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Design of Superlens for Nano-imaging

Info: 7511 words (30 pages) Dissertation
Published: 11th Dec 2019

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Tags: MedicineMedical TechnologyBiomedical Science

Abstract

This dissertation concentrates on the improvement of a new optical imaging technology so as to look at those tiny objects that cannot be seen by our eyes and typical optical magnifying instruments. The current furthest reaches of most optical magnifying lens are 200nm, which is the size of the littlest microscopic organisms; but, these magnifying lenses cannot picture most hazardous infections and subcellular subtle elements of human cells whose size is littler than 200nm. This project helps in improving optical framework of cutting edge imaging devices.

1. Introduction

The Conventional glass lenses have been an integral part of any optical system for many decades. They are essential to capture details of an object. Their refracting surfaces are either spherical or non-spherical; however, most tools have spherical lenses e.g., contact lenses, telescope or microscope etc. In a real environment to get an image, we need three components: (a) a light source– that transmits the light waves towards the object, (b) an object– that reflects the light waves towards the lens and (c) a lens– that captures the object’s information based on reflected light. The conventional lenses work on a physical principle i.e., in order to get an image of an item, the size of that item must be at least half of the wavelength of light. Using this principle, the conventional microscope can capture smallest bacteria whose size is around 200nm under white light illumination. Moreover, conventional lens can capture easily and properly when there are far fields of electromagnetic radiations.

In many applications, it is desirable to have a properly focused image of an item in near fields of electromagnetic radiations i.e., the light remains only at the surface of the object. Moreover, it is also desirable to have a resolution beyond the resolution of existing traditional lenses i.e., the objects that are smaller than half the size of light’s wavelength can also be seen. In order to meet the above-mentioned desires, the scientists have coined the term “Superlens”.  The basic working principle of a superlens is to employ double negative metamaterials to reach beyond the diffraction limit. Initially this concept faced many difficulties and challenges because of fabrication problems related to double negative meta-materials; however, in 2000 a simple form of superlens was proposed using silver slab. In 2005, Melville, D. and Blaikie (2005) argued that a high-resolution image can be projected by employing  planar silver layer in the near field. A thorough experimentation was performed. To this end, a modified conformal-mask photolithography was employed. In this process silver layers were coated onto a tungsten-on-glass mask. Encouraging results were obtained. Since then, the development of superlens has gained considerable attention of researchers and practitioners.

This project focuses on the development of a new optical imaging technology in order to examine those tiny objects that cannot be seen by our eyes and normal optical microscopes. As mentioned earlier, the existing limit of most optical microscopes is 200nm, which is the size of the smallest bacteria. However, these microscopes are unable to image most dangerous viruses and subcellular details of human cells whose size is smaller than 200nm.

This project will help in gaining invaluable experiences in optical system design, simulation, and lab prototype of state-of-the-art imaging devices and performance evaluation.

Rest of this report is structured as follows: Section 2 provides background information and literature review related to superlens development; Section3 details the research methodology; Section 4 outlines the research plan; Section 5 provides the time line of this project and Section 5 shows initial results.

2. Meta­materials

The exploration of optics is jogged upon the capacity to handle “dielectric” reaction of materials involved. This implies that how can the flow of light be directed. Nowadays, all devices are made by intelligent control of the refractive index. This results in incalculable innovations and social leaps forward. Our capacity to manufacture these devices has dependably been a mix of both fortunes and creativity. Creativity is essential to saddle the EM power and quantum mechanics for “communications”, and a bunch of different applications. Without a doubt, development of strands of silica more slender than human hair and numerous kilometres long is an exceptional example of human’s intelligence.   In addition, all the equipment is developed to transmit and get immeasurable amounts of data at terabit rates is really exceptional achievement. However, it is noteworthy that the entire attempt may have been disputable if the good fortunes of finding a material that exclusive ingests “0.2 dB/km” was missing. Similarly, there is a minor control over the discharge wavelength in case of laser; depending rather on the plenitude  of different “dielectric” and “semiconductor” gems that can be observed in nature to give something that will create light at the “frequency” of intrigue. It has been acknowledged long back that while the “optical reaction” of natural materials is “fixed”. However, it is conceivable to modify this reaction by handling materials. By utilizing “composites” it is conceivable to evacuate a portion of the components of fortunes from the unearthly reliance of ingestion and scrambling and make these wonders more convenient.

