Showing papers on "Zone plate published in 2016"
TL;DR: A new compact instrument designed for scanning transmission X-ray microscopy that has piezo-driven linear stages, making it small and light, and solving the vibration problem common to high-resolution microscopy is presented.
Abstract: We present a new compact instrument designed for scanning transmission X-ray microscopy. It has piezo-driven linear stages, making it small and light. Optical components from the virtual source point to the detector are located on a single optical table, resulting in a portable instrument that can be operated at a general-purpose spectroscopy beamline without requiring any major reconstruction. Careful consideration has been given to solving the vibration problem common to high-resolution microscopy, so as not to affect the spatial resolution determined by the Fresnel zone plate. Results on bacteriogenic iron oxides, single particle aerosols, and rare-earth permanent magnets are presented as examples of its performance under diverse applications.
59 citations
TL;DR: In this paper, a low-cost and light-weight dielectric Fresnel zone plate lens was fabricated in one process with the tailored permittivities, which provided 7.3-12.8 dB gain over the frequency band from 8 to 12 GHz.
Abstract: 3D-printing has been used for rapidly prototyping a low-cost and light-weight dielectric Fresnel zone plate lens. This lens was comprised of four dielectric zones and they were fabricated in one process with the tailored permittivities. Measurements show that this lens provides 7.3–12.8 dB gain enhancement over the frequency band from 8 to 12 GHz.
43 citations
TL;DR: A novel passive focusing system for Air-Coupled Ultrasonic (ACU) piezoelectric transducers which is inspired by the Newtonian-Cassegrain telescope concept, which has a coaxial design, which eases the transducers positioning and use in many applications, and is less bulky than off-axis mirrors.
38 citations
TL;DR: In this article, a sapphire-based Fresnel zone plate (FZP) was fabricated by femtosecond laser direct writing assisted with subsequent wet etching.
Abstract: Here, we report a sapphire-based Fresnel zone plate (FZP), which is fabricated by femtosecond laser direct writing assisted with subsequent wet etching. With this method, we solved the problem of high surface roughness caused by ultrafast femtosecond laser processing. We have obtained $\sim 12$ -nm average surface roughness smaller than 1/25 of the optical working wavelength. As-formed sapphire FZP also exhibited a well-defined geometry. More importantly, ultraviolet (UV) light focusing and imaging can be easily achieved. Due to the high material hardness, thermal and chemical stabilities of sapphire, such sapphire FZP, may have great potential in UV imaging and focusing under some harsh environments.
36 citations
TL;DR: The experimental results show that the FZP beam can simultaneously trap multiple particles positioned in different focal planes of the FzP beam, owing to the multiple foci and self-reconstruction property of the foci-based beam.
Abstract: We demonstrate optical manipulation with an optical beam generated by a fractral zone plate (FZP). The experimental results show that the FZP beam can simultaneously trap multiple particles positioned in different focal planes of the FZP beam, owing to the multiple foci and self-reconstruction property of the FZP beam. The FZP beam can also be used to construct three-dimensional optical tweezers for potential applications.
29 citations
TL;DR: In this paper, a waveband-selective diffraction device was developed by micro-patterning of a photoresponsive self-organized helical liquid crystal superstructure.
Abstract: A waveband-selective diffraction device, possessing dynamic and reversible light manipulation of its waveband-selectivity within a wide spectral range (∼140 nm), was developed by micro-patterning of a photoresponsive self-organized helical liquid crystal superstructure. Distinct from a conventional liquid crystal diffraction device, applied in a wide band from ultraviolet to near infrared wherein the diffracting light is due to the alternate phase modulation caused by the difference on liquid crystal arrangement, herein, the diffraction was mainly induced by an alternate transmittance/reflectance (i.e., amplitude) modulation to an incident light with a certain wavelength located in a selective reflection band of a binary patterned helical liquid crystal layer, producing diffraction both on the transmission and reflection sides of the sample. The waveband-selectivity was determined and manipulated by appropriately controlling the reflection band of the patterned helical liquid crystals. A prominent advantage compared to the majority of other liquid crystal polymer based devices is the electric responsiveness of such a device in addition to its photoresponsiveness. Moreover, an excellent light reconfiguration, exhibiting an erasing of the grating, followed by a rewriting of a Fresnel zone plate was achieved.
