Amplification Of Femtosecond Pulses Research Articles

Amplification, absorption, and lossless propagation of femtosecond pulses in semiconductor amplifiers

Light propagation in semiconductor amplifiers is investigated numerically for femtosecond pulses whose frequency spectra are fully inside the gain region. Whereas amplification is observed for low-intensity pulses, lossless propagation and even pulse absorption are found for large input intensities. These novel features arise from the competition between amplifying and absorbing states in the semiconductor continuum.

Role of pump-induced dispersion on femtosecond soliton amplification in erbium-doped fibers: erratum

The limitation to the amplification of femtosecond pulses by erbium-doped fibers owing to the soliton self-frequency shift may be overcome by using a dispersion-shifted fiber. We show that this result holds irrespective of the relatively large residual frequency-dependent chromatic dispersion that is associated with the pumping of the doping ions. Nevertheless, resonant dispersion may lead to temporal broadening and distortion of the amplified pulse.

Spectral broadening and compression of femtosecond light pulses that pass through dye amplifiers

The amplification of femtosecond light pulses in multistage as well as in traveling-wave dye amplifiers is studied numerically, taking into account group velocity dispersion, self-phase modulation that is due to Kerr-type nonlinearity, and gain depletion. The combined action of these processes results in a spectral broadening that can be utilized for pulse compression. The results are compared with experimental findings.

Amplification of femtosecond pulses in a passive, all-fiber soliton source

We report a theoretical and experimental study of the amplification of femtosecond soliton pulses generated by a passively mode-locked fiber laser in a high-gain erbium-doped fiber amplifier (EDFA). Results on the spectral and temporal evolution of 450-fs soliton pulses propagating within an EDFA are presented. Power gains as high as 30 dB and the generation of sub-100-fs Raman colored solitons are observed. The results are found to be well described by the theoretical model presented.

Dispersion-free amplification of femtosecond dye-laser pulses

Amplification of femtosecond pulses through spatial expansion and recompression in a temporally nondispersive grating apparatus is demonstrated. The system used does not lengthen the pulse, provides higher gain than conventional amplifiers, and separates effectively the amplified spontaneous emission from the signal. The output pulse duration is easily controlled from tau(min) = 50 fs to several hundred femtoseconds by fine adjustment of the components used in the spatially dispersive scheme.

Femtosecond pulse amplification at 250 kHz with a Ti:sapphire regenerative amplifier and application to continuum generation

Ultrashort optical pulses have been amplified to 1.7 μJ of energy at a repetition rate of 250 kHz with a novel cw argon-pumped Ti:sapphire regenerative amplifier. Acousto-optic switching of the amplifier is used to achieve the high repetition rate. Chirped-pulse amplification is used to avoid nonlinear effects in the amplifier. After recompression, 1-μJ, 130-fs pulses are obtained and are used to generate a white-light continuum in an ethylene glycol jet.

Role of pump-induced dispersion on femtosecond soliton amplification in erbium-doped fibers

The limitation to the amplification of femtosecond pulses by erbium-doped fibers owing to the soliton self-frequency shift may be overcome by using a dispersion-shifted fiber. We show that this result holds irrespective of the relatively large residual frequency-dependent chromatic dispersion that is associated with the pumping of the doping ions. Nevertheless, resonant dispersion may lead to temporal broadening and distortion of the amplified pulse.

Amplification of femtosecond pulses in a spatially dispersive scheme

The amplification of 20-fs-duration pulses in an amplifier with spatial dispersion in the gain medium (dye) is theoretically analyzed. Pulse self-shaping was observed during amplification, and further shaping was achieved by spatially modulating the pump. This spatial modulation of the pump permits the elimination of pulse broadening in the amplifier, even in the saturation regime. The possibility of using a compound medium with an ultrabroadband gain profile is also discussed.

Kilohertz-rate continuum generation by amplification of femtosecond pulses near 15 μm

A NaCl color-center amplifier is used to amplify femtosecond pulses from an additive-pulse mode-locked laser at wavelengths between 1.52 and 1.60 microm. Pulse energies of several microjoules are obtained with pulse widths as short as 100 fs at kilohertz repetition rates. These pulses have been used to generate a continuum in a variety of solid and liquid media for hours without optical damage. The continuum generated in BaF(2) covers the wavelength range of 400 nm < lambda < 3.5 microm.

High gain amplification of femtosecond pulses with low amplified spontaneous emission in a multipass dye cell

We present a multipass femtosecond amplifier pumped by a Nd-YAG laser where the gain medium is given by a variable length dye cell. This system allows amplification factors up to 5 · 106 and output pulse energies of 150 μJ, while restricting the contribution of amplified spontaneous emission to 0.5% of the total output energy, without using any saturable absorber stage. A detailed study of the output pulsewidth as a function of the duration of the input chirped pulse is also presented.

