In the modeling of supercontinuum generation in photonic crystal fibers by ultrashort pulses, the knowledge of the
higher-order dispersion terms of the fiber are necessary to achieve a good approximation between the simulated and
experimental spectra. However, these parameters are usually not provided by the manufacturer. In this work, we present
the numerical estimation of the higher-order dispersion terms for a nonlinear photonic crystal fiber with hexagonal holes.
For the simulation, we chose a commercial fiber with a high nonlinear response (Blazephotonics NL-2.4-8). The fiber
was designed with a small core diameter of 2.4 μm and a triangular pattern of air holes in the cladding with a pitch of
2.9 μm. Through the free software, MIT Photonic Bands, the structure of the fiber was modeled and the effective
refractive index, as well as the dispersion terms curves are estimated. From our results, the zero-dispersion wavelength of
the fiber resulted to be of 800 nm and at this wavelength, the higher-order dispersion terms were: β2=0, β3=0.05 ps3/km,
β4=-7.03×10-5 ps4/km, β5=1.4×10-7 ps5/km, β6=-4.163×10-10 ps6/km, β7=1.118×10-12 ps7/km. The zero-dispersion
wavelength and the dispersion slope estimated at this wavelength agree with the values reported by the manufacturer.
Here we report on the first CENAM realization of the phase-shift method for chromatic dispersion measurements in
mono-mode phase-shifted optical fibers used for the telecommunications C-band (1 550 nm). This chromatic dispersion
measurement and calibration capability development at CENAM will provide the Mexican telecommunications industry
with a formally established SI units traceability source, thus promoting this rapidly growing and high impact economic
sector competitiveness in Mexico. We also identified a 40 MHz modulation frequency, a 2.5 nm wavelength step and the
1 535 nm to 1 570 nm wavelength scanning range, as the optimum experimental parameters that have to be set in order
to obtain experimental data which numerical Sellmeier polynomials fittings produce representative determinations for
the group delay and the chromatic dispersion. We also obtained 1 549.388 nm ± 0.098 nm, (k=1), for the zero dispersion
wavelength, and 0.719 7 ps-nm-2 ± 0.005 5 ps·nm-2, (k=1), for the zero dispersion slope of the tested optical fiber.
A numerical study of the effects of tapering a hollow-core photonic bandgap fiber (HC-PBGF) on the spatial
parameters: effective area, nonlinear parameter and dispersion parameter is presented. The taper on the fiber is
modeled by scaling the cross section of the original fiber geometry. Both the air and the silica contribution to the
effective area and the nonlinear parameter are shown. The obtained results show a blueshift of the transmission
band and of the zero-dispersion wavelength. By tapering the fiber 30%, the transmission band and the zerodispersion
wavelength blueshift around 300 nm and 320 nm, respectively. HC-PBGFs have made possible the
study of nonlinear optical effects and by tapering the fiber, such nonlinear phenomena can be made stronger.
The optical anisotropy of a semiconductor surface can have different origins, such as, local-field effects, the electro-optics effect, reconstruction, surface dislocations, and surface roughness. A comprehensive, quantitative picture on how these effects are related to surface optical anisotropies (SOA) can now be obtained thanks to the progress in the modeling of optical properties of surfaces. Linear optical spectra can now be calculated very accurately even for large and complex surface structures. This allows a much better understanding of the origin of specific SOA. In this paper we make a review focused on the microscopic origin of SOA and the present state of the art in the study of reflectance anisotropy spectroscopy of semiconductor surfaces.
A push-broom imaging camera with time expansion, selected for its ability to generate images with high resolution and high radiometric signal, is described for accurate site-certification from space. The imaging system providing the high resolution imaging requires a sensor with an increased dwell time to generate a high radiometric signal. This may be accomplished by pointing the camera at each pixel for a longer interval of time than that available due to the sensor motion in the push-broom imaging configuration. This is referred to as the push-broom imaging with time expansion. The use of the camera with time expansion may be applicable to any remote sensing imaging problem that requires simultaneously high spatial resolution and a high level of radiometric signal. For surveying a Martian landing site, it is necessitated by the imaging from an autonomous orbiting sensor that's speed is determined by its orbit and the planet mass.
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