Showing papers on "Zone plate published in 2020"

Electrically focus-tuneable ultrathin lens for high-resolution square subpixels.

Abstract: Owing to the tremendous demands for high-resolution pixel-scale thin lenses in displays, we developed a graphene-based ultrathin square subpixel lens (USSL) capable of electrically tuneable focusing (ETF) with a performance competitive with that of a typical mechanical refractive lens. The fringe field due to a voltage bias in the graphene proves that our ETF-USSL can focus light onto a single point regardless of the wavelength of the visible light—by controlling the carriers at the Dirac point using radially patterned graphene layers, the focal length of the planar structure can be adjusted without changing the curvature or position of the lens. A high focusing efficiency of over 60% at a visible wavelength of 405 nm was achieved with a lens thickness of <13 nm, and a change of 19.42% in the focal length with a 9% increase in transmission was exhibited under a driving voltage. This design is first presented as an ETF-USSL that can be controlled in pixel units of flat panel displays for visible light. It can be easily applied as an add-on to high resolution, slim displays and provides a new direction for the application of multifunctional autostereoscopic displays. Graphene-based ultrathin lenses with an electrically tuneable focal length could prove useful for providing displays with autostereoscopic 3D functionality, multiview or privacy protection. Developed by scientists in South Korea, the UK and the US, the lenses are just 13 nm thick and are based on a Fresnel Zone Plate (FZP) design made from a series of concentric rings of graphene on a glass substrate. Consisting of up to 5 layers of graphene that is patterned by focused ion-beam milling, the lenses offer a 60% transmission in the visible region and a focal length of 200–300 µm that can be tuned within ~20% range by applying a DC bias voltage. The applied voltage changes the charge carrier density in the graphene, modifying the topology of the FZP and thus its focusing behaviour.

Soft x-ray microscopy with 7 nm resolution

Abstract: The availability of intense soft x-ray beams with tunable energy and polarization has pushed the development of highly sensitive, element-specific, and noninvasive microscopy techniques to investigate condensed matter with high spatial and temporal resolution. The short wavelengths of soft x-rays promise to reach spatial resolutions in the deep single-digit nanometer regime, providing unprecedented access to magnetic phenomena at fundamental length scales. Despite considerable efforts in soft x-ray microscopy techniques, a two-dimensional resolution of 10 nm has not yet been surpassed in direct imaging. Here, we report on a significant step beyond this long-standing limit by combining newly developed soft x-ray Fresnel zone plate lenses with advanced precision in scanning control and careful optical design. With this approach, we achieve an image resolution of 7 nm. By combining this highly precise microscopy technique with the x-ray magnetic circular dichroism effect, we reveal dimensionality effects in an ensemble of interacting magnetic nanoparticles. Such effects are topical in current nanomagnetism research and highlight the opportunities of high-resolution soft x-ray microscopy in magnetism research and beyond.

Motionless optical scanning holography.

Abstract: Optical scanning holography (OSH) is an attractive technique since 3D information can be obtained with a single pixel detector. However, OSH requires an interferometer, scanning architecture, and a frequency shifter to scan a time-varying Fresnel zone plate (FZP), which makes the optical setup complicated. To reduce the complexity, the polarization sensitivity of a spatial light modulator (SLM) is applied. The proposed method implements a time-varying FZP with an in-line optical setup by using only an SLM. Observing results for a USAF pattern and a fluorescent bead reveals the feasibility of the new motionless holographic 3D imaging technique.

Fibonacci terahertz imaging by silicon diffractive optics

Abstract: Fibonacci or bifocal terahertz (THz) imaging is demonstrated experimentally employing silicon diffractive zone plate (SDZP) in a continuous wave mode. Images simultaneously recorded in two different planes are exhibited at 0.6 THz frequency with the spatial resolution of wavelength. Multi-focus imaging operation of the Fibonacci lens is compared with a performance of the conventional silicon phase zone plate. Spatial profiles and focal depth features are discussed varying the frequency from 0.3 THz to 0.6 THz. Good agreement between experimental results and simulation data is revealed.

Direct observation of spin-wave focusing by a Fresnel lens

Abstract: Spin waves are discussed as promising information carrier for beyond complementary metal-oxide semiconductor data processing. One major challenge is guiding and steering of spin waves in a uniform film. Here, we explore the use of diffractive optics for these tasks by nanoscale real-space imaging using x-ray microscopy and careful analysis with micromagnetic simulations. We discuss the properties of the focused caustic beams that are generated by a Fresnel-type zone plate and demonstrate control and steering of the focal spot. Thus, we present a steerable and intense nanometer-sized spin-wave source. Potentially, this could be used to selectively illuminate magnonic devices like nano-oscillators.

