Laser direct writing technique is employed to fabricate microstructures, including gratings (buried and surface) and two-dimensional photonic crystal-like structures, in bulk poly(methylmethacrylate) (PMMA) and poly(dimethylsiloxane) (PDMS) using $\sim 100$ femtosecond (fs) pulses. The variation of structure size with different writing conditions (focussing, speed and energy) was investigated in detail. Diffraction efficiencies of the gratings were calculated and the changes in diffraction efficiency (DE) as a function of period, energy and scanning speed were evaluated. Highest diffraction efficiencies of 34% and 10%, for the first order, were obtained in PMMA and PDMS respectively. Heat treatment of these gratings demonstrated small improvement in the diffraction efficiency. Several applications resulting from these structures are discussed. Fs modification in PMMA and PDMS demonstrated emission when excited at a wavelength of 514 nm. We attempted to prepare buried waveguides in PMMA with higher refractive index at the core. We have successfully fabricated branched and curved structures in PMMA and PDMS finding impending applications in microfluidics.
Volume 94, 2020
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