Diffraction Zone Research Articles

Atmospheric, Non-Contact and High Speed Electro Chemical Machining Processes for X-Ray Optics

High resolution X-ray focusing optics is critical component in many spatially resolved techniques at many synchrotron facilities, such as micro X-ray fluorescence, micro-diffraction, and micro-spectroscopy. In order for these optics to achieve modern capability goals, they must embody various key performance attributes such as a minimum in spatial resolution, a maximum in focusing efficiency, a practical working distance (no more than a few meters), and ideally robust achromaticity (negligible photon energy dependence). The state of the art in X-ray optics encompasses, among others, diffractive zone plate optics, Kirkpatrick-Baez (K-B) mirrors, and compound refractive lenses (CRLs). Among these, only K-B mirrors provide highly efficient collection of X-ray photons and essentially perfect achromaticity, but require elliptical mirrors of exceptionally precise figure and placement, as well as sub-nanometer smoothness1. In attempting to identify potential advances in X-ray optics beyond this state of the art, one promising solution is the design of single-bounce, axially symmetric mirror optics with parabolic inner profiles capable of focusing x-rays simultaneously in two orthogonal directions, which may overcome the long focal length limitation of KB mirrors. Manufacture of such precise optics as these novel one-bounce mirrors or the traditional K-B mirrors requires highly advanced surface finishing techniques. Silicon is mostly used in this application due to its low CTE, low thermal deformation, low z, high reflectivity, and low radiation adsorption. The conventional manufacturing approaches used to prepare aspherical, low roughness, and high-z coated silicon mirrors, included Ion Beam Figuring, Elastic Emission Machining (EEM), Plasma Machining, Lapping/Polishing2,3. Of these techniques the Plasma and Ion Beam approaches require vacuum atmosphere for processing limiting the size of the components that can be produced. Meanwhile, EEM can achieve better final finishes (up to 1 A) under atmospheric, non-contact conditions, however it is several orders of magnitude slower (0.1 to 0.001 µm/min) than these approaches. Furthermore, contact machining techniques like Lapping/Polishing tend to lead to surface defects that must be removed prior to mirror usage. Therefore, the design of low cost/high speed machining and polishing systems that can form high resolution x-ray focusing optics over large mirror areas is critical for the formation of next generation of x-ray optics. This paper will discuss ongoing efforts by Faraday to design an atmospheric, non-contact, low cost/high speed electrochemical machining process to produce next-generation ellipsoidal x-ray optics via a scalable pulse-reverse electrochemical manufacturing approach. Unlike conventional electrochemical surface finishing processes, the pulse-reverse process does not require low conductivity/high viscosity electrolytes or the addition of hazardous chemical species (like HF) to remove the oxide film associated with electropolishing of passive and strongly passive materials like Si. This paper will focus on the potential of pulse/pulse reverse electrofinishing process to produce optics such as Kirkpatrick-Baez mirrors and compound refractive lenses for X-ray optic technologies being used at synchrotron facilities. In particular, this talk will discuss fundamental processing techniques and the performance observed in ongoing studies. Initial trials of atmospheric, non-contact process demonstrated a material removal rate of 40 µm/h which is 100 times faster than currently used EEM technique. Acknowledgement This material is based upon ‎work supported by the Department of Energy under ‎Award No‎. ‎DE‎-‎ SC0015201. References S. Matsuyama., et.al., “Textbook for hard X-ray focusing with Kirkpatrick-Baez optics.” Online resource: http://cheiron2009.spring8.or.jp/images/PDF/Practicals?16_29XLU.pdf. Accessed 15 Oct 2015. H. Takino., et.al., “ Ultraprecision Machining of Optical Surfaces.” Nikon Corporation.Y. Mori., et.al., “Development of plasma chemical vaporization machining and elastic emission machining systems for coherent X-ray optics.” SPIE 4501, 2001.

