Chirped Pulse Amplification Technique Research Articles

High idler conversion with an intracavity optical parametric oscillator and difference frequency generation

Tunable mid IR generation is analyzed with an optical parametric oscillator (OSO) and difference frequency generation (DFG) based on two periodically poled gratings. To obtain chirped-pulse amplification techniques, in the difference frequency generation the group-velocity must be matched. If grating periods are selected, appropriately, the wider tunable range of output pulse can be obtained. Because the group velocity is matched, the parametric bandwidth and the maximum effective length will be enhanced. We theoretically demonstrate high idler conversion in a femtosecond optical parametric oscillators with two different and cascaded periodically poled gratings. In the first grating the signal and the idler 1 are generated, while in the second one, the midwave infrared idler 2 is generated. The dependence of the lengths of the two cavities on the conversion efficiency is discussed.

Electron capture acceleration channel in a slit laser beam

Using numerical simulations, the authors find that the electrons can be captured and accelerated to high energies (GeV) in a slit laser beam with an intensity of Iλ2∼1020W∕cm2μm2, where λ is the laser wavelength in units of μm. The range of the optimum incident energy is very wide, even up to GeV. These results are of interest for experiments because the relatively low intensity can be achieved with present chirped pulse amplification technique and a wide range of incident energies means that a multistage acceleration is possible.

Generation of chirped pulses at high repetition rate with a Ti：sapphire regenerative amplifier

We present a method to obtain a laser pulse train at high repetition rate for the Ti：sapphire laser system based on the chirped pulse amplification technique. The conventional working mode of the Pockels cell in the Ti：regenerative amplifier is modified. At a certain dumping time, a portion of the amplified seed pulse is dumped out of the cavity by a certain dumping ration every time the pulse runs around the cavity. Thenceforward, the chirped pulses at high repetition rate are generated. Based on the Franz-Nodvik amplification theory，a theoretical model of the regenerative amplifier is established and the analysis of the dependence of the pulse sequence on the dumping time and dumping ratio is given by numerical computation. With a pumping energy of 35mJ and a dumping ratio of 1/2, a fourteen-pulse sequence at 100MHz with pulse energy of 0.02mJ is obtained at a finite period of time in a pumping cycle.

Performance of multilayer dielectric grating irradiated by ultrashort optical pulse

In the ultrashort pulse high-energy laser system based on chirped pulse amplification technique, multilayer dielectric grating with good output waveform and high laser induced damage threshold plays an important role. Based on Fourier spectral transform and rigorous modal method, optical characteristic of multilayer dielectric grating under irradiation of ultrashort optical pulse is analyzed. The results show that the reflected pulse at the -1 order exhibits asymmetrical Gaussian shape with oscillatory tail in the front edge and decreasing energy when the reflection bandwidth is narrower than the frequency bandwidth of the incident pulse with Guassian shape. The effect of structure parameters of multilayer dielectric grating on the reflection bandwidth are discussed in detail, which provides guidance to the design of multilayer dielectric grating with desired reflection bandwidth. Finally, near-field distribution of multilayer dielectric grating is analyzed to study its damages induced by ultrashort pulses.

Autoresonant beat-wave generation

Autoresonance offers an efficient and robust means for the ponderomotive excitation of nonlinear Langmuir waves by phase-locking of the plasma wave to the slowly chirped beat frequency of the driving lasers via adiabatic passage through resonance. This mechanism is analyzed for the case of a cold, relativistic, underdense electron plasma, and its suitability for particle acceleration is discussed. Compared to traditional approaches, this new autoresonant scheme achieves larger accelerating electric fields for given laser intensity; the plasma wave excitation is much more robust to variations in plasma density; it is largely insensitive to the precise choice of chirp rate, provided only that it is sufficiently slow; and the suitability of the resulting plasma wave for accelerator applications is, in some respects, superior. As in previous schemes, modulational instabilities of the ionic background ultimately limit the useful interaction time, but nevertheless peak electric fields approaching the wave-breaking limit seem readily attainable. The total frequency shift required is only of the order of a few percent of the laser carrier frequency, and might be implemented with relatively little additional modification to existing systems based on chirped pulse amplification techniques, or, with somewhat greater technological effort, using a CO2 or other gas laser system.

