Search results for "Rash"
showing 10 items of 377 documents
Theory of Raman effect on solitons in optical fibre systems: impact and control processes for high-speed long-distance transmission lines
2004
We examine the effects of stimulated Raman scattering on ultra-short pulses propagating in optical fibre systems. We demonstrate that the existing theories for the Raman-induced soliton self-frequency shift give consistent results in a restricted domain of pulse width which excludes important practical applications to high-speed soliton transmission systems. We present a general theory for the soliton self-frequency shift (SSFS), which applies to any pulse whose spectral bandwidth lies within the third-order telecommunication window. We also show that the harmful impact of the SSFS in high-speed long-distance transmission lines can be suppressed by use of filters whose central frequency is …
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.
Gouy wave modes: undistorted pulse focalization in a dispersive medium.
2007
Gouy wave modes are linear waves with finite energy that propagate without distortion at any phase and group velocity through a focal region in a dispersive medium. These features make them potentially useful for the onset and control of nonlinear interactions.
Ultrafast sequential charge transfer in a double quantum dot
2010
We use optimal control theory to construct external electric fields which coherently transfer the electronic charge in a double quantum-dot system. Without truncation of the eigenstates we operate on desired superpositions of the states in order to prepare the system to a localized state and to coherently transfer the charge from one well to another. Within a fixed time interval, the optimal processes are shown to occur through several excited states. The obtained yields are generally between 99% and 99.99% depending on the field constraints, and they are not dramatically affected by strict frequency filters which make the fields (e.g., laser pulses) closer to experimental realism. Finally …
Stroboscopic Space Tag for Optical Time-Resolved Measurements with a Charge Coupled Device Detector
2018
Time-resolved measurements are extensively employed in the study of light–matter interaction at the nanoscale such as the exciton dynamics in semiconductors or the ultrafast intraband transitions in metals. Importantly, single-photon correlation, quantum state tomography, and other techniques devoted to the characterization of quantum optics systems rely on time-resolved experiments, whose resolution which is bound to the time response of the detector and related electronics. For this reason, multiplexing or beam deflection techniques have been recently proposed to overcome the detector resolution and thus measure the final photon distribution characteristics. Taking advantage of both strat…
Ultrafast and Energy-Efficient Quenching of Spin Order: Antiferromagnetism Beats Ferromagnetism
2017
By comparing femtosecond laser pulse induced ferro- and antiferromagnetic dynamics in one and the same material - metallic dysprosium - we show both to behave fundamentally different. Antiferromagnetic order is considerably faster and much more efficiently manipulated by optical excitation than its ferromagnetic counterpart. We assign the fast and extremely efficient process in the antiferromagnet to an interatomic transfer of angular momentum within the spin system. Our findings do not only reveal this angular momentum transfer channel effective in antiferromagnets and other magnetic structures with non-parallel spin alignment, they also point out a possible route towards energy-efficient …
Space-Time Analogies in Optics
2011
Abstract The so-called space-time analogy constitutes a source of inspiration to understand, engineer, and implement new systems for ultrafast optical signal processing based on concepts borrowed from the well-established field of Fourier Optics. In this review, we start by describing in a comprehensive manner the most basic notions of this analogy and discuss some recent developments with state-of-the-art technology, including the silicon-chip-based time lens and ultra-dispersive Raman devices, among others. Apart from the applications in optical communications, special emphasis is paid on the collateral benefits that the “ultra” appellative brings in fields as diverse as optical frequency…
Tracking Autoionizing-Wave-Packet Dynamics at the 1-fs Temporal Scale
2010
We present time-resolved studies and Fourier transform spectroscopy of inner-shell excited states undergoing Auger decay and doubly excited autoionizing states, utilizing coherent extreme-ultraviolet (XUV) radiation continua. Series of states spanning a range of ∼4 eV are excited simultaneously. An XUV probe pulse tracks the oscillatory and decaying evolution of the formed wave packet. The Fourier transform of the measured trace reproduces the spectrum of the series. The present work paves the way for ultrabroadband XUV spectroscopy and studies of ultrafast dynamics in all states of matter.
Nonlinear dynamics of temporal optical soliton molecules in lasers
2007
Recent experiments demonstrate that fiber laser cavities are able to support various multisoliton complexes, analogous to soliton molecules. These advances, which could have impact on optical information transmission or storage, are guided by the concept of dissipative soliton and supported by numerical simulations. DOI: 10.2529/PIERS060828120520 As passively mode-locked lasers rely strongly on nonlinear dissipation, there is a growing interest in understanding various pulse dynamics in terms of the dynamics of dissipative solitons [1]. In particular, the interaction between dissipative temporal solitons can lead to the formation of stable multi-soliton complexes. The stability of multi-sol…
All-Fibered High-Quality 20-GHz and 40-GHz Picosecond Pulse Generator
2011
International audience; In this work, we investigate the generation of 20 and 40 GHz pulse trains by nonlinear compression of an initial beating in a cavity-less optical-fiber-based configuration. High temporal stability is obtained by generating the sinusoidal beating by means of an intensity modulator driven by an external clock. The residual timing jitter induced by the RF phase modulation is then reduced by managing the cumulated dispersion of the compression line whereas complete polarization stabilization is obtained thanks to a modified setup including a Faraday rotator mirror. Finally a high-quality 160 Gbit/s signal is generated from our low duty-cycle 40 GHz pulse source thanks to…