Manipulation Of Light Propagation Research Articles

Thermo-optic effect induced tunable phase controlled propagation of solitons in a Jaynes-Cummings-Hubbard model.

The manipulation of light propagation has garnered significant attention in discrete periodic photon structures. In this study, we investigate the impact of an adjustable phase on soliton behavior within a one-dimensional (1D) coupled cavity array. Each cavity is doped with two-level qubits, and the system can be effectively described by a Jaynes-Cummings-Hubbard model (JC-Hubbard model). By numerically exploring the photonic phase, we reveal that it introduces an additional degree of flexibility in controlling soliton propagation. This flexibility encompasses dispersion relations, propagation direction, transverse velocity, and stability conditions. We observe that soliton styles transition with changes in the tunneling phase. At a phase of 0, solitons form due to the delicate balance between spatial dispersion and system nonlinearity. When the phase increases to π/2, solitons vanish because spatial dispersion is significantly suppressed. The underlying theory explains this suppression, which arises from the opposite phase ±θ. Interestingly, standard temporal solitons emerge in the discrete periodic cavity array. Our investigation has broader applicability extending to various discrete structures, encompassing but not limited to waveguide arrays and optomechanical cavity arrays.

Nanoscale multi-beam lithography of photonic crystals with ultrafast laser

Photonic crystals are utilized in many noteworthy applications like optical communications, light flow control, and quantum optics. Photonic crystal with nanoscale structure is important for the manipulation of light propagation in visible and near-infrared range. Herein, we propose a novel multi beam lithography method to fabricate photonic crystal with nanoscale structure without cracking. Using multi-beam ultrafast laser processing and etching, parallel channels with subwavelength gap are obtained in yttrium aluminum garnet crystal. Combining optical simulation based on Debye diffraction, we experimentally show the gap width of parallel channels can be controlled at nanoscale by changing phase holograms. With the superimposed phase hologram designing, functional structures of complicated channel arrays distribution can be created in crystal. Optical gratings of different periods are fabricated, which can diffract incident light in particular ways. This approach can efficiently manufacture nanostructures with controllable gap, and offer an alternative to the fabrication of complex photonic crystal for integrated photonics applications.

Super‐Resolved Bulk States of Photonic Crystals With Cathodoluminescence Microscopy

AbstractProgress in photonic crystals (PhCs) enables the advanced manipulation of light propagation, leading to strong light–matter interactions and unconventional applications. To explore the physical nature and realize the precise and efficient control of position‐dependent light–matter interactions, the direct deep‐subwavelength characterization of PhC states is pivotal. Here, the super‐resolved visualization of bulk states in the z‐direction asymmetric dielectric PhC is realized by characterizing the radiative local density of optical states, including the etched hole area. An accelerating voltage scanning approach is proposed to selectively probe bulk states and substrates, elucidating the electron–matter interactions affected by the electron‐beam energy. The bulk state energy is demonstrated to be confined inside structure holes as shown by the cathodoluminescence intensity mappings of PhCs with different geometrical parameters, enabling the design of a silicon‐based high‐quality cavity in the visible range. This work provides a deep investigation of the depth‐dependent interaction between the electron beam and dielectric PhCs, promoting the characterization of PhC delocalized modes. The deep‐subwavelength detail of bulk state benefits the future nanoscale manipulation of light–matter interactions and the optimization of quantum emission devices.

