@article{5530, author = {J. Burghoorn and V. F. Anderegg and T. O. Klaassen and W. T. Wenckebach and R. J. Bakker and A. F. G. van der Meer and D. Oepts and P. W. van Amersfoort}, title = {Free-Electron Laser-Induced 2-Photon Absorption in Hg1-Xcdxte}, abstract = {The powerful output of FELIX, the recently built Rijnhuizen free-electron laser, is used for the first frequency dependent study of nonlinear optical excitation of Hg1-xCdxTe in the far-infrared spectral region. Two-photon interband absorption has been investigated as a function of power and wavelength from 20 to 40 mum. This nonlinear optical absorption is used to perform autocorrelation experiments yielding the length of the micropulses of the free-electron laser on a femtosecond time scale. The predicted dependence of the micropulse length on the synchronization between optical and electron pulses in the laser cavity is observed.}, year = {1992}, journal = {Applied Physics Letters}, volume = {61}, number = {19}, pages = {2320-2322}, month = {Nov 9}, isbn = {0003-6951}, doi = {10.1063/1.108230}, language = {eng}, }