Femtosecond kinetics of reflection of mirrors with saturable absorption

Abstract

The kinetics of mirrors with saturable absorption is investigated by a pump-probe singlefrequency technique in reflection of femtosecond pulse radiation with the central wavelength of 1040 nm. The double modulation method with probe radiation detection at the summary frequency allows suppressing the scattered pump radiation contribution and reaching the reflection change sensitivity at a level of 10⁻⁵. The kinetics of recovery of the linear reflectivity of the mirror including resonant quantum wells with nanostructured barriers is studied for the surface density of photons in pump pulses of (0.3–5.8) · 10¹⁴ cm⁻². The time of electron-hole recombination (7.8 ps) is found to be appreciably shorter than in samples with quantum wells separated by thick barriers; the time of ionization of excitons localized in quantum wells (0.2–0.4 ps) increases with the pump intensity.