In past few decades, another arrangement of procedures for processing material reaction is rapidly enrapturing the attentions of researchers. These approaches are now developed into an undeniable field under the name of “metamaterials research”. The term metamaterials implies a composite medium with “negative penetrability” and “permittivity”. Due to this, the name metamaterial turned out to be solidly appended to DNG materials. This definition later expanded to incorporate all media inferring their plainly visible optical properties from an synthetic “sub-wavelength structure”. Practically, in any case, metamaterials regularly turned into a catch-all term, alluding to all manufactured media with unordinary EM properties. The advancement of metametrials has opened numerous avenues in optical material science. It does as such by significantly growing parameter space open for controlling light, possibly making ready for gadgets with extraordinary abilities. A no less huge motivation to consider metamaterials is basically the way that the field gives a chance to investigate numerous areas in material science. Inside the setting of metamaterials one can rethink and test standard elucidations of diffraction theories etc.

The most energizing forthcoming uses of metamaterials lie in the optical space. Subsequently, much exertion has been coordinated into bringing their working wavelengths ever lower, from centimeters in mid 2000s [15], to the infrared range in 2005 [19, 20], to obvious in 2007, when negative refraction was exhibited tentatively for wavelengths as short as 772 nm [21]. Regardless of the colossal advances in nanofabrication methods that made those tests conceivable, producing metamaterials that show negative refraction what’s more, related marvels at such high frequencies presents numerous challenges. The most testing part of the built electromagnetic reaction is the required negative attractive porousness. Negative porousness is a consequence of a full reaction by a small scale conductive structure. For a compelling negative porousness reaction, these miniaturized scale resonators must live in subwavelength unit cells. Subsequently, to achieve negative penetrability for THz and higher frequencies, one must turn to lithographic techniques in organizing the materials. For the optical frequencies, completely three-dimensional subwavelength designing is right now unfeasible. Beside the assembling troubles, negative attractive reaction presents another noteworthy test. The reverberation in the genuine part of attractive porousness which prompts negative estimations of _ is essentially joined by a spike in its fanciful segment. This prompts high assimilation at the working frequencies of attractive negative record metamaterials, which can fundamentally debilitate gadget execution [22].

In the mission to limit misfortunes, it ended up noticeably judicious to analyze methods for acquiring negative refraction without turning to optical attraction. A few gatherings appeared that negative refraction can emerge for light in reasonably outlined photonic gems [23, 24, 25, 26]. From the stance of misfortunes, photonic gems are for the most part better than attractive metamaterials [26]. Nonetheless, photonic bandgap gadgets exhibit a number of the same manufacture challenges as attractive metamaterials, particularly for 3D structures. While the trademark components of photonic precious stones are less complex and bigger (and henceforth less demanding to create), the photonic band conduct is unequivocally touchy to clutter, requiring high assembling exactness.

In the prologue to this proposition, we gave one meaning of metamaterials as “fake media with surprising electromagnetic properties”. This definition is intentionally ambiguous: what is bizarre to one individual may appear to be very normal to another. Besides, the subjective development of this discernment can contrast rather radically as one increases information about the subject. At times, things that appear to be surprising toward the begin will end up plainly ordinary as the request advances. In numerous different cases, the riddle just develops as learning amasses. The scientist may feel as confounded as ever – yet, on a larger amount and about more critical things. This is typically an indication of a decent research issue.

The investigation of metamaterials by and large, and hyperbolic metamaterials specifically, falls solidly in this last classification of issues. Anisotropic metamaterials with hyperbolic scattering relations were initially proposed as a basic other option to contrarily refractive media working by means of attractive resonances. The fundamental working standards of allpoint negative refraction of hyperbolic materials are straightforward for anybody that has examined birefringence. Notwithstanding this shallow effortlessness, this class of metamaterials exhibits strange properties that go a long ways past the geometry of refraction. For instance, we have seen that with suitable limit conditions, negative refraction brings about negative stage speed. We have demonstrated how this wonder emerges in metallic, dielectric, and bilayer waveguides and concentrated its suggestions in making moderate light gadgets.

