optical parametric chirped-pulse amplification (original) (raw)
Acronym: OPCPA
Definition: parametric amplification of chirped ultrashort pulses
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light pulses,
methods
Related: chirped-pulse amplificationoptical parametric amplifiersoptical amplifierschromatic dispersionnonlinearitiesultrashort pulsespulse compression
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Contents
What is Optical Parametric Chirped-pulse Amplification?
The concept of chirped-pulse amplification was originally developed for the amplification of ultrashort pulses with laser amplifiers, but it was soon realized that it is also very suitable for optical parametric amplifiers (OPAs), another kind of ultrafast amplifiers. At high pulse energies, these devices also profit from a strong reduction in the peak intensities by amplifying temporally stretched (chirped) pulses. Stretching to chirped signal pulse durations of the order of 1 ns makes it possible to apply much higher pump energies and therefore to obtain much higher amplified pulse energies.
Furthermore, one no longer needs ultrashort pump pulses, but can rather resort to powerful and comparatively simple Q-switched lasers as pump sources in the nanosecond regime. (Note that a parametric amplifier, in contrast to a laser amplifier, requires pump pulses with durations similar to those of the signal pulses because there is no energy storage in the gain medium.)
Advantages of the OPCPA Concept
Compared with classical chirped-pulse amplification based on laser gain media, OPCPA has a number of important advantages:
- The parametric gain within a single pass through a nonlinear crystal can be many tens of decibels, so that OPCPA systems require fewer amplification stages (often just one), usually do not involve complicated multipass geometries, and can thus be built with much simpler and more compact setups.
- Parametric amplification is possible in a wide range of wavelengths. (Note, however, that an ultrabroad gain bandwidth is achieved only under certain phase-matching conditions.)
- With optimized phase-matching conditions, the gain bandwidth can be very large, allowing very short (few-femtosecond) high-energy pulses to be generated.
- Thermal effects in the amplifier crystal, such as thermal lensing, are much weaker than in a laser amplifier, since there is only a small amount of heating due to weak parasitic absorption. This together with the very high quantum efficiency allows for scaling to very high energy and peak power levels, and also to a high beam quality of the amplified pulses.
- The generated idler wave can sometimes also be used.
- As the parametric gain occurs only within the duration of the pump pulse, one avoids the problems of power losses by amplified spontaneous emission in high-gain laser amplifiers. Also, one can easily generate high-energy pulses with very high intensity contrast, i.e. with a very low level of power before the actual pulse.
On the other hand, disadvantages of the OPCPA concept (compared with classical CPA with laser amplifiers) are
- the requirement to match the pump and signal pulse durations, and to synchronize the seed and pump laser
- the requirement for a high pump beam quality
- the limited aperture of most available nonlinear crystals
- the complicated details of phase-matching issues
Terawatt and Petawatt Peak Powers
Some large laser facilities, which originally started with more traditional chirped-pulse amplification, have adopted the OPCPA technique for achieving extremely high peak powers [6, 7, 14, 15, 16]. Such systems employ at least two amplification stages, with a preamplifier typically based on a borate crystal (BBO or LBO), whereas KDP is used for the final amplifier stage because of the possibility to fabricate KDP crystals with very large useful apertures. A titaniumâsapphire laser can serve as the seed source, and high-energy frequency-doubled Q-switched lasers generate the pump pulses. In some cases, a laser amplifier (with moderate gain) is used for the last amplifier stage, but all-parametric systems are also under investigation. The latter already reach peak powers of hundreds of terawatts [17], and it is expected that multi-petawatt peak powers will be reached soon.
Few-cycle Pulse Amplification
The largest amplification bandwidth can be reached with certain noncollinear phase-matching schemes, based on, e.g., a BBO amplifier crystal pumped with few-picosecond pulses from a frequency-doubled mode-locked titaniumâsapphire laser. The term noncollinear optical parametric amplifier (NOPA) has been coined. Compared with the above-mentioned high-energy systems, NOPAs typically operate with a relatively short interaction length, much shorter pump pulses and correspondingly lower amplified pulse energies, but reach compressed pulse durations in the few-cycle regime down to â 4â5 femtoseconds. For simplicity, the seed pulse can be taken from a supercontinuum derived from the pump laser itself, avoiding the need to synchronize a separate seed laser with the pump laser.
A range of interesting concepts can be utilized in this domain. For example, one may realize wideband phase matching (â_achromatic phase matching_â) by angularly dispersing the signal beam such that each frequency component of the signal is properly phase-matched. Similar effects are achieved with tilting of the pulse fronts in the amplifier crystal (pulse front matched geometry); even in a collinear geometry, this allows for a very large phase-matching bandwidth [2, 5]. Wavelength tuning, which makes such systems very interesting for various scientific applications, is sometimes possible in a relatively wide range. Another important issue is the precise optimization of stretcher/compressor setups [9].
Compact Systems
The use of highly nonlinear quasi-phase-matched crystals allows for very high gains with moderate pump pulse energies. Although such systems typically generate pulses with durations of hundreds of femtoseconds and energies of microjoules or up to a few millijoules, these performance values are sufficient for a wide range of applications, and such systems can be made very compact and efficient.
Frequently Asked Questions
What is optical parametric chirped-pulse amplification (OPCPA)?
OPCPA is a technique used to amplify ultrashort pulses to very high energy levels. It applies the principle of chirped-pulse amplification to an optical parametric amplifier, where a pulse is temporally stretched before amplification and recompressed afterward.
What are the main advantages of OPCPA over laser-based amplification?
