beam guiding devices for guiding a laser beam , in particular in a direction towards a target region for producing extreme ultraviolet radiation , include an adjustment device for adjusting a beam diameter and an aperture angle of the laser beam . the adjustment device includes a first mirror having a first curved reflecting surface , a second mirror having a second curved reflecting surface , a third mirror having a third curved reflecting surface , a fourth mirror having a fourth curved reflecting surface , and a movement device configured to adjust the beam diameter and the aperture angle of the laser beam by moving the first reflecting surface and the fourth reflecting surface relative to one another and , independently thereof , moving the second reflecting surface and the third reflecting surface together relative to the first reflecting surface and the fourth reflecting surface .