Maybe more essentially, we exhibited that the unbounded scattering branches modify the very essentials of wave proliferation in mass hyperbolic materials, which, thus, empowers novel gadgets with a huge number of imminent applications, the most noticeable of which we depicted in this work. We have perceived how subjectively expansive estimations of the wave vector (restricted just by the material designing scale)  can be utilized for subwavelength light control and centering. This is possibly vital for nonlinear optical gadgets, which work at high field powers. In the imaging area, we have seen that the high-k mass waves can couple to high spatial recurrence Fourier field music, which exponentially rot in free space.

We can then utilize disseminating from a subwavelength structure, or amplification in round and hollow geometry, to change over those high-k music into engendering waves,  along these lines gathering subwavelength data in the far field. Beside just permitting high-k modes, the hyperbolic way of scattering recommends that the thickness of such states is (formally) unbounded. We concentrated the resultant peculiarity in the photonic thickness of states and its part in making radiative rot channels that improve the fluorescence of a dipole producer. We likewise talked about its part in empowering the hyperlens, where it permits engendering of high rakish energy states. These additional diffusing channels fill in as additional data channels conveying subwavelength data.

In the last part of this theory, we concentrated on the possibility of optical recognition as a disseminating issue and introduced a specific way to deal with optical fingerprinting that depended on identifying high spatial recurrence signals scattered from a subwavelength grinding. While the proposed gadgets did not require hyperbolic scattering, we found that anisotropic designing was critical in deciding the spatial frequencies that can be tested by a subwavelength structure.

As we close this postulation, it is normal to look ahead and remark quickly on the present advancement of metamaterials when all is said in done, and hyperbolic metamaterials in specific. In the basic part, we displayed a plot itemizing the number of metamaterials-related distributions delivered in the course of the most recent 12 years. Rethinking this plot, we see that the underlying time of energy and fervor (and exponential development, as reflected by the quantity of distributions) has now offered path to a period that a few analysts have portrayed as “calm evaluation” [110]. During the time spent this evaluation, it has been noticed that the concentration is moving from considering metamaterials as materials, to considering them principally as gadgets [110]. This postulation has exhibited an unmistakable case of this advancement. In fact, we invested most of the energy talking about gadgets empowered by the bizarre properties of hyperbolic media.

In the coming years, we hope to see the development of metamaterial gadgets with tunable, switchable, or nonlinear reaction. Hyperbolic metamaterials have each chance to be at the front line of this examination. All things considered, the capacity to tailor electromagnetic reaction of planar heterostructures which was utilized to illustrate the primary allsemiconductor hyperbolic metamaterial [62] has turned out to be normal in dynamic optoelectronic gadgets, (for example, quantum course lasers), and in addition in photonic gem what’s more, plasmonic frameworks. What’s more, we have just started to begin to expose what’s underneath in discovering uses of the thickness of states “hypersingularity”. Planned research in this zone traverses the range from planning materials for vitality gathering, to making optical analogs of fascinating quantum gravity impacts, for example, metric moves [6].

At last, we might want to express one more seek after hyperbolic metamaterials. In October of 2009, 13.5 million Americans had an opportunity to see the “customary” f_ <0; _ < 0g metamaterials showing up on the whiteboard having a place with the characters of the hit prime time CBS demonstrate The Big Bang Theory (Fig. 6.1). We  immovably trust that hyperbolic metamaterials are similarly as meriting to be specified on system TV, and will bend over backward to campaign for their appearance.

3. Background

In past few decades, Superlens has been researchers’ interests. The superlens is known for conquering the optical-diffraction constrains by gathering engendering and fleeting waves through NIM (“negative index materials”). A chunk of material with “negative permittivity” will go about as superlens. On the premise of this rule, Li (2009) worked on the superlens in light of silver/dielectric multilayer from hypothetical and trial viewpoints. In the hypothetical work, the “anisotropic superlens” was considered. A chunk of lens made of such sort of medium could change over fleeting waves into proliferating nature using the “coupling modes”. Thus has an immaculate resolution. The “near-field superlens” comprising of reciprocal meta-materials is one of the major application. In this case, the diffraction impacts in first chunk are remunerated in the second section. This second slab will have the integral anisotropic permittivity. The authors argued that by tuning the viable permittivity, a nearfield superlens could be developed. Another application is the FSL (“far-field superlens”), in which the picture “sub-diffraction” items can be exchanged to the external surface and great picture fidelity could be figured realized. The authors created near-field superlens gadgets, the imaging property of them were physically described. Initially, the ART was utilized to quantify the transmission characteristics of proliferating waves in various superlens gadgets; the outcomes demonstrate that the superlens with Fabry-Perot cavity has an “omni-directional transmission property. Every single test result concurs well with simulated outcomes. The near-field imaging process constitutes the second trial step. A photolithographic system was used to show the full superlens characteristic. The superlens veil with different resolutions was created by focusing on beam. The optimal superlens gadgets were manufactured. Subwavelength imaging resolution was acknowledged. All these outcomes additionally concur well with hypothetical forecasts.