Optical meta-cage based on phase gradient metagrating

<sec>How to effectively control the refraction, reflection, propagation and wavefront of electromagnetic wave or light is always one of the advanced researches in the field of optics. In recent years, much effort has been devoted to both theoretical and experimental studies of optical phase gradient metagratings (PGMs) due to the fundamental interest and practical importance of PGMs, such as the generalized Snell’s law (GSL). Typically, the PGMs are constructed as periodic gratings consisting of a supercell spatially repeated along an interface, and each supercell consists of <i>m</i> unit cells, with <i>m</i> being an integer. The key idea of PGMs is to introduce an abrupt phase shift covering the range from 0 to <inline-formula><tex-math id="M2">\begin{document}$2\pi $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20221696_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20221696_M2.png"/></alternatives></inline-formula> discretely through <i>m</i> unit cells to ensure the complete control of the outgoing waves. The phase gradient provides a new degree of freedom for the manipulation of light propagation, which has allowed a series of ultrathin devices to realize anomalous scattering, the photon spin Hall effect, and many other phenomena.</sec><sec>Intuitively, the number of unit cells <i>m</i> in a supercell does not influence the PGM diffraction characteristics, except that a small value of <i>m</i> will lead to a reduced diffraction efficiency. However, some recent studies have shown that the integer <i>m</i> plays a fundamental role in determining the high-order PGM diffractions when the incident angle is beyond the critical angle predicted by the GSL. In particular, for high-order PGM diffractions, <i>m</i> leads to a new set of diffraction equations expressed as</sec><sec> <inline-formula><tex-math id="M3">\begin{document}$ \left\{ {\begin{aligned} &{{k_x} = k_x^t - nG,{\text{ for odd L,}}} \\ &{{k_x} = k_x^r - nG,{\text{ for even L}}{\text{. }}} \end{aligned}} \right. $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20221696_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20221696_M3.png"/></alternatives></inline-formula></sec><sec>In addition to the phase gradient, the integer number of unit cells <i>m</i> in a supercell is another degree of freedom that can be employed to control the light propagation. By the parity of <i>m</i>, the higher-order outgoing wave can be reversed between the anomalous transmission channel and the anomalous reflection channel.</sec><sec>In this work, according to the concept of abrupt phase and the parity-dependent diffraction law in phase gradient metagrating, we theoretically design and study an optical meta-cage. The meta-cage is a periodic structure with one period that contains <i>m</i> different unit cells. Through numerical simulations and rigorous analytical calculations, we find that the ability of meta-cage to trap light is related to the parity of the number of unit cells <i>m</i> in a supercell. Specifically, when the number of unit cells is odd, the point source placed in the meta-cage can perfectly radiate out of the meta-cage without any reflection. On the contrary, when the number of unit cells is even, the point source can hardly radiate out of the meta-cage, and all the energy is localized within the meta-cage. Moreover, such a phenomenon is robust against the disorder. These results can provide new ideas and theoretical guidance for designing new radar radome and photonic isolation devices.</sec>

Arbitrary active control of the Pancharatnam-Berry phase in a terahertz metasurface.

Active phase-control metasurfaces show outstanding capability in the active manipulation of light propagation, while the previous active phase control methods have many constraints in the cost of simulation or the phase modulation range. In this paper, we design and demonstrate a phase controlled metastructure based on two circular split ring resonators (CSRRs) composed of silicon and Au with different widths, which can continuously achieve an arbitrary Pancharatnam-Berry (PB) phase between -π and π before or after active control. The PB phase of such a metasurface before active control is determined by the rotation angle of the Au-composed CSRR, while the PB phase after active control is determined by the rotation angle of the silicon-composed CSRR. And active control of the PB phase is realized by varying conductivity of silicon under an external optical pump. Based on this metastructure, active control of light deflection, metalens with arbitrary reconfigurable focal points and achromatic metalens under selective frequencies are designed and simulated. Moreover, the experimental results demonstrate that focal spots of metalens can be actively controlled by the optical pump, in accord with the simulated ones. Our metastructure implements a plethora of metasurfaces' active phase modulation and provides applications in active light manipulation.