OPCPA offers very high gain in a single pass, enabling simpler and more compact setups. It also provides a very broad gain bandwidth for few-cycle pulse generation, minimal thermal effects for high beam quality, and excellent pulse contrast.
Why can OPCPA systems use nanosecond pump lasers?
In OPCPA, the signal pulse is stretched to a duration of nanoseconds. Since parametric amplification is an instantaneous process that requires temporal overlap between pump and signal, this allows the use of powerful and simple Q-switched lasers with nanosecond pulse durations.
How can OPCPA generate extremely high peak powers?
By stretching the pulses, the peak intensity during amplification is kept below the damage threshold of the optics, allowing for much higher pulse energies. Combined with low thermal effects and the availability of large-aperture nonlinear crystals, this allows scaling to terawatt and even petawatt peak powers.
What is a noncollinear optical parametric amplifier (NOPA)?
A NOPA is a specific type of optical parametric amplifier where the pump and signal beams are not parallel. This noncollinear geometry allows for very broad phase-matching bandwidth, making NOPAs ideal for amplifying pulses to few-cycle durations, often down to a few femtoseconds.
Suppliers
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Optical parametric chirped-pulse amplification (OPCPA) is currently the only laser technology that simultaneously provides the high peak and average power along with few-cycle pulse duration required by the most demanding scientific applications. Our portfolio of cutting edge OPCPA products is based on years of experience in developing and manufacturing optical parametric amplifiers and femtosecond lasers. The few-cycle, CEP-stable pulses come either in a compact table-top ORPHEUS-OPCPA or a large, TW-level OPCPA-HE, similar to SYLOS at ELI ALPS.
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TOPTICAâs FemtoFiber dichro midIR generates radiation at 3 Îźm â 15 Îźm. Based on difference frequency generation of two optically synchronized laser pulses at tunable wavelengths of 1 â 2 Îźm a highly stable broadband emission of approximately 400 cmâ1 is generated. Here, the output at 1560 nm of an erbium-doped ultrafast fiber laser is superimposed with the long or short wavelength part of a supercontinuum.
The CEO-free mid-IR laser pulses are applied to attosecond spectroscopy where the extreme UV pulses consist of only a few optical cycles. The conversion of mid-IR radiation to extreme UV is accomplished by high harmonic generation. First, the mid-IR pulses are subject to optical parametric chirped amplification (OPCPA). Then, the intense laser fields are launched into an atomic beam or a gas-filled hollow core fibre to generate extreme UV attosecond laser pulses via high harmonics.
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Class 5 Photonics delivers ultrafast, high-power laser technology at outstanding performance to advance demanding applications from bio-imaging to ultrafast material science and attosecond science. Our robust optical parametric chirped pulse amplifiers (OPCPA) provide high-power, tunable femtosecond pulses at user-friendly operation.
Features of the White Dwarf OPCPA 5 W:
- compact and user-friendly
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- pumped by Coherent Monaco industrial femtosecond laser
- high-performance, ultrafast OPCPA
- pump-probe configuration
- pumped by Yb-based laser up to 300 W and 3 mJ
- our award-winning flagship product
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- pumped by kW-class Yb:YAG Innoslab amplifiers or thin-disk lasers
Bibliography
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| [16] | L. J. Waxer et al., âHigh-energy petawatt capability for the Omega laserâ, Opt. Photon. News 16 (7), 30 (2005); doi:10.1364/OPN.16.7.000030 |
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| [18] | F. Ă. Ilday and F. X. Kärtner, âCavity-enhanced optical parametric chirped-pulse amplificationâ, Opt. Lett. 31 (5), 637 (2006); doi:10.1364/OL.31.000637 |
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| [21] | S. Adachi et al., â5-fs, multi-mJ, CEP-locked parametric chirped-pulse amplifier pumped by a 450-nm source at 1 kHzâ, Opt. Express 16 (19), 14341 (2008); doi:10.1364/OE.16.014341 |
| [22] | J. Rothhardt et al., âHigh average and peak power few-cycle laser pulses delivered by fiber pumped OPCPA systemâ, Opt. Express 18 (12), 12719 (2010); doi:10.1364/OE.18.012719 |
| [23] | C. Caucheteur et al., âExperimental demonstration of optical parametric chirped pulse amplification in optical fiberâ, Opt. Lett. 35 (11), 1786 (2010); doi:10.1364/OL.35.001786 |
| [24] | S. Witte and K. S. E. Eikema, âUltrafast optical parametric chirped-pulse amplificationâ, J. Sel. Top. Quantum Electron. 18 (1), 296 (2012); doi:10.1109/JSTQE.2011.2118370 |
| [25] | D. E. Rivas et al., âNext generation driver for attosecond and laser-plasma physicsâ, Nature Sci. Rep. 7, article 5224 (2017); doi:10.1038/s41598-017-05082-w |
| [26] | W. Fu and F. W. Wise, âNormal-dispersion fiber optical parametric chirped-pulse amplificationâ, Opt. Lett. 43 (21), 5331 (2018); doi:10.1364/OL.43.005331 |
| [27] | M. Kretschmar et al., âThin-disk laser-pumped OPCPA system delivering 4.4 TW few-cycle pulsesâ, Opt. Express 28 (23), 34574 (2020); doi:10.1364/OE.404077 |
| [28] | L. Xu and E. J. Takahashi, âDual-chirped optical parametric amplification of high-energy single-cycle laser pulsesâ, Nature Photonics 18, 99 (2024); doi:10.1038/s41566-023-01331-9 |
(Suggest additional literature!)
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