29 citations
TL;DR: It is demonstrated that, for an MRSSZP with topological charge 2, an array of dark cores is formed, which have phase structures similar to that of the interference of optical vortices with opposite topological charges.
Abstract: Herein, we present a so-called multiregion spiral square zone plate (MRSSZP), in which a spiral square zone plate is divided into a few regions, so that every region is composed of Fresnel zones, and the first zone of a given region is the same as the last zone of the previous region from a transmission point of view. We show that an MRSSZP can generate unique features of an array of an optical vortex with topological charge ±1, so that the number of vortices is directly related to the number of regions. We also demonstrate that, for an MRSSZP with topological charge 2, an array of dark cores is formed, which have phase structures similar to that of the interference of optical vortices with opposite topological charges. Besides, the focused vortex array follows a modulo-4 transmutation rule. In addition, when the topological charge becomes multiples of 4, an array of focal bright spots surrounded by a dark ring is generated. Numerical and experimental results verify the superior features of an MRSSZP.
28 citations
TL;DR: Simulations and experiments successfully showed the real-time tunability of the focusing properties such as peak intensity, focal spot sizes and focal lengths and it is foreseeable that such a hybrid FZP may find wider applications in lab-on-a-chip systems and optical devices.
Abstract: A Fresnel zone plate (FZP) is a unique diffractive optical device and widely used in integrated optical systems such as interferometers and antennas. A traditional FZP utilizes solid materials and cannot be modulated in real time for desired focusing properties. This paper reports a tunable optofluidic FZP based on a solid–liquid hybrid structure. This FZP consists of two parts including a fast microfluidic mixer, which can adjust the refractive index of liquids from 1.332 to 1.432, and subsequently an optical FZP with a solid–liquid combination. Simulations and experiments successfully showed the real-time tunability of the focusing properties such as peak intensity, focal spot sizes and focal lengths. The focal spot size can be modulated from 16 μm to 80 μm at λ0 = 532 nm in experiments with focal length changes of approximately 700 μm. Moreover, it can be easily switched between focusing, defocusing and collimation. The dispersion with different wavelengths was also investigated, showing that these types of focusing properties are quite different from a traditional optofluidic lens by refraction or reflection. It is foreseeable that such a hybrid FZP may find wider applications in lab-on-a-chip systems and optical devices.
20 citations
TL;DR: It is shown that, as a transparent plane-parallel plate is illuminated at a boundary region by a monochromatic beam of light, Fresnel diffraction occurs because of the abrupt change in phase imposed by the finite change in refractive index at the plate boundary.
Abstract: A method based on the Fresnel diffraction of light from the phase step is introduced for measuring effective focal length (EFL) and back focal length (BFL) of optical imaging systems. It is shown that, as a transparent plane-parallel plate is illuminated at a boundary region by a monochromatic beam of light, Fresnel diffraction occurs because of the abrupt change in phase imposed by the finite change in refractive index at the plate boundary. Variation of the incident angle in a convergent (or divergent) beam of light causes the periodic intensity along the central fringe of the diffraction pattern. The measurement of the extrema position of the intensity distribution accurately provides the EFL and BFL. The technique is easy to apply and can measure a wide range of both positive and negative focal lengths. The measuring setup can be very compact with low mechanical and optical noises. As examples of this technique, the EFLs of five different lenses are experimentally obtained. The results are quite consistent with the values indicated by the lens manufacturer.
18 citations
TL;DR: To the authors' knowledge, this is the first implementation of polarization conversion and subwavelength focusing of light using a pair of transmission micro-optic elements.
