Particle-in-cell simulations of relativistically strong laser pulses
interacting with overdense plasma targets predict that coherent motion
of electrons leads to the efficient generation of strong attosecond
electromagnetic pulses and dense attosecond electron bunches. The
optimal conditions for these attosecond phenomena are achieved, when
few-cycle laser pulses are focused to a wavelength-limited spot,
producing maximal intensity and maximal gradients with a given energy.
The natural synchronism of these attosecond phenomena should enable a
kind of relativistic attosecond optoelectronics.