Method for making thin crystalline or polycrystalline layers. The method includes electrochemically etching a crystalline silicon template to form a porous double layer thereon, the double layer including a highly porous deeper layer and a less porous shallower layer. The shallower layer is irradiated with a short laser pulse selected to recrystallize the shallower layer resulting in a crystalline layer. Silicon is deposited on the recrystallized shallower layer and the silicon is irradiated with a short laser pulse selected to crystalize the silicon leaving a layer of crystallized silicon on the template. Thereafter, the layer of crystallized silicon is separated from the template. The process of the invention can be used to make optoelectronic devices.