Far-infrared streak camera [using Rydberg atom photocathode]

Summary form only given. The spectral range at which conventional streak camera systems operate is limited by the spectral response of the photocathode used. For most photocathode materials, the sensitivity is limited to wavelengths shorter than 1.5 /spl mu/m. Beyond this wavelength, the quantum efficiency of the photocathode becomes negligible. The temporal profile of mid- and far-infrared light pulses can thus not be measured directly using a conventional streak camera. We constructed an atomic streak camera in which the photocathode used in conventional streak cameras is replaced by a sample of gas phase Rydberg atoms for the conversion from photons to electrons. Due to the low binding energy of the electrons of Rydberg atoms, the IR photon energy is already sufficient to photoionize the atoms and create electrons. The combination of a low ionization threshold with the high photoionization cross section makes a Rydberg atom photocathode very suitable for use in an IR streak camera.