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Ultrafast Amplifiers

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Definition: amplifiers for ultrashort optical pulses

German: Ultrakurzpulsverstärker

Categories: optical amplifiers, light pulses

How to cite the article; suggest additional literature

Ultrafast amplifiers are optical amplifiers which are applied to ultrashort pulses. Some of these devices are used for amplifying high repetition rate pulse trains, leading to a high average power whereas the pulse energy remains moderate. In other cases, a much higher gain is applied to pulses at lower repetition rates, leading to high pulse energies and correspondingly huge peak powers. Enormously high optical intensities, sometimes above 1016 W/cm2, are achieved by focusing such intense pulses tightly on some target.

As an example, consider the output of some mode-locked laser, consisting of 100-fs pulses with a repetition rate of 100 MHz and an average power of 0.1 W. The pulse energy is then 0.1 W / 100 MHz = 1 nJ, and the peak power is somewhat below 10 kW (depending on the pulse shape). A high-power amplifier, applied to the full pulse repetition rate, may raise the average power to 10 W, thus increasing the pulse energy to 100 nJ. In addition, a pulse picker before the amplifier may be used to reduce the pulse repetition rate to 1 kHz. If the high-power amplifier can still raise the average power to 10 W, the pulse energy is now 10 mJ, and the peak power nearly 100 GW.

Special Requirements for Ultrafast Amplifiers

Beyond the general technical issues of optical amplifiers, ultrafast devices meet a number of additional challenges:

Examples of Possible Performance Figures

The requirements on ultrafast amplifiers in terms of pulse energy, pulse duration, repetition rate, mean wavelength, etc., are very diverse. Correspondingly, very different types of devices are used. The following list gives some typical examples of the performance reached by different types of systems:

The performance figures of commercial ultrafast amplifier systems often greatly lag behind the best performance values achieved in scientific experiments. In many cases, a main reason is that experimental systems rely on techniques or components which cannot be used in commercial devices due to a lack of stability and robustness. For example, complex fiber-based systems have been demonstrated which contain multiple transitions between fibers and free-space optics. All-fiber amplifier systems can be made, but these do not reach the performance levels of systems containing bulk-optical elements. In other cases, optical components are operated close to their damage threshold; for commercial devices, a larger safety margin is required. Another problem can be the use of very special parts, which are difficult to procure.

Applications

Ultrafast amplifiers find diverse applications:

Industrial applications are often made difficult by the complexity and cost of ultrafast amplifier systems, sometimes also by a lack of robustness. Further technological progress may improve the situation.

Bibliography

[1]M. D. Perry et al., “Petawatt laser pulses”, Opt. Lett. 24 (3), 160 (1999)
[2]J. Limpert et al., “High-power ultrafast fiber laser systems”, IEEE J. Sel. Top. Quantum Electron. 12 (2), 233 (2006)
[3]F. Salin, “Ultrafast solid-state amplifiers”, in Ultrafast Lasers: Technology and Applications (eds. M. Fermann, A. Galvanauskas, G. Sucha), Marcel Dekker, New York (2002), Chapter 2, p. 61–88
[4]A. Galvanauskas, “Ultrashort-pulse fiber amplifiers”, in Ultrafast Lasers: Technology and Applications (eds. M. Fermann, A. Galvanauskas, G. Sucha), Marcel Dekker, New York (2002), Chapter 4, p. 155–218
[5]G. Cerulla and C. Manzoni, “Solid-state ultrafast optical parametric amplifiers”, in Solid-State Lasers and Applications (ed. A. Sennaroglu), CRC Press, Boca Raton (2007), Chapter 11, pp. 437–472
[6]R. Paschotta, tutorial on "Fiber Amplifiers", part 8 on ultrafast amplifiers
[7]R. Paschotta, tutorial on "Modeling of Fiber Amplifiers and Lasers"

(Suggest additional literature!)

See also: amplifiers, multipass amplifiers, regenerative amplifiers, chirped-pulse amplification, divided-pulse amplification, ultrafast lasers, Spotlight article 2008-06-20
and other articles in the categories optical amplifiers, light pulses

In the RP Photonics Buyer's Guide, 25 suppliers for ultrafast amplifiers are listed.

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