The development of perfect lens using DNG meta-materials opened an approach to get a resolution of an image past the customary constraints of diffraction. However, due to the challenges in manufacturing the DNG meta-materials, the uses of this kind of lens have been astounded. As mentioned before, the lens made of silver slab proposed in and experimental results are showed in 2005. A great deal of works is presented afterwards. In the experiments, the “silver film” was embedded into a “photolithographic” gadget and the “sub-diffraction” sample was cut on PR.  It is essential to understand that silver is not DNG material but ENG material. Results demonstrated that when light went into the ENG or MNG film, the vitality stream would enter the film with the course perpendicular to the film surface. This implies that the “zero-refraction” happens. Subsequently, the imaging by ENG or MNG is created by the engraving impact, rather than the twofold concentration happening in DNG. The computation comes about in view of the zero-refraction standard concurred with the empirical results. Often superlens is synonym with ENG or MNG film rather than a DNG perfect lens. As the superlens works in a convoluted “photolithograph device”; parameters such as real and imaginary parts of “permittivity” govern the picture quality. Zhao et al. (2016) researched on these parameters and stated that zero-refraction impact is the characteristic property of the metal superlens. The image quality will be impacted by the dielectrics at the two sides of the superlens. This leads to conclusion that in order to acquir best image: (a) both dielectrics ought to have a similar permittivities and (b) the sum of “real part” of the permittivity and dielectric permittivity should be equal to1.

Diffraction limited is a term commonly associated with conventional lenses i.e., these lenses cannot see the objects whose size is less than half the illumination wavelength. This implies that under white illumination, conventional lenses can resolve features of the object whose size is more than 200-250 nm.  Yan et al. (2016) developed a superlens that has 100nm resolution, which means that the improvement is twice as compare to the conventional lens. In this hybrid work, the authors combined the conventional lens with the supersensing coverslip-like microsphere lens. To achieve this integration, 3D printed lens adaptor was used. The authors argued that the proposed lens has the potential to become a commercial product and will help to transform microscope into a nanoscope. In a prior but similar work Taubner et al. (2006) combined superlensing with scanning near-field optical microscopy to get the advantages of both configurations to achieve an efficient imaging system.

Wang et al. (2004) demonstrated the concepts of unrestricted superlensing. To this end, 2D photonic crystals with triangular shape were used to perform unrestricted superlensing. The results showed that rules of geometric optics are applied on the refraction of light.  However, when 2D square shapped photonic crystals were used, then geometric optics was not followed. That was an interesting observation in the field of restricted superlensing.

Cheng et al. (2013) proposed a new anisotropic metamaterial device called “hybrid-superlens hyperlens”. This device consists of two layers: (a) the upper planar superlens and (b) lower cylindrical hyperlens. The authors demonstrated that the novel lens could enhance and transfer the frequencies pertaining to space to the far fields by using its feature of multidirectional response. The simulation and numerical results has verified the designated methodology. By using hyperlens, super-resolution of 100nm has been achieved with the source of incident wavelength of 405nm which is smaller than the diffraction limit. It is interesting to note that like previous mentioned works, a new objective lens can be derived by combining hyperlens with ordinary lens for magnifying an image to its super fine features. That innovative device has applications in different grounds such as, such as photolithography, planar integrated optical devices, and DVD technology.