Emergence of Fresnel diffraction zones in gravitational lensing by a cosmic string

The possibility to detect cosmic strings – topological defects of early Universe, by means of wave effects in gravitational lensing is discussed. To find the optimal observation conditions, we define the hyperbolic-shaped Fresnel observation zones associated with the diffraction maxima and analyse the frequency patterns of wave amplification corresponding to different alignments. In particular, we show that diffraction of gravitational waves by the string may lead to significant amplification at cosmological distances. The wave properties we found are quite different from what one would expect, for instance, from light scattered off a thin wire or slit, since a cosmic string, as a topological defect, gives no shadow at all.

Generation of a controlled double-ring-shaped radially polarized spiral laser beam using a combination of a binary axicon with an interference polarizer

A new optical system is proposed for the generation of radially polarized spiral laser beams in the form of a controlled narrow double ring. The system is based on the conversion of conical wavefronts passing through an interference polarizing plate. A double conical wavefront is formed by a diffractive axicon and the obtained nonuniformly polarized beam is collimated by a refractive axicon. During the beam formation the amplitude distribution can be controlled by the redistribution of energy between the diffraction orders due to a modification of the profile of the diffractive element zones. A double-ring-shaped radially polarized beam is experimentally obtained with the help of a binary phase axicon.

Defined distribution forming in the near diffraction zone based on expansion of finite propagation operator eigenfunctions

This study considers the solution of the inverse diffraction problem for 1D finite (in the spatial and spectral regions) optical signal propagation operator in free space of the near zone (over a distance of several wavelengths). The beam propagation distance and the intervals of input domain and spatial frequency are the parameters of the operator. They change the set of the eigenvalues and eigenfunctions determining the number of degrees of freedom for approximation of a defined distribution. We have solved the inverse problem, namely we have performed the calculation of the input signals ensuring the forming of the defined distributions at various distances.

A desktop extreme ultraviolet microscope based on a compact laser-plasma light source

A compact, desktop size microscope, based on laser-plasma source and equipped with reflective condenser and diffractive Fresnel zone plate objective, operating in the extreme ultraviolet (EUV) region at the wavelength of 13.8 nm, was developed. The microscope is capable of capturing magnified images of objects with 95-nm full-pitch spatial resolution (48 nm 25–75% KE) and exposure time as low as a few seconds, combining reasonable acquisition conditions with stand-alone desktop footprint. Such EUV microscope can be regarded as a complementary imaging tool to already existing, well-established ones. Details about the microscope, characterization, resolution estimation and real sample images are presented and discussed.

Application of nanoimprinting technique for fabrication of trifocal diffractive lens with sine-like radial profile.

The fabrication of submicron-height sine-like relief of a trifocal diffractive zone plate using a nanoimprinting technique is studied. The zone plate is intended for use in combined trifocal diffractive–refractive lenses and provides the possibility to form trifocal intraocular lenses with predetermined light intensity distribution between foci. The optical properties of the designed zone plate having the optical powers 3 D, 0, −3D in the three main diffraction orders are theoretically and experimentally investigated. The results of the theoretical investigations are in good agreement with experimental measurements. The effects of the pupil size (lens diameter) as well as the wavelength-dependent behavior of the zone plate are also discussed.

Metasurfaces based dual wavelength diffractive lenses.

We demonstrate experimentally and by simulations a method for using thin nanostructured plasmonic metasurfaces to design diffractive Fresnel zone plate lenses that focus pairs of wavelengths to a single focal point. The metasurfaces are made of tightly packed cross and rod shaped optical nanoantennas with strong polarization and wavelength selectivity. This selectivity allows multiplexing two different lenses with low spectral crosstalk on the same substrate and to address any superposition of the two colors at the focus of the lenses by controlling the polarization of light. This concept can open the door to use ultrathin diffractive lenses in fluorescence microscopy and in stimulated emission depletion microscopy.

Dielectrophoretically controlled Fresnel zone plate.

