A desirable feature of optical data storage processes is that they provide high contrast between the image and background. Thermal marking techniques are inherently advantageous in this regard, because of the nonlinearity of the response, A thermal method for lithography on polymer films has been developed based on selective exposure of the films to infrared laser radiation passing through a mask, Radiation induced crystallization, melting and ablation have been demonstrated with the processes prevailing at different levels of radiation intensity, These methods are capable of producing high resolution images with excellent edge acuity and minimal Interference from diffraction. The absence of diffraction effects is due to the nonlinear response of the polymer film to the radiation. The best resolution obtained to date (submicron) is limited by the size of the smallest features present on the masks used to create the pattern. The ultimate resolution achievable by these methods is presently unknown.