Tunable hard x-ray nanofocusing with Fresnel zone plates fabricated using deep etching

Abstract: Fresnel zone plates are used widely for x-ray nanofocusing, due to their ease of alignment and energy tunability. Their spatial resolution is limited in part by their outermost zone width drN, while their efficiency is limited in part by their thickness tzp. We demonstrate the use of Fresnel zone plate optics for x-ray nanofocusing with drN=16nm outermost zone width and a thickness of about tzp=1.8µm (or an aspect ratio of 110) with an absolute focusing efficiency of 4.7% at 12 keV, and 6.2% at 10 keV. Using partially coherent illumination at 12 keV, the zone plate delivered a FWHM focus of 46×60nm at 12 keV, with the first-order coherent mode in a ptychographic reconstruction showing a probe size of 16 nm FWHM. These optics were fabricated using a combination of metal-assisted chemical etching and atomic layer deposition for the diffracting structures, and silicon wafer back-thinning to produce optics useful for real applications. This approach should enable new higher resolution views of thick materials, especially when energy tunability is required.

A Millimeter-Wave Fabry–Pérot Cavity Antenna Using Fresnel Zone Plate Integrated PRS

Abstract: This communication introduces a new structure of a partially reflective surface (PRS) to realize gain enhancement for a millimeter-wave Fabry–Perot Cavity (FPC) antenna. It is the first attempt at applying a Fresnel zone plate (FZP) to a single-layer PRS, which contributes to a significant gain improvement. The proposed antenna consists of a feeding source, a substrate-integrated quasi-curve reflector, and the proposed PRS. With the quasi-curve reflector, multiple resonate modes are excited, providing a wide 3 dB gain bandwidth. For validation, a prototype of millimeter-wave FPC antenna is designed and measured. The antenna can be implemented by low-cost and mature printed-circuit-board (PCB) technology. The antenna yields a measured impedance bandwidth of 17.8% from 54 to 64.5 GHz and a 3 dB gain bandwidth of 13.3% from 56 to 64 GHz. The measured peak gain is 21 dBi at broadside direction. This antenna finds potential applications in high-speed communications at the millimeter-wave spectrum.

3D nanoprinted kinoform spiral zone plates on fiber facets for high-efficiency focused vortex beam generation

Abstract: In this paper, we propose and demonstrate an all-fiber high-efficiency focused vortex beam generator. The generator is fabricated by integrating a kinoform spiral zone plate (KSZP) on the top of the composite fiber structure using fs-laser two-photon polymerization 3D nanoprinting. The KSZP with spiral continuous-surface relief feature is designed by superimposing a spiral phase into a kinoform lens, which can efficiently concentrate and transform an all incident beam to a single-focus vortex beam, without the undesired zero-order diffracted light and extra high-order focus. Under arbitrary polarized light incident conditions, experiment results show that the focusing efficiency and vortex purity of the all-fiber generators are over 60% and 86%, respectively, which is much higher than that of a traditional binary SZP integrated on an optical fiber facet. In addition, characteristics of the generated vortex beam, such as focal spot, focal length and vortex topological charge are numerically designed and experimentally investigated. The experimental results agree well with the numerical simulation model using the FDTD algorithm. Due to the compact size, flexible design, polarization insensitivity, high focusing efficiency and high vortex purity, the proposed all-fiber photonic devices have promising potential in optical communication, particle manipulation and quantum computation applications.

Wavelength-tunable focusing via a Fresnel zone microsphere.

Abstract: In this Letter, a novel, to the best of our knowledge, structural configuration on a transparent microsphere is proposed to engineer the focusing light field. By patterning a hybrid diffractive Fresnel zone plate structure on a partially milled microsphere using a focused ion beam, wavelength-dependent switching between mono-focal and multi-focal functionalities can be achieved. Generation of on-axis tri-foci and mono-focus light fields under high numerical-aperture (${\rm NA}\gt {0.67}$NA>0.67) conditions at two working wavelengths (405 nm and 808 nm) have been demonstrated both numerically and experimentally.

Recent progress in synchrotron radiation 3D-4D nano-imaging based on X-ray full-field microscopy.

