aInstitute of Ion-Beam Physics and Materials Research, Forschungszentrum Dresden Rossendorf, P.O. Box 510119, 01314 Dresden, Germany
bFraunhofer-Institute for Applied Solid State Physics, Tullastrasse 72, D-79108 Freiburg, Germany
Abstract:
The two-photon QWIP comprises three equidistant subbands, namely two bound states localized in the quantum well and an extended state in the continuum. This device is very promising for quadratic autocorrelation measurements of pulsed mid-infrared lasers due to its resonantly enhanced optical nonlinearity and sub-ps time resolution. We report on interferometric autocorrelation measurements of ps optical pulses from a free-electron laser (FEL). The intense FEL radiation further allows us to study the saturation properties of two-photon QWIPs at liquid nitrogen temperature and their detection properties at 300 K. The device is well suited for standard diagnostics of the FEL pulse shape via interferometric autocorrelation.