Akhter and Akhtar (2014) designed a left-handed metamaterial (LHM) lens for superresolution mm-wave imaging applications. It shows negative unity refractive index for two different millimeter wave frequency bands. The LHM lens bends the electromagnetic wave in a way, which cannot be achieved by ordinary lens. By placing LHM lens near to the point source results a focused beam. It also affirmed by simulation and numerical results of electric field and the power distribution pattern, enhanced super-resolution imaging achieved for proposed millimeter wave bands.

Lens has widely used in all engineering applications. Some applications such as consumer antenna applications require relatively thin and light weight lens. Fresnel zone plate lenses (FZPL) finds their usefulness in these applications (Black and Wiltse, 1987). They are also easy to mould to fit our needs. The traditional fabrication process is not fit to make these lenses as these processes are prone to error. The advanced 3D printing technology is used fabricate this kind of lens using fused deposition modelling (FDM) Makerbot Replicator 2X. 3D printed lens also have good performance. Using 3D printing the entire machining process is eliminated and scattering of lens is also eliminated. Traditional methods take longer time to manufacture lens as compared to 3D printer.

Another latent answer to beat diffraction restrict is to use microsphere superlens, which is absolutely “dielectric” and therefore is normally free of loss. The principle elements influencing resolution are: (a) “wavelength”, (b) “geometric structure”, and (c) “refractive index”. Super-resolution is achieved through fleeting wave propagation in the near-field created in the “spheres”. It is essential to select appropriate parameter windows in order to have super-resolution focusing. Wang et al. initially presented a 50 nm resolution superlens in 2011. The essential setup was exceptionally straightforward. The “silica microbeads” were self-gathered on the surface and then spheres were employed for imaging. The silica superlenses amplified the objects and threw the amplified virtual picture onto the traditional lenses. Diverse examples had been specifically presented in higher resolution without marking. But, real applications require control. One idea was to develop microsphere with a fine glass “micropipette”. The authors 2011 recommend another idea to utilize “TiO2” or “BaTiO3”. The pinnacle bended surface in the plan is utilized to lessen the impact of aggregate inner “reflection”. This approach helped in following ways: (a) the entire lens can be effectively situated and controlled by the client needs; (b) scanning is currently conceivable; (c) Higher resolution can be accomplished; this is on account of in this outline the strong inundation component adds to the resolution improvement. The authors showed that lines with size 40 nm can be obviously imaged with the superlens with improved performance. Hypothetical investigation additionally affirms the new design.

Pang et al. (2015) shown experimentally that barium titanate (BaTiO3) glass microsphere immersed in the liquid can be used for super-resolution imaging. In this research paper, the authors have taken spectrum analysis method to investigate the influences of liquid immersion to microsphere imaging. This method has taken for modelling the propagation of evanescent wave field of the object’s spectrum. By tracking the propagation, the imaging resolution and magnification of different liquid-immersion can be achieved. To verify this analysis, the modelling and simulation of imaging process has also taken. The results show that super-resolution can be achieved when BaTiO3 microsphere is immersed in liquid with moderate refractive index. Similarly, a lower refractive index of the immersed-liquid will have a larger magnification. The spectrum-analysis method can be used to study other parameter’s influences on the microsphere imaging, including the distance between object and microsphere, refractive index of microsphere, the diameter of microsphere and so on.

In optical fiber transmission system, the basic requirement is the integration of photonic devices. When the data rate will exceed the limit of 10Tb/s then there will be more demand to increase the integration of photonic devices in optical fiber transmission. To tackle this problem size of the photonic matrix, Ohtsu, M. and Kobayashi (2002) argued that switching devices should be further reduced to a sub wave length scale. The purpose of this reduction is to integrate more 1000×1000 Input and output channels on substrate.  In nanophotonic integrated circuit(IC) optical near field is used as a carrier for the propagation of the signal from one nanometric dot to another.  Utilization of local electromagnetic interactions between a smaller number of nanometric elements and an optical near field is very relatively more useful to solve the technical problems in optical industry in future because all the devices are nanometric dots and wires which have been used in the circuit.

