Showing papers on "Zone plate published in 2013"

Sub-5 nm hard x-ray point focusing by a combined Kirkpatrick-Baez mirror and multilayer zone plate

Abstract: Compound optics such as lens systems can overcome the limitations concerning resolution, efficiency, or aberrations which fabrication constraints would impose on any single optical element. In this work we demonstrate unprecedented sub-5 nm point focusing of hard x-rays, based on the combination of a high gain Kirkpatrick-Baez (KB) mirror system and a high resolution W/Si multilayer zone plate (MZP) for ultra-short focal length f. The pre-focusing allows limiting the MZP radius to below 2 μm, compatible with the required 5 nm structure width and essentially unlimited aspect ratios, provided by enabling fabrication technology based on pulsed laser deposition (PLD) and focused ion beam (FIB).

Using Rotatable Planar Phase Shifting Surfaces to Steer a High-Gain Beam

Abstract: Phase shifting surface (PSS) technology has been used to develop a 30 GHz beam steering antenna. The concept is similar to that of a pair of dielectric wedges placed in front of a primary antenna for beam steering. The initial prototype antenna is made of a horn-fed PSS phase-correcting Fresnel zone plate above which are placed two rotatable circular linear phase progression PSSs. These PSSs have rotation capability along their planes. Their rotation allows for achieving beam steering in the upper hemisphere. An additional prototype antenna makes use of a rotatable offset-beam PSS phase-correcting Fresnel zone plate and a single linear phase progression PSS to achieve beam steering with a higher aperture efficiency. These prototypes confirm the feasibility of using PSS technology for achieving a lightweight, low-cost and efficient beam steering antenna.

270-GHz LTCC-Integrated High Gain Cavity-Backed Fresnel Zone Plate Lens Antenna

Abstract: A compact cavity-backed Fresnel zone plate (FZP) lens antenna, integrated in low-temperature co-fired ceramic (LTCC) is proposed to achieve high gain at 270 GHz band. The gain is enhanced by using the back cavity formed by a via sidewall and a ground plane. A compact feeding transition is proposed to realize the broadband impedance matching in order to reduce the considerably large reflection at high permittivity substrate-air interface when the antenna is directly fed by an external air-filled waveguide. The measured results show that the proposed cavity-backed FZP lens antenna achieves a boresight gain of 20.8 dBi at 270 GHz and a 3-dB gain bandwidth of 9.1 GHz (266.2–275.3 GHz).

Dynamic zone plate augmented vision eyeglasses

Abstract: A method, an apparatus, and a computer program product for modulating optics in a display are provided. An apparatus forms a plurality of zone plates in a liquid crystal using electric fields. Each zone plate has a center, and the centers are aligned along a first axis of the display. The apparatus moves the plurality of zone plates in a first direction along a second axis of the display different from the first axis of the display, while maintaining alignment of the centers of the plurality of zone plates along the first axis. Such movement is provided through repositioning of electric fields through the liquid crystal.

Modulation of a super-Gaussian optical needle with high-NA Fresnel zone plate.

Abstract: A high NA Fresnel zone plate (FZP) is studied using vectorial angular spectrum theory for realizing the sharpest possible super-Gaussian optical needle with purely longitudinal polarization illuminated by a radially polarized vector beam. Strong dispersion of the FZP results in a light field resembling a super-Gaussian optical needle by selecting an optimal FZP structural wavelength relative to the illumination wavelength and inserting a narrow comb window function into the center-shaded FZP. A 25 μm long longitudinally polarized flattop optical needle with a transverse beam width of about 0.366λ is focused at a distance of 222.5 μm away from a binary amplitude 3.46 mm diameter FZP for a 532.4 nm wavelength in free space.

Angular spectrum simulation of X-ray focusing by Fresnel zone plates

Abstract: A computing simulation routine to model any type of circularly symmetric diffractive X-ray element has been implemented. The wavefield transmitted beyond the diffractive structures is numerically computed by the angular spectrum propagation method to an arbitrary propagation distance. Cylindrical symmetry is exploited to reduce the computation and memory requirements while preserving the accuracy of the numerical calculation through a quasi-discrete Hankel transform algorithm, an approach described by Guizar-Sicairos & Gutierrez-Vega [J. Opt. Soc. Am. A, (2004), 21, 53–58]. In particular, the code has been used to investigate the requirements for the stacking of two high-resolution Fresnel zone plates with an outermost zone width of 20 nm.

