Tunable femtosecond radiation in the mid-infrared for time- resolved absorption in semiconductors.

We describe the generation of 350 fs pulses tunable between 2.3 and 5.5microns by seeded optical parametric amplification. These pulses are synchronized with visible pulses for time- resolved absorption and reflectivity in semiconductors with 500 fs resolution. Applications to plasma resonance in Ge and to photogenerated charged soliton dynamics in trans-polyacetylene are presented.