Microfabrication of UV-transparent fluoropolymer using high-repetition femtosecond oscillator

Surface microfabrication of a UV-transparent fluoropolymer (CYTOP) was achieved using direct laser ablation with a femtosecond (fs) oscillator. The commercially available CYTOP is highly transparent and has a low refractive index comparable to that of water. Therefore, this polymer is a candidate biochip material for application in the field of tissue engineering. We have previously developed techniques for microfabrication of CYTOP using nanosecond and amplified fs laser ablation, both followed by wet etching and annealing. However, these techniques were not suitable for some industrial applications due to the generation of debris and cracks around the ablated areas, which called for prolonged etching during the fabrication process. To overcome these problems, we have attempted to directly ablate the surface of a CYTOP substrate using a high-repetition fs oscillator and compared the results with fabrication using an amplified fs laser at a low repetition rate. Consequently, ablation with the fs oscillator resulted in high-quality surface microfabrication of the CYTOP substrate. The fundamental characteristics of CYTOP microfabrication using the fs oscillator were investigated. We also demonstrate the fabrication of a transmission diffraction grating on CYTOP using the fs oscillator, and measure the diffraction efficiency of the grating using a 632 nm He–Ne laser.