Comparative analysis of direct laser writing and nanoimprint lithography for fabrication of optical phase elements

We report a comparison between two commercially available methods for printing phase shaping optical microstructures. Phase elements that convert a zero-order Hermite-Gaussian (HG₀₀) mode into higher-order modes (HG₁₀, HG₀₁, HG₂₀, and HG₀₂) were fabricated by 3D-direct laser writing (3D-DLW) and nanoimprint lithography (NIL). The structures in each method were characterized and the corresponding beam qualities were analyzed. The direct comparison of equivalent optical devices enables us to reveal the limitations and advantages of the two fabrication methods in order to optimize the fabrication of useful optical microstructure devices. 3D-DLW enables sharper edges and a straightforward lithography process, while NIL enables fabrication of thinner elements, and allows using a larger variety of optical materials including sol-gel glasses, which possess better surface optical quality.