Search results for "PULSE SHAPING"
showing 10 items of 93 documents
Pulse shaping in mode-locked fiber lasers by in-cavity spectral filter
2014
International audience; We numerically show the possibility of pulse shaping in a passively mode-locked fiber laser by inclusion of a spectral filter into the laser cavity. Depending on the amplitude transfer function of the filter, we are able to achieve various regimes of advanced temporal waveform generation, including ones featuring bright and dark parabolic-, flat-top-, triangular- and saw-tooth-profiled pulses. The results demonstrate the strong potential of an in-cavity spectral pulse shaper for controlling the dynamics of mode-locked fiber lasers.
Effects of fourth-order fiber dispersion on ultrashort parabolic optical pulses in the normal dispersion regime
2011
International audience; We propose a new method for the generation of both triangular-shaped optical pulses and flat-top, coherent supercontinuum spectra using the effect of fourth-order dispersion on parabolic pulses in a passive, normally dispersive highly nonlinear fiber. The pulse re-shaping process is described qualitatively and is compared to numerical simulations.
Ultimate field-free molecular alignment by combined adiabatic-impulsive field design
2008
We show that a laser pulse designed as an adiabatic ramp followed by a kick allows one to reach a perfect postpulse molecular alignment, free of saturation. The mechanism is based on an optimized distribution of the energy between a weakly efficient but non saturating adiabatic ramp and an efficient but saturating impulsive field. Unprecedent degrees of alignment are predicted using state-of-the-art pulse shaping techniques and non-destructive field intensities. The scheme can be extended to reach high degrees of orientation of polar molecules using designed half-cycle pulses.
Filtering out intersymbol interference in spread-spectrum communication systems
1979
In this letter the transfer characteristic of the optimum filter suitable for eliminating intersymbol interference in pseudo-noise spread-spectrum communication systems is determined. Such a characteristic is independent of the code sequence employed.
High harmonics generation from structured nanorings
2014
In this work we study the radiation diffused by a fictitious structured nanoring driven by an intense laser field. In our model we consider an electron moving through a cosine-shape potential. The results show that the ring, under particular conditions, emits a wide spectrum of harmonics.
Multi-spectral photoplethysmography technique for parallel monitoring of pulse shapes at different tissue depths
2011
A photoplethysmography (PPG) signal can provide very useful information about a subject's hemodynamic status in a hospital or home environment. A newly developed portable multi-spectral photoplethysmography device has been used for studies of 11 healthy subjects. Multi-spectral photoplethysmography (MS-PPG) biosensor intended for analysis of peripheral blood volume pulsations at different vascular depths has been designed and experimentally tested. Multi-spectral monitoring was performed by means of a three–wavelengths (405 nm, 660 nm and 780 nm) laser diode and a single photodiode with multi-channel signal output processing. The proposed methodology and potential clinical applications are …
Artificial neural networks for nonlinear pulse shaping in optical fibers
2020
International audience; We use a supervised machine-learning model based on a neural network to predict the temporal and spectral intensity profiles of the pulses that form upon nonlinear propagation in optical fibers with both normal and anomalous second-order dispersion. We also show that the model is able to retrieve the parameters of the nonlinear propagation from the pulses observed at the output of the fiber. Various initial pulse shapes as well as initially chirped pulses are investigated.
Formation of Femtosecond Parabolic Pulses in Normal-Dispersion Optical Fibers
2013
We have shown through extensive numerical simulations that application of passive nonlinear reshaping in normal-dispersion optical fibers could produce femtosecond parabolic pulses (a few hundreds fs) modern femtosecond lasers and commercially available fibers.
Controlling the carrier-envelope phase of few-cycle focused laser beams with a dispersive beam expander
2008
We report on a procedure to focalize few-cycle laser pulses in dispersive media with controlled waveform. Stationarity of the carrier-envelope phase for extended depth of focus is attained by shaping the spatial dispersion of the ultrashort beam. An adjustable group velocity is locally tuned in order to match a prescribed phase velocity at focus. A hybrid diffractive-refractive lens system is proposed to drive the wavefield to an immersion microscope objective under convenient broadband modulation. Numerical simulations demonstrate robustness over positioning of this dispersive beam expander.
Transform-limited spectral compression by self-phase modulation of amplitude-shaped pulses with negative chirp
2011
International audience; Spectral compression by self-phase modulation of amplitude- and phase-shaped pulses is demonstrated as superior compared to pulses that have only been phase shaped. We synthesize linearly negatively chirped parabolic pulses, which we send through a nonlinear photonic crystal fiber, in which self-phase modulation compresses the spectrum of the pulses to within 20% of the Fourier transform limit.