doping provided control over the separation between the zero-dispersion
wavelength and the 1064-nm wavelength of a Q-switched Nd:YAG pump laser. Supercontinua
generated independently in each core of the same piece of fiber displayed clear
and repeatable differences due to the influence of germanium doping on refractive index and
four-wave mixing. The spectral evolution of the subnanosecond pump pulses injected into
the different cores was accurately reproduced by numerical simulations
Nonlinear optics in multimode fibers
We overview the emerging field of nonlinear optics in multimode optical fibers, which enable new methods for the ultrafast
light-activated control of temporal, spatial and spectral degrees of freedom of intense pulsed light beams
Chromatic confocal setup for displacement measurement using a supercontinuum light source
Chromatic confocal microscopy is a technique to measure distances by analyzing the spectrum of the light reflected by a sample. The key element of the confocal setup is a dispersive lens, which focuses
different wavelengths at different distances from the lens. In this paper,a novel setup realized with a
supercontinuum light source and a spatial filter composed by reflective elements is described.The supercontinuum source is implemented by injecting high power pulses from a microchip laser into a
Ge-doped microstructured optical fiber. The usage of metallic parabolic mirrors, for the focusing and
collimation required in the spatial filter, lets the dispersive lens be the only dispersive element of the
confocal setup and improves the efficiency of the spatial filter itself. A silicon-based spectrometer is
used for the acquisition of the spectra, which are normalized and Gaussian-fitted before extracting the
displacement information. A complete calibration is performed, and the set of wavelengths from
500 nm to 900 nm can be mapped into a280 um measuring range. The obtained relativ eaccuracy of
0.36% shows an enhancement of almost one order of magnitude when compared to other supercontinuum-based confocal systems
Nonlinear dynamics of spatio-temporal waves in multimode fibres
Nonlinear multimode fibers provide an intriguing test-bed for exploring complex
spatio-temporal beam dynamics. We overview recent experimental observations of Kerr beam
self-cleaning, parametric sideband series and supercontinuum generation in passive and active
multimode optical fibers
Spatio-temporal beam dynamics in multimode nonlinear optical fibers
ABSTRACT
We overview recent advances in the spatio-temporal nonlinear dynamics of optical pulses propagating in multimode optical fibers. The Kerr effect leads to spatial beam self-cleaning in a graded-index multimode optical fiber, followed by sideband series generation spanning multiple octaves. Effectively single mode supercontinuum spanning from the visible to the mid-infrared was also demonstrated. Enhancement of Kerr beam self-cleaning was observed in active fiber with quasi-step index profile. Moreover, mutual self-cleaning was recently reported for both the fundamental and the second harmonic beams in optically poled multimode fibers with cubic and quadratic nonlinearity
Nonlinear polarization dynamics of Kerr beam self-cleaning in a GRIN multimode optical fiber
We experimentally study polarization dynamics of Kerr beam self-cleaning in a
graded-index multimode optical fiber. We show that spatial beam cleaning is
accompanied by nonlinear polarization rotation, and a substantial increase of
the degree of linear polarization.Comment: 5 pages, 6 figure
Efficiency of dispersive wave generation in dual concentric core microstructured fiber
We describe the generation of powerful dispersive waves that are observed
when pumping a dual concentric core microstructured fiber by means of a
sub-nanosecond laser emitting at the wavelength of~1064 nm. The presence of
three zeros in the dispersion curve, their spectral separation from the pump
wavelength, and the complex dynamics of solitons originated by the pump pulse
break-up, all contribute to boost the amplitude of the dispersive wave on the
long-wavelength side of the pump. The measured conversion efficiency towards
the dispersive wave at 1548 nm is as high as 50%. Our experimental analysis of
the output spectra is completed by the acquisition of the time delays of the
different spectral components. Numerical simulations and an analytical
perturbative analysis identify the central wavelength of the red-shifted pump
solitons and the dispersion profile of the fiber as the key parameters for
determining the efficiency of the dispersive wave generation process.Comment: 11 pages, 12 figure
Kerr Frequency Combs in a Bichromatically Pumped Nonlinear Fiber Ring Cavity
We report numerical and experimental studies of four-wave mixing processes emerging from dual-frequency pumping of a passive fibre ring cavity. We observe the emission of a periodic train of nearly-background-free soliton pulses associated with Kerr frequency combs
Modeling of enhanced field confinement and scattering by optical wire antennas.
We describe the application of full-wave and semi-analytical numerical tools for the modeling of optical wire antennas, with the aim of providing novel guidelines for analysis and design. The concept of antenna impedance at optical frequencies is reviewed by means of finite-element simulations, whereas a surface-impedance integral equation is derived in order to perform an accurate and efficient calculation of the current distribution, and thereby to determine the equivalent-circuit parameters. These are introduced into simple circuits models, directly borrowed from radio frequency, which are applied in order to model the phenomena of enhanced field confinement at the feed gap and light scattering by optical antennas illuminated by plane waves
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