Chirped pulse amplification CPA

Recent developments in ultrashort, high-peak-power laser systems, based on the chirped pulse amplification (CPA) technique, have opened up a new regime of laser-matter interactions [1,2]. The application of such laser pulses can currently yield laser peak intensities well above 1020 W cm 2 at high repetition rates [3]. One of the important features of such interactions is that the duration of the laser pulse is much shorter than the typical time scale of hydrodynamic plasma expansion, which allows isochoric heating of matter, i.e., the generation of hot plasmas at near-solid density [4], The heated region remains in this dense state for 1-2 ps before significant expansion occurs. 

This was first achieved by the Teramobile system [14]. The laser itself is based on the chirped pulse amplification (CPA) technique [33,34], with a Ti Sapphire oscillator and a Nd YAG pumped Ti Sapphire amplification chain. It provides 350 mJ pulses with 70 fs duration resulting in a peak power of 5 TW at a wavelength around 800 nm, with a repetition rate of 10 Hz. Its integration in the reduced space of the mobile laboratory required a particularly compact design (Fig. 14.6). The classical compressor set-up has been improved into a chirp generator to pre-compensate the group velocity dispersion (GVD) in air. Combined with an adjustable focus, this permits to... 

Chirped pulse amplification (CPA) [1,2] is a new technique to achieve extremely high optical intensities in compact laser systems. The basic idea, which has its counterpart in radar technology, is illustrated in Fig. 1 [3]. An initial, short pulse... 

A commercial chirped pulse amplification (CPA) Ti sapphire laser system (Spectra Physics, Spitfire), providing linearly polarized pulses with pulse duration of 120 fs and at a wavelength of = 800 nm, was used for irradiation. The laser pulse energy was measured by means of a pyroelectric detector (Ophir, PE-9). In the fs-irradiation set-up, the sample was placed at 36° of the normal incidence in the focal plane of a 15 cm lens resulting in an elliptical laser spot on the surface. The samples were irradiated at two laser fluences (2.6 and 5.6 J/cm ) with different number of pulses (1-50 pulses)... 

FIGURE 13 Schematic of a typical chirped pulse amplification (CPA) setup. 

The problem is overcome by using a technique called chirped pulse amplification (CPA). The initial femtosecond pulse is stretched in time using temporal dispersion to advantage. This is followed by amplification of apulse, now with much longer pulse duration (and accordingly lower peak fluence). Subsequently, the pulse is recompressed to its original pulse duration (see Figure 4.15). 

Fig. 11.36. (a) Schematic diagram of chirped pulse amplification (CPA) (b) P sign of pulse stretcher with a grating pair [11.95]... 

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