A pulse stretcher includes a single pass pulse stretcher. An optical system is arranged around the single pass pulse stretcher. A beam enters the single pass stretcher and is reflected in a helical path using the optical system for multiple passes through the single pass pulse stretcher. The single pass pulse stretcher can include two 90.degree. prisms, with a beam splitter located therebetween. The optical system can include first and second prisms. At least one of the first and second prisms can be a roof prism. The first and second prisms can have at least one surface oriented so as to direct the beam into the helical path. The optical system can have at least one mirror, or a plurality of mirrors.