We propose an all-optical limiter based on the thermally induced intervalley transfer of electrons from&Ggr;-valley states with forbidden normal-incidence intersubband interactions to L-valley states which absorb strongly. Detailed modeling of the device performance in the short-pulse regime(⩽100ns) yields that the output intensity for a limiter with only 10&percent; insertion loss at low excitation levels will remain clamped over a dynamic range of 25–40.