Genetic algorithm optimization of grating coupled near-field interference lithography systems at extreme numerical apertures

Grating coupled near-field interference lithography has the ability to produce deep-subwavelength interference patterns. Simulations of these systems is very computationally intensive. An inverse design procedure employing a genetic algorithm is utilized here to massively reduce the computational load and allow for the design of systems capable of interfering extremely high numerical apertures. This method is used to optimize systems with an interference patterns with a half pitch of $\lambda /40$ corresponding to a numerical aperture of 20. It is also used to demonstrate interference of higher $|m|$ diffraction orders. (paper)