Abstract: The advent of high-flux, high-brilliance synchrotron radiation (SR) has prompted the development of high-resolution X-ray imaging techniques such as full-field microscopy, holography, coherent diffraction imaging and ptychography. These techniques have strong potential to establish non-destructive three- and four-dimensional nano-imaging when combined with computed tomography (CT), called nano-tomography (nano-CT). X-ray nano-CTs based on full-field microscopy are now routinely available and widely used. Here we discuss the current status and some applications of nano-CT using a Fresnel zone plate as an objective. Optical properties of full-field microscopy, such as spatial resolution and off-axis aberration, which determine the effective field of view, are also discussed, especially in relation to 3D tomographic imaging.

Ultrasonic tunable focusing by a stretchable phase-reversal Fresnel zone plate

Abstract: This paper reports a stretchable silicone phase-reversal (PR) Fresnel zone plate (FZP) that can focus ultrasonic energy at different focal lengths with a high transmission coefficient in water. Unlike a traditional FZP that creates focused by constructive interference of waves diffracted through open annular zones in an opaque screen, the silicone PR-FZP takes advantage of all the zones of the FZP contribute to the focal area by adding phase compensation regions instead of opaque regions. More interestingly, the silicone PR-FZP can be stretched, and the focal length increases gradually with the unchanged full width at half maximum as the PR-FZP is stretched. The aforementioned performance aspects are verified in both experiments and simulations. The proposed stretchable PR-FZP with a tunable focal length has potential applications in the broad field of ultrasonics, such as ultrasonic imaging and ultrasound neuromodulation.

Active-spiral Fresnel zone plate with tunable focal length for airborne generation of focused acoustic vortices

Abstract: We present a simple and efficient method for generating focused acoustic vortices in air over a wide range of ultrasonic frequencies by means of an Active-Spiral Fresnel Zone Plate. An important advantage of this device is that the focal length can be finely and continuously tuned by setting the operation frequency. The role of the different design parameters is analyzed in terms of the minimum beam width and the focal depth of the resulting field, allowing an optimized device according to the application. Experimental results show very good agreement with numerical simulations.

Metal-Assisted Chemical Etching and Electroless Deposition for Fabrication of Hard X-ray Pd/Si Zone Plates.

Abstract: Zone plates are diffractive optics commonly used in X-ray microscopes. Here, we present a wet-chemical approach for fabricating high aspect ratio Pd/Si zone plate optics aimed at the hard X-ray regime. A Si zone plate mold is fabricated via metal-assisted chemical etching (MACE) and further metalized with Pd via electroless deposition (ELD). MACE results in vertical Si zones with high aspect ratios. The observed MACE rate with our zone plate design is 700 nm/min. The ELD metallization yields a Pd density of 10.7 g/cm 3 , a value slightly lower than the theoretical density of 12 g/cm 3 . Fabricated zone plates have a grid design, 1:1 line-to-space-ratio, 30 nm outermost zone width, and an aspect ratio of 30:1. At 9 keV X-ray energy, the zone plate device shows a first order diffraction efficiency of 1.9%, measured at the MAX IV NanoMAX beamline. With this work, the possibility is opened to fabricate X-ray zone plates with low-cost etching and metallization methods.

Multifocus off-axis zone plates for x-ray free-electron laser experiments

Abstract: X-ray free-electron lasers (XFELs) are paving the way towards new experiments in many scientific fields, such as ultrafast science, nonlinear spectroscopy, and coherent imaging. However, the strong intensity fluctuations inherent to the lasing process in these sources often lead to problems in signal normalization. In order to address this challenge, we designed, fabricated, and characterized diffractive x-ray optics that combine the focusing properties of a Fresnel zone plate with the beam-splitting capability of a grating in a single diffractive optical element. The possibility to split the incident beam into identical copies allows for direct shot-to-shot normalization of the sample signal, thereby greatly enhancing the signal-to-noise ratio in experiments with XFEL radiation. Here we propose two schemes for the design of such diffractive x-ray optical elements for splitting and focusing an incoming beam into up to three foci by merging a grating with a focusing zone plate. By varying the duty cycle of the grating or the relative shift of the Fresnel zone plate structure, we are able to tune the relative intensities of the different diffraction orders to achieve the desired splitting ratios. Experimental confirmation of the design is provided with soft x-ray light (540 eV) and shows a good agreement with calculations, confirming the suitability of this approach for XFEL experiments.

Fresnel zone plate development for x-ray radiography of hydrodynamic instabilities at the National Ignition Facility.