Hard X-ray imaging microscopy using X-ray guide tube as beam condenser for field illumination

Abstract: An optical system for illumination of object in x-ray imaging microscopy is developed. The optical system is a beam condenser consisting of a single-bounce conical-shape mono-capillary (x-ray guide tube: XGT) made of Pyrex glass. The XGT condenser was tested at the beam line 47XU of SPring-8 using a Fresnel zone plate as an objective lens. Comparing with the microscope without beam condenser, the flux density is improved by a factor of 12–20 in the x-ray energy range of 6–8 keV. Test patterns with a 50 nm-structure are clearly resolved at 8 keV with an exposure time less than 1 s.

Phase defect characterization on an extreme-ultraviolet blank mask using microcoherent extreme-ultraviolet scatterometry microscope

Abstract: Defect-free mask production is a critical issue in extreme-ultraviolet (EUV) lithography. On EUV masks, phase defects are buried by multilayer coating, which is a serious EUV-specific issue. These defects should be hidden or be compensated completely by the absorber pattern for the production of defect-free masks. A phase image of the phase defects at the EUV lithography exposure wavelength is essential to characterize the defects. For characterization of phase defects, the authors have developed the microcoherent EUV scatterometry microscope (micro-CSM). This system is lensless and is based on a coherent diffraction imaging method, which records diffraction images. The intensity and phase images of the defects are reconstructed through iterative calculations. The micro-CSM system has focusing optics of a Fresnel zone plate to observe small defect. The detection size limits of the phase defects were a width of 25 nm and a depth of 1.4 nm. Diffraction images from an asymmetric phase defect were related well to the defect shapes and volumes. The defect position was also inspected by mapping image that was measured using by step-and-repeat observation. The actinic defect signals were observed by the micro-CSM system.

Focusing and imaging of a virtual all-optical tunable terahertz Fresnel zone plate.

Abstract: A virtual all-optical tunable terahertz Fresnel zone plate is achieved utilizing the localized distribution of the transient electron plasma on a silicon wafer. Its focusing and imaging performance are experimentally demonstrated. Experimental results show that the effect of the virtual zone plate is the same as an actual one. Adjusting the spatial pattern of the electron plasma, the central wavelength and the focal length of the virtual zone plate can be all-optically dynamically steered. The research is a significant step to the development of tunable optical imaging elements.

Tabletop single-shot extreme ultraviolet Fourier transform holography of an extended object.

Abstract: We demonstrate single and multi-shot Fourier transform holography with the use of a tabletop extreme ultraviolet laser. The reference wave was produced by a Fresnel zone plate with a central opening that allowed the incident beam to illuminate the sample directly. The high reference wave intensity allows for larger objects to be imaged compared to mask-based lensless Fourier transform holography techniques. We obtain a spatial resolution of 169 nm from a single laser pulse and a resolution of 128 nm from an accumulation of 20 laser pulses for an object ~11x11μm2 in size. This experiment utilized a tabletop extreme ultraviolet laser that produces a highly coherent ~1.2 ns laser pulse at 46.9 nm wavelength.

The Photo-Injected Fresnel Zone Plate Antenna: Optoelectronic Beam Steering at mm-Wave Frequencies

Abstract: We present an overview of the photo-injected Fresnel zone plate antenna (piFZPA) method for non-mechanical optoelectronic beam steering. The piFZPA method enables rapid beam steering, over moderate field-of-views, at both mm-wave and submm-wave frequencies, that is suitable for a wide range of imaging and non-imaging applications. This paper develops a theoretical framework that details the design of piFZPAs and provides an understanding to, and optimization of, the piFZPA performance. As an example device, we present preliminary experimental scanning data on a transmission-type piFZPA, operating at 94 GHz, that relies on commercially available visible display technologies for plasma generation and reconfiguration. The experimental data is shown to agree well with numerical simulations and validates the theoretical framework.