3. Focusing on small particles

There are various ways in which research on superlens is progressing and various techniques are employed to focus on small particles. One of the new approaches to focus on tiny objects is to employ nanobeads. Nanobeads are surrounding us-and are, some may contend, utilized too as often as possible in everything, yet another historic application is uncovering concealed universes. By utilizing new strong “3D superlenses”, very tiny objects can be seen. Outlining the quality of the new superlens, the researchers depict seeing surprisingly, the real data on the surface of a Blu-ray disc. Current magnifying instruments can’t see the depressions containing the information; however, now even the information itself is uncovered with the help of superlenses. To this end, moment-bead like lens structures at first glance is to be analyzed. These structures go about as an extra lens to amplify the surface components already undetectable to a typical lens. Made of a great many nanobeads, the “spheres” separate the light shaft. Each dab emits the light and thus acts like individual torch. It is the little size of each light emission which enlightens the surface, amplifying the settling capacity of the magnifying instrument to exceptional levels.

Previously, it was considered impossible to view objects whose size is less than 200nm due to physical laws; but, superlenses have been the new objective since the start of 21st century, with different labs and groups inquiring about various models and materials. Wang et al. utilized TiO2 nanoparticles as the fundamental component. These nanoparticles can twist light to a higher degree than water. To clarify, when putting a spoon into titanium dioxide, it can be seen a bigger bend as compare to the bend of spoon in water. The reason behind this observation is that every “sphere” refracts the light to a high intensity and parts the beam of light; thus, a huge number of individual light emissions are made. With the help of these millions of small light-beams; inconspicuous details can be seen these days. The upsides of the innovation are that TiO2 is shabby and promptly accessible, and as opposed to purchasing another magnifying instrument, the lenses are connected to the material to be seen, instead of to the microscope. The upcoming challenge in this technology is to employ this innovation for use in biological and medical applications; this would not require the present utilization of laser light etc. which change the specimens being seen; instead, the new lens will be utilized to see germs and infections not visible in past.

4. Types of optics (Wave optics vs ray optics )

Fluorescence imaging has its underlying foundations in “optics” and “molecular physics”. The interaction of the “light-matter” is the key for understanding atomic wonder. For the oversimplified reason of solid light-matter association, fluorescence imaging has picked up noticeable value over other imaging systems and has discovered wide applications in fields extending from “biophysics” to “optical engineering”. The key favourable position of this communication is the capacity to take after “biological processes” in their local state, in this manner opening-up a substantial number of unanswered inquiries that have been requested for hundreds of years.

Besides, numerous inward working of the cells is as yet a puzzle. Just now, we can disentangle these riddles with the advancement of intense high resolution magnifying lens that permit perception of particle working with close “molecular-size” resolution. Molecules of intrigue are regularly labeled with “fluorescent markers” and took after while cell performs key molecular-level errands. The upside of this type of microscopy is its capacity to perform utilitarian studies that are uncommon in different types of imaging.

Visible intensities constitute a moment part of an electromagnetic (EM) spectrum. In this way, light is administered by similar rules that can be employed on different other members. All the individuals from EM range proliferate as two commonly coupled vector fields: (a) “electric field” and (b) “magnetic field”. This stems from the way that, “electric field” impacts “magnetic field” and the other way around. The very reality that the light has been controlled for quite a long time before the presence of its “vectorial” portrayal gathers that light can be dealt with in a disentangled way also to explain everyday occasions. An inexact method for treating light is alluded as “scalar theory”, which is “ray optics” and “wave optics”. At the point when light engendering through the “objects”, which are by far greater than the wavelength, then it would be not clear to have a “wave nature”. In such a circumstance, one can depict light as a group of beams exuding by a “source” and engendering in the direction of the “object”. Amid this, the light complies with an arrangement of geometrical principles and proposes.

4. 1 Ray optics

Ray optics has been utilized for quite a long time. This keeps on awing and is an imperative instrument for the improvement of future optical magnifying instruments. Ray optics is by a long shot the easiest concept of light. Beams are utilized to depict light. Ray optics in combination with scientific principles of geometry can be utilized to portray basic optical concepts e.g., “reflection” and “refraction”. This effectively clarifies the picture development utilizing straightforward optical components e.g., “lens” and “mirrors” etc. The picture position can be gotten by essentially following the beam that complies with the representing hypothesizes of ray optics. To begin with, a heap of beams can be developed at the target and their ways can be taken after. The aggregation of beams on the coveted plane decides the yield picture. For instance, different beams radiating from a source can be followed through a “intermediate bioconvex lens” and took after on the opposite side. The thickness of beams anytime gives the image position.

