Performance analysis of single-focus phase singularity based on elliptical reflective annulus quadrangle-element coded spiral zone plates

Optical vortices generated by the conventional vortex lens are usually disturbed by the undesired higher-order foci,which may lead to additional artifacts and thus degrade the contrast sensitivity. In this work, we propose an efficient methodology to combine the merit of elliptical reflective zone plates(ERZPs) and the advantage of spiral zone plates(SZPs) in establishing a specific single optical element, termed elliptical reflective annulus quadrangle-element coded spiral zone plates(ERAQSZPs) to generate single-focus phase singularity. Differing from the abrupt reflectance of the ERZPs, a series of randomly distributed nanometer apertures are adopted to realize the sinusoidal reflectance. Typically, according to our physical design, the ERAQSZPs are fabricated on a bulk substrate;therefore, the new idea can significantly reduce the difficulty in the fabrication process. Based on the Kirchhoff diffraction theory and convolution theorem, the focusing performance of ERAQSZPs is calculated. The results reveal that apart from the capability of generating optical vortices,ERAQSZPs can also integrate the function of focusing, energy selection, higher-order foci elimination, as well as high spectral resolution together. In addition, the focusing properties can be further improved by appropriately adjusting the parameters, such as zone number and the size of the consisted primitives. These findings are expected to direct a new direction toward improving the performance of optical capture, x-ray fluorescence spectra, and forbidden transition.

Highly sensitive diamond X-ray detector array for high-temperature applications

Diamond is a highly suitable material for X-ray detectors that can function effectively in harsh environments due to its unique properties such as ultrawide bandgap,high radiation resistance,excellent carrier mobility as well as remarkable chemical and thermal stability.However,the sensitivity of diamond X-ray detectors needs further improvement due to the relatively low X-ray absorption efficiency of diamond,and the exploration of singlecrystal diamond array imaging still remains unexplored.In the current work,a 10310 X-ray photodetector array was constructed from single-crystal diamond.To improve the sensitivity of the diamond X-ray detector,an asymmetric sandwich electrode structure was utilized.Additionally,trenches were created through laser cutting to prevent crosstalk between adjacent pixels.The diamond X-ray detector array exhibits exceptional performance,including a low detection limit of 4.9 nGy s^(-1),a sensitivity of 14.3 mC Gy^(-1) cm^(-2),and a light-dark current ratio of 18,312,which are among the most favorable values ever reported for diamond X-ray detectors.Furthermore,these diamond X-ray detectors can operate at high temperatures up to 450℃,making them suitable for development in harsh environments.

Full-Stokes metasurface polarimetry requiring only a single measurement

Polarization is crucial in various fields such as imaging,sensing,and substance detection.A compact,fast,and accurate polarization detection device is vital for these applications.Herein,we demonstrate a multifocus metalens for terahertz polarization detection that requires only a single measurement to obtain complete polarization parameters and reconstruct the polarization state of the incident field.The individual subarrays of this metalens convert each of the six polarized components into the same polarization,which in turn links the Stokes parameters to these six foci.The incident linear polarizations and elliptical polarizations are characterized by Stokes parameters and polarization ellipses.Simulations and experimental results show that the scheme can accurately detect the incident polarization with a single measurement.The proposed metasurface polarimetry may find applications in the fields of real-time terahertz detection and integrated optics.

Terahertz metasurface polarization detection employing vortex pattern recognition

The manipulation and detection of polarization states play a crucial role in the application of 6G terahertz communication.Nonetheless,the development of compact and versatile polarization detection devices capable of detecting arbitrary polarizations continues to be a challenging endeavor.Here,we demonstrate a terahertz polarization detection scheme by performing mode purity analysis and multidimensional analysis of the transmitted vortex field.The power of the proposed polarization recognition is verified by using three polarization trajectories,including linear polarizations,circular polarizations,and elliptical polarizations.Using the reconstructed complete polarization parameters,the detected polarization states are characterized using polarization ellipses,Poincarésphere,and full-Stokes parameters.The experimental results validate the power of this scheme in polarization detection.This scheme holds promise for applications in polarization imaging and terahertz communication.

All-silicon chiral metasurfaces and wavefront shaping assisted by interference

Chiral metasurfaces have different electromagnetic responses with circularly polarized lights,showing as circular dichroism and optical activity.Here,a novel kind of all-silicon chiral metasurface is proposed by introducing destructive interference between achiral meta-atoms.The maximum value of circular dichroism spectra can reach 0.49.By adding an antireflective layer at the side of the silicon substrate,the maximum circular dichroism reaches 0.54.What is more,the bandwidth of circular dichroism greater than 0.4 reaches 0.15 THz.Two samples are fabricated to verify the feasibility of this scheme,and the experimental results are in good agreement with the simulations.In addition,the proposed scheme can also be used to generate various interesting functions,such as beam control and vortex generator.This flexible and efficient implementation solution of chiral metasurface can bring new ideas to the development of chiral devices in the future.

Generation of single-focus phase singularity by the annulusquadrangle-element coded binary square spiral zone plates

Optical vortices(OVs) with unique square symmetry are widely used in various applications including particle manipulation,microscopy, and image processing. However, the undesired higher-order foci introduced by the conventional vortex lens such as square spiral zone plates(SSZPs) may lead to additional artifacts and thus degrade contrast sensitivity. In this endeavor, herein,we propose a methodology to combine the merit of SSZPs and the advantage of Gabor zone plates(GZPs) in establishing a specific single optical element, termed binary single focused square spiral zone plates(BSSZPs). In contrast to the abrupt transitions of the SSZPs, our central idea aims to realize the sinusoidal transmittance along the radial direction of SSZPs by a series of randomly distributed annulus-quadrangle-shaped nanometer structure apertures. The innovative design can simultaneously generate OVs with unique square symmetry, and eliminate the interference of higher-order foci along the propagation direction. Guided by our theoretical predication, the focusing property of such optics was further experimentally demonstrated.These findings are expected to direct new avenue towards improving the performance of optical image processing and alignment system.

Generation of X-ray vortex with ultra-long depth of focus using axial line-focused spiral zone plates

We propose axial line-focused spiral zone plates （ALFSZPs） for generating tightly focused X-ray vortex beams with ultra-long depth of focus （DOF） along the propagation direction. In this typical design, compared with the conventional spiral zone plates （SZPs） under the same numerical aperture （NA）, the DOF of ALFSZPs has been extended to an ultra-length by optimizing the corresponding parameters. Besides, it also exhibits lower side lobes and smaller dark cores in the whole focus volume. The diameters of dark cores increase as the topological charge value increases.