Efficient focusing of 8 keV X-rays with multilayer Fresnel zone plates fabricated by atomic layer deposition and focused ion beam milling

Abstract: Fresnel zone plates (FZPs) recently showed significant improvement by focusing soft X-rays down to ∼10 nm. In contrast to soft X-rays, generally a very high aspect ratio FZP is needed for efficient focusing of hard X-rays. Therefore, FZPs had limited success in the hard X-ray range owing to difficulties of manufacturing high-aspect-ratio zone plates using conventional techniques. Here, employing a method of fabrication based on atomic layer deposition (ALD) and focused ion beam (FIB) milling, FZPs with very high aspect ratios were prepared. Such multilayer FZPs with outermost zone widths of 10 and 35 nm and aspect ratios of up to 243 were tested for their focusing properties at 8 keV and shown to focus hard X-rays efficiently. This success was enabled by the outstanding layer quality thanks to ALD. Via the use of FIB for slicing the multilayer structures, desired aspect ratios could be obtained by precisely controlling the thickness. Experimental diffraction efficiencies of multilayer FZPs fabricated via this combination reached up to 15.58% at 8 keV. In addition, scanning transmission X-ray microscopy experiments at 1.5 keV were carried out using one of the multilayer FZPs and resolved a 60 nm feature size. Finally, the prospective of different material combinations with various outermost zone widths at 8 and 17 keV is discussed in the light of the coupled wave theory and the thin-grating approximation. Al2O3/Ir is outlined as a promising future material candidate for extremely high resolution with a theoretical efficiency of more than 20% for as small an outermost zone width as 10 nm at 17 keV.

Terahertz zone plates with integrated laser-ablated bandpass filters

Abstract: Properties of zone plates with integrated bandpass filters were simulated numerically and demonstrated experimentally for 0.76 THz frequency. Finite-difference time-domain simulations were used to predict properties of a conventional zone plate and laser-ablated zone plate with resonant filter areas. Zone plates were produced employing laser direct writing and characterised by Fourier spectroscopy and an optically pumped terahertz laser.

X-ray phase microscopy using the speckle tracking technique

Abstract: Hard X-ray phase microscopy using the Speckle Tracking technique is presented and the practical implementation of this microscope explained. It is demonstrated that the spatial resolution of the Speckle Tracking technique can be pushed down to the nanometer scale without sacrificing the angular sensitivity, which is in the tens of nanoradians range. Moreover, the method is suitable for the analysis of dynamic samples. Experimental demonstration of the method is given for the case of phase imaging of micrometer size polystyrene spheres using a Fresnel zone plate as a magnifying optical element.

Subwavelength focusing of laser light by microoptics

Abstract: Near-field scanning optical microscope (NSOM) measurements revealed that a linearly polarized Gaussian beam of wavelength λ = 532 nm focused with a binary zone plate (ZP) of focal length λ, radius 7 μm, and groove depth 510 nm, fabricated in hydrogen silsesquioxane, produces a focal spot of size FWHM = (0.44 ± 0.02)λ, with the side lobes being lower than 10% of the intensity peak in the focus. Replacing the incident 532 nm wavelength with a 633 nm wavelength resulted in a 1.8 times shorter focal length and a tighter (in terms of wavelengths) focal spot of FWHM = (0.40 ± 0.02)λ. This value is smaller than the scalar diffraction-limited size in vacuum, FWHM = 0.51λ. This is the smallest focal spot so far experimentally obtained for a binary phase ZP and the root-mean-square deviation of the experimental curve from a FDTD simulation is 5%. We show that the metallic pyramid-shaped cantilever with a 100-nm-hole in the tip that is used in the NSOM is only able to detect the transverse electric field component. ...

Projection apparatus and transparent screen for it

Abstract: There is provided a projection apparatus using an oblique projection optical system, which generates little reflection loss by providing a linear Fresnel lens at an incident surface in the case where the apparatus is used as a linear system, wherein said linear Fresnel lens makes total reflection of image light, and is capable of obtaining total surface property with good brightness in a region with small incident angle onto a screen, by using a total reflection Fresnel lens and a refraction Fresnel lens in combination. In addition, total surface property with further good brightness can be obtained by using a plurality of projection image display apparatuses in the same projection apparatus.

X-ray wavefront characterization of a Fresnel zone plate using a two-dimensional grating interferometer

Abstract: The x-ray wavefront downstream of a Fresnel zone plate (FZP) was characterized using a two-dimensional grating interferometer. Transverse wavefront slope maps, measured using a raster phase-stepping scan, allowed accurate phase reconstruction of the x-ray beam. Wavefront measurements revealed that the wavefront error is very sensitive to the input beam entering the FZP. A small stack of one-dimensional compound refractive lenses was used to introduce astigmatism in the probing x-ray beam to investigate the contribution of the incoming beam in contrast to the optical aberrations. Experimental data were shown to be consistent with theoretical calculations.

