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Hard X-ray imaging microscopy with self-imaging phenomenon
摘要： The self-imaging phenomenon referred to as the Talbot effect in the field of optics was discovered by H.F. Talbot in the 1830s, and is now widely used for imaging using not only visible light but also X-rays, electrons, neutrons, and matter waves. In this review, the author introduces the current progress being made in hard-X-ray imaging microscopy based on the self-imaging phenomenon. Hard-X-ray imaging microscopy is a promising technique for non-destructively visualizing internal structures in specimens with a spatial resolution up to a few tens of nanometers. The use of the self-imaging phenomenon makes it possible to realize highly sensitive phase-contrast X-ray imaging microscopes. These approaches have several advantages over conventional X-ray imaging microscopes, including the widely used Zernike X-ray phase-contrast microscopes, and can provide a powerful way of quantitative visualization with a high spatial resolution and a high sensitivity even for thick specimens.
关键词： grating,Talbot effect,interferometry,X-ray imaging,X-ray microscopy
更新于2025-09-19 17:15:36
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Talbot Effect in Embedded Gratings Inscribed with Femtosecond Laser in Transparent Media
摘要： Since the first refractive index modification of transparent materials was achieved via femtosecond laser micromachining, the fabrication of bulk inscribed 3D optical elements has been insistently pursued. This method has been extensively used to generate a variety of photonic devices such as waveguides, couplers or amplifiers, which enabled a large number of technological breakthroughs. In particular, the fabrication of glass embedded volume-phase gratings (VPG) has been studied in detail by many authors. Currently, the process for manufacturing VPGs involves the use of dichromated gelatin hologram recording, which is accomplished sealing the gelatin between two layers of glass. Using femtosecond laser inscribing technique, VPGs can be fabricated in a more direct, robust and environmental friendly way. Only a few studies have been reported on the near-field diffraction properties of the femtosecond laser fabricated VPGs. Among the different peculiarities that are observed in the microscale propagation of the light, one of the most studied phenomenon is the Talbot effect or also called self-imaging. Caused by the interference of waves with quadratic relative phases, when a grating is illuminated with a collimated monochromatic light, exact images of the illuminated grating are formed at a distance (cid:1852)(cid:3021) = p2/λ, where p is the period of the grating. In this presentation, we will show the fabrication of an embedded grating that generates a high contrast Talbot effect. VPGs with periods of 10 (cid:80)m and different Q parameters are fabricated with a 500 kHz diode-pumped ultrafast fiber amplifier Satsuma system of λ=1030 nm. The VPGs are fabricated in fused silica and nanocrystal doped glass (OG530). It is observed that the width, thickness and refractive index profile of the generated modification zone depends on the laser processing conditions such as pulse energy, repetition rate or processing depth. The gratings are characterized with far-field diffraction measurements and microscopy images of the cross-sections. Also, the near-field intensity profiles generated by the VPGs are measured to visualize the Talbot effect (Fig. 1 a). The experimental setup for the near-field includes a collimated 633nm laser beam and a 20× microscope objective selectively displaced with a resolution of 5 μm. The Talbot planes are formed at a distances of the order of ~ 100 (cid:80)m. The dependence of the contrast of the intensity profiles on the VPG laser processing condition is analyzed. Our results show that high contrast Talbot effect is achieved when the phase difference generated by the VPG is optimized (Fig. 1 b)).
关键词： transparent media,self-imaging,volume-phase gratings,femtosecond laser,Talbot effect,embedded gratings
更新于2025-09-12 10:27:22