A new ripple formation mechanism is observed in excimer-laser irradiated polycrystalline silicon (polysilicon) films on oxidized silicon wafers. The ripples form for polysilicon films capped with a thin oxide, and for laser fluences that completely melt the buried polysilicon. The resulting ripples are unlike those previously reported in that (1) their wavelength cannot be predicted by Rayleigh’s diffraction condition, (2) their wave fronts are arranged in chaotic patterns, rather than parallel lines, and (3) the wave fronts can be manipulated by changing the polysilicon surface topology. The characteristics of these ripples are investigated in the context of understanding the underlying physics. ©1997 American Institute of Physics.