Switchability is a highly sought after feature for planar optical systems. Suspensions of nanomaterials can be used for generating controllable changes in such systems. We report a planar diffractive microfluidic lens which integrates controlled dielectrophoresis (DEP) for trapping suspended nanomaterials. Silicon and tungsten oxide nanoparticle suspensions are used. These nanomaterials are trapped in such a way as to form alternating opaque and transparent rings using the DEP forces on demand. These rings form a planar diffractive Fresnel zone plate to focus the incident light. The Fresnel zone plate is tuned for the visible light region and the lens can be turned on (DEP applied) or off (DEP removed) in a controlled manner. This proof of concept demonstration can be further expanded for a variety of switchable optical devices and can be integrated with lab-on-a-chip and optofluidic devices.

Stochastic Analysis of Scattered Field by Building Facades Using Polynomial Chaos

This paper presents a statistical assessment of scattered field from a building facade having rando m physical and geometrical parameters. A simple inhomogeneous model is considered for the building and the calculation met hod is based on Green's functions. The basis of polynomial chaos expansion method is explained and applied to estimate the sca ttered electric field from a building facade having 8 random parameters, in specular and non-specular scenarios. Uncertainty analysis and total output distribution are discussed in differen t diffraction zones of the building. IRELESS communications, particularly mobile networks, experienced a great expansion worldwide. These networks are very dense in urban areas and th e electromagnetic field distribution is highly depend ent on city structures. It is essential to have predictive tool s to assess as accurately as possible the distribution of electrom agnetic fields in order to enable optimized implementation of base stations and respect the constraints regarding huma n exposure. Wave propagation simulators are based on different models of urban environment with different assumptions on the building architectural details. Given the adopted model, the y incorporate appropriate calculation methods. We can mention empirical, statistical, theoretical, site-specific models or a combination of them to generate a hybrid model (1). Empirical models (2) are based on the extensive measurement campaigns and are highly related to the structure of the city . Statistical models (3) are also based on measurements and are u sed to give wide band multipath model of the environment. Theoretical (physical) (4) models are obtained by i mposing some general idealized conditions on the geometry. They usually use physical optics with or without diffrac tion phenomena. Site-specific models (5) depend on a lar ge number of parameters which are related to a given s ite and their computing time, depending on the complexity o f the environment, can be long. These models usually employ ray

Diffraction of collinear correlated photon pairs by an ultrasonic wave within Raman–Nath and intermediate region

The phenomenon of collinear correlated photon pairs diffraction by an ultrasonic wave is investigated within Raman–Nath and intermediate region. The numbers of single photons and photon pairs counts in discrete diffraction orders were measured as functions of the Raman–Nath parameter. Similarly, the number of coincidence photon counts in separate diffraction orders was also investigated. It was shown experimentally that the phenomenon of photon pairs diffraction by an ultrasonic wave happens at angles identical to those corresponding to single photons diffraction. It was also demonstrated that in case of Raman–Nath diffraction the number of photon pairs in a selected, nth, diffraction order varies with the Raman–Nath parameter changes as an nth order Bessel function of the first kind, raised to the fourth power. Whilst in the so-called intermediate diffraction zone, the number of diffracted photon pairs varies as squared intensity of a diffracted light beam consisting of single photons. Moreover, it was revealed that correlations between photons in selected diffraction orders change with the Raman–Nath parameter variation as products of relevant intensities of light in the considered diffraction orders. Finally, it should be emphasized that the presented formulae describing diffraction of collinear correlated proton pairs by an ultrasonic wave are in a very good agreement with corresponding experimental data, for both Raman–Nath and intermediate diffraction.

Rigorous method to solute the slit diffraction

The authors present a semianalytical method to rigorous solute the slit diffraction in this paper, and it can be used to calculate the field located at an arbitrary depth of the diffraction zone. And some expressions of the diffraction field in the double-slit are also given. Finally, the space distribution of the diffraction field located at three transmission depths was numerically calculated.

