Chirped Pulse Amplification

Authored by: Donna Strickland

Handbook of Laser Technology and Applications

Print publication date:  June  2021
Online publication date:  June  2021

Print ISBN: 9781138032613
eBook ISBN: 9781315389561
Adobe ISBN:

10.1201/b21828-22

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Abstract

With the advent of the laser, optical waves were powerful enough for the first time to cause non-linear interactions with media [1]. Since then, the pursuit for higher power lasers has continued unabated. Non-linear interactions respond to instantaneous power rather than average power. For laser pulses, the peak instantaneous power is defined as the pulse energy over the pulse duration and so can be increased in one of two ways, increasing the energy or decreasing the pulse duration. Increasing the energy requires further amplification stages, which are necessarily larger to handle the higher energy. On the other hand, reducing the pulse duration is done at the oscillator stage and so the amplification system remains the same size. In the 1980s when Chirped Pulse Amplification (CPA) was invented, mode-locked dye lasers had achieved the shortest pulse durations of ~100 fs at wavelengths of ~600 nm [2]. Dye lasers though are low-storage-energy lasers and so could not achieve high peak powers. The high-energy lasers were solid-state lasers, typically Nd:glass used for laser fusion, at wavelengths of ~1060 nm and 10 kJ energy levels had been achieved [3]. The wavelengths were incompatible, but that was not the only reason that short pulses were not amplified in the large energy amplifiers. If a short pulse is amplified up to high energy in a solid-state laser, the peak power is sufficient for non-linear optics to occur in the lasing medium and cause self-focusing, where the beam collapses on itself [3]. The self-focusing causes damage to the laser rods, so high-energy amplification was limited to nanosecond long pulses.

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