A general calculation of the 3-D disk of least confusion using skew ray tracing

A general and analytical method is proposed to determine the 3-D contour of the disk of least confusion (DLC) produced by an optical system for a point light source located at any arbitrary position in the object space. By using the skew ray tracing method, the sensitivity method, and the Jacobian matrix, we can analytically obtain the caustic and the marginal rays. Consequently, the DLC can be determined by the intersection of the obtained caustic and marginal rays. In addition, this proposed method covers common cases with special light sources, e.g. mutually parallel incident rays parallel to the optical axis, or a point light source located on the optical axis. This proposed methodology will be useful in the analysis of rays and in the design of optical systems with a general point light source. A general case is used as illustrative example to validate its applications.     

类特异材料半导体复合结构中的电子Tamm态

通过选取具有特殊能带结构的半导体材料碲镉汞(Hg_1-xCd_xTe), 类比电磁体系得到了电子体系中的类单负材料、类双负材料等类特异材料, 然后将其组合成一维复合异质结构. 通过数值计算, 发现复合结构中存在新型电子Tamm态, 包括返向电子Tamm态和含类近零折射率材料复合结构中的电子Tamm态. 这些结果拓展了人们对电子Tamm态的认识.     

Experimental demonstration of a light-ray-direction-flipping METATOY based on confocal lenticular arrays

We show, theoretically and experimentally, that a sheet formed by two confocal lenticular arrays can flip one component of the local light-ray direction. Ray-optically, such a sheet is equivalent to a Dove-prism sheet, an example of a METATOY (metamaterial for rays), a structure that changes the direction of transmitted light rays in a way that cannot be performed perfectly wave-optically.     

Broadband slow light metamaterial based on a double-continuum Fano resonance

We propose a concept of a low-symmetry three-dimensional metamaterial exhibiting a double-continuum Fano (DCF) optical resonance. Such metamaterial is described as a birefringent medium supporting a discrete dark electromagnetic state weakly coupled to the continua of two nondegenerate bright bands of orthogonal polarizations. It is demonstrated that light propagation through such DCF metamaterial can be slowed down over a broad frequency range when the medium parameters (e.g., frequency of the dark mode) are adiabatically changed along the optical path. Using a specific metamaterial implementation, we demonstrate that the DCF approach to slow light is superior to that of the electromagnetically induced transparency because it enables spectrally uniform group velocity and transmission coefficient.     

Methods for calculating the vergence of an astigmatic ray bundle in an optical system that contains a freeform surface

A method using the generalized Coddington equations enables calculating the vergence of an astigmatic ray bundle in the vicinity of a skew ray in an optical system containing a freeform surface. Because this method requires time-consuming calculations, however, there is still room for increasing the calculation speed. In addition, this method cannot be applied to optical systems containing a medium with a gradient index. Therefore, we propose two new calculation methods in this paper. The first method, using differential ray tracing, enables us to shorten computation time by using simpler algorithms than those used by conventional methods. The second method, using proximate rays, employs only the ray data obtained from the rays exiting an optical system. Therefore, this method can be applied to an optical system that contains a medium with a gradient index. We show some sample applications of these methods in the field of ophthalmic optics.     

Engineering optical gradient force from coupled surface plasmon polariton modes in nanoscale plasmonic waveguides

We explore the dispersion properties and optical gradient forces from mutual coupling of surface plasmon polariton(SPP) modes at two interfaces of nanoscale plasmonic waveguides with hyperbolic metamaterial cladding.With Maxwell's equations and Maxwell stress tensor,we calculate and compare the dispersion relation and optical gradient force for symmetric and antisymmetric SPP modes in two kinds of nanoscale plasmonic waveguides.The numerical results show that the optical gradient force between two coupled hyperbolic metamaterial waveguides can be engineered flexibly by adjusting the waveguide structure parameters.Importantly,an alternative way to boost the optical gradient force is provided through engineering the hyperbolic metamaterial cladding of suitable orientation.These special optical properties will open the door for potential optomechanical applications,such as optical tweezers and actuators.     