New laser crystals for the generation of ultrashort pulses

Since the beginning of the 1990s, titanium sapphire has become the crystal of choice for the development of ultrashort laser systems producing very short and powerful pulses using the Chirped Pulse Amplification technique. In parallel to these developments leading to commercial products, new laser crystals have been studied in order to reach directly other wavelength ranges and to overcome the need to develop cw or pulsed green laser to pump the titanium sapphire crystal. In order to be able to directly pump the crystals with a very efficient and high-power semiconductor laser, new crystals doped with chromium or ytterbium ions have been developed. This article will review the latest development in this research field with the best performances obtained in terms of pulse duration. To cite this article: F. Druon et al., C. R. Physique 8 (2007).

Synthetic aperture compression scheme for a multipetawatt high-energy laser

High-energy petawatt lasers using the chirped-pulse amplification technique require meter-sized gratings to limit the beam fluence on the surface of the grating. An alternative, studied by many groups, is a mosaic grating consisting of smaller, coherently added gratings. We propose what we believe to be a new compression scheme consisting of beam phasing instead of grating mosaic phasing. This synthetic aperture compression scheme allows us to control the beam thanks to a unique segmented mirror equipped with three degrees of freedom. With this configuration, the beam is divided into small subapertures adapted to the classical grating size. After compression, these subapertures are coherently added before the focusing stage. Therefore the alignment processes are simplified.

Fully digital frequency stabilization of IR fiber-coupled laser

We present a stabilized semiconductor laser system designed to operate as a fiber-optic front-end master oscillator of a pulsed high-power iodine laser Prague Asterix Laser System (PALS). The replacement of the PALS master oscillator is a part of a broader effort to rebuild PALS into a laser generating shorter pulses with higher pulse power by the technique of optical parametric chirped pulse amplification. With an operating wavelength of 1315.15nm the stabilized laser master oscillator is based on a telecommunication single-frequency distributed feedback diode. The frequency stabilization is derived from transitions in thermally dissociated iodine. Locking to the selected transition is fully automatic and the control system employs a unique combination of control loops derived from temperature and absorption to overcome the problem of narrow locking range of a single absorption line.

Prepulse-free, multi-terawatt, sub-30-fs laser system

We have built a prepulse-free, multi-terawatt, ultrashort pulse laser system, which combines both conventional laser amplification and optical parametric chirped pulse amplification (OPCPA) techniques. By employing an OPCPA system after the regenerative amplifier in a Ti:sapphire chirped pulse amplification laser chain, we have dramatically enhanced the prepulse contrast by 6 orders of magnitude. A prepulse contrast of better than 4.4 x 10-11 has been measured with a high energy broadband pulse of 24 mJ at 10 Hz repetition rate from the OPCPA system. Using a subsequent four-pass Ti:sapphire amplifier, we have achieved an amplified energy of 279 mJ and an ultrashort recompressed amplified pulse duration of 23.5 fs, corresponding to the peak powers for OPCPA and four-pass amplifier of 0.5 TW and 5.9 TW, respectively.

90 mJ parametric chirped pulse amplification of 10 fs pulses

We demonstrate the amplification of broadband pulses from a Ti:Sapphire oscillator by non-collinear optical parametric chirped-pulse amplification technique in a type-I BBO crystal to energies of 90 mJ. Partial compression of the amplified pulses is demonstrated down to a 10 fs duration. These parameters come in combination with good spatial quality and focusability of the amplified beam.

Broadband amplification in non-linear crystals using controlled angular dispersion of signal beam

Recent advances in high intensity laser technology, such as the optical parametric chirped pulse amplification technique, allow the amplification of broadband pulses to high energies, by parametric interaction in a non-linear crystal. In this article, angular dispersion of the signal beam inside the non-linear media is added to a common setup to improve the non-collinear phase matching range. A comparative study of the performance of BBO, LBO and KDP using this geometry is undertaken. Computer simulations show that both BBO and LBO are excellent broadband performers. Although the maximum bandwidth of KDP does not broaden, we show how to avoid its severe narrowing below the degeneracy wavelength.

Two-color chirped-pulse amplification in an ultrabroadband Ti:sapphire ring regenerative amplifier.

We have developed a high-energy, ultrabroadband Ti:sapphire ring regenerative amplifier capable of producing in excess of 20-mJ output at a 10-Hz repetition rate. The technique of chirped-pulse amplification is used to generate two-color, time-synchronized pulses with central wavelength separations of up to approximately 120 nm and with a total energy of 10 mJ by use of a regenerative pulse-shaping technique. Mid-infrared pulses tunable from 6 to 11 microm are generated by difference frequency mixing the two-color outputs.

