A system uses a femtosecond laser beam to polish a surface of an optical element to optical smoothness. The system includes a fixture, a laser system, and a controller. The fixture holds the optical element. The laser system generates the femtosecond laser beam. The femtosecond laser beam includes converging laser pulses with a pulse duration less than 900 femtoseconds. The controller controls relative positioning of the surface of the optical element and the femtosecond laser beam so that a waist of the femtosecond laser beam is outside the optical element and 0.5-2.0 Rayleigh ranges away from the surface of the optical element. Also, an intensity of the femtosecond laser beam at the surface of the optical element is sufficient to ablate the surface.