Amplification of femtosecond pulses in single-mode fiber waveguides activated with Er3+ions

An experimental investigation was made of the process of amplification of femtosecond pulses in single-mode fiber waveguides activated with erbium ions. The amplified pulses were compressed from 80 to 55 fs in the course of their propagation. The energy of the pulses was estimated to be 5 nJ. The maximum gain was 26 dB.

Efficient amplification and tunable frequency conversion of femtosecond pulses

A two-stage femtosecond pulse amplification scheme is reported that is based on a pulse stretching-recompression procedure. Starting with 30 fs pulses of 10 nJ of a non-cw dye laser system, pulses of 50 fs duration are obtained with 60 μJ energy at 565 nm. An energy conversion efficiency of 2% is accomplished for the dye amplifier using pump pulses of 2 ns and a highly viscous solvent. Tunable femtosecond pulses are demonstrated by continuum generation of the amplified fs pulse in a 2 mm quartz plate and subsequent filtering in a graded interference filter in a spectral range larger than 200 nm. Cross correlation measurements indicate a duration of the converted pulses as short as 50 fs, close to the Fourier transformation limit.

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

Temporal and spectral profiles of a linearly polarized ultrashort laser pulse modulated by a copropagating perpendicularly polarized strong laser pulse with the same frequency in condensed matter have been modeled. Degenerate cross-phase modulation can be applied to femtosecond optical pulse compression and amplification without the use of gratings or prisms and to signal processing owing to the small walk-off and the degenerate four-wave mixing between the pump and probe pulses. In a double pump compression case, the pulse duration of the probe pulse has been reduced by a factor of 15 with the energy gain of over fourfold. This result gives a power gain of 60-fold.

Amplification of femtosecond pulses in Er 3+ -doped single-mode optical fibres

Femtosecond pulse amplification in Er3+-doped single-mode optical fibres has been experimentally investigated. The effect of amplified pulse compression from 80 to 55 fs has been observed. The amplified pulse energy was evaluated as 5 nJ. Maximum gain for the amplified signal was 26 dB.

Combined self-phase modulation and amplification of femtosecond light pulses

The influence of depletable amplification, group velocity dispersion and self-phase modulation due to Kerr-type nonlinearity on pulse shaping in femtosecond pulse amplification has been calculated. With gain depletion which is typical for the last stage of multi-stage amplifiers, spectral broadening occurs which, under certain conditions, can be utilized for pulse compression. This spectral broadening as well as a predicted spectral shift is compared with experimental results.

Chirped pulse amplification of 300 fs pulses in an alexandrite regenerative amplifier

The amplification of femtosecond dye laser pulses up to the 3.5-mJ level in an alexandrite regenerative amplifier is discussed. An expansion/compression system using diffraction gratings allows chirped amplification techniques to be used to produce peak powers upwards of 1 GW. Limitations in the chirped pulse amplification of ultrashort pulses due to intracavity dispersive elements are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

High-repetition-rate amplification of tunable femtosecond pulses with a q-switched CW Nd:YAG pumping laser

Frequency-tunable femtosecond pulses from a hybridly mode-locked dye laser system are amplified 10 3 times using a compact CW Nd:YAG pumping laser Q-switched at 1 kHz repetition rate. This practical laser system produces amplified tunable 14 fs pulses with a fiber compressor.

Background-free determination of the duration of ultraviolet radiation pulses generated by a femtosecond excimer system

Background-free determination of the duration of femtosecond ultraviolet radiation pulses generated in an excimer system was performed for the first time. The method of noncollinear second harmonic generation on reflection from the surface of a nonlinear crystal was used. It was found that amplification of femtosecond pulses in an XeCl excimer amplifier did not exhibit coherent effects.

Neodymium lasers as a source of synchronized high-power optical pulses

The recent considerable progress in the development of solid-state lasers, primarily neodymium-based lasers for use as sources of short, synchronized, high-power optical pulses, is reviewed. The amplification of femtosecond optical pulses using synchronous amplification techniques with these lasers has proved particularly applicable to experimentation. The authors also presents a laser design which combines several advantageous qualities into a single laser cavity. >

Femtosecond optical pulse amplification

A number of techniques have been developed for amplification of optical pulses of approximately 100-fs duration. These amplifiers span a wide range of operating parameters from kilowatt to gigawatt peak powers and from 10 Hz to megahertz repetition rates. Amplification of femtosecond pulses has also been demonstrated at several wavelengths including visible, near-infrared, and ultraviolet regions. Several problems arise when amplifying short optical pulses to very high intensities. The problems are discussed and the state of the art of femtosecond optical pulse amplification is reviewed. >