General method for determining the sensor readings of motion measurement systems by using skew-ray tracing method

High-accuracy laser-based optoelectronic motion- and position-measuring systems typically utilize light rays that travel from one optical boundary surface to another to perform motion and/or position measurements. It is not a simple task to accurately determine the equations of these sensor readings in terms of positional/angular motions. This problem is addressed in this paper by application of the analytic skew-ray tracing methodology as computed by the finite-difference methodology. An illustrative example of a motion-measurement system and comparison of the position-sensing detector (PSD) readings are given to validate the proposed methodology. It is shown that the proposed methodology can provide accurate expressions of PSD readings. It is also shown that the performance of a corner-cube retro-reflector is better than a cat's eye retro-reflector in positional/angular motion measurement systems.     

Stopping light all optically

We show that light pulses can be stopped and stored coherently, with an all-optical adiabatic and reversible pulse bandwidth compression process. Such a process overcomes the fundamental bandwidth-delay constraint in optics and can generate arbitrarily small group velocities for any light pulse with a given bandwidth, without any coherent or resonant light-matter interactions. We exhibit this process in optical resonators, where the bandwidth compression is accomplished only by small refractive-index modulations performed at moderate speeds.     

Phase space description of vignetting in optical systems

A general theory of vignetting in real optical systems has been developed. Considered a beam of light rays limited by a field stop, an aperture stop inside of the real optical system (aberration vignetting) and a stop outside of it (natural vignetting). It is shown that each of these 2D-stops can be replaced by a virtual 4D-phase stop, and the result stop for 4D-phase result stops is their intersection. In case of an axially-symmetrical optical system with circular stop openings all phase stops are solids of revolution and can be fully characterized by their meridional cross sections in a 3D-space, which can be easily drawn.     

Conservative and dissipative fiber Bragg solitons (a review)

We present a comparative review of two classes of optical solitons—conservative and dissipative solitons—propagating in single-mode optical fibers in which refractive-index gratings are induced such that their period is comparable with the radiation wavelength. Fibers that have the Kerr nonlinearity and negligibly small losses and that do not gain radiation (conservative system) are described by traditional equations of the approximation of slowly varying amplitudes, and effects caused by the nonlinearity of the medium, such as nonlinear switching, optical bistability, and formation of conservative Bragg solitons are considered. It is shown that the passage beyond the scope of the approximation of slowly varying amplitudes makes it possible to describe new important effects, including localization of soliton centers near maxima of the refractive-index grating. Bright and dark conservative solitons are demonstrated, which are formed when the Kerr nonlinearity is replaced by the nonlinearity of two-level atomic systems. The properties of conservative solitons in resonance semiconductor Bragg structures with quantum wells are considered. Results of experimental studies of nonlinear effects in fibers with Bragg gratings are presented. For an active single-mode fiber with a Bragg refractive-index grating and nonlinear gain and absorption, dissipative solitons are described using the approximation of slowly varying amplitudes and inertialess nonlinearity. It is shown that the dissipative factors qualitatively change the properties of solitons compared to the conservative case. Using the Maxwell-Bloch equations, it is demonstrated that the ratio between the gain and absorption relaxation times significantly affects the stability of localized structures. The interaction of dissipative optical Bragg solitons is described. It is shown that, beyond the scope of the approximation of slowly varying amplitudes, the average velocity of propagating dissipative Bragg solitons acquires only discrete values, and formation of pairs of solitons with two values of the phase difference becomes possible. For a birefringent fiber, dissipative vector optical Bragg solitons are demonstrated.     

General method for determining the first order gradients of skew rays of optical systems with non-coplanar optical axes

Current commercial software for the analysis and design of optical systems uses finite difference (FD) approximation methodology to estimate the gradient matrix of a ray with respect to system variables. However, FD estimates are intrinsically inaccurate and are subject to gross error when the denominator is excessively small relative to the numerator. This paper avoids these problems and determines the gradient matrix of the exit ray traveling along an optical system with a non-coplanar axis. To achieve this, the gradient matrix of the rays reflected/refracted by flat or spherical boundary surfaces are first determined by directly differentiating the skew-ray tracing equations. By introducing a Jacobian matrix, which represents the partial derivatives specifying the rates of changes between boundary variables and element variables, one can obtain the gradient matrix of the exit ray of an element with respect to its independent variables. This methodology will be useful in the analysis of rays and in design of optical systems with non-coplanar axis. A right-angle prism is used as illustrative example to validate its applications.     

