Strong [ital K][alpha] emission in picosecond laser-plasma interactions

[ital K][alpha] emission is observed from the interaction of a picosecond, 1.05 [mu]m laser pulse at 4[times]10[sup 15] W/cm[sup 2] with a silicon target coated with various thicknesses of aluminum. Strong [ital K][alpha] emission requires a [ital p]-polarized, high-intensity-contrast laser pulse. At 7.1 A, the [ital K][alpha] yield is 1.5[times]10[sup 8] photons/sr with a duration of emission of [le]8 ps and a source area of 1.6[times]10[sup [minus]6] cm[sup 2]. The radiance is [ge]3[times]10[sup 9] W/cm[sup 2] sr. Monte Carlo simulations have suggested that under these conditions [ital K][alpha] emission is a promising candidate for an efficient, ultra-short-duration x-ray source at [similar to]1.5 A.