Pulsed-laser induced shock wave development in fused silica is analyzed using nonlinear wave mechanics and applied to thin-film spallation experiments. Due to the negative nonlinear elasticity of fused silica, a laser-induced Gaussian stress pulse evolves into a shock after travelling a certain distance in a fused silica substrate. Experimental observations confirm theoretical predictions of shock development. A decompression shock forms and greatly enhances interfacial failure of a thin film deposited on the substrate. The effectiveness of this wave mechanism is further demonstrated by the successful application in testing ultra-thin low dielectric film/Si substrate interfaces.