Chirped pulse amplification (CPA) is a technique used in laser physics to amplify ultrashort laser pulses to high energies without causing damage to the amplifying medium. The method was first proposed by Gérard Mourou and Donna Strickland in the mid-1980s and has since become a fundamental technology in the field of high-intensity laser systems.
The basic idea behind chirped-pulse amplification involves stretching the duration of a short laser pulse temporally (chirping) before it enters the amplification stage. This elongated pulse is then amplified to higher energy levels without damaging the amplifying medium. After amplification, the amplified pulse is compressed back to its original short duration.
The key steps in chirped-pulse amplification are as follows:
Stretching: The initial ultrashort pulse is temporally stretched using dispersive elements, such as diffraction gratings or prisms. This stretching increases the pulse duration while keeping the total energy constant.
Amplification: The stretched pulse is then amplified in a laser amplifier. Since the pulse has been temporally stretched, the intensity of the pulse in the amplification medium is reduced, preventing damage to the medium.
Compression: After amplification, the pulse is compressed back to its original short duration using the inverse process of the initial stretching. This is typically achieved with additional dispersive elements that compensate for the temporal stretching.
The main advantage of CPA is that it allows for the amplification of high-energy ultrashort pulses without causing damage to the amplifying medium. This has been crucial in the development of high-intensity laser systems, enabling the generation of extremely powerful laser pulses used in various scientific and industrial applications, including laser fusion research, particle acceleration, and the study of ultrafast phenomena in physics and chemistry.