A strong enhancement of two-photon absorption (TPA) has been demonstrated in a 30-period GaAs/AlAs multilayer with a GaAs halfwavelength (/2) cavity layer. In order to measure the time-resolved TPA signals, we successfully developed a selective etching process using an etch-stopper structure consisting of 5-nm-thick AlAs and 200-nm-thick Al 0:3 Ga 0:7 As double layers for removing the GaAs substrate. An analysis of the observed TPA results reveals that the average light intensity of the multilayer cavity is 41 times larger than that of a GaAs bulk sample. The obtained enhancement factor is in good agreement with the simulated value (45 times larger), which is determined from the simulated light intensity distribution by the conventional transfer matrix method.