Abstract: The study of Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities in a planar geometry at high energy densities at the National Ignition Facility (NIF) requires high spatial resolution imaging. We demonstrate the potential of Fresnel zone plates (FZPs) to achieve resolution that would unlock such studies. FZPs are circular aperiodic gratings that use diffraction to focus x rays and produce an image with high spatial resolution. Taking into account the NIF's challenging environment, we have designed a specific array of five FZPs for a zinc backlighter to take a radiograph of a target with 9 keV x rays. We measured a mean resolution for the FZP of 1.9µm±0.5µm and a ±1mm depth of focus at an x-ray calibration facility as well as a 2.3µm±0.4µm resolution on a resolution wire mesh shot on the NIF. We also performed an in-depth analysis of the image quality to assess the capability to resolve the small features present in RT and RM instabilities.

Spatially divided phase-shifting motionless optical scanning holography

Abstract: Motionless optical scanning holography (MOSH) has been proposed for three-dimensional incoherent imaging in single-pixel holography with a simple optical setup. To reduce the measurement time in MOSH, a spatially divided phase-shifting technique is introduced. The proposed method realizes measurements four times faster than the original MOSH, owing to the simultaneous lateral and phase shifts of a time-varying Fresnel zone plate. A hologram reproduced by the proposed method forms a spatially multiplexed phase-shifting hologram similar to parallel phase-shifting digital holography. The effectiveness of the proposed method is numerically and experimentally verified.

Bifocal Ultrasound Focusing Using Bi-Fresnel Zone Plate Lenses

Abstract: In this work, we present a bifocal Fresnel zone plate (BiFZP) capable of generating focusing profiles with two different foci. The performance of the BiFZP is demonstrated in the ultrasound domain, with a very good agreement between the experimental measurements and the finite element method (FEM) simulations. This lens becomes an appealing alternative to other dual-focusing lenses, in which the foci location can only be set at a limited range of positions, such as M-bonacci zone plates. Moreover, the variation of the operating frequency has also been analyzed, providing an additional dynamic control parameter in this type of lenses.

High-NA achromatic diffractive lensing for arbitrary dual-wavelengths enabled by hybridized metal-insulator-metal cavities

Abstract: A new type of diffractive lens based on hybridized Fabry−Perot (FP) cavities with high-NA and achromatic features for arbitrary dual-wavelengths is theoretically proposed and demonstrated. We utilize the subwavelength-scale metal−insulator−metal nanocavity to form a Fresnel zone plate (MIM-FZP) that benefits from both spectral selectivity and high numerical aperture (NA > 0.9) to enable lensing functionality. By taking advantage of the different transmission orders from MIM, any arbitrary dual-wavelength achromatic focusing design is achieved. Using this approach, we merge two independent MIM-FZP designs and realize achromatic focusing performance at the selected dual-wavelength of 400/600 nm. Furthermore, the achromatic lens also exhibits a crucial potential for dynamically tuning of the operation wavelengths and focusing lengths as actively scaling the core layer thickness of MIM. The unique MIM-FZP design can be practically fabricated using a grayscale lithography technique. We believe such high-NA and achromatic optical devices enjoy great simplicity for structural design and can easily find applications including high-resolution imaging, new-generation integrated optoelectronic devices, confocal collimation, and achromatic lens, etc.

Hard X-ray nano-holotomography with a Fresnel zone plate

Abstract: X-ray phase contrast nanotomography enables imaging of a wide range of samples with high spatial resolution in 3D. Near-field holography, as one of the major phase contrast techniques, is often implemented using X-ray optics such as Kirkpatrick-Baez mirrors, waveguides and compound refractive lenses. However, these optics are often tailor-made for a specific beamline and challenging to implement and align. Here, we present a near-field holography setup based on Fresnel zone plates which is fast and easy to align and provides a smooth illumination and flat field. The imaging quality of different types of Fresnel zone plates is compared in terms of the flat-field quality, the achievable resolution and exposure efficiency i.e. the photons arriving at the detector. Overall, this setup is capable of imaging different types of samples at high spatial resolution of below 100 nm in 3D with access to the quantitative phase information.

Polarization-Independent Metasurface Lens Based on Binary Phase Fresnel Zone Plate.

