Nonlinear and short pulse effects

Authored by: Günter Steinmeyer

Handbook of Optoelectronics

Print publication date:  October  2017
Online publication date:  October  2017

Print ISBN: 9781482241785
eBook ISBN: 9781315157009
Adobe ISBN:

10.1201/9781315157009-9

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Abstract

The science and technology of ultrafast pulses has, in recent years, come of age, becoming ever more important in the real world. In the early days of lasers, efforts concentrated on getting lasers to operate as continuous light sources. Compared to conventional light sources, continuous-wave (cw) lasers perfectly concentrate light in the plane transverse to the propagation direction, which gives rise to the extreme high brightness of laser beams. Nevertheless, a continuous laser ignores the third dimension along the propagation direction for further possible concentration of energy. Using mode-locking, the light field circulating through a mode-locked laser can be temporally focused within one millionth of the total cavity length, which translates to a pulse duration of a few femtoseconds compared to a total cavity roundtrip time of several nanoseconds. The peak power, even in an oscillator pulse, readily reaches hundreds of kilowatts. Employing the method of chirped-pulse amplification, one can easily generate pulses with multiple gigawatt peak power, which exceeds the continuous capabilities of several nuclear power plants for the duration of a few femtoseconds. The advantages of having lasers operating with very short pulses are currently being realized more and more in both industry and science. An ultrashort pulse can process material surfaces by action of its extreme electric field strength without causing internal heating or melting. This nonthermal interaction may be applied to ablate material for analysis or to create gaseous phases as desired. In spectroscopy, very short pulses can be used to investigate very fast chemical reactions or trigger fast photochemical reactions and observe features that would be impossible to observe using slower processes, leading to far greater understanding of the science and technology involved. This enables the interim states of such reactions to be observed, whereas previously only the starting materials and end products would be apparent. To make use of this, it is necessary to be able to generate ultrashort pulses and also to be able to measure the pulses that have been created. This chapter describes the science and technology in this rapidly developing field.

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