Abstract
We have used a novel type of nanos true lured metallic surface as a target for high-intensity laser interaction. The new metallic or semiconductor target structure is electro chemically produced on arbitrary surface shapes and sizes.1 The infrared to x-ray conversion efficiencies from the interaction of an intense I-ps laser pulse with this nanowire structure are factors of 4 and 50 times greater than for comparable flat targets in the spectral ranges around 125 eV and above 1 keV, respectively. X-ray conversion efficiencies front the nanowire target and from previously investigated grating and ‘smoke’ targets1 are compared with that of flat targets for various angle of incidence and polarization of the TW laser pulse (Fig. 1). Streak cam era results show that a bright picosecond x-ray pulse is emitted from the near-solid density plasma created from the nano wire target. The measured x-ray pulse length is resolution limited (≤5 ps) for emission above 1keV (Fig. 2), and is 20–25 ps for the XUV radiation regime. A model that uses an “effective” dielectric constant describes the nanowire target as an absorbing uniaxial material. This is used to optimize the structure parameters for: (1) minimum Fresnel losses on the vacuum-structured target interface (Fig. 3); and (2) highest light absorption in the structured layer in the small-signal regime. Closure of the nanowite structure is not expected during the first part of the picosecond laser pulse. An extension of the effective- dielectric model for the plasma absorption regime is discussed.
© 1997 Optical Society of America
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