A simple and convenient means of fabricating concave microlens arrays direct on silica glass by using the local fictive temperature modification of fused silica is presented. This method is based on the fact that an increased fictive temperature results in a much higher HF acid etching rate of fused silica. Combining the abrupt local fictive temperature enhancement by the CO laser pulse and the subsequent etching by the HF acid solution, concave microlens arrays with high fill factors, excellent smoothness, and optical performance are generated on fused silica.
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