Papers by Keyword: Two-Photon Absorption

Abstract: A laser-based experimental system was developed to investigate Single Event Burnout (SEB) in high-voltage silicon carbide (SiC) devices. By enabling transient measurements under high reverse-bias conditions, the setup emulates ion-induced charge generation with femtosecond laser pulses. Time-resolved waveforms and charge collection trends were obtained, showing consistency with previous heavy ion experiments. This confirms the system’s capability to reproduce SEB-relevant dynamics. Further improvements in spatial resolution and impedance matching are required for detailed analysis of internal charge transport mechanisms.

Abstract: Optical Beam Induced Current (OBIC) measurements are performed on 4H-SiC avalanche diodes with a very thin and a highly doped active region. A pulsed green laser, with a wavelength of 532 nm, illuminates a reverse biased diode leading to generate electron-hole pairs in the space charge region. Comparison between the 4H-SiC bandgap and the incident photon energy shows that single photon absorption process can be neglected and two-photon absorption process dominates in this case. Ionization rates are then extracted from multiplication curve in a high electric field range (3 to 5 MV.cm^–1). Results are in good agreement with previous ones obtained on the same diodes using single photon absorption process.

Abstract: Fundamentals of two-photon photopolymerization have been introduced and a 3D femtosecond laser micro-nanofabrication system has been built. In this paper, 3D CAD data model based on femtosecond laser micro-nanofabrication system have been also discussed. The 3D various sphere-rod photonic crystal structure mimicking real atom structures in electronic crystals have been fabricated.

Abstract: As one kind of organic photochromic optical storage material, fulgides are well-known for their thermally irreversibility. The two-photon absorption 3D optical storage technology is one of the hot research topics in the field of high-density information storage. Using optical image storage technology the recording and reading rates can be improved. In this paper, it’s found that in one kind of 3-indoly-benzylfulgimide/PMMA film, there exits two-photon absorption property. And depending on this property, the two-photon absorption photochromic optical image storage was realized in an indoly-benzylfulgimide/PMMA film. It is proved that the N-benzyl-1,3,4-trimethyl-2-(2-methyl-) indoly-fulgimide has potential application in the two-photon absorption 3D optical storage.

Abstract: Two new three-branched s-triazine derivatives with near-octupolar symmetry have been synthesized. In each of them, two branches have donor groups attaching to their ends, while the other one has none. Their photophysical characteristics, such as UV–vis spectra, fluorescence spectra and two-photon excited fluorescence spectra, are compared with their octuplar analogs in which all the three branches are ended by donor group. The little structural difference results in great decline of single-photon absorptivity and single-photon excited fluorescence, as well as the two-photon excitated fluorescence.

Abstract: Two-photon three-dimensional optical data storage is an important method to realize high density storage and ultra-high density storage. This paper introduces the the basic principle of two-photon photobleaching optical storage, describes two-photon three-dimensional optical storage system and the absorption and fluorescence spectra of a new type of photobleaching materials BASF in detail, carries out the experimental study that two-photon information is written and read out against a new photobleaching material of BASF using femtosecond pulse laser wavelength is 800nm, and realize two layers of optical information storage, the information point spacing is 8μm and the interlayer distance is 15μm; two-layer information point signal strength is recognized using Recognition algorithm. The experiment proved that new photobleaching material of BASF can be used for two-photon three-dimensional optical storage, that has laid a solid foundation for the high-density and ultra-high density optical information storage materials research.

Abstract: A novel multibranched chromophore containing carbazole moiety，4, 4´, 4´´-tris(9-carbazyl-trans-styryl) triphenylamine (TCSTPA)，was synthesized and characterized by ¹HNMR and elemental analysis. A larger two-photon absorption (TPA) cross section of the chromophore was obtained as high as 2350 GM compared to that of the traditional linear chromophore when pumped by a femtosecond laser at 800 nm. Microstructure based on TPA induced polymerization with a spatial resolution of submicron was fabricated under much lower incident laser power using TCSTPA as a TPA photoinitiator and a multifunctional resin of pentaerythritol triacrylate (PETA) as a polymerizable monomer. The result indicates potential applications of this kind of chromophores with multibranched structural motif in the fabrication of polymer and functional microdevices.

Abstract: A novel multibranched nonlinear dye，4, 4´, 4´´-tris(9-carbazyl-trans-styryl) triphenylamine (TCSTPA)，has been designed and synthesized aimed at two-photon absorption applications. Two-photon absorption cross section of the multibranched dye was obtained as high as 2.35×10^-47 cm⁴ s photon^-1 molecule^-1 pumped with femtosecond laser beam at 800 nm. One-photon and two-photon absorption optical properties were demonstrated in solutions. Three-dimensional (3D) optical data storage experiments were carried out by two-photon photobleaching in the multibranched-dye doped polymethylmethacryate (PMMA) with a 3D data storage density of approximate 14 Gbits/cm³. Research on the two-photon photobleaching ability shows the novel two-photon absorption dye with multibranched molecular motif has higher photosensitivity than traditional linear two-photon absorption dyes do.

Abstract: In this work, the crystallization of different silicon based thin films as the precursor of crystallization was investigated by femto-second laser with 800 nm wavelength. The linear absorption coefficient of a-Si films at that wavelength is quit lower than the other structures of Si-based thin film, which has no related with the incident light energy. However, we found that the crystallization of a-Si films was better than μc-Si films as the precursor. We use Z-scan techniques to prove that the two-photon absorption effect would be responsible for the crystallization. And unlike the linear absorption, the two-photon absorption effect is correlated with the incident light energy, as well as the micro-structure of the silicon based film. At the end of the paper, the crystallization by laser with wavelength longer than the absorption limit was discussed.