Multi-channel optomechanically induced amplification in a parity-time-symmetric Laguerre-Gaussian rovibrational-cavity system

This paper studies the response of a parity-time-symmetric Laguerre-Gaussian-cavity optomechanical system to a weak probe field, where an active cavity is coupled to a Laguerre-Gaussian rovibrational-cavity system. It is shown that three-amplification-peak profile emerges for the probe transmission. The transmission rate can be adjusted by controlling the coupling coefficient, the pump amplitude and the topological charge. Besides, we find that the light transmission group delay can be altered between positive and negative value by adjusting the coupling coefficient and the topological charge. This study can be applied to light propagation manipulation and quantum precision measurement.

Tunable fast to slow light and second-order sideband generation in an optomechanical system with phonon pump

We theoretically demonstrate optomechanically induced transparency (OMIT) and its related coherent optical propagation properties such as fast and slow light effects in a cavity optomechanical system driven by a weak coherent phonon pump for suitable parametric and detuning regimes. The probe transmission spectrum experiences different processes under different detuning regimes, and the numerical simulations indicating a tunable and controllable fast-to-slow light propagation can be achieved by controlling the driving amplitudes and phase of the phonon pump. Further, the second-order sideband (SOS) generation is also demonstrated in the system, and it is found that the efficiency of the SOS generation can be significantly enhanced with manipulating the phonon pump in the resonance regime with numerical simulations. More interestingly, the SOS generation is also sensitive to the detuning (the off-resonance regime), and a robust SOS can be induced and the efficiency of the SOS generation even presents mode splitting which is similar to the linear OMIT. These results lead to good tunability of SOS generation and may find applications in manipulation of light propagation.

OAM-basis transmission matrix in optics: a novel approach to manipulate light propagation through scattering media

Transmission matrix (TM) is an ideal theoretical model describing light propagation through scattering media. Until now, most of the present TMs utilize the eigenstates of spatial position as input and output bases. Thus, they describe the relationship between the spatial distributions of two light fields. Here, we demonstrate that wider relationships between the light fields could be described by a TM. As a significant example, we propose a generalized TM with the eigenstates of OAM as input bases - OAM-basis TM. With the measured OAM-basis TM, we achieved single-spot and multiple-spot focusing, verifying its availability in light propagation manipulation. The distinct eigenchannels property was also discussed. The OAM-basis TM has broadened the definition of TM. Meanwhile, it will open new perspectives for OAM-based communication, as well as the applications of wavefront shaping technology in biomedical photonics and optical communication.

Exceptional points enhancing second-order sideband generation in a whispering-gallery-mode microresonator optomechanical system coupled with nanoparticles

We theoretically investigate the second-order sideband generation (SSG) in a whispering-gallery-mode (WGM) microresonator optomechanical system, in which the WGM microresonator couples with two nanoparticles. The nanoparticles can induce the optical coupling of the clockwise (CW) and the counterclockwise (CCW) WGM fields. And by continuously adjusting the relative phase angle between two nanoparticles, two eigenmodes of the optomechanical system coalesce and the so-called exceptional points (EPs) emerge periodically. It is shown that in the WGM microresonator optomechanical system coupled with nanoparticles in the second-order sideband can be generated due to the nonlinear optomechanical interactions, modulated periodically by the relative phase angle between two nanoparticles, and enhanced significantly at the EPs. Particularly, considering the frequency shift caused by the nanoparticles at the EPs, the generation and absorption of the second-order sideband can be flexibly realized. These results may have potential applications for high precision measurements and the manipulation of light propagation in optical cavities.

A Multi‐Foci Metalens with Polarization‐Rotated Focal Points

AbstractBenefiting from the unprecedented capability of metasurfaces in the manipulation of light propagation, metalenses can provide novel functions that are very challenging or impossible to achieve with conventional lenses. Here, an approach to realizing multi‐foci metalenses is proposed and experimentally demonstrated with polarization‐rotated focal points based on geometric metasurfaces. Multi‐foci metalenses with various polarization rotation directions are developed using silicon pillars with spatially variant orientations. The focusing characteristic and longitudinal polarization‐dependent imaging capability are demonstrated upon the illumination of a linearly polarized light beam. The uniqueness of this multi‐foci metalens with polarization‐rotated focal points may open a new avenue for imaging, sensing, and information processing.

