Laser optics for a {gamma}-{gamma} collider

The constraints on an optical system to convert the electron beams to {gamma}-ray beams for a {gamma}-{gamma} collider are considered. We show that the range of possible designs is limited by the requirement of near head-on collisions and present a design which achieves two passes of the laser pulse with arbitrary control of the polarization. For certain polarization combinations, four passes appear possible. 16 refs., 7 figs., 6 tabs.