The intensity‐dependent rotation of elliptically polarized light by carbon disulfide is used to discriminate against low‐intensity laser light and pass high‐intensity pulses through crossed polarizers. The transmitted intensity is shown to be proportional to the third power of the incident intensity. This technique has been used to reduce base‐line noise and low‐intensity pulses in the output pulse train of a mode‐locked Nd : YAG oscillator.