Equations of motion for the magnetization in an optically oriented spin system

The spin system is present in conditions of optical orientation and magnetic resonance. The equations of motion are derived for coherent and incoherent excitation. In the latter case (light propagating along the magnetic field) the equations take the form of Bloch's equations and contain the relaxation times ₁ and ₂ as well as the equilibrium z component m_oz, these being dependent on the light intensity. Coherent excitation (circularly polarized light propagating perpendicular to the magnetic field, or two rays perpendicular and parallel to the magnetic field, or two rays perpendicular and parallel to the field) produces equations containing the equilibrium transverse magnetizations produced by optical orientation. In both cases the frequency of the magnetic resonance is shifted by an amount proportional to the light intensity.     

激光半主动制导导引头光学系统的设计

根据四象限探测器的工作原理,激光半主动导引头光学系统所成光斑需均匀分布在探测器靶面上。首先分析此类光学系统像差特点,提出像差的设计方案,然后通过使用CODE V设计一套光学系统,利用痕迹图、包围能量等定性评价系统光斑质量。在不同视场时,通过LightTools光机分析软件追迹1106根光线,得到探测器靶面的光线分布,利用Matlab处理数据并绘制角度-输出响应曲线,利用该曲线可精确评价探测器靶面的光斑性能。     

Spatial optical (2+1)‐dimensional scalar‐ and vector‐solitons in saturable nonlinear media

(2+1)‐dimensional optical spatial solitons have become a major field of research in nonlinear physics throughout the last decade due to their potential in adaptive optical communication technologies. With the help of photorefractive crystals that supply the required type of nonlinearity for soliton generation, we are able to demonstrate experimentally the formation, the dynamic properties, and especially the interaction of solitary waves, which were so far only known from general soliton theory. Among the complex interaction scenarios of scalar solitons, we reveal a distinct behavior denoted as anomalous interaction, which is unique in soliton‐supporting systems. Further on, we realize highly parallel, light‐induced waveguide configurations based on photorefractive screening solitons that give rise to technical applications towards waveguide couplers and dividers as well as all‐optical information processing devices where light is controlled by light itself. Finally, we demonstrate the generation, stability and propagation dynamics of multi‐component or vector solitons, multipole transverse optical structures bearing a complex geometry. In analogy to the particle‐light dualism of scalar solitons, various types of vector solitons can ‐ in a broader sense ‐ be interpreted as molecules of light.     

Many-body quantum electrodynamics networks: Non-equilibrium condensed matter physics with light

We review recent developments regarding the quantum dynamics and many-body physics with light, in superconducting circuits and Josephson analogues, by analogy with atomic physics. We start with quantum impurity models addressing dissipative and driven systems. Both theorists and experimentalists are making efforts towards the characterization of these non-equilibrium quantum systems. We show how Josephson junction systems can implement the equivalent of the Kondo effect with microwave photons. The Kondo effect can be characterized by a renormalized light frequency and a peak in the Rayleigh elastic transmission of a photon. We also address the physics of hybrid systems comprising mesoscopic quantum dot devices coupled with an electromagnetic resonator. Then, we discuss extensions to Quantum Electrodynamics (QED) Networks allowing one to engineer the Jaynes–Cummings lattice and Rabi lattice models through the presence of superconducting qubits in the cavities. This opens the door to novel many-body physics with light out of equilibrium, in relation with the Mott–superfluid transition observed with ultra-cold atoms in optical lattices. Then, we summarize recent theoretical predictions for realizing topological phases with light. Synthetic gauge fields and spin–orbit couplings have been successfully implemented in quantum materials and with ultra-cold atoms in optical lattices — using time-dependent Floquet perturbations periodic in time, for example — as well as in photonic lattice systems. Finally, we discuss the Josephson effect related to Bose–Hubbard models in ladder and two-dimensional geometries, producing phase coherence and Meissner currents. The Bose–Hubbard model is related to the Jaynes–Cummings lattice model in the large detuning limit between light and matter (the superconducting qubits). In the presence of synthetic gauge fields, we show that Meissner currents subsist in an insulating Mott phase.     

