Pioneered at CUOS, the program of Relativistic Nonlinear Optics in the λ³ Regime (where optical pulse energy is focused to a volume of a few cubic wavelengths) has initiated research into new possibilities and applications of light at its extreme limit of concentration.

A very natural scheme for generation of isolated attosecond pulses was discovered. Based only on relativistic coherent motion of electrons, which deflect the incident laser pulse at each half-cycle into different directions and compress the radiation, this scheme gives the expectation of obtaining 10 % efficiency for attosecond pulse formation. In general, the short pulse formation occurs whenever relativistically strong laser pulses interact with near-critical or overcritical plasmas, but, more responsive plasmas act more efficiently. With the generation of these extremely short attosecond pulses, intensification can also occur.

Further studying the details of laser-plasma interaction in the λ³ regime, we have also discovered that attosecond electron bunches as well can be generated under similar conditions. These dense electron bunches can provide a path to near-unity conversion efficiency of the counter-propagating radiation to coherent x-rays.