Generation and enhancement of sum sideband in a quadratically coupled optomechanical system with parametric interactions.

We investigate theoretically the generation and enhancement of sum sideband in a quadratically coupled optomechanical system with parametric interactions. It is shown that the generation of frequency components at the sum sideband stems from the nonlinear optomechanical interactions via two-phonon processes in the quadratically coupled optomechanical system, while an optical parametric amplifier (OPA) inside the system can considerably improve the sum sideband generation (SSG). The dependence of SSG on the system parameters, including the power of the control field, the frequency detuning of the probe fields and the nonlinear gain of OPA are analyzed in detail. Our analytic calculation indicates that the SSG can be obtained even under weak driven fields and greatly enhanced via meeting the matching conditions. The effect of SSG may have potential applications for achieving measurement of electric charge (or other weak forces) with higher precision and on-chip manipulation of light propagation.

Effects of a chiral atomic medium on the manipulation of light birefringence and lateral Goos–Hänchen shifts via Kerr nonlinearity and local field effects

We present a new scheme to report on the effects of a five-level chiral atomic medium on the lateral Goos–Hänchen (GH) shift in Gaussian probe beams via Kerr nonlinearity (KNL) and local field effects. The physical realization of birefringence in absorption, dispersion, reflection and transmission beams is investigated, with special emphasis on the manipulation of absolute and fractional change in lateral GH shifts in birefringence transmission and reflection beams, via local fields and Kerr nonlinearity. We have employed a semiclassical atomic density-matrix formalism so as to obtain the expression for electric and magnetic susceptibilities of the chiral medium and the corresponding chirality coefficients in conjunction with Kerr and local fields, both separately and in combination. Stationary-phase theory is used to compute GH shift from the calculated birefringent reflection and transmission coefficients of probe beams. A negative and positive GH shift is observed in reflection and transmission beams, respectively, subjected to local field and Kerr effect. In contrast, a positive GH shift is observed in both reflection and transmission beams in the presence of both local field and Kerr effects. The local and Kerr fields also alter the divergence angle between left and right circularly polarized birefringence beams. GH shift depends on incident angle and probe detuning. The anisotropy of medium is lessened by switching ON the Kerr field in the medium. We observed a positive fractional change of ±30% in the GH shift in the birefringence reflection beam in the presence of a local field without KNL, while a 20% fractional GH shift was observed in the presence of both local field and KNL effects. Our results suggest promising applications in nonlinear optical, plasmonic and biophotonic devices for the manipulation of light propagation and optical signal processing.

Optical Performance Study of Gyroid‐Structured TiO2 Photonic Crystals Replicated from Natural Templates Using a Sol‐Gel Method

AbstractPhotonic crystals with novel nanostructures have attracted huge attention due to their potential applications in manipulation of light propagation and next‐generation energy and information technologies. In this work, TiO2 photonic crystals with 3D bicontinuous gyroid structure in visible light wavelength range are successfully fabricated by templating from natural templates using a sol‐gel method. This is the first time to report controlling the volume fraction (VF) through regulating the rinsing time of templates in the sol‐gel precursor. Gyroid‐structured TiO2 photonic crystals (GTPCs) with different VFs, 3.2, 8.0, and 13.5% are obtained. Combined with finite‐difference time‐domain simulations, the photonic bandgap properties of the GTPCs are systematically studied. Based on this work, one step is moved further toward the exploitation of the optical performance of the GTPCs in visible light wavelength range beyond the previous simulation works.

Wave dynamics on toroidal surface.