Abstract: We have investigated a four-sector transmission polarization converter (4-SPC) for a wavelength of 633 nm, that enables the conversion of a linearly polarized incident beam into a mixture of linearly and azimuthally polarized beams. It was numerically shown that by placing a Fresnel zone plate of focal length 532 nm immediately after the 4-SPC, the incident light can be focused into an oblong subwavelength focal spot whose size is smaller than the diffraction limit (with width and breadth, respectively, measuring FWHM = 0.28λ and FWHM = 0.45λ, where λ is the incident wavelength and FWHM stands for full-width at half maximum of the intensity). After passing through the 4-SPC, light propagates in free space over a distance of 300 μm before being focused by a Fresnel zone plate (ZP), resulting in focal spot measuring 0.42λ and 0.81λ. The focal spot was measured by a near-field microscope SNOM, and the transverse E-field component of the focal spot was calculated to be 0.42λ and 0.59λ. This numerical result was verified experimentally, giving a focal spot of smaller and larger size, respectively, measuring 0.46λ and 0.57λ. To our knowledge, this is the first implementation of polarization conversion and subwavelength focusing of light using a pair of transmission micro-optic elements.
17 citations
TL;DR: In this paper, the axial location of the main focus and axial distance between two neighboring foci of the fractional fractal zone plate (FZP) beam can be precisely customized.
Abstract: Free-space propagations of the optical beams generated by the fractal zone plates with fractional structural parameters [i.e., fractional fractal zone plate (FZP)] are analytically studied in this paper. The results demonstrate that the axial location of the main focus and axial distance between two neighboring foci of the fractional FZP beam can be precisely customized. Furthermore, we first demonstrate optical manipulation with the fractional FZP beam. The experimental results verified that such an FZP beam can simultaneously trap multiple particles positioned in different focal planes of the beam, owing to the multiple foci and self-reconstruction property of the FZP beam. The customized locations of trapped particles can also be realized by the fractional FZP beam, which would be useful for constructing three-dimensional optical tweezers.
TL;DR: In this article, an amplitude spiral orthogonal zone plate (ASOZP) is proposed for generating optical vortices by overlapping closely a vertical spiral one-dimensional zone plate and a horizontal one.
TL;DR: In this article, the fabrication of large-scale eight-level phase-type Fresnel zone plate arrays (FZPAs) by femtosecond-laser direct writing technology was reported.
28 Jan 2016
TL;DR: In this paper, a hard x-ray imaging microscopy and microtomography system was developed at the beamline 37XU of SPring-8, achieving a spatial resolution of about 50 nm in two-dimensional imaging at 6 keV xray energy using a Fresnel zone plate objective with an outermost zone width of 35 nm.
Abstract: A hard x-ray imaging microscopy and microtomography system is now being developed at the beamline 37XU of SPring-8. In the latest improvement, a spatial resolution of about 50 nm is achieved in two-dimensional imaging at 6 keV x-ray energy using a Fresnel zone plate objective with an outermost zone width of 35 nm. In the tomographic measurement, a spatial resolution of about 100 nm is achieved at 8 keV using an x-ray guide tube condenser optic and a Fresnel zone plate objective with an outermost zone width of 50 nm.
TL;DR: In this paper, an improved nanofabrication method of high aspect ratio tungsten structures for use in high efficiency nanofocusing hard X-ray zone plates was presented.
TL;DR: In this article, a table-top transmission soft X-ray (SXR) microscope, using a laboratory incoherent capillary discharge source has been carried out, achieving half-pitch spatial resolution of the microscope approaches 100 nm, as demonstrated by the knife-edge test.
Abstract: The development and demonstration of a table-top transmission soft X-ray (SXR) microscope, using a laboratory incoherent capillary discharge source has been carried out. This Z-pinching capillary discharge water-window SXR source, is a first of its kind to be used for high spatial resolution microscopy at λ = 2.88 nm (430 eV) . A grazing incidence ellipsoidal condenser mirror is used for focusing of the SXR radiation at the sample plane. The Fresnel zone plate objective lens is used for imaging of the sample onto a back-illuminated (BI) CCD camera. The achieved half-pitch spatial resolution of the microscope approaches 100 nm, as demonstrated by the knife-edge test. Details about the source, and the construction of the microscope are presented and discussed. Additionally, the SXR images of various samples, proving applicability of such microscope for observation of objects in the nanoscale, are shown.