Subwavelength superfocusing with a dipole-wave-reciprocal binary zone plate

Abstract: We propose an idea of using a convergent dipole wave at the aperture, radiated from a dipole at distance of z0, to produce a perfect focusing at z0. We verified this idea through simulation and experimental observation. It is demonstrated that the zone plate designed based on the idea can provide a subwavelength superfocusing by effectively bending the surface waves in a Fresnel region of 100 nm to a couple of wavelengths and is suitable for a situation where a superresolution at a micro working distance is essential.

Micro Fresnel Zone Plate Lens Inscribed on a Hard Polymer Clad Fiber Using Femtosecond Pulsed Laser

Abstract: We report a novel process to directly inscribe a Fresnel zone plate (FZP) lens on the cleaved facet of a hard clad polymer fiber using a femtosecond pulsed laser. The FZPs are designed by adopting modal analysis and free-space diffraction, which are experimentally implemented by locally ablating silica glass using femtosecond laser pulses. A good agreement between the design and fabricated FZP lens is obtained with an exceptionally long focal length over 600 m, which can have a strong potential in all-fiber beam shaping technology and optical interconnections.

Microstructure formation in a thick polymer by electrostatic-induced lithography

Abstract: This article demonstrates the manufacturing of microstructures in a thick polymer using electrostatic-induced lithography. Unlike previous work reported elsewhere, it focuses on the fabrication of structures from meso- to micro-scale. The electrostatic-induced lithography technique is proven to work with not only dc voltage but also ac voltage. Microstructures including microchannels, sinusoidal surface profile microstructures, waveguide core, microlens array and binary Fresnel zone plate have been successfully fabricated. The aspect ratio obtained for some samples is up to 4.5:1. The whole fabrication process is fast, cost-effective in terms of the simple experimental setup and no photosensitive material is needed. This process is expected to find applications in microfluidics, photonics or micro-opto-electro-mechanical systems.

Interferometer-controlled soft X-ray scanning photoemission microscope at SOLEIL

Abstract: ANTARES beamline (BL), a new soft X-ray scanning photoemission microscope located at the SOLEIL synchrotron storage ring has been recently designed, built and commissioned. The implemented interferometer control allows the accurate measurement of the transverse position of the Fresnel zone plate (FZP) relative to the sample. An effective sample position feedback has been achieved during experiments in static mode, with a fixed FZP position required to perform nano Angle-Resolved Photoelectron Spectroscopy (Nano-ARPES) measurements. Likewise, long-term stability has been attained for the FZP position relative to the sample during the translation of the FZP when performing typical X-ray absorption experiments around the absorption edges of light elements. Moreover, a fully automatic feedback digital control of the interferometric system provides extremely low orthogonal distortion of the recorded two-dimensional images. The microscope is diffraction limited with the resolution set to several tens of nanometers by the quality of the zone plates. Details on the design of the interferometric system and a brief description of the first commissioning results are presented here.

A case study of novel X-ray Optics for FEL sources

Abstract: We suggest optical schemes for the European X-ray Free Electron Laser facility (XFEL.EU) in Hamburg: a single element X-ray spectrometer on the basis of a reflection zone plate (RZP) for single-shot diagnostics; and a two-element soft X-ray spectrometer on the basis of two RZPs to carry out Resonant Inelastic X-ray Scattering (RIXS) experiments. With this setup, a full map of the sample spectrum is obtainable in a single measurement. The main advantage of using zone plates is the possibility to enable dispersion and focusing in one step. Moreover, highest possible X-ray transmission is achieved by using the minimum number of optical elements. Taking into account the European XFEL beam parameters, our simulations, concerning the RIXS experiment, produced very promising results, reaching an energy resolution (E/ΔE) of up to 30,000 at photon energy of 1 keV. When applied as a single shot spectrometer the energy resolution for RZP is of the same order of magnitude.

