Amplification Of Ultrashort Laser Pulses Research Articles

Design of a large-mode-area tapered fiber amplifier for amplification of ultrashort laser pulses at 1535 nm wavelength

We design a W-type large-mode-area erbium doped tapered fiber with effective mode area varying from 1770 µm2 to 840 µm2with tolerance ± 0.0005 in refractive indices of different layers of fiber. The beam quality of the pulses is ensured by effective single-mode operation. We investigate the amplification of high power femtosecond pulses in this fiber by using nonlinear Schrodinger equation including gain term. It is solved using split-step Fourier method for both up-tapered (effective mode area increasing along the length) and down tapered (effective mode area decreasing along the length) fiber configurations at centered around 1535 nm wavelength. In both configurations of fiber, input pulse parameters like peak power, pulse width, and fiber length are calculated for maximum amplification with the least amount of pulse shape distortion. In down-tapered configuration, we numerically demonstrate the amplification of 1 kW peak power, 560 fs duration pulse to 3.6 MW peak power, 12 fs amplified pulse. In up-tapered configuration, we obtain the amplification of 2 kW, 565 fs input pulse to ∼7.9 MW peak power, ∼11 fs pulse. The fiber is useful for amplifying high-power laser pulses, and the resulting pulses can be used for laser processing, spectroscopy, and remote sensing.

Research on amplification of ultrashort laser pulses at 1.03 µm in gain-managed nonlinearity regime

Research on amplification of ultrashort laser pulses at 1.03 µm in gain-managed nonlinearity regime

Laser amplification in Yb:YAG thin rods of different geometries: simulation and experiment

A numerical model for simulation of broadband amplification in a thin rod and thin-tapered-rod active elements was developed. The amplification of ultrashort laser pulses in three gain modules of different geometries was studied experimentally; the results of the experiments were used for validation of the elaborated numerical model. A laser system consisting of an ultrafast solid-state master oscillator and a two-stage thin-rod amplifier was constructed. With the use of the developed numerical model, optimization of the active elements’ parameters was carried out in order to increase the output power of the elaborated laser system.

Amplification of ultra-short laser pulses via resonant backward Raman amplification in plasma

In this paper, we have examined the possibility of using resonant backward Raman amplification (BRA) as an efficient mechanism in amplifying the low intensity ultra-short (≤fs) pulses using plasma as intermediate amplifying medium; such pulses are anticipated to get produced in the form of the secondary sources at ALPS (Attosecond Light Pulse Source) center of ELI (Extreme Light Infrastructure). In preliminary assessment of the scheme, the analytical expressions for the pump/seed laser pulses and plasma characteristic features are obtained which concisely describe the parameter regime of resonant BRA applicability in achieving significant amplification. The consistency of the scheme in the context of ELI-ALPS sources has been validated through particle in cell (PIC) simulations. The peak intensity of the amplified seed pulse predicted via simulation results is found in reasonable agreement with the analytical estimates. Utilizing these analytical expressions as a basis in perspective of ELI-ALPS parameter access, a specific example displaying the key plasma and laser parameters for amplifying weak seed pulse has been configured; the limitations and conceivable remedies in resonant BRA implementation have also been highlighted.

Analytical model for synchronous Raman amplification of high-energy ultrashort pulses in optical fibers

The amplification of ultrashort laser pulses to high energy and average power in optical fibers involves management of nonlinearity, gain bandwidth, dispersion, and saturation. In this paper, we investigate the use of stimulated Raman scattering in optical fibers for high-energy pulse amplification. The amplification of femtosecond pulses stretched to picosecond or even nanosecond durations by synchronized pump pulses is considered, assuming a carrier frequency difference close to the Raman gain peak frequency. An analytical solution for the pulse amplitude and phase profiles that includes the complete Raman gain spectrum plus self- and cross-phase modulation is given. To demonstrate the potential of this approach, we propose an amplifier-shifter setup with standard fibers to generate microjoule pulses with a duration around 100 fs at 1078 nm from a 250-fs nanojoule oscillator at 1030 nm. Simulations of an additional Raman amplifier stage with rod-type fibers resulted in pulse energies of a few millijoules, durations near 150 fs and peak powers larger than 10 GW after compression.