TL;DR: In this article, a dynamic mask lithography system was used to fabricate a polymer-stabilized blue-phase Fresnel lens, which features polarization-insensitivity, a broad temperature range, submillisecond response and high spatial frequency.
Abstract: In this paper, we use a dynamic mask lithography system to fabricate a polymer-stabilized blue-phase Fresnel lens. Fresnel-zone patterned light is directly generated by a programmable spatial light modulator and then projected onto the blue phase precursor. As blue phase is cured, a Fresnel-zone refractive index distribution is achieved simultaneously. The fabricated Fresnel lens features polarization-insensitivity, a broad temperature range, submillisecond response and high spatial frequency. With easy fabrication and programmable flexibility, this method has great potential for various optical applications.
TL;DR: In this paper, an optically and electrically controllable Fresnel lens in a 90° twisted-nematic liquid crystal (LC) cell with a photoconductive polymer layer was presented.
Abstract: This letter presents an optically and electrically controllable Fresnel lens in a 90° twisted-nematic liquid crystal (LC) cell with a photoconductive polymer layer. A dc voltage was applied to the cell irradiated using an interference pattern obtained from a Sagnac interferometer. The dc electric field caused the accumulation of ionic impurities on the substrates, thereby reducing the strength of the electric field in the cell. Light illumination caused an increase in the conductivity of the photoconductive layer, increasing the electric field in the bright zones of the interference pattern. The difference in the electric fields in the bright and dark zones led to discrepancies in the reorientation of the LC, allowing it to be tuned by adjusting the intensity of the Fresnel pattern and the applied dc voltage.
TL;DR: The use of synchrotron radiation along with Fresnel zone plate optics to perform absorption contrast tomography for analyzing nanoscale features of fine second phase particles distributed in the tin matrix, which are representative of the bulk microstructure.
Abstract: Three-dimensional (3D) nondestructive microstructural characterization was performed using full-field transmission X-ray microscopy on an Sn-rich alloy, at a spatial resolution of 60 nm. This study highlights the use of synchrotron radiation along with Fresnel zone plate optics to perform absorption contrast tomography for analyzing nanoscale features of fine second phase particles distributed in the tin matrix, which are representative of the bulk microstructure. The 3D reconstruction was also used to quantify microstructural details of the analyzed volume.
TL;DR: In this paper, a micro-coherent EUV scatterometry microscope (micro-CSM) was developed to evaluate defects on extreme ultraviolet (EUV) masks at the blank state of manufacturing.
Abstract: To evaluate defects on extreme ultraviolet (EUV) masks at the blank state of manufacturing, we developed a micro-coherent EUV scatterometry microscope (micro-CSM). The illumination source is coherent EUV light with a 140 nm focus diameter on the defect using a Fresnel zone plate. This system directly observes the reflection and diffraction signals from a phase defect. The phase and the intensity image of the defect are reconstructed with the diffraction images using ptychography, which is an algorithm of the coherent diffraction imaging. We observed programmed phase defect on a blank EUV mask. Phase distributions of these programmed defects were well reconstructed quantitatively. The micro-CSM is a very powerful tool to review an EUV phase defect.
28 Jan 2016
TL;DR: In this article, a tilted-zone multilayer Laue lens was fabricated and compared with parallel-zone MLLs and found that they exhibit improved efficiency across their entire pupil.