4.2 WAVE OPTICS

In past, it was assumed that light engenders as waves. In previous section, it was discussed that the majority of the imaging parameters can be resolved utilizing ray optics. Along these lines, it was never felt the need to define another theory unless a portion of the striking optical impacts are watched. These impacts are beyond the limits of ray optics thus the need to figure out another theory was felt to clarify these impacts. This novice theory depends on light’s wave-like nature. Basically, this concept is propelled by water-waves and soundwaves. Wherever two wave peaks meet the amplitude of the resulting wave lifts than the amplitudes of each individual waves, and the amplitude of the resulting wave diminishes when trough and peak of two waves meet. Unexpectedly, obstruction and diffraction impacts are appeared by every one of the EM spectrum members. Along these lines, the wave theory is appropriate to the whole range and includes the ray optics.

Ray optics is fit for characterizing a large portion of the optical marvels in which the light’s wavelength is adequately little when contrasted with the target size through which it is engendering. For the wave optics, the beginning stage is the depiction of the field and is called as wave-function. All other parameters can then be ascertained from the wavefunction. It is to be noticed that, that wave-function is itself not a physically quantifiable. Instead, its modulus is quantifiable. Like ray optics, the postulates shape the reason for understanding a few impacts that falls outside the bounds of ray optics. In any case, wave optics is not the ultimate concept. Before long, it will be understood the impediment of wave optics and it will be compelled to figure an advanced theory for portraying “vectorial” properties of light.

To summaries, it can be contended that wave optics must contain ray optics as a constraining case; however, that disregards the commonsense reality of computational intricacy. Ray optics is incredible for the constraining instance of things substantially bigger than a diameter of wavelength-lens and so forth. So most optical outline is completed utilizing ray optics. It’s basic, brisk, and achieves results. Wave optics turns out to be more imperative when things approach the measure of a wavelength and so forth. Additionally, ray optics limits in regards to “polarization”. On the other hand, wave optics experiences serious difficulties distortions, particularly non-symmetric variations.

5. Mie theory

Mie theory explains the dissipation of light using particles i.e., the material that constitutes an area with refractive index (RI) that varies from the index of the environment (EI). The swaying electrons in the molecules of these “particles” superimpose to yield a solid origin of scattered radiation. Likewise, the patterns from every one of the dipoles don’t scratch off in everything except the forward heading of the “incident” light, yet rather meddle in a radiation design. Consequently, particles “diffuse” light in different directions with shifting efficiency.

Gustav Mie in 1908 presented an answer for the issue of light dissipating by “homogeneous sphere particles”. Mie’s established arrangement is portrayed regarding two parameters: NR and X i.e., the extent of refractive index variance amongst “particle” and “medium” communicated as the proportion of the N for particle and medium,

RI

NR =

EI

the extent of the surface of refractive index bungle which is the “antenna” for re-radiation of EM vitality, communicated as X, and is the proportion of the circumference of the sphere to the wavelength of light in the medium,  2(radius)

X =

EI

A Mie theory figuring will yield the productivity of disseminating which relates the “crosssectional” territory of dispersing (S), to the genuine geometrical cross-sectional region of the molecule (A). At last, the diffusing coefficient is identified with the result of scattered number thickness and the cross-sectional territory of dispersing.

6. Saddle points

The presence of numerous local minima makes the optical design task difficult. In conventional design, the consequence of “local optimization” basically relies upon the selection of the starting point. However, when the unpredictability of the design process expands, the designer step by step loses the capacity to locate a decent starting point by an exertion of mind, and depends progressively on experimentation. There are techniques such as genetic algorithms etc. that have reduced the initialization problem, yet the selection of an underlying arrangement that leads to an optimal solution still remains a noteworthy challenge, particularly when the quantity of parameters is expansive. Getting away from an unacceptable “local minima” is difficult task. Random selection can be considered for effortlessness the straightforward procedure as far as local minima selection is concerned. However, it is expected that optimization the outcome will be considerably different. For a superior comprehension of the way of the trouble, we can think as far as bowls of attraction. The arrangement of every beginning setup that prompt similar minima after optimization is known as the bowl of attraction for that “minimum”. The problem space is then partitioned into bowls of attraction comparing to the distinctive “local” minima exhibit in the “optimization” step. In the event that the “perturbation” is excessively feeble, the annoyed framework won’t achieve the bowl border and after “local optimization” will come back to the known extrema; if the “perturbation” is excessively solid, it might hop over a few bowls, with the danger of missing great solution. Nonetheless, a “neighbouring minimum” can be effectively found if a point on the bowl border can be distinguished, just by “crossing” the border there. Saddle points are such focuses on bowl border.