Abstract: Based on the binary phase Fresnel zone plate (FZP), a polarization-independent metasurface lens that is able to focus incident light with any polarization state, including circular, linear, and elliptical polarizations, has been proposed and investigated. We demonstrate that the metasurface lens consisting of metal subwavelength slits can operate in a wide bandwidth in the visible range, and has a higher focusing efficiency than that of an amplitude FZP lens without phase modulation. A multi-focus FZP metasurface lens has also been designed and investigated. The proposed lens can provide potential applications in integrated nanophotonic devices without polarization limitations.

Effect of tilt on circular zone plate performance

Abstract: Fresnel zone plates are frequently used as focusing and imaging optics in x-ray microscopy, as they provide the ease of use of normal incidence optics. We consider here the effects of tilt misalignment on their optical performance, both in the thin optics limit and in the case of zone plates that are sufficiently thick so that volume diffraction effects come into play. Using multislice propagation, we show that simple analytical models describe the tilt sensitivity of thin zone plates and the thickness at which volume diffraction must be considered, and examine numerically the performance of example zone plates for soft x-ray focusing at 0.5 keV and hard x-ray focusing at 10 keV.

Composite spiral multi-value zone plates

Abstract: We present composite spiral multi-value phase zone plates that are achieved by sectioning a spiral multi-value phase zone plate into several radial regions. Each region is composed of specially structured Fresnel zones with optimized phase values and an embedded basic topological charge. In numerical studies, it is shown that the proposed element is capable of producing equal intensity arrays of petal-like modes as well as dark optical ring lattice structures along the optical axis in multiple focal planes of the diffractive element. Additionally, it is demonstrated that the generated petal-like modes can be rotated in a controllable manner by implementing an angular frequency shift between the two composited spiral multi-value phase zone plates. We also illustrate that the rotation angle is independent of the diffraction order. Experimental results are included to verify the theoretical outcomes, where the phase pattern of the composite spiral multi-value zone plate is encoded onto a spatial light modulator.

Hard X-ray ptychography for optics characterization using a partially coherent synchrotron source

Abstract: Ptychography is a scanning coherent diffraction imaging technique which provides high resolution imaging and complete spatial information of the complex electric field probe and sample transmission function. Its ability to accurately determine the illumination probe has led to its use at modern synchrotrons and free-electron lasers as a wavefront-sensing technique for optics alignment, monitoring and correction. Recent developments in the ptychography reconstruction process now incorporate a modal decomposition of the illuminating probe and relax the restriction of using sources with high spatial coherence. In this article a practical implementation of hard X-ray ptychography from a partially coherent X-ray source with a large number of modes is demonstrated experimentally. A strongly diffracting Siemens star test sample is imaged using the focused beam produced by either a Fresnel zone plate or beryllium compound refractive lens. The recovered probe from each optic is back propagated in order to plot the beam caustic and determine the precise focal size and position. The power distribution of the reconstructed probe modes also allows the quantification of the beams coherence and is compared with the values predicted by a Gaussian–Schell model and the optics exit intensity.

Multi-beam X-ray ptychography for high-throughput coherent diffraction imaging

Abstract: X-ray ptychography is a rapidly developing coherent diffraction imaging technique that provides nanoscale resolution on extended field-of-view. However, the requirement of coherence and the scanning mechanism limit the throughput of ptychographic imaging. In this paper, we propose X-ray ptychography using multiple illuminations instead of single illumination in conventional ptychography. Multiple locations of the sample are simultaneously imaged by spatially separated X-ray beams, therefore, the obtained field-of-view in one scan can be enlarged by a factor equal to the number of illuminations. We have demonstrated this technique experimentally using two X-ray beams focused by a house-made Fresnel zone plate array. Two areas of the object and corresponding double illuminations were successfully reconstructed from diffraction patterns acquired in one scan, with image quality similar with those obtained by conventional single-beam ptychography in sequence. Multi-beam ptychography approach increases the imaging speed, providing an efficient way for high-resolution imaging of large extended specimens.

Cascaded Fresnel Lens Antenna for Scan Loss Mitigation in Millimeter-Wave Access Points

Abstract: Millimeter-wave lens antennas will be essential for future wireless access. Conventionally, they increase the gain in the boresight direction only. In this article, cascaded Fresnel zone plate lenses are combined with a phased array to increase the gain at wide steering angles of ±52°. The side lenses are tilted to align with the maximum steering angle and cascaded to increase the focusing gain. The inner lenses increase the gain by 2.45 dB at boresight, and by 3.19 dB at the maximum steering angle. When the side lenses are repositioned, the simulated focusing gain increases to 4.69 dB. Asymmetric amplitude distributions are proposed to prevent the main lobe from splitting. An eight-element seven-lens prototype operating at 28 GHz achieved a gain from 12.96 to 15.35 dBi with a bandwidth of at least 1.3 GHz for all measured beam directions. The maximum measured azimuthal beamwidth was 27°. A design procedure and a theoretical analysis of diffraction through the lenses are provided. By increasing the SNR, this beamforming antenna could improve the coverage of three-sector 5G microcell base stations, and support gigabit wireless links for vehicular, rail, and satellite communications.

