A method is developed to fabricate large areas of microlens arrays on flexible substrates of polycarbonate sheets via maskless laser interference patterning. A frequency quadrupled nanosecond pulsed Nd:YAG laser with 266nm wavelength is used to generate two-beam interference patterns. Crossed-grid periodical patterns are fabricated through double exposure by turning the sample 90 degrees between exposures. The microlens array period is adjustable from submicron to many microns by changing the interference angles. From Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM) measurements, representative 3.2µm, 2.4µm, and 900nm diameter microlens arrays are obtained on the modified area spanning one square centimetre. Optical property tests show that the microlens array can be used for imaging. Although the experimental results are demonstrated on polycarbonate substrates, the method can be applied to other materials which are suitable for deep-UV laser ablation. The experimental results suggest that our method has the potential for fast and low-cost production of microlens arrays on flexible polymer substrates.

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