Self similar solution of superradiant amplification of ultrashort laser pulses in plasma

Based on the self-similar method, superradiant amplification of ultrashort laser pulses by the counterpropagating pump in a plasma is investigated. Here, we present a governing system of partial differential equations for the signal pulse and the motion of the electrons. These equations are transformed to ordinary differential equations by the self-similar method and numerically solved. It is found that the increase of the signal intensity is proportional to the square of the propagation distance and the signal frequency has a red shift. Also, depending on the pulse width, the signal breaks up into a train of short pulses or its duration decreases with the inverse square root of the distance. Moreover, we identified two distinct categories of the electrons by the phase space analysis. In the beginning, one of them is trapped in the ponderomotive potential well and oscillates while the other is untrapped. Over time, electrons of the second kind also join to the trapped electrons. In the potential well, the electrons are bunched to form an electron density grating which reflects the pump pulse into the signal pulse. It is shown that the backscattered intensity is enhanced with the increase of the electron bunching parameter which leads to the enhanced efficiency of superradiant amplification.

Amplification of Ultrashort Laser Pulses by Brillouin Backscattering in Plasmas

Plasma media, by exciting Raman (electron) or Brillouin (ion) waves, have been used to transfer energy from moderately long, high-energy light pulses to short ones. Using multidimensional kinetic simulations, we define here the optimum window in which a Brillouin scheme can be exploited for amplification and compression of short laser pulses over short distances to very high power. We also show that shaping the plasma allows for increasing the efficiency of the process while minimizing other unwanted plasma processes. Moreover, we show that, contrary to what was traditionally thought (i.e., using Brillouin in gases for nanosecond pulse compression), this scheme is able to amplify pulses of extremely short duration.

Generation of mid-IR and visible radiation from four-wave amplification of ultrashort laser pulses in transparent dielectrics

We analyze and simulate the generation of mid-IR radiation from the propagation of bichromatic laser pulses in transparent, centrosymmetric dielectrics. The process relies on using the beatwave associated with the bichromatic pulse to seed four-wave parametric amplification in the mid-IR. We derive propagation equations describing the evolution of the pump waves and scattered waves including the effects of third-order nonlinearity, dispersion, and finite laser spot size. An expression for the growth rate of the scattered waves due to four-wave mixing is derived in the limit of negligible pump depletion and is characterized for various transparent dielectric materials. For fused silica, it is found that a bichromatic pump with wavelengths near 1 μm can generate forward-directed radiation near 3 μm. Fully explicit particle-in-cell modeling shows exponential growth and high conversion efficiency to mid-IR and visible radiation when the beat-wave-generated frequency comb is tuned to overlap the gain band of the four-wave amplification process.

Amplification and generation of radiation at the 42Γ → 1,22Γ transition of the Kr2F molecule in an electron-beam-pumped wide-aperture laser

The radiation amplification and oscillation are obtained in an electron-beam-pumped Berdysh laser with an active volume of 10 L in the visible range from 430 to 470 nm at the broadband 42Γ → 1,22Γ transition in the triatomic Kr2F molecule of interest for amplification of ultrashort laser pulses. It is shown that, along with absorption of laser radiation in the active medium, the amplification dynamics is considerably determined by short-lived absorption induced in the amplifier windows by bremsstrahlung X-rays. For the specific pump power 0.6 — 0.7 MW cm-3, the gain, corrected for nonstationary absorption, was ∼10-3 cm-1. A scheme of a Kr2F amplifier is proposed for amplification of ultrashort pulses up to multiterawatt peak powers in the active volume ∼10 L.

Spatially dispersive regenerative amplification of ultrashort laser pulses

A novel CPA-system with a spatially dispersive Yb:KYW-based regenerative amplifier is presented. Three prisms inside the amplifier divide the seed pulses from an Yb fiber laser system into spatially separated spectral components that pass through different volumes of the active medium and are amplified independently. This concept allows overcoming the effect of gain-narrowing. The spatially dispersive amplifier delivers laser pulses with energies of up to 30 microJ at a repetition rate of 100 kHz. Successful compression of the amplified pulses down to 171 fs is demonstrated.

Influence of gas circulation on stimulated Raman scattering and amplification of ultrashort laser pulses in methane

Applying gas recirculation in a high pressure cell, laser pulses of 1ps at 400nm and with a repetition rate of 1kHz were frequency shifted by stimulated Raman scattering and amplification in methane gas at high pressure. We studied the influence of gas recirculation on the conversion efficiencies into the Stokes and anti-Stokes components as well as on their spatial distributions and spectral shapes using generator and generator-amplifier arrangements. For high pump energies, recirculation in the generator cell decreases conversion efficiency into the first Stokes component whereas it increases conversion into higher Stokes and anti-Stokes components. It results in a significantly improved spatial characteristics of the frequency-shifted radiation, however, is accompanied by a substantial spectral broadening. Using gas recirculation in the generator-amplifier arrangement we achieved a conversion efficiency into the first Stokes component of about 50% with highly improved spatial and spectral characteristics.

Amplification of ultrashort laser pulses upon stimulated Compton scattering in plasma

Stimulated Compton scattering of counterpropagating laser beams in a moving plasma is studied theoretically. It is shown that, by using Compton scattering, picosecond or femtosecond laser pulses can be amplified under certain conditions by two-three orders of magnitude.

