Abstract
Femtosecond transient laser-induced grating (LIG) experiments were performed in planar optical waveguides made of luminescent silicon quantum dots. The LIG was created by interference of two pulses from the frequency-doubled output of a Ti–sapphire laser (400 nm, 400 fs, 1 kHz). The LIG exhibits an extremely fast decay in time (several picoseconds) that was found to decrease with decreasing grating period. The standard models based on lateral carrier diffusion cannot explain this observation (this procedure yields an unrealistically high diffusion constant of 420 cm2 s−1). Instead, the results are explained by exciton diffusion and/or enhanced exciton radiative decay rate in a cavity represented by the periodically modulated planar waveguide (Purcell effect).
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