Micrograting Polymerization Fabrication with a Single Femtosecond Laser Pulse at 400 nm Wavelength

High diffraction efficiency refractive index-modulated holographic micrograting on a polymer thin film was obtained with a single femtosecond laser pulse interference and photo-polymerization. The diffractive efficiency of the micrograting with an He-Ne laser is up to 78% when the thickness of the film is 90μm, which corresponds to the refractive index-modulation as large as 2.4 x 10^-3. The compared experiment with a femtosecond oscillator laser indicated that a single femtosecond laser pulse has the advantages in laser machining over the cw holography method such as high fabrication speed, good surface structure and high diffractive efficiency.