Sensitivity of an optimized contour mask technique to errors in fabricating piecewise continuous relief diffractive optical elements

This paper considers the effect of errors in the technological process using an optimized contour mask technique for fabricating piecewise continuous relief diffractive optical elements on the reduction in the backward slopes of diffraction zones and the increase in the diffraction efficiency of the elements. The process parameter tolerances necessary for the implementation of the method are within the parameters of the standard microelectronic processes and equipment. The proposed method can be useful for laser writing systems and projection lithography that form the relief in a photoresist with a backward slope width exceeding 1 µm since it provides a significant improvement in the performance of the fabricated diffraction structures.

Subdiffraction field localisation in the scattering of femtosecond laser radiation by a dielectric microsphere

The time dynamics of the optical field was theoretically considered in the near-field diffraction zone in the scattering of a femtosecond laser pulse by a transparent spherical microparticle. The spatial region of field focusing by the particle (the ‘photonic jet’ zone) was investigated; the evolution of the jet shape and the peak intensity in this region were analysed. For the first time it was determined that an extremely tight optical field localisation to a subdiffraction size is possible at a certain (resonance) temporal stage of photonic jet development.

Research on Hybrid Ray-tracing at 2.4 GHz in Man-Made Forests

The shadow of diffraction, which account for the growth of trees based on wireless sensors and automatic acquisition of environmental information, were presented to meet the requirements for a wireless sensor network in a forest. there’s a necessity to avoid the dead zone of signal diffraction when laying wireless sensor in the forest, the integration of SBR and UTD is applied to study the impact of 2.4GHz radio-frequency signal on the path loss characteristics in the forest. Shadow fading is studied by considering random variations of trees height and position. Path loss to subscribers located in a forest are found using refraction and diffraction concepts. This paper achieved the ray location from the receive pint to field point by using back-ray tracing method and computed the response electric field relative to each ray by using UTD. This article presents an overview of popular prediction models and describes electric field algorithms that are based on the authors' experience, to improve their accuracy. Take the poplar planted forest for instance. The measured value and simulated value were compared, finding good consistency between them, which indicates that SBR and UTD can effectively predict the path loss characteristics in the forest. DOI: http://dx.doi.org/10.11591/telkomnika.v11i7.2833 Full Text: PDF

Comparison of subwavelength focusing properties of diffraction and Fresnel zone plate plasmonic planar lenses

The subwavelength focusing properties of diffractive plasmonic planar lenses (DPLs) and Fresnel zone plate plasmonic planar lenses (FZPs) have been compared in this paper. To that end, we use the same lens material, incident wavelength, thickness and focal length for comparison. Both DPLs and FZPs consist of central circular slits surrounded by transparent and opaque zones and can get clear focusing performances. By using the rigorous electromagnetic numerical method, the fields in the focal region are analyzed in detail, and our results demonstrate that FZP can generate higher transmission efficiency, and higher peak field intensity at the focal plane. Focusing polarization properties of the lens illuminated by linearly polarized state, are calculated and analyzed also. The numerical results show that both the DPL and the FZP produce asymmetrical focal spot distributions with a low f-number. To the FZP, the full-width at half-maximum (FWHM) varies from 256nm (along y-axis) to 516nm(along x-axis) and to the DPL, the FWHM varies from 256nm(along y-axis) to 580nm(along x-axis), respectively. But for a high f-number, the asymmetrical performance of the focal spot will be reduced due to complicated electromagnetical field interferences and micro waveguide effect. Otherwise, the DPL can get a higher depolarization effect than the FZP does.

The influence of the vortex phase on the random wandering of a Laguerre–Gaussian beam propagating in a turbulent atmosphere: a numerical experiment

A numerical experiment is used to study the variance of the wandering of a Laguerre–Gaussian laser beam propagating in a turbulent atmosphere. It is shown that a laser beam with an initial intensity distribution coinciding with that of the Laguerre–Gaussian beam but not having a vortex phase distribution is less resistant to the action of atmospheric turbulence than the Laguerre–Gaussian beam except in the near diffraction zone. The regularities of the beam wandering associated with the values of the azimuth and radial indices of the beam as well as with the intensity and the outer scale of the turbulence are determined.

