Possibility of using self-focusing for increasing contrast and narrowing of ultrashort light pulses

An investigation is made of the influence of self-focusing on the shape of ultrashort light pulses passing through a stable two-component medium containing an inhomogeneous screen inside the resonator. In this system, the radiation losses decrease with increasing radius of the beam on the screen. It is shown that instantaneous self-focusing increases the contrast and produces a narrow peak at the maximum of an ultrashort pulse.