Search results for "Òptica"
showing 10 items of 205 documents
Three-dimensional imaging through patterned type-1 microscopy
2022
We report a scanning non-confocal fluorescence microscopy scheme that provides images with optical sectioning and with a lateral resolution that surpasses by a factor of two the diffraction resolution limit. This technique is based on the type-1 microscopy concept combined with patterned illumination. The method does not require the application of phase-shifting or post-processing algorithms and provides artifact-free superresolved 3D images. We have validated the theory by means of experimental data.
On the performance of a linearized dual parallel Mach Zehnder electro-optic modulator
2014
The performance of a dual parallel differential Mach-Zehnder modulator broadband linearization architecture is analysed. This study provides experimental and analytical results showing an enhancement up to 20 dB in the 3rd-order intermodulation distortion factor at 5 GHz using RF and optical asymmetrical feeding factors.
Nonlinear higher-order polariton topological insulator
2020
We address the resonant response and bistability of the exciton-polariton corner states in a higher-order nonlinear topological insulator realized with kagome arrangement of microcavity pillars. Such states are resonantly excited and exist due to the balance between pump and losses, on the one hand, and between nonlinearity and dispersion in inhomogeneous potential landscape, on the other hand, for pump energy around eigen-energies of corresponding linear localized modes. Localization of the nonlinear corner states in a higher-order topological insulator can be efficiently controlled by tuning pump energy. We link the mechanism of corner state formation with symmetry of the truncated kagome…
Design of All-Normal Dispersion Microstructured Optical Fiber on Silica Platform for Generation of Pulse-Preserving Supercontinuum Under Excitation a…
2017
We investigated numerically the possibility of all normal dispersion fiber design for near-infrared supercontinuum generation based on a standard air-silica microstructure. The design procedure includes finding of target dispersion profile and subsequent finding of appropriate geometrical fiber design by inverse dispersion engineering. It was shown that the tailoring of dispersion profile could increase the spectral width of generated supercontinuum while maintaining perfect spectral flatness. Conditions necessary for wide and flat supercontinuum generation as well as restrictions imposed by chosen materials were discussed. As a result of design and optimization procedure, an air-silica des…
Q-switched mode locking noise-like pulse generation from a thulium-doped all-fiber laser based on nonlinear polarization rotation
2021
Abstract Q-switched mode locking (QML) noise-like pulse (NLP) emission from an all-fiber thulium-doped laser based on the nonlinear polarization rotation effect is reported. The QML emission is obtained in a cavity with net anomalous dispersion in a pump power interval in between the CW laser threshold and the threshold of the NLP regime. Highest-energy QML pulses were observed with a repetition rate of 812 kHz with a pump power of 520 mW at the optical wavelength of 1881.09 nm. A maximum overall energy of 460 nJ at an average output power of 6.4 mW was reached, which corresponds to a burst of mode-locked noise-like sub-pulses with 8.7 ns of pulse duration within a QML envelope of 11 µs. Th…
Surface-Impedance Formulation for Hollow-Core Waveguides Based on Subwavelength Gratings
2022
A rigorous Surface Impedance (SI) formulation for planar waveguides is presented. This modal technique splits the modal analysis of the waveguide in two steps. First, we obtain the modes characteristic equations as a function of the SI and, second, we need to obtain the surface impedance values using either analytical or numerical methods. We validate the technique by comparison with well-known analytical cases: the parallel-plate waveguide with losses and the dielectric slab waveguide. Then, we analyze an optical hollow-core waveguide de ned by two high-contrast subwavelength gratings validating our results by comparison with reported values. Finally, we show the potential of our formulati…
Effects of an intervening airgap on the two fundamental modes of a surface waveguide
1987
The introduction of an intervening airgap in a circular surface waveguide is investigated. The radial field structure and the propagation characteristics of the two fundamental modes are shown, as well as their dependence on the airgap and the frequency. The thickness of the airgap is a new parameter that might be used to improve the propagation characteristics of the surface waveguide as a low-loss transmission line, or to control the penetration of the fields in the surrounding medium, allowing a design of the waveguide as a leaky transmission line.
Dissipative soliton resonance in a full polarization-maintaining fiber ring laser at different values of dispersion
2016
We investigated the dissipative solitons resonance in an ytterbium-doped fiber ring laser in which all the elements are polarization maintaining (PM). A semiconductor saturable absorber mirror was used as a mode-locker. The cavity included a normal dispersion single-mode fiber (SMF) and an anomalous dispersion photonic crystal fiber. The change of the length of the PM SMF allows the variation of the net-normal dispersion of the cavity in the range from 0.022 ps2 to 0.262 ps2. As the absolute value of the net-normal dispersion increases from 0.022 ps2 to 0.21 ps2, a square-shaped single pulse transformed to a single right-angle trapezoid-shaped pulse, and, at the dispersion of 0.262 ps2, to …
Highly tunable optically switched time delay line for transversal filtering
2003
A novel tunable dispersion device, based on two chirped fibre gratings subjected to non-uniform magnetic fields, is presented. A large degree of tunability is achieved from 250 to 750 ps/nm. This is used to demonstrate RF filtering in the 3-11 GHz range.
Wavelength-codified fiber laser hydrogen detector
2005
We report a scheme for an optical hydrogen detector that codifies the information in wavelength. The system is based on an erbium-doped fiber laser with two coupled cavities and a Palladium-coated tapered fiber within one of the laser cavities. The tapered fiber acts as the hydrogen-sensing element. When the sensing element is exposed to a hydrogen atmosphere, its attenuation decreases changing the cavity losses. This change leads the system to switch lasing from the wavelength of the auxiliary cavity to the characteristic wavelength of the cavity which contains the sensing element. The detection level can be shifted by adjusting the reflective elements of the cavity containing the sensing …