1 July 1994 OPTICS COMMUNICATIONS s . __ M $1 4 ._ ELSEVIEK Optics Communications 109 ( 1994) 288-295 A 1 TW KrF laser using chirped pulse amplification I.N. Ross, A.R. Damerell, E.J. Divall, J. Evans, G.J. Hirst, C.J. Hooker, J.R. Houliston, M.H. Key, J.M.D. Lister, K. Osvay, M.J. Shaw Central Laser Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OXI 1 OQX, UK Received 22 December 1993 Chirped pulse amplification (CPA) and recompression have been used in a large aperture KrF laser system. The power fo- cused onto target in a 300 fs pulse reached 1 TW with an irradiance of - lOI W/cm*. 1. Introduction Much progress has been made recently in the de- velopment and applications of high power ultrashort pulse lasers using chirped pulse amplification (CPA) [ 11. Most effort has been invested in solid state sys- tems [2-71 yielding powers up to 50 TW in pulse lengths down to 500 fs and focused intensities on tar- get approaching 1OL9 W/cm2 at wavelengths in the range 0.8-l. 1 pm. Excimer lasers have potential for higher intensity and shorter pulse by virtue of their ultraviolet wavelength, large bandwidth and good beam quality. CPA and recompression using the fre- quency chirp introduced by self-phase modulation (SPM) and group velocity dispersion (GVD) have been demonstrated [ 8,9 1. Preliminary studies have been made of a full grating stretcher - grating com- pressor CPA system for KrF [ 10 ] to demonstrate the feasibility of this approach and we now report a dem- onstration on a large KrF system. performance for short pulses shown in Fig. 1. As a result of the power limit due to nonlinear effects the saturated energy limit (2 J) can only be achieved for pulses longer than N 10 ps. Consequently a CPA sys- tem can access the full stored energy if the pulse is stretched to at least 10 ps. It can then be recom- pressed to N 100 fs (limited by the gain bandwidth), thus providing a power capability of 14 TW taking into account a loss of 70% in the grating compressor. Such a system, if operating at the diffraction limit, would give a radiance ( = zyxwvutsrqponmlkjihgfedcba P/A2 [ 121) or 1.6X 10” W/cm2 ster and an intensity at the focus of an F/4 optic of 0.8 x 102’ W/cm’. Even allowing for a beam divergence larger than the diffraction limit, the po- tential to achieve high focused intensities was a con- siderable incentive for setting up a CPA system on SPRITE. 3. Design consideration 3.1. Stretcher- compressor design 2. Chirped pulse amplification applied to a KrF laser This laser is based on a 27 cm aperture e-beam pumped KrF amplified SPRITE [ 111 which has a Single pass grating arrangements (Fig. 2 ) were used for both stretcher (folded geometry) and compressor using 3600 lines per mm gratings operating close to 0030-4018/94/$07.00 0 1994 Elsevier Science B.V. All rights reserved SsDIOO30-4018(94)00181-S