Abstract: Multilayer Laue lenses (MLLs) capitalize on the developments in multilayer deposition technologies for fabricating reflective coatings, specifically undertaken for EUV lithography, where layer thicknesses of several nanometers can be achieved. MLLs are deposited layer by layer, with their thicknesses following the zone plate law, and then pieces are sliced and extracted for use in focusing. Rays are reflected in the Laue geometry. The efficiency of a MLL can be very high, and is maximized by making the slice equal to about a half Pendellosung period so that most energy is transferred from the undiffracted to the diffracted beam, and by ensuring that the Bragg condition is met at each point in the zone plate. This latter condition requires that the layers are tilted to the beam by an amount that varies with layer position; e.g. for focusing a collimated beam, the layers should be normal to a cylinder of radius of twice the focal length. We have fabricated such tilted-zone MLLs and find that they exhibit improved efficiency across their entire pupil as compared with parallel-zone MLLs. This leads to a higher effective NA of the optic and hence higher resolution.
TL;DR: Simulation results strongly indicate a good trapping ability, for particles under 150 µm in diameter, in the minimum energy location, which can be useful for cell or microorganism manipulation.
Abstract: In this paper, acoustic tweezers which use beam forming performed by a Fresnel zone plate are proposed. The performance has been demonstrated by finite element analysis, including the acoustic intensity, acoustic pressure, acoustic potential energy, gradient force, and particle distribution. The acoustic tweezers use an ultrasound beam produced by a lead zirconate titanate (PZT) transducer operating at 2.4 MHz and 100 Vpeak-to-peak in a water medium. The design of the Fresnel lens (zone plate) is based on air reflection, acoustic impedance matching, and the Fresnel half-wave band (FHWB) theory. This acoustic Fresnel lens can produce gradient force and acoustic potential wells that allow the capture and manipulation of single particles or clusters of particles. Simulation results strongly indicate a good trapping ability, for particles under 150 µm in diameter, in the minimum energy location. This can be useful for cell or microorganism manipulation.
Patent•
07 Dec 2016
TL;DR: In this article, a pure-phase code of a two-dimensional uniform-strength vortex optical grating was obtained through analytic operation and an optimization algorithm respectively, phase information of the pure phase codes was overlaid, a lens factor was introduced, discretized phase values were loaded to a spatial light modulator according to the pixel number and the pixel size of the spatial light, and then the corresponding three-dimensional vortex arrays can be obtained.
Abstract: The invention relates to an integrating method of three-dimensional spatial distribution vortex arrays, and belongs to the field of diffraction optics. A pure-phase code of a two-dimensional uniform-strength vortex optical grating and a pure-phase code of a spiral Dammam wave zone plate are obtained through analytic operation and an optimization algorithm respectively, phase information of the pure-phase codes is overlaid, a lens factor is introduced, discretized phase values are loaded to a spatial light modulator according to the pixel number and the pixel size of the spatial light modulator, and then the corresponding three-dimensional vortex arrays can be obtained. According to the method, the equal-strength and regular-distribution three-dimensional vortex arrays can be obtained, and each vortex beam in the arrays has the specific topological charge number.
10 Apr 2016
TL;DR: In this article, a Fresnel Zone Plate (FZPL) antenna working in the V band with half phase correction is reported, and a low cost and straightforward technological process is used to manufacture the dielectric lens using only one foam material whose the Dielectric constant is controlled.
Abstract: A Fresnel Zone Plate lens (FZPL) antenna working in V band is reported in this paper with half phase correction. A low cost and straightforward technological process is used to manufacture the dielectric lens using only one foam material whose the dielectric constant is controlled. Simulation and measurement results are in good agreement that confirms the viability of such a process to fabricate inhomogeneous structures. Good loss efficiency (73% at 60GHz) is obtained for this FZPL design.
TL;DR: In this article, the possibility of X-ray phase contrast imaging using a three-block interferometer consisting of bi-level Fresnel zone plates is considered, which operates in the amplitude division mode and does not impose strong requirements to spatial and temporal coherences of an initial radiation.
