This was not altogether his fault, of course; he had done work in astronomy, and in this work, he had noticed a similar type of pattern, and so thought that nature had a unity in this sense. It did not, but confirmation bias would dominate Ptolemy’s thinking on this matter. What he did next, however, was to stop searching for the answer to why light behaves in this way, because he thought that he had found the answer. 4 Nor, in fact, did any of his contemporaries. This shows how necessary all components of the scientific community are: yes, we need primary researchers that determine new relationships, but we also need reviewers and secondary researchers that try to check or replicate those relationships. Without both working together, we could find all the wrong relationships and think- because they give good results- that they are wholly correct. Following this work, though, a line of scientists would study the relationships that Ptolemy had seen, each producing wholly correct results that are consistent with modern study of **optics**. For instance, Ibn al-Haitham (a.k.a. Alhazen) would study Ptolemy’s work and produce work in the early 1200s CE toward a refraction law. Qutb al-Din al-Shirazi and Kamal al-Din al-Farisi would be among the first to study and trace the path of light through large spheres of water, becoming some of the first to explain the **optics** of a rainbow- and not only this, but a double rainbow, and the first observation of a triple or tertiary rainbow in 1304 5 . Theodoric of Freiburg, a French- German monk, would conduct work in this area, and his surviving diagrams are remarkable in their consistency with modern understanding of rainbows.

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Why use Magic for teaching **Optics**? Magicians know that, once the surprise has worn off, the audience will seek to understand how the trick works. The aim of every teacher is to interest their students, and a magic trick will bring them to ask how? And why? And how can I create one myself? In this article we consider a project I gave in 2006. I summa- rize the project scopes, the student theoretical studies, their “new” Grand Illusion realization. I conclude by the weak and strong points of this approach… but let’s not reveal all the secrets just yet! Whatever the student’s professional ambitions, they will be able to see the impact that originality and creativity have when combined with an interest in one’s work. The students know how to “perform” a magic trick for their family and friends, a trick that they will be able to explain and so enjoy a certain amount of success. Sharing a mathematical/physical demonstration is not easy and that they do so means that they will have worked on, understood and are capable of explaining this knowledge. Isn’t this the aim of all teaching?

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Graphene, the ideal 2DEG, is the most suitable system for electron **optics**. It has a substantially large carrier mean free path as large as a few microns [10], yielding a robust ballistic transport regime. Additionally, the two basis atoms with 3-fold symmetry in the graphene unit cell result in a semimetallic electronic band effec- tively described by a (2+1) dimensional Dirac cone. Therefore, the quasiparticles in graphene share several relativistic properties with photons, described by a (3+1) dimensional Dirac cone, although those two are intrinsically different from each other (e.g., graphene electrons are charged fermions but photons are uncharged bosons).

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This research is a building block for future Underwater Free Space **Optics**. With this study and analysis of the optical properties of water we have tried to explain the nature of attenuation of light in water. Combining chlorophyll estimating techniques and the single parameter model we have presented a systematic framework to define the losses in the medium. Giving the scattering of light more importance, we have explained empirically as well as theoretical how scattering influences the total attenuation of light. Adopting the theory of beam spread function with multipath time dispersion, we have also tried to validate these efforts with a controlled sea water experiment. A method to evaluate the power budget for an underwater free space optical link is detailed that would prove helpful in completing the problem from in context to link engineering.

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Polaritons are quasiparticles resulting from electric or magnetic dipole-carrying excitations within a material strongly coupling to electromagnetic waves that travel within them. Thus, the photons of light moving within a dispersive, or polaritonic, material are not freely prop- agating but are held back by their interaction with the present dipoles. This forms what is known in quantum **optics** as a dressed state where the photon is in essence "dressed" with the material excitation. An important feature of polaritonic materials is the formation of photonic band gaps in the dispersion relation of the material without any constructed periodicity in the material structure. Bands of energies forbidden to travel in the material occur when the coupling between the photons and the medium’s excitations are approximately at resonance. The condition of resonance we refer to is that of both waves having nearly equal frequencies and wavevectors [1].

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Protection against tapping can be done through cable surveillance and monitoring signals i.e. monitoring signals can be send around fiber such that any attempt to bend the fiber will raise the alarm or we can integrate electrical conductors into fiber cable such that when cable is tampered it will raise the alarm [3]. Fiber cable can also be monitored with optical time domain reflectometer if tapping is detected within the fiber trace. Pilot tone method can also be used to detect transmission disruptions [3], [4]. Encryption can also be done to secure data in fiber **optics** [5].Each method has strengths and weaknesses with respect to the attack methods, and none can provide full protection.

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F. Line-of-Sight Obstructions: Light has not been able to passing the opaque mediums, objects like birds, planes and people. Due to this reason light beam can be blocked and the services momentarily may get interrupted and the services resume instantly when the light path is cleared. To avoid this problem, we can use multi-beam technology with compatibility of the systems. G. Safety: All Free Space **Optics** technology is strictly moderated to ensure that the criteria are followed to limit any risks.

