The photoluminescence decay of GaAs/AlGaAs quantum wells was successfully measured at room temperature by using 660‐nm picosecond light pulses from an AlGaInP diode laser driven by short pulse current. Our experimental results reveal that picosecond light pulses from visible diode lasers may be widely applicable, in place of mode‐locked gas, solid‐state, or dye lasers, for studying the fast carrier recombination properties of many kinds of materials including GaAs and AlGaAs in the wavelength region of deep red to infrared.