Evolution of the vortex and the asymmetrical parts of orbital angular momentum in separable first-order optical systems

We analyze the evolution of the vortex and the asymmetrical parts of orbital angular momentum during its propagation through separable first-order optical systems. We find that the evolution of the vortex part depends on only parameters a(x), a(y), b(x), and b(y) of the ray transformation matrix and that isotropic systems with the same ratio b/a produce the same change of the vortex part of the orbital angular momentum. Finally, it is shown that, when light propagates through an optical fiber with a quadratic refractive-index profile, the vortex part of the orbital angular momentum cannot change its sign more than four times per period.     

Dynamics and thermodynamics of a simple model similar to self-gravitating systems: the HMF model

We discuss the dynamics and thermodynamics of the Hamiltonian Mean Field model (HMF) which is a prototypical system with long-range interactions. The HMF model can be seen as the one Fourier component of a one-dimensional self-gravitating system. Interestingly, it exhibits many features of real self-gravitating systems (violent relaxation, persistence of metaequilibrium states, slow collisional dynamics, phase transitions,...) while avoiding complicated problems posed by the singularity of the gravitational potential at short distances and by the absence of a large-scale confinement. We stress the deep analogy between the HMF model and self-gravitating systems by developing a complete parallel between these two systems. This allows us to apply many technics introduced in plasma physics and astrophysics to a new problem and to see how the results depend on the dimension of space and on the form of the potential of interaction. This comparative study brings new light in the statistical mechanics of self-gravitating systems. We also mention simple astrophysical applications of the HMF model in relation with the formation of bars in spiral galaxies.     

Dynamics of plasma formation and permanent structural transformation in ZBLAN excited by tightly focused femtosecond laser pulses

Time-resolved dynamics of plasma formation and bulk refractive-index modification in fluoride glass (ZBLAN) excited by a tightly focused femtosecond (130 fs) Ti:sapphire laser (λ_p=790 nm) was observed in situ. The femtosecond time-resolved pump–probe measurement with perpendicularly linear polarized beams was used to study the dynamics of both plasma formation and induced permanent structural transformation with refractive-index change. In the refractive-index domain, the lifetime of induced plasma formation is ～35 ps and structural transition time for forming the refractive-index change is ～80 ps. In the optical damage domain, however, the lifetime of induced plasma formation is ～40 ps and structural transition time for forming the optical damage is ～140 ps. We found that the process of refractive-index bulk modification is significantly different from that of optical cracks. From the diffraction efficiency of Kogelnik's coupled mode theory, the maximum value of refractive-index change (Δn) was estimated to be 1.3×10^?2. By the scanning of fluoride glass on the optical X–Y–Z stages, the fabrication of internal grating with refractive-index modification was demonstrated in fluoride glass using tightly focused femtosecond laser.     

Geometrical aberrations of self-imaged line gratings

We analyze the properties of a self-imaging system from the point of view of aberration theory. We examine analytically and numerically the geometrical aberrations that are observed in the self-image of a parallel-line grating. We first derive the raytracing equations for determining the optical path of a self-imaging ray with the order of diffraction l. We then obtain the third- and fifth-order contributions to ray aberrations which arise from the difference between the optical paths of a self-imaging ray and of an actual ray. We show that the overall ray aberrations are entirely undercorrected. The ray aberrations approach zero as the ratio of the grating constant to the wavelength of light becomes large enough. In a case of unit magnification, no curvatures are observed in the self-imaged lines. If the magnification is bigger than unity, the light rays passing through the point in a positive or negative domain of the aperture variable contribute to the formation of the curved images. The image evaluation technique discussed here can be useful in the various applications related to the self-image formation of a parallel-line grating and it can also provide insight into the self-imaging of other periodic objects.