Study on scattering properties of the metal wire gating in a THz band based on Green function method

The present paper utilizes the Green function method to analyze the scattering properties of the metal wire grating in the THz band, and further to study the influence of the diffraction on the transfer characteristic of the metal wire grating. Results prove that the transmission amplitude of the incident electromagnetic wave is increasing monotonously with the enlargement of the value of a/, and it arrives at the maximum in the zero-order diffraction limit. Due to the strengthened effect of diffraction, transmission curves of the incident electromagnetic wave show oscillation in the critical frequency transition region. Due to the diffraction effect, the transmission amplitude of the incident electromagnetic wave demonstrates an overall decline in the diffraction zone, and it is decreasing monotonously with the enlargement in the value of a/. Compared with microwave transmission line method, this method can aliminate the restriction that the wavelength of the incident electromagnetic wave must be greater than the wire grating constant, and the thickness of wire grating must be far less than the metal line width. This method could be used to analyze the distribution of the electromagnetic properties of the system accurately; and it will be a generally suitable one.

Increase in laser beam resistance to random inhomogeneities of atmospheric permittivity with an optical vortex included in the beam structure

The role of the vortical phase in the initial structure of the wave field of a laser beam propagating in the turbulent atmosphere in statistical regularities of beam wandering is studied. It is found that in the near diffraction zone the variances of wandering of the vortical beam and the fundamental Gaussian beam turns out to be identical, if the initial radius of the Gaussian beam is equal to the radius of the ring intensity distribution of the vortical beam. In the far diffraction zone, the vortical beam wanders more slightly than the Gaussian beam with the same effective radius of the initial intensity distribution does. It is also shown that laser beams with the initial ring intensity distribution similar to the intensity distribution of a vortical beam, but not having the vortical phase distribution, are less resistant to the atmospheric turbulence than the vortical beam.

Comparison of spray congealing and melt emulsification methods for the incorporation of the water-soluble salbutamol sulphate in lipid microparticles

Context: Salbutamol sulphate is widely used as bronchodilator for the treatment of asthma. Its use is limited by the relatively short duration of action and hence sustained delivery of salbutamol sulphate offers potential benefits to patients.Objective: This study explores the preparation of lipid microparticles (LMs) as biocompatible carrier for the prolonged release of salbutamol sulphate.Materials and methods: The LMs were produced using different lipidic materials and surfactants, by classical melt emulsification-based methods (oil-in-water and water-in-oil-in-water emulsions) and the spray congealing technique.Results: For the LMs obtained by melt emulsification a lack of release modulation was observed. On the other hand, the sustained release of salbutamol sulphate was achieved with glyceryl behenate microparticles prepared by spray congealing. These LMs were characterized by scanning electron microscopy, X-ray diffractometry and differential scanning calorimetry. The drug loading was 4.72% (w/w). The particle size distribution measured by laser diffraction and electrical zone sensing was represented by a volume median diameter (Dv50) of 51.7–71.4 µm. Increasing the atomization air pressure from 4 to 8 bar produced a decrease of the Dv50 to 12.7–17.5 µm.Conclusions: Incorporation of the hydrophilic salbutamol sulphate into LMs with sustained release characteristics was achieved by spray congealing.

Anomalous diffraction of light in liquid upon the ultrasonic coagulation of suspended microparticles

Anomalous diffraction by the periodic filamentary structure that consists of coagulated heavy particles in water is experimentally studied under the conditions for the standing acoustic wave in cavity. The diffraction is sensitive to both the conventional photoelastic effect and the filamentary structure. The width of the narrow beams that are formed in the near-field diffraction zone is several times less than the aperture of the incident beam, and the narrow beams propagate in space with the same angular divergence as the incident broad beam does.