Very short far‐infrared (FIR) pulses have been generated by cavity dumping an optically pumped molecular gas laser using optical switching techniques. The active element used is an intracavity semiconductor, which is placed under the Brewster angle with respect to the optical axes. This element is made highly reflective by the sudden increase of the free‐carrier concentration, induced by above band‐gap illumination. In this way high power (∝1 kW) FIR pulses with a duration less than 10 ns can be produced.