Research Methodology

Quantitative research is the validation of system using mathematical, statistical or computational techniques.  These methods can be used to verify that whether the obtained results are true with respect to the standard theoretical values. Quantitative methods seem to fit well in this project. This will be a simulation-based implementation/research where a superlens will be designed and experiments will be performed to evaluate the correctness, completeness, and novelty of the simulation. To this end, we shall fit analytical near-field image profiles on the simulated lens in order to get quantitative estimates. It is important to mention that the negative-index of the objects used in the experiments shall be known.

Research Objectives

  1. To perform a methodical review of scholarly research papers to comprehend the knowledge in field of Superlens development.
  2. To  have  basic  understanding  of  various  synthetically  developed metamaeterials.
  3. To gain imaging knowledge of existing metamaterials for the development of superlens.
  4. To develop a simulation of superlens that can work in static mode.
  5. To extend the simulation of superlens in order to make it work in scanning mode.
  6. Under white light illumination, the goal is to achieve 50nm resolution.
  7. To compare the proposed superlens with state-of-the-art superlenses.

*talk about interpolation.

*And am using some of the information from this paper ,, you can reference it or take some information from it http://drzwang.com/onewebmedia/PhysRevB.70.035418_2004.pdf

This website is recommended from the supervisor:

http://drzwang.com/publications.html

2.3 Experimental section

Matlab program:

First, the main data consist of xz points or yz points and u , v vectors. The following is an example of the data which are taken from the DSIMie program (XZ data)..

the x ,z are the points and only the the real parts of X and z points will be taking ( u , v) in order to plot the light flow.

Manipulating data:

The raw data cant be plot directly, so we need to modify it to plot it.

First, reshaping the x , and y data to make their size is the  square root of the size of x or Z points.

Then extracting the first row to create the mesh grid:

Then creating the mesh grid to plot the light flow on. After creating the mesh gird the real parts of x and z will be reshaped as the same as x and z .

The code:

TO plot the light flow a streamslice command s used and the inputs are x , z (mish grid) , u ,v (reshaped real parts of x nd z points) and the line density of the plot.

The code:

streamslice(x,y,u,v,linedensity);

The same for the intensity:

1- Graphical user interface:

there are two buttons one for import the main data( xz points or yz points , and u and v vectors to plot the light flow)and the other button for the importing the intensity of the data.

On the box next to the import buttons, the directory of the fie will be shown:

and that’s the main GUI:

  • The intensity box to chose the what intensity to view
  • The line density box to chose the line density of the graph
  • Line color to chose the line color
  • The Line box to let the line visible or not
  • The 3d box to change the angle of view from 2D to 3D.
  • Save plot button to save the plot
  • The Clear button to clear the plot and the data
  • the color map to chose the color map to plot
  • the surf option to plot the data using surf command showing the intensity
  • the log10 option to plot the log10 of the data to emphasize it.
  • The saddle point box to detect the saddle point on the plot and plot a red circle on it (as shown in the graph).

Applications:

Light interaction with plasmonic particles. The diameter of the Gold particle is 40 nm and the surrounding medium is water. Illuminated by a plane wave of light at λ = 515 nm. (1) shows the electric field distribution.  (DATA taking from DSIMIe 2019)

Only light flow  only intensity with “hot”color map   light flow+intensity

the intensity along the z-axis(taking the graph from DSIMie)

λ = 515 nm where the light is most absorbing.

  1. Design
  2. Implementation
  3. Results and discussion

3. conclusions

References

Zhao, C., Zhou, Y.S., Zhang, Y. and Wang, H.Y., 2016. The imaging properties of the metal superlens. Optics Communications, 368, pp.180-184.

Li, G., 2009. Superlens design and fabrication.

Wang, Z.B., Yan, B., Yue, L., Leach, R.K. and Luk’yanchuk, B., Solid-Immersion Microsphere Superlens.

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