Azodye-doped Polymethylmethacrylate Research Articles

Effects of writing conditions on the photoinduced birefringence in azodye-doped polymers by a femtosecond laser

Birefringence in azodye-doped polymethylmethacrylate (PMMA) and azodye-doped inorganic–organic hybrid silica was induced by multiphoton excitation of a femtosecond laser. Comparing the growth kinetics of the photoinduced birefringence (PB) in the two matrixes, we concluded the mechanisms of photoinduced anisotropy were different and azodye-PMMA was much better for applications in optical storage. We also found that the growth rate and saturation value of the PB in azodye-PMMA were dominated by either peak or average power of the laser, strongly depended on writing conditions. An optimal control of the PB by varying writing conditions was indispensable to fully realize optical storage.

Multiphoton-induced periodic microstructures inside bulk azodye-doped polymers by multibeam laser interference

We report on multiphoton-induced periodic microstructures inside bulk polymers by multibeam interference of femtosecond laser pulses at a wavelength of 800 nm, which is out of the linear absorption range of the polymer sample. Two-dimensional structures and three-dimensional periodic microstructures were fabricated inside bulk azodye-doped polymethylmethacrylate by four-beam interference and five-beam interference, respectively. The Raman spectra measurements for the photomodified area of the sample before and after irradiation with the writing light showed that the periodic microstructures probably arose from photoinduced decomposition reaction of azodye molecules through multiphoton absorption.

Phase-matched second-harmonic generation in bulk azodye-doped polymers by all-optical poling

We demonstrate phase-matched second-harmonic generation (SHG) in bulk azodye-doped polymethylmethacrylate using an all-optical poling technique. During the seeding process, samples were irradiated simultaneously by coherent superposition of the fundamental and the second-harmonic light of a nanosecond laser. The measurements for the dependence of SHG on the sample thickness show that the SHG signals increase with the increase in thickness of the samples, indicating that a χ(2) grating that satisfies the phase-matching condition for SHG could be optically induced in the polymer samples.

Photoinduced birefringence of azodye-doped materials by a femtosecond laser.

Birefringence in azodye-doped polymethylmethacrylate and azodye-doped silica hybrid materials was induced by the two-photon excitation of a femtosecond laser. The growth and the relaxation characteristics of the photoinduced birefringence in the two types of material were investigated, and the probe transmittance for the induced birefringence was estimated to be 92%. Furthermore, an optical image storage based on this photoinduced birefringence was demonstrated.

Photofabrication of periodic microstructures in azodye-doped polymers by interference of laser beams

Volume holographic gratings and two-dimensional periodic microstructures in azodye-doped polymethylmethacrylate were fabricated, respectively, by interference of two coherent beams of a femtosecond laser and by interference of three coherent beams of a nanosecond laser. The dependence of the first-order Bragg diffraction efficiency and the photoinduced refractive-index modulation of the gratings on the intensity of the writing light was investigated. The measurements of the absorption spectra before and after irradiation with the writing light suggest that the photoinduced gratings were refractive-index-modulated gratings, which arose from a photoinduced decomposition reaction of the azodye molecules through multiphoton absorption. In the experiments involving the interference of three beams, the period of the two-dimensional periodic microstructures was changed by adjusting the angle between the three writing beams.

Photoinduced permanent gratings inside bulk azodye-doped polymers by the coherent field of a femtosecond laser

Permanent holographic gratings were fabricated in bulk azodye-doped polymethylmethacrylate by the coherent field of a femtosecond laser. Optical microscopy and atomic force microscopy observations revealed that the gratings consist of two parts, surface relief gratings on both surfaces and refractive index modulated volume gratings in the interior of the polymers. The diffraction efficiency of the first-order Bragg for the gratings was estimated to be 90%.

Photoinduced phase-matched second-harmonic generation in azodye-doped polymer films

Phase-matched second-harmonic generation (SHG) in azodye-doped polymethylmethacrylate films was demonstrated using the nonresonant optical poling technique. During the seeding process, samples were irradiated simultaneously by coherent superposition of the fundamental and the second-harmonic light of a femtosecond laser. Optical poling experiments were performed at three wavelengths of 1500, 1320, and 1300 nm, respectively. The quadratic dependence of SHG on the film thickness showed that a χ(2) grating that satisfied the phase-matching condition for SHG was optically induced in the polymer films. The SHG conversion efficiency of a 105 μm thick film was estimated to be about 2%. A relaxation retardation effect of the photoinduced χ(2) was also observed in the thick films.