High efficiency x-ray nanofocusing by the blazed stacking of binary zone plates

Abstract: The focusing efficiency of binary Fresnel zone plate lenses is fundamentally limited and higher efficiency requires a multi step lens profile. To overcome the manufacturing problems of high resolution and high efficiency multistep zone plates, we investigate the concept of stacking two different binary zone plates in each other’s optical near-field. We use a coarse zone plate with π phase shift and a double density fine zone plate with π/2 phase shift to produce an effective 4- step profile. Using a compact experimental setup with piezo actuators for alignment, we demonstrated 47.1% focusing efficiency at 6.5 keV using a pair of 500 μm diameter and 200 nm smallest zone width. Furthermore, we present a spatially resolved characterization method using multiple diffraction orders to identify manufacturing errors, alignment errors and pattern distortions and their effect on diffraction efficiency.

Hologram recording apparatus

Abstract: PURPOSE: A hologram recording device is provided to correct the distortion of the hologram of an object by forming a non-linear Fresnel zone plate with scan beams for hologram recording. CONSTITUTION: A light source (110) generates an electromagnetic wave. A dividing means (120) divides the electromagnetic wave into a first beam and a second beam. An interference means (160) interferes the first and second beams and forms an interference beam of a non-linear Fresnel zone plate shape. A scan means (165) uses the interference beam for scanning an object. An optical detection means (175) detects the beam reflected from the object. [Reference numerals] (110) Light source; (120) Dividing unit; (130) Frequency shift unit; (135) Signal producing unit; (180) Electronic processing unit; (181) Heterodyne extracting unit; (183) Signal processing unit; (184) Storing unit; (185) Scan controller; (AA) Function generator; (BB) Optical system

Image formation model for photon sieves

Abstract: A photon sieve, modification of a Fresnel zone plate, has been recently proposed to achieve higher resolution imaging and spectroscopy at UV and x-ray wavelengths. In this paper, we present Fresnel imaging formulas that relate the output of a photon sieve imaging system to its input, originating from either a coherent or incoherent extended source. By using a well-known model for the zone plate, we also provide approximations to these imaging formulas, which are more efficient to compute. These imaging relations for both photon sieve and the approximate model are crucial for effectively analyzing and solving the inverse problems that arise from the new imaging modalities enabled by photon sieves. We illustrate this by formulating the forward model of the image formation process for an application in polychromatic imaging.

Single-focus x-ray zone plate by stagger arrangement of zones.

Abstract: In this paper a novel single-focus x-ray zone plate is proposed by stagger arrangement of zones, which would be technically easier to manufacture. Theoretical design shows that the transmission function of the plate is a cosine function of radius, like that of a Gabor zone plate. Numerical simulation at the wavelength of 0.275 nm shows that the plate is of single-order focusing, with spatial resolution limit the same as that of the corresponding conventional zone plate, and the first-order diffraction efficiency of 11.5%. The plate can also work for single-order focusing at other x-ray wavelengths.

Fresnel lens and optical device

Abstract: A refractive Fresnel lens used for an optical system including an image plane, which includes a plurality of zone lens surfaces disposed concentrically and a plurality of side wall surfaces each formed between adjacent zone lens surfaces, is characterized in that the side wall surfaces are modulated so as to spatially spread in the image plane noise light due to reflection and/or refraction at the side wall surfaces.

The Beynon Gabor zone plate: a new tool for de Broglie matter waves and hard X-rays? An off axis and focus intensity investigation

Abstract: Optical elements based on Fresnel zones are used in a range of applications, from X-ray telescopy to microscopy and recently also in the manipulation of de Broglie matter waves. In 1992 Beynon and co-workers presented a binary Gabor type zone plate (henceforth referred to as the Beynon Gabor zone plate). Because this zone plate has no higher order foci, it is in principle a very attractive candidate for focusing of de Broglie matter waves and in some cases X-rays. So far the Beynon Gabor zone plate investigations presented in the literature have concentrated on the intensity distribution along the optical axis and in the focal plane. Here we present a detailed numerical investigation of the Beynon Gabor zone plate, including an investigation of the off-optical axis, off focal plane intensity distribution for point source illumination. We show that at integer fractions of the focal length, the beam becomes nearly toroidal (doughnut-shaped). This offers potentially interesting new possibilities for de Broglie matter wave and X-ray optics, for example in STED-like applications. We further show that the increased intensity at the focal point predicted in the literature for a particular Beynon Gabor zone plate transmission function configuration is an artifact due to the lack of sampling nodes. We support our calculations with experimental measurements in the visible light range, using a Beynon Gabor zone plate fabricated with electron beam lithography.