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Tham khảo tài liệu 'coherence and ultrashort pulse laser emission part 16', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Two-PhotonPolymerization of Inorganic-Organic Hybrid Polymers as Scalable Technology Using Ultra-Short Laser Pulses 591 b detector 1 lens cuvette lens detector 2 beam splitter aperture opt. Fig. 5. Experimental setup for the z scan. a 3D view and b schematic sketch of the setup. In Figure 5 a 3D presentation of the experimental setup for the z-scan experiment as well as a schematic sketch is shown which was used to determine the TPA absorption cross-sections of the photoinitiators. As laser wavelength 515 nm pulses were used which were split with a beam splitter for providing reference and transmission signal. The transmitted beam is then focused using a lens and detected with a 9.8 mm photodiode detector 2 . Optionally a variable aperture and an additional lens are located in front of the photodiode. The photoinitiators were dissolved in methylisobutylketone in a 1 mm quartz glass cuvette which is moved along the beam propagation path with a 75 mm linear travel stage. The signal-to-noise ratio was improved by recording multiple scans for each measurement. For the determination of the absorption cross-sections non-linear refraction should be neglectable. This can be achieved by an open-aperture scan where the transmitted signal only depends on the non-linear absorption which is dominated by TPA. The fraction of non-linear refraction can be determined by using the aperture in front of the detecting photodiode resulting in additional signals in the transmission curve Sheikbahae et al. 1989 . Aside a high absorption cross-section of the photoinitiators a high chemical reactivity of the hybrid resins is required. A first insight into their reactivity in selected hybrid polymer systems was deducted from photo-DSC photo-differential scanning calorimetry measurements of the ORMOCER initiator formulations. It has to be mentioned however that the underlying reaction is initiated in a classical one-photon process which already gives a good measure of the reaction enthalpy .