Imaging properties of generalized composite aperiodic zone plates.

Abstract: Generalized composite aperiodic zone plates (GCAZPs) are proposed to generate clearer images at focal planes. The images can be produced by a target object at infinity based on a collimator. The proposed zone plate consists of the proposed radial zone plate (RZP), whose original radius is not zero, and the common aperiodic zone plate, which has the coincident first-order diffraction area and the same axial first-order diffraction intensity distribution. The GCAZPs are applicable for the other aperiodic zone plates. Moreover, the modulation transfer function curve of the GCAZP is basically above that of the corresponding common aperiodic zone plate. Compared with the common aperiodic zone plates, the GCAZPs have the foci with higher intensity and the images with higher contrast at the same focal planes. In addition, a GCAZP with an arbitrary size can be designed. The construction method of the GCAZP is illustrated in details. Furthermore, it has been also proved numerically and experimentally that the GCAZPs are used to generate the clearer images than the corresponding common aperiodic zone plates. The proposed zone plates are applicable to generate clear images and trap particles stably at multiple planes simultaneously.

Dual‐Wavelength Focusing through Fresnel Zone Plate Fabricated in Lithium Niobate Crystal by Femtosecond Laser Micromachining

Abstract: Fresnel zone plate (FZP) is a kind of diffractive optical element that produces amplitude and phase modulation of light. The FZP is also known as the diffractive lens and has a wide range of applications with the wavelength ranging from visible to X-ray. Nowadays, many methods have been proposed to produce FZP for beam focusing, including photolithography combined with etching technique, spatial light modulator (SLM) method, and laser lithography technique. However, these methods achieved beam focusing with monochromatic light in the linear optics and had some limitations when applied to the nonlinear field. Nonlinear frequency conversion using the quadratic nonlinear crystals is an important technique to generate coherent radiation in wavelengths when compact and efficient laser sources are not available. It is worth noting that the nonlinear harmonic beam shaping has attracted intense interest in recent years and has been studied in various applications. A novel method to integrate the beam-shaping process within the nonlinear materials is by the use of nonlinear photonic crystals (NPCs). Using the electric-field poling technique or femtosecond laser micromachining, the second-order nonlinear coefficient χ of the NPC can be spatially modulated. In our previous research, we have proposed a method to realize the efficient 2D nonlinear wavefront shaping in amplitude-type NPCs by femtosecond laser micromachining. Nowadays, with the rapid progress of technology, the implementation of the nonlinear beam focusing is in great demand. In this article, we demonstrated the realization of the dual-wavelength focusing of second-harmonic (SH) and fundamental frequency (FF) via a diffractive lens in lithium niobate (LiNbO3) crystal. The diffractive lens was fabricated by femtosecond laser micromachining and had a geometric FZP pattern with 0 or þ1 binary modulation of quadratic susceptibility. We named this SH diffractive lens in LiNbO3 as amplitude-type nonlinear FZP (A-NFZP). The modulated A-NFZP was cut for a specific angle between the optical axis and the z-axis of the crystal, where the phase-matching condition is fulfilled through the birefringence phase matching (BPM) in the longitudinal direction. We have fabricated the A-NFZP with a 1 cm focal length at the wavelength of 1064 nm. The evolution of the SH beam focusing intensity patterns in the direction of beam propagation has been theoretically and experimentally studied. In general, the FZP is divided into three types: phase-type FZP, amplitude-type FZP, and phase-amplitude-type (amplitude and phase hybrid) FZP. As the femtosecond laser micromachining can modulate the LiNbO3 crystal with either an entirely positive or an erased zero quadratic susceptibility throughout the interaction region, we chose the amplitudetype FZP to fabricate. The A-NFZP consists of transparent and opaque zones, as shown in Figure 1. Also, we use the positive zone plate with a transparent center to illustrate. The transparent and opaque zones that make up the FZP are determined by Equation (1) and (2); the position where the diffracted light converges at one point is defined by Equation (3) and (4):