Architecture of a blue high contrast multiterawatt ultrashort laser

The strategy used to develop an innovative high contrast multiterawatt femtosecond laser chain based on a hybrid (solid/gas) technology is reported. The laser system includes a Ti:sapphire oscillator generating 50 fs pulses at 950 nm, an optical parametric chirped pulse amplification stage, a second harmonic frequency converter for pulse temporal cleaning, and a final photolytical XeF(C–A) excimer amplifier for direct high peak-power amplification of ultrashort laser pulses in the blue (475 nm) spectral region. Several important issues concerning the design of the laser front-end, the energy extraction and beam phase control in the high peak-power XeF(C–A) amplifier are theoretically addressed. A detailed description of the XeF(C–A) amplifier and careful measurements of its energetic, optical and pumping characteristics are also given, together with the first pilot amplification experiments in the low density XeF(C–A) medium to assert the significance of our approach.

Reaching the Nonlinear Regime of Raman Amplification of Ultrashort Laser Pulses

The intensity of a subpicosecond laser pulse was amplified by a factor of up to 1000 using the Raman backscatter interaction in a 2 mm long gas jet plasma. The process of Raman amplification reached the nonlinear regime, with the intensity of the amplified pulse exceeding that of the pump pulse by more than an order of magnitude. Features unique to the nonlinear regime such as gain saturation, bandwidth broadening, and pulse shortening were observed. Simulation and theory are in qualitative agreement with the measurements.

Observation of superradiant amplification of ultrashort laser pulses in a plasma.

We demonstrate the amplification of a femtosecond signal pulse in an underdense plasma by a novel mechanism called superradiant amplification. The pulse is amplified by a counterpropagating few picosecond long pump pulse. In the superradiant regime, the ponderomotive forces exceed the electrostatic forces and arrange the plasma electrons to reflect the pump light into the signal pulse. We found a significant amplification in energy and intensity. The time structure of the amplified signal pulse carries intrinsic features of the superradiant regime. Sub-10-fs pulses of petawatt power appear feasible.

Amplification of ultrashort laser pulses by a resonant Raman scheme in a gas-jet plasma.

Raman amplification of subpicosecond laser pulses up to 95 times is demonstrated at corresponding frequencies in a gas-jet plasma. The larger amplification is accompanied by a broader bandwidth and shorter pulse duration. Theoretical simulations show a qualitative agreement with the measurements, and the effects of the plasma conditions and laser intensities are discussed.

Direct amplification of picosecond pulses in neodymium glass with a power density above 100 GW cm-2

A scheme for amplification of ultrashort laser pulses is studied, which is used in experiments on symmetrisation of ablation pressure with the help of a prepulse upon acceleration of foils by laser radiation of high brightness. The possibility of direct amplification of short pulses before their expansion in order to increase the energy contrast is considered. In experiments performed on the PICO facility, the amplification of a 10-ps pulse with a power density exceeding 100 GW cm-2 is demonstrated with the gain equal to 1.2 and the inversion drop above 30 %.

Amplification of ultrashort laser pulses in the photolytically driven XeF(C–A) active medium

Amplification of ultrashort laser pulses is demonstrated in a gas medium of the photolytical XeF(C–A) laser. A gas mixture of XeF2:N2:Ar was excited by vacuum-ultraviolet radiation produced by a high-current multichannel sliding discharge, which was initiated along one side of dielectric laser cavity. A small-signal gain of 1.6×10−3 cm−1 is observed for a seed pulse at 488 nm with ∼150 fs duration. The use of a second optical source together with the device optimization promise a multiple increase in the gain and the obtaining of high-contrast TW femtosecond pulses as a result of direct amplification, without application of a stretching/compression technique.

Demonstration of ultrashort laser pulse amplification in plasmas by a counterpropagating pumping beam

We experimentally demonstrated amplification of ultrashort laser pulses (200 fs pulses) in microcapillary plasmas by a counterpropagating pumping beam. Energy amplification as large as a factor of 5 was observed. Importantly, a nonlinear pump depletion regime must have been accessed, since the parameters support not only the amplification of the pulse, but an absolutely growing instability if the pump is not depleted. Further indication of accessing the nonlinear depletion is indicated by the relative insensitivity to the initial pulse energy.

Degenerate cross-phase modulation for pulse compression and amplification of ultrashort laser pulses: erratum

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text Q. Z. Wang, P. P. Ho, and R. R. Alfano, "Degenerate cross-phase modulation for pulse compression and amplification of ultrashort laser pulses: erratum," Opt. Lett. 15, 1488-1488 (1990) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article