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Assessment of functionals for TDDFT calculations of one- and two-photon absorption properties of neutral and anionic fluorescent proteins chromophores
摘要： Performance of DFT functionals with different percentage of exact Hartree-Fock exchange energy (EX) is assessed for recovery of the CC2 reference one- (OPA) and two-photon absorption (TPA) spectra of fluorescent proteins chromophores in vacuo. The investigated DFT functionals, together with their EX contributions are: BLYP (0%), B3LYP (20%), B1LYP (25%), BHandHLYP (50%) and CAM-B3LYP (19% at short range and 65% at long range). Our test set consists of anionic and neutral chromophores as naturally occuring in the fluorescent proteins. For the first time, we compare TDDFT and CC2 methods for higher excited states, than the S1 state, exhibiting relatively large TPA intensity. Our TDDFT results for neutral chromophores reveal an increase of excitation energies as well as TPA and OPA intensities errors, compared to CC2-derived results, as the DFT functional contains less exact exchange. The long-range-corrected CAM-B3LYP functional performs the best, closely followed by BHandHLYP, while BLYP usually significantly underestimates all investigated spectral properties, hence being the worst in reproducing the reference CC2 results. The hybrid B3LYP and B1LYP functionals can be roughly placed in between. We propose that TDDFT may underestimate the TPA intensities for neutral chromophores of fluorescent proteins due to underestimated oscillator strengths between some excited states. In case of anionic chromophores, we find that B3LYP and B1LYP functionals overcome others in terms of reproducing CC2 excitation energies. On the other hand, however, TPA intensity is usually significantly underestimated and in this respect CAM-B3LYP functional seems to be again superior. In contrast to the case of neutral chromophores, it seems that large magnitude of excited-state dipole moment or change in dipole moment upon excitation may be the driving force behind high TPA transition moments.
关键词： fluorescent proteins chromophores,one-photon absorption,DFT functionals,two-photon absorption,TDDFT,CC2
更新于2025-09-23 15:21:21
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Implementation and assessment of a low-cost 3D laser platform controlled by open software for printing polymeric micro-structures
摘要： A low-cost 3D opto-mechatronic platform controlled by free-source software with optical and mechanical resolutions of 120 μm and 10 μm, respectively, was developed to fabricate micro-pedestals in grid presentation and diffractive optical elements such as micro-square and micro-slits. Direct laser writing (DLW) and low-one photon absorption (LOPA) were employed as the fabrication protocol and the physical phenomena involved in the platform control and development of the micrometric structures. A laser pointer, one of the lowest-cost lasers in the market, centered at 532 nm with an intensity of 65 mW, was used to polymerize the SU8-2050 photoresist through the DLW procedures. The printing process was carried out by using a 5X and 10X microscope objectives with numerical apertures of 0.13 and 0.25, respectively. The point spread function demonstrated the geometrical variations and the field intensity distribution about the focal plane, where the Debye-Wolf approximation is valid, which were used for comparison purposes. Ray tracing simulations were in addition presented demonstrating how light interacts with the SU8-film and how out of focus condition plays a fundamental role in the final size of the printed micro-pattern. Finally, two optical diffractive elements and their diffraction patterns in the Fraunhofer regime were presented.
关键词： low-one photon absorption,micro-fabrication,direct laser writing,optical diffraction
更新于2025-09-19 17:13:59
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Direct CW-Laser Writing Sub-Diffraction-Limit Nanopore Array Based on the Low One-Photon Absorption of Polymer
摘要： A large area nanopore array with controllable consistency has been fabricated by direct laser writing (DLW) technique with ultralow one-photon absorption (LOPA). In this technique, a doughnut-shape beam generated by 532 nm continuous-wave laser through a vortex phase plate was focused into the thin film of SU8 photoresist by a high numerical aperture objective. The low absorption of the photoresist at the excitation wavelength allowed controllable fabricating structures with sub-diffraction-limit feature size and high aspect ratio. With point-by-point scanning fabrication, nanopore array with the pore’s internal diameter, about ten percent of incident laser wavelength, far smaller than Abbe’s diffraction limit was achieved. The influences of the exposure intensity and exposure time on the fabricated nanopore size and shape were also investigated by scanning electron microscope (SEM).
关键词： ultralow one-photon absorption,direct laser writing,nanopore,doughnut-shaped beam
更新于2025-09-19 17:13:59