Search results for "Modulation"
showing 10 items of 948 documents
Acousto-optical multiple interference devices
2008
We present a new concept for waveguide acousto-optical devices based on coupled MachZehnder interferometers driven by acoustic waves. These acousto-optical multiple interference devices use the periodic refractive index modulation induced by the acoustic wave to realize functionalities such as ON/OFF switching for an arbitrary time interval, as well as for efficient light modulation at high harmonics of the acoustic frequency and pulse shaping for, e.g., integrated Q-switches. We also discuss application of the concepts to light modulation by very high acoustic frequencies, where the acoustic wavelengths become much shorter than the optical ones.
Spectral analog of the Gouy phase shift
2013
We demonstrate the existence of the spectral phase shift a pulse experiences when it is subjected to spectral focusing. This $\frac{\ensuremath{\pi}}{2}$ phase shift is the spectral analog of the Gouy phase shift a 2D beam experiences when it crosses its focal plane. This spectral Gouy phase shift is measured using spectral interference between a reference pulse and a negatively chirped parabolic pulse experiencing spectral focusing in a nonlinear photonic crystal fiber. To avoid inherent phase instability in the measurement, both reference and parabolic pulses are generated with a $4\mathrm{\text{\ensuremath{-}}}f$ pulse shaper and copropagate in the same fiber. We measure a spectral phase…
Mechanism of hollow-core-fiber infrared-supercontinuum compression with bulk material
2010
We numerically investigate the pulse compression mechanism in the infrared spectral range based on the successive action of nonlinear pulse propagation in a hollow-core fiber followed by linear propagation through bulk material. We found an excellent agreement of simulated pulse properties with experimental results at 1.8 {mu}m in the two-optical-cycle regime close to the Fourier limit. In particular, the spectral phase asymmetry attributable to self-steepening combined with self-phase modulation is a necessary prerequisite for subsequent compensation by the phase introduced by glass material in the anomalous dispersion regime. The excellent agreement of the model enabled simulating pressur…
Temporal self-imaging effect for chirped laser pulse sequences: Repetition rate and duty cycle tunability
2005
We express parabolic-dispersion-induced transformations of a linearly chirped signal in terms of those suffered by the unchirped version of the same input signal. Specifically, we unveil that any amount of chirping and dispersion produces, aside from a scale factor, the same pulse-distortion effect as a certain parabolic dispersion in the unchirped input. This relevant result allows us to derive, as a particular case, the dispersion condition that leads to the temporal self-imaging phenomenon for laser pulse sequences globally affected by a quadratic-phase modulation. This combined action of chirping and dispersion is proposed as a technique for generating laser pulse sequences with customi…
Polarization instability in anisotropic-cavity degenerate four-wave mixing
2000
Abstract The emission and stability properties of a plane-wave model of intracavity degenerate four-wave mixing including self- and cross-phase modulation are studied. A Kerr medium inside an anisotropic cavity in which a linearly polarized field is injected is considered. Cavity anisotropy leads to qualitative new phenomena such as a subcritical polarization instability.
Real-time binary-amplitude phase-only filters.
2008
A real-time binary-amplitude phase-only filter (BAPOF) implemented in available phase-only modulators is presented. The BAPOF has an amplitude transmission equal to one only in a region of support, while the transmission is equal to zero in the complementary region. To implement zero transmission in a phase-only modulator we propose to add a linear phase to the region of support. In this way the correlation desired is obtained off axis. Computer simulations and experimental results obtained with this technique are given.
Bifurcations and multiple-period soliton pulsations in a passively mode-locked fiber laser
2004
The multiple-period pulsations of the soliton parameters in a passively mode-locked fiber laser were discussed numerically and experimentally. It was found that the pulse acquired a periodic evolution that was not related to the round-trip time and consisted of many round trips. The macroperiodicity existed independently or in combination with other periodicity such as period doubling, tripling etc. Analysis shows that the new periods in the soliton modulation appear at bifurcation point related to certain points related to certain values of the cavity parameters.
Four-wave-mixing coherent oscillator with frequency shifted feedback and misaligned pump waves.
2009
The effect of the pump waves misalignment on the oscillation spectra and oscillation intensity of a semilinear photorefractive oscillator is studied numerically and compared with the results of the experiment performed with a KNbO3:Fe,Ag crystal.
Nonlinear pulse shaping by coherent addition of multiple redshifted solitons
2011
International audience; The injection of a phase- and amplitude-shaped pulse into a photonic-crystal fiber provides additional degrees of freedom that can significantly influence the nature of nonlinear propagation and nonlinear and dispersive interactions. This strong sensitivity of nonlinear effects-particularly the Raman soliton self-frequency shift-greatly extends the parameter space available to generate tailored output fields for applications such as microscopic imaging. By numerical simulations, we identify the relevant interpulse interactions, and we experimentally demonstrate the additional capabilities of this nonlinear pulse-shaping method.
Vortex beam generation and other advanced optics experiments reproduced with a twisted-nematic liquid-crystal display with limited phase modulation
2016
In this work we propose the use of twisted-nematic liquid-crystal spatial light modulators (TN-LC-SLM) as a useful tool for training students in the manipulation of light beams with phase-only masks. In particular, we focus the work on the realization of phase-only gratings and phase-only spiral phases for the generation of vortex beams, beams carrying orbital angular momentum (OAM). Despite the extensive activity in this field, its experimental implementation for educational purposes is limited because it requires the use of very expensive high-resolution liquid-crystal on silicon (LCOS) SLMs. Here, we show that a low-cost experimental implementation can be done with older TNLC technology.…