研究目的
To generate and control orbital angular momentum beams at soft X-ray wavelengths using diffractive optics for probing and manipulating the electronic structure of matter.
研究成果
The study successfully generated soft X-ray OAM beams using diffractive optics, achieving up to 30? angular momentum per photon. The developed tools, including OAM analysers and superposition generators, enable new spectroscopic and scattering methods for probing topological states of matter, with potential applications in X-ray microscopy and quantum material characterization.
研究不足
The gratings require coherent illumination to imprint phase singularities, limiting applicability to sources with high transverse coherence. Grating patterns were limited to small diameters (5 or 10 μm) due to wavelength-dependent coherence lengths, potentially restricting scalability and broader applications.
1：Experimental Design and Method Selection:
The study involved designing and fabricating binary amplitude diffraction gratings (fork gratings) to produce orbital angular momentum (OAM)-carrying beams, specifically Laguerre–Gauss and Hermite–Gauss modes. The theoretical basis includes the transmission function of fork gratings and simulations of diffraction patterns.
2：Sample Selection and Data Sources:
Diffractive optics were fabricated on gold substrates using focused-ion-beam milling. Soft X-ray diffraction measurements were performed using a coherent X-ray beam from the Advanced Light Source.
3：List of Experimental Equipment and Materials:
Equipment includes a Helios focused ion beam machine for fabrication, a Coherent X-ray Scattering Beamline for diffraction, an Andor CCD detector for recording patterns, gold substrates, Si3N4 membranes, and Si frames.
4：Experimental Procedures and Operational Workflow:
Gratings were fabricated with specific periods and dislocation defects. Diffraction was measured with soft X-rays at 492 mm from the sample, using a beam block to intercept the zero order. Patterns were recorded over a wavelength range.
5：Data Analysis Methods:
Diffraction patterns were analyzed by performing Fourier transforms of the product of analyser binary amplitude and incident beam amplitude functions, with intensities calculated as the modulus squared.
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