Abstract: The possibility of X-ray phase contrast imaging using already suggested three-block interferometer consisting of bi-level Fresnel zone plates is considered. The interferometer operates in the amplitude-division mode and does not impose strong requirements to spatial and temporal coherences of an initial radiation. The use of the Fresnel zone plates as the interferometer blocks allows one to obtain an optically magnified image of an object and to condense the radiation incident on the tested object.
30 Aug 2016
TL;DR: In this article, a table-top soft x-ray microscope based on a long-term stable and nearly debris-free laser plasma from a pulsed nitrogen gas jet target is presented.
Abstract: A table-top soft x-ray microscope based on a long-term stable and nearly debris-free laser plasma from a pulsed nitrogen gas jet target is presented. The microscope operates in the “water window” region at 2.88 nm wavelength. The emitted soft x-ray radiation is focused by an ellipsoidal condenser mirror into the object plane and a sample is imaged using a Fresnel zone plate onto a CCD camera. The spatial resolution of the microscope is about 50 nm demonstrated for a Siemens star test pattern.
10 Apr 2016
TL;DR: In this paper, the design and fabrication of a zone plate Fresnel lens is presented. And the dielectric zones are fabricated with different infill percentage to create tailored dielectrics constants to achieve 18 dBi directivity at 10 GHz when illuminated by a waveguide source.
Abstract: This paper presents the design and fabrication of a zone plate Fresnel lens. 3D Printing is used for rapid prototyping this low-cost and light-weight lens to operate at 10 GHz. This lens is comprised of four different 3D printed dielectric zones to form phase compensation in a Fresnel lens. The dielectric zones are fabricated with different infill percentage to create tailored dielectric constants. The dielectric lens offers 18 dBi directivity at 10 GHz when illuminated by a waveguide source.
TL;DR: In this article, a numerical Fourier transform is introduced in the iterative reconstruction process to replace the lens or zone plate used in the current CMI technique to adopt the constraint on the Fourier components of the exit wave field of the sample.
Abstract: We propose a lens-free coherent modulation imaging (CMI) method for reconstructing a general complex-valued wave field from a single frame of a diffraction pattern. A numerical Fourier transform is introduced in the iterative reconstruction process to replace the lens or zone plate used in the current CMI technique to adopt the constraint on the Fourier components of the exit wave field of the sample. While the complexity of the experimental setup is remarkably reduced by replacing the zone plate and additional accessories with the numerical processing, the energy fluence loss induced by the undesired diffraction orders of the zone plate can be also avoided. The feasibility of the proposed technique is verified experimentally with visible light.
TL;DR: In this paper, the effect of the structured parameters on the focusing properties of square zone plate was studied in detail, and it was shown that the main lobe is well modified, as well as the side lobes are reduced in comparison to that of the square Zone plate.
Abstract: We introduce and study a novel type of square zone plate, in which square Fresnel zones are azimuthally structured. The effect of the structured parameters on its focusing properties were studied in detail. Simulations show that the main lobe is well modified, as well as the side lobes are reduced in comparison to that of the square zone plate. In addition, by showing that the corners-originated beams have destructive contribution on the resolution as well as diffractive efficiency, most of the rectangle dark zones were shifted toward the corners in order to get higher diffraction efficiency. Having been shifted the dark rectangle zones, we demonstrated that focusing efficiency of square zone plate including both resolution and signal to noise ratio are also more enhanced. Additionally, simulation results are also verified by experiments.
10 Nov 2016
TL;DR: In this article, the imaginary part of the complex image indicates zero in the vicinity of the in-focus position, by using this characteristic, a new 3D-sensing algorithm which generates depth images without light sources or binocular vision was established.
Abstract: Lensless light-field imaging technology with Fresnel zone aperture reconstructs a complex image, composed of complex numbers, from captured sensor images. In the present study, we found that the imaginary part of the complex image indicates zero in the vicinity of the in-focus position. By using this characteristic, we established a new 3D-sensing algorithm which generates depth images without light sources or binocular vision. The algorithm enables compact 3D-sensors suitable for various applications, e.g. smartphones, robots, and vehicles.