Search results for "Chirp"
showing 10 items of 73 documents
The cancellation of nonlinear and dispersive phase components on the fundamental optical fiber soliton: a pedagogical note
2001
We consider the separate effects of nonlinear and dispersive propagation on a hyperbolic secant pulse propagating in an optical fiber. In particular, for small propagation distances, we present a straightforward derivation of the time-varying phase components developed across the pulse due to self-phase modulation (SPM) and group velocity dispersion (GVD). In this limit, we show that GVD is associated with a nonparabolic temporal phase which can exactly cancel the nonlinear phase component due to SPM across the entire pulse profile. The cancellation condition gives the launch condition for a fundamental optical fiber soliton.
OPCPA using beams shaped by diffractive optical elements
2011
Optical parametric chirped pulse amplification (OPCPA) is becoming a widely accepted technique for the generation of high energy ultrashort laser pulses. Flat-top spatial profile pump beams can improve the efficiency of OPCPA, however such beams can be energetically costly to generate and are difficult to implement for low pump energy systems. An elegant and efficient solution to the generation of flat-top spatial profiles is the use of a diffractive optical element (DOE), however these devices distort the geometric phase of the pulses, possibly making them unsuitable for phase coherent interactions such as OPCPA.
Spectral compression of optical parabolic similaritons
2007
We numerically investigate the spectral recompression experienced by a self-similar parabolic pulse with an anormal initial chirp. Spectral compression factors above 10 and high-quality output pulses can be predicted.
Frequency chirped continuous-wave sodium laser guide stars: modeling and optimization
2020
We numerically study a method to increase the photon return flux of continuous-wave laser guide stars using one-dimensional atomic cooling principles. The method relies on chirping the laser towards higher frequencies following the change in velocity of sodium atoms due to recoil, which raises atomic populations available for laser excitation within the Doppler distribution. The efficiency of this effect grows with the average number of atomic excitations between two atomic collisions in the mesosphere. We find the parameters for maximizing the return flux and evaluate the performance of chirping for operation at La Palma. According to our simulations, the optimal chirp rate lies between 0.…
Millimeter-wave and microwave signal generation by low-bandwidth electro-optic phase modulation
2009
We propose, analyze and numerically illustrate a photonic-based technique for waveform generation of electrical signals approaching the 50 GHz bandwidth with time apertures as large as a few nanoseconds, by low-frequency, up to 2 GHz, electro-optic phase modulation of time-stretched optical pulses. Synthesis of the electrical waveform relies on phase-to-amplitude conversion of the modulated signal by a group delay dispersion circuit designed to behave as a transversal filter with N taps. Although arbitrary waveform generation capabilities are limited, a wide variety of user-defined signals are numerically demonstrated by appropriately designing the low-frequency signal driving the electro-o…
Lossless equalization of frequency combs
2008
Frequency combs obtained by sinusoidal phase modulation of narrow-band continuous-wave lasers are widely used in the field of optical communications. However, the resulting spectral envelope of the comb is not at. In this Letter, we propose a general and eficient approach to achieve at frequency combs with tunable bandwidth. The idea is based on a two-step process. First, eficient generation of a train with temporal at-top-pulse profile is required. Second, we use large parabolic phase modulation in every train period in order to map the temporal intensity shape into the spectral domain. In this way, the resulting spectral envelope is at and the size is tunable with the chirping rate. Two d…
INFLUENCE OF THE INITIAL PHASE PROFILE ON THE ASYMPTOTIC SELF-SIMILAR PARABOLIC DYNAMICS
2009
International audience; We describe the influence of the initial phase profile on the convergence towards asymptotic self-similar parabolic shape. More precisely, based on numerical simulations, we discuss the impact of an initial linear chirp and a p phase shift. If the parabolic shape has been found to describe accurately the pulse envelope, dark structures can appear and evolve also self-similarly on the parabolic background.
Nonlinear spectrum broadening cancellation by sinusoidal phase modulation
2017
International audience; We propose and experimentally demonstrate a new approach to dramatically reduce the spectral broadening induced by self-phase modulation occurring in a Kerr medium. By using a temporal sinusoidal phase modulation, we efficiently cancel to a large extend the chirp induced by the nonlinear effect. Experimental validation carried out in a passive or amplifying fiber confirm the interest of the technic for the mitigation of spectral expansion of long pulses.
Parabolic pulse evolution in normally dispersive fiber amplifiers preceding the similariton formation regime
2006
We show analytically and numerically that parabolic pulses and similaritons are not always synonyms and that a self-phase modulation amplification regime can precede the self-similar evolution. The properties of the recompressed pulses after SPM amplification are investigated. We also demonstrate that negatively chirped parabolic pulses can exhibit a spectral recompression during amplification leading to high-power chirp-free parabolic pulses at the amplifier output.
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…