ABSTRACT
We investigate high harmonics generated from rubidium atoms irradiated simultaneously by an intense 3.5 microm fundamental field and a weak cw diode laser. When 5p, 5d, and 4d excited states are populated through cascade excitation or deexcitation, orders-of-magnitude increases in harmonic yield as compared with the ground state are observed. It appears that, quite unexpectedly, the population accumulated in the 4d state alone is responsible for the observed enhancement.
ABSTRACT
We show in theory and simulation that the supercontinuum generation from an initial continuous wave field in a highly nonlinear fiber operating near the zero-dispersion point can be significantly enhanced with the aid of dispersion management. We characterize the spectral broaden-ing as a process initiated by modulational instability, but driven by the zero-dispersion dynamics of an N-soliton interacting with the asymmetric phase profile generated by the Raman effect, self-steepening effect, and/or higher-order dispersion. Higher N-soliton values lead to shorter pulses and a broader spectrum. This insight allows us to use dispersion management in conjunction with modulational instability to effectively increase the N value and greatly enhance the supercontiuum generation process.
ABSTRACT
We demonstrate that high-order harmonics generated by short, intense laser pulses in gases provide an interesting radiation source for extreme ultraviolet interferometry, since they are tunable, coherent, of short pulse duration, and simple to manipulate. Harmonics from the 9th to the 15th are used to measure the thickness of an aluminum layer. The 11th harmonic is used to determine the spatial distribution of the electron density of a plasma produced by a 300-ps laser. Electronic densities higher than 2-10(20)electrons/cm>(3) are measured.