Ultra-short high-intensity laser pulse generationand amplification

Since the beginning of the 1990s the generation of high-intensitylaser pulses has known an unprecedented evolution thanks to the conjunction ofthe possibility of the chirped pulse technique and the availability ofspectrally broad-band laser media. Lasers capable of producing multi-terawattpulses can now be built on few optical tables in a small laboratory. We reviewthe generation and the amplification of ultra-short pulses by the chirpedpulse amplification technique.

Prospect for 100TW/90fs X-ray driver using optical parametric chirped pulse amplifiers

The optical parametric chirped pulse amplification (OPCPA) technique is promising for constructing a 100-TW/90-fs laser system. This laser system consists of a diode-pumped Nd:phosphate oscillator, two LBO preamplifiers and a final power KDP amplifier. A noncollinear BBO-I optical parametric amplifier pumped by a Q-switched and frequency-doubled Nd:YAG laser has been demonstrated. The temporally-stretched chirped signal laser pulses with a bandwidth of 36nm(FWHM) are amplified without limitation in bandwidth and distortion in the spectrum. The gain bandwidth is very sensitive to the pump-signal angle. Variation of this angle of ∼1 5mrad can significantly reduce the amplified bandwidth and results in a significant distortion of the amplified spectrum.

54-fs, 1-GW, 1-kHz pulse amplification in Cr:forsterite

30-fs pulses at 1.22 microm are produced by a self-mode-locked Cr:forsterite laser and amplified in a Cr:forsterite regenerative amplifier by a chirped-pulse amplification technique. 54-fs, 1-GW pulses at a 1-kHz repetition rate are obtained.

Kilohertz Cr:forsterite regenerative amplifier

We report on a tunable regenerative amplifier that is operational in the near-infrared spectral region from 1230 to 1280 nm based on the vibronic laser material Cr:forsterite. Utilizing the technique of chirped-pulse amplification, we generated pulses as short as 150 fs at 1255 nm at a repetition rate of 1 kHz. Pulse amplification of more than 5 x 10(5) times was observed, with recorded output pulse energies of 34 muJ . Implementation of a second-harmonic generator yielded 110-fs-duration pulses of 7-muJ energy at 625 nm.

High power ultrafast lasers

In this article, we review progress in the development of high peak-power ultrafast lasers, and discuss in detail the design issues which determine the performance of these systems. Presently, lasers capable of generating terawatt peak powers with unprecedented short pulse duration can now be built on a single optical table in a small-scale laboratory, while large-scale lasers can generate peak power of over a petawatt. This progress is made possible by the use of the chirped-pulse amplification technique, combined with the use of broad-bandwidth laser materials such as Ti:sapphire, and the development of techniques for generating and propagating very short (10–30 fs) duration light pulses. We also briefly summarize some of the new scientific advances made possible by this technology, such as the generation of coherent femtosecond x-ray pulses, and the generation of MeV-energy electron beams and high-energy ions.

High-average-power kilohertz-repetition-rate sub-100-fs Ti:sapphire amplifier system

We report on a femtosecond Ti:sapphire laser amplifier system that generates pulse energies >5 mJ at a 1-kHz repetition rate. The system consists of regenerative and multipass amplifiers and uses the technique of chirped-pulse amplification. When the system was seeded with 70-fs pulses at 800 nm from a self-mode-locked Ti:sapphire oscillator, amplified pulses of 94-fs duration at a repetition rate of 1 kHz and an average output power of 5.4 W were produced. The amplified pulse-repetition rate is variable from 250 Hz to 3 kHz. Pulse energies of >7.5 mJ were obtained at 500 and 250 Hz.

An FEL scheme for generating high-power optical beams for gamma-gamma colliders based on chirped pulse amplification techniques

A method to produce high-power optical beams for converting high-energy electron beams to TeV gamma rays via Compton backscattering in the next generation linear colliders is proposed. The scheme is an application of the chirped pulse amplification technique to a single pass, high-gain free-electron laser.

Bulk chirped Bragg reflectors for light pulse compression and expansion

Bulk chirped Bragg reflectors are proposed as optical dispersive devices for the chirp pulse amplification technique. These transversal filters allow to synthesize any monotonous group delay time law versus optical frequency with a positive or negative slope.