Yield and temporal characterization of high-order harmonics from intense midinfrared excitation of a cesium vapor
Cesium vapor produced high harmonic radiation in the visible/UV spectral range when interacting with a tightly focused, intense midinfrared source. It was found that the measured yields of harmonic orders 9-17 yielded quantitative agreement with numerical simulations. Using an autocorrelation method, the 5th-9th harmonic orders were generated with sufficient pulse energies for direct temporal measurements. The cause of the spectral broadening was found to be a blueshift connected to a strong time-dependent ionization.