The process of light-induced crystallization (LIC) of nanometer-thick amorphous silicon (a-Si) layers in Si / SiO ₂ multiquantum wells (MQW) was investigated using Raman spectroscopy. In the present investigations, a laser was employed as the light source. An analysis of obtained and previously published results suggests strong influence of radiation wavelength on the outcome of the process. Namely, for certain ranges of wavelengths and radiation fluxes the crystallization proceeds through the light-induced solid phase crystallization (LISPC) process. An optimal set of radiation wavelength and flux values allows formation of fully crystallized and almost strain-free layers of nanocrystalline silicon (Si-nc). The difference in the absorption coefficients between a-Si and Si-nc was considered responsible for the obtained results. A mechanism explaining the wavelength and the radiation flux dependence was proposed. Understanding of the mechanism of LISPC in MQW structures would allow improving the LIC processes for thin silicon films.