We have also examined the possibility of creating macroscopic superposi tion states, or Schrödinger cat states, using two-species BECs. Our scheme can be likened to a non-linear quantum **optics** experiment, except that the nonlin earities are provided by collisions between atoms rather than non-linear crys tals or feedback electronics. Within the context of a two-mode approximation, we show that it is possible to use a series of laser fields working in conjunc tion with the normal atom-atom collisions to produce states which consist of a coherent superposition of two classically observable states, one containing an excess number of atoms in one species and one containing an excess in the other species. As with other Schrödinger cat schemes, the experimental reali sation of such states would be a formidable challenge. Perhaps the most seri ous limitation would come from decoherence. We have made a first attempt at analysing the effects of such decoherence by simulating particular detection sequences, and have found a fitted expression for the maximum number of atom detections permissible for a cat of a given size. We have also looked at the effects of finite temperature on the system and have presented a plausible argument that our scheme might be better in this regard than another recent proposal [2].

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Diamond turning (DT) of plastics is an efficient method to create versatile optical surfaces. Their performance is influenced by a wide variety of factors such as glass transition temperature of the polymer, material properties and operator controlled cutting conditions. Diamond turning is a precision lathe operation where workpiece material is removed by a single crystal diamond tool. The DT process is typically performed on a machine with precise hydrostatic bearings and axis displacement control using interferometric measurements or linear encoders. DT allows for the creation of optical surfaces. Current non-diamond turned production of lenses is done using two main methods. The first involves compression molding of the polymer followed by multi-step grinding to achieve the desired surface finish. Finally, the workpiece is beveled to prevent surface damage from the sharp edges of the workpiece [1]. The second method involves high pressure injection into a mold of the desired geometry. After the mold is filled, the liquid polymer is allowed to cool and solidify. The workpiece is then polished to the desired surface finish [2]. While these two methods are effective for mass production, the DT process enables flexibility in the production process. This allows cost effective production of small batches of asymmetric and off axis **optics** with excellent form and finish. Single point diamond turning (SPDT) is one of the common methods to create plastic **optics**.

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Apart from the development in quantum **optics**, there are also great achievements visi- ble in mathematical physics which support the theoretical understanding of the described phenomena. On the one hand, the mathematical frame for coherent states is steadily de- veloped throughout analysis, on the other hand one can see the development that super- symmetric quantum mechanics and discrete Schr¨odinger theory become related to essential problems in quantum **optics**.

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In response to this need, the work presented herein addresses the major topics rele- vant to marine optical radiometry aiming at an assessment of the overall radiometric uncertainties. After a general introduction on marine **optics** and radiometry, the objective is pursued by: (i) addressing the problem of in-air absolute radiometric cal- ibration, investigating non-cosine response of collectors for irradiance measurements and characterizing the wet response of in–water radiometers; (ii) discussing meth- ods and requirements for the deployment of field radiometers and for data analysis; and (iii) investigating techniques for the removal of artifacts produced by instrument self-shading, deployment superstructures, bottom effects and surface roughness. The implication of radiometric uncertainty is then discussed through the application of quality assured data to the development of algorithms for the quantification of sea- water constituents and the validation of satellite derived products.

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The RCS of simple shaped objects such as a finite plate, a cylinder, and a sphere etc. is represented analyti- cally in [1]. For more complex shaped targets, numerical calculations were needed. The boundary element me- thod (BEM) [2] and finite element method (FEM) [3] were used at low frequency. These methods give accurate results but require a long computer running time. At high frequency, methods such as physical **optics** (PO) [4], geometric **optics** (GO) [5], physical theory of diffraction [6] and geometric theory of diffraction [7] provide rel- atively quick solutions. At present, most numerical calculations of RCS for a target such as a ship at high fre-

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Although entanglement correlation experiments are now found even in some undergraduate labs, they are often very hard to align and to maintain. Our proposal, although modest in scope as a space experiment, is a major technological challenge requiring a redesign of the typical sprawl in an **optics** lab such that it can be incor- porated into a satellite that is running autonomously. This is a tremendous challenge, requiring a multidisciplinary team of specialists in quantum **optics**, satellite physics and electrical engineering.

with the variations of the direct and reflected signal with frequency. The measured gain at 14 GHz was around 6.0 dBi and keeps around 0.5 dB below the theoretical one in the 10-dB return loss bandwidth. Based on these re- sults and preliminary theoretical checks of some modifi- cations of the structure, oriented to symmetrize the current distributions on it, the proposed quasi-**optics**- inspired design methodology for low-profile endfire an- tenna can be considered experimentally validated.

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Abstract—The prediction of Radar Cross Section (RCS) of complex targets which present shadowing effects is an interesting challenge. This paper deals with the problem of shadowing effects in the computation of electromagnetic scattering by a complex target using Iterative Physical **Optics** (IPO). The original IPO is limited to cavities applications, but a generalized IPO can be applied to arbitrary geometries. This paper proposes a comparison between the classical PO approach and a physical approach based on shadow radiation (around forward direction) with PO approximation for the consideration of shadowing effects in generalized IPO. Based on the integral equations, a rigorous demonstration of this physical shadowing is provided. Then simulation results illustrate the interest of using physical shadowing both from the transmitter and towards the receiver, compared to the classical approach.

