Infrared Free-Electron Laser Measurement of the Photon Drag Effect in P-Silicon

We report the use of FELIX (free electron laser for infrared experiments) to study photon drag in p-silicon over the wavelength range 25-80-mu-m. Previous 'spot' measurements using a pulsed water vapour laser had indicated high response at 28 and 33-mu-m associated with transitions within the valence band. These earlier results have been confirmed and the main futures of the extended photon drag spectrum are also explainable by reference to the valence band structure. A practical outcome of the experiment is the design of a subnanosecond response time detector to observe the 1GHz frequency micropulse output from FELIX.