The amorphous to polycrystalline transition in thin silicon layers is accompanied by a large change in optical transmission in the visible. By inducing this transition by laser annealing, high‐resolution optical recording and visible‐light readout have been demonstrated. As an optical recording material, amorphous silicon layers offer characteristics of high information‐storage density, long‐term stability, and negligible degradation upon repeated readout. Such an optical image in a thin silicon layer can be converted to a relief pattern by taking advantage of the difference in etch rate between amorphous and polycrystalline silicon, thus providing a method of producing patterns in silicon layers without use of intermediate photo‐resist steps.