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Many textbooks on classical **optics** introduce the concept of polarized and unpolarized light with the help of the Jones and Stokes-Mueller calculi, respectively 关 19 兴 . In these cal- culi, the description of classical polarization of light is for- mally identical to the quantum description of pure and mixed states of two-level systems, respectively 关22兴. In the Jones calculus, the electric field of a quasimonochromatic polar- ized beam of light which propagates close to the z direction, is represented by a complex-valued two-dimensional vector, the so-called Jones vector E僆 C 2 : E= E 0 x + E 1 y, where the

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In this paper we describe the progress in the study of scale-free optical propagation when the cooling rate is above threshold value. In order to grasp the core idea behind scale-free **optics**, paraxial ray scalar approximation, has been considered. Diffraction-free (zero effective wavelength) solutions of equation(5) are scale free. This effect has been found in the Gaussian exact solution for 2

Antennas have played an important role in many modern technological innovations ranging from Marconi's first transatlantic wireless transmission through Sir Henry Tizard's radar to modern cellular communications. Now enabled with two recent developments - transformations **optics** and the design and fabrication of novel electromagnetic materials, antenna engineers have been equipped with new design tools which provide entirely fresh solutions to classical problems restricted by fundamental physics such as the Chu-Harrington Limit in electrically small antennas, and enable new ways to manipulate the emission, propagation and absorption of EM radiation. This goes far beyond what can be accomplished with traditional materials in the form of lenses and mirrors, requiring both nano-composites and also those with properties that do not exist in nature (i.e., metamaterials [1]). TO has emerged as a new paradigm for EM design, providing equivalent material properties through a well-chosen change of coordinates, in order to achieve unprecedented wave manipulation [2, 3]. This is essential for the development of conformal antennas or flat panel antennas for both SATCOM and aerospace applications. The required material properties are complex (both permittivity and permeability are generally anisotropic and spatially varying). TO is at the heart of exciting ideas such as shaped reflectors and lens [4] with beam scanning and collimation capabilities while keeping low profiles and small RCS. Traditional phased arrays have limitations in wide- angle beam-steering while TO based radome designs have opened up new possibilities to quest for low-cost and compact phased arrays. Earlier work of TO based antennas utilized fully benefits of metamaterials, which contain both electric and magnetic material properties being anisotropic and frequency-dispersive. Peculiar radiation performances can be achieved with the sacrifices in antenna gain as well as the bandwidth. Approximations can be made in several engineering oriented designs by restricting the use of no-resonating and magnetic metamaterials. The approach has led to the emergence of several novel lens antenna designs, notably a flat Luneburg lens [4]. Flat Luneburg lens antennas arise from industrial challenges on highly conformal and directive antennas, which are broadband, beam-steerable and possess low sidelobes under high power operations. The design methodology has consequently been applied to demonstrate antennas at high frequencies ranging from millimeter wave to **optics**. Quasi-conformal transformation **optics**, the idea

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Diffraction effects are traditionally classified into either Fresnel or Fraun- hofer types. Fresnel diffraction is primarily concerned with what happens to light in the immediate neighborhood of a diffracting object or aperture. It is thus only of concern when the illumination source is close to this aperture or object, known as the near field. Consequently, Fresnel diffraction is rarely important in most classical optical setups, but it becomes very important in such applications as digital **optics**, fiber **optics**, and near-field microscopy. Fraunhofer diffraction, however, is often important even in simple optical systems. This is the light-spreading effect of an aperture when the aperture (or object) is illuminated with an infinite source (plane-wave illumination) and the light is sensed at an infinite distance (far-field) from this aperture. From these overly simple definitions, one might assume that Fraunhofer diffraction is important only in optical systems with infinite conjugate, whereas Fresnel diffraction equations should be considered at finite conju- gate ratios. Not so. A lens or lens system of finite positive focal length with plane-wave input maps the far-field diffraction pattern of its aperture onto the focal plane; therefore, it is Fraunhofer diffraction that determines the limiting performance of optical systems. More generally, at any conjugate ratio, far-field angles are transformed into spatial displacements in the image plane.

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(1) Photons traveling through linear-optical networks are known to have some of the best coherence properties of any quantum system accessible to current experiments. From a “traditional” quantum computing standpoint, the disadvantages of photons are that they have no direct coupling to one another, and also that they are extremely difficult to store (they are, after all, traveling at the speed of light). There have been ingenious proposals for working around these problems, including the schemes of Knill, Laflamme, and Milburn [43] and Gottesman, Kitaev, and Preskill [32], both of which require the additional resource of adaptive measurements. By contrast, rather than trying to remedy photons’ disadvantages as qubits, our proposal simply never uses photons as qubits at all, and thereby gets the coherence advantages of linear **optics** without having to address the disadvantages.

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