Femtosecond laser written microstructures in PMMA and PDMS at 800 nm for photonic applications

Microstructures, including gratings and photonic crystal like structures, have been fabricated in bulk Poly(methyl methacrylate) [PMMA] and Polydimethylsiloxane [PDMS] using femtosecond pulses. The variation of structure width with different writing conditions (focusing, speed, energy) has been investigated. Physical characterization of the structures was performed using laser confocal and SEM techniques. Structural modifications at the focal volume have been investigated using micro-Raman, UV-visible, and Fluorescence spectroscopic techniques. Diffraction efficiencies of the gratings were calculated followed by the refractive index change in PDMS and PMMA. Highest diffraction efficiencies of 34% and 10%, for the first order, were observed in PMMA and PDMS respectively. Refractive index change of 10⁻³ and higher could be achieved. Fabrication of micro channels on the surface and within the bulk was also attempted. We present our results on the fabrication and characterization of these microstructures and microchannels. Several applications resulting from these structures are discussed.