Wave dynamics on curved surfaces has attracted growing attention due to its close resemblance to the warped space time governed by general relativity. It also opens up opportunities for designing functional optical devices such as geodesic lenses. In this work we study the wave dynamics on the surface of a torus, a shape of considerable interest due to its nontrivial topology. Governed by the conservation of angular momentum, light propagates on the torus in two different types of modes: one is able to twist around and sweep through the whole surface of the torus; the other is confined within a certain angular range along the torus latitude direction. The confined mode exhibits an interesting self focusing or imaging behavior, which, similar to a geometric lens, shows no dependence of wavelength and thus suffers no chromatic aberration. By changing the geometric parameters of the torus, both the focusing point and the focusing distance can be controlled. Our work provides a new approach to manipulation of light propagation on a curved surface under the conservation of angular momentum.

Group‐Velocity‐Controlled and Gate‐Tunable Directional Excitation of Polaritons in Graphene‐Boron Nitride Heterostructures

AbstractA fundamental building block in nano‐photonics is the ability to directionally excite highly squeezed optical mode dynamically, particularly with an electrical bias. Such capabilities would enable the active manipulation of light propagation for information processing and transfer. However, when the optical source is built‐in, it remains challenging to steer the excitation directionality in a flexible way. Here, a mechanism is revealed for tunable directional excitation of highly squeezed polaritons in graphene‐hexagonal boron nitride (hBN) heterostructures. The effect relies on controlling the sign of the group velocity of the coupled plasmon‐phonon polaritons, which can be flipped by simply tuning the chemical potential of graphene (through electrostatic gating) in the heterostructures. Graphene‐hBN heterostructures thus present a promising platform toward nano‐photonic circuits and nano‐devices with electrically reconfigurable functionalities.

Multifunctional Light Sword Metasurface Lens

The depth of focus of an imaging system determines the range of change for both the position of focal plane and image plane. Although a typical light sword optical element with angular modulation of phase transmittance can extend its focus of depth due to its angular variation of the optical power, it lacks rotational symmetry and exhibits a junction, rendering its fabrication extremely difficult. Optical metasurfaces provide an unusual approach to develop such a device due to their unprecedented capability in the manipulation of light propagation in a desirable manner. We propose and experimentally demonstrate a light sword metasurface lens with multiple functionalities. The position of focal segments can be controlled by changing the polarization state of the incident light. The developed ultrathin, ultraflat device can facilitate device miniaturization and system integration and may find applications in various fields such as optical coupling, imaging, and interconnections.

Kuznetsov-Ma Soliton Dynamics Based on the Mechanical Effect of Light.

A Kuznetsov-Ma soliton that exhibits an unusual pulsating dynamics has attracted particular attention in hydrodynamics and plasma physics in the context of understanding nonlinear coherent phenomena. Here, we demonstrate theoretically the formation of a novel form of Kuznetsov-Ma soliton in a microfabricated optomechanical array, where both photonic and phononic evolutionary dynamics exhibit periodic structure and coherent localized behavior enabled by radiation-pressure coupling of optical fields and mechanical oscillations, which is a manifestation of the unique property of optomechanical systems. Numerical calculations of the optomechanical dynamics show an excellent agreement with this theory. In addition to providing insight into optomechanical nonlinearity, optomechanical Kuznetsov-Ma soliton dynamics fundamentally broadens the regime of cavity optomechanics and may find applications in on-chip manipulation of light propagation.

“Black” Titania Coatings Composed of Sol–Gel Imprinted Mie Resonators Arrays

Optical technologies and devices rely on the controlled manipulation of light propagation through a medium. This is generally governed by the inherent effective refractive index of the material as well as by its structure and dimensionality. Although a precise control over light propagation with sub‐wavelength size objects is a crucial issue for a plethora of applications, the widely used fabrication methods remain cumbersome and expensive. Here, a sol–gel dip‐coating method combined with nanoimprinting lithography on arbitrary glass and silicon substrates is implemented for the fabrication of TiO2‐based dielectric Mie resonators. The technique allows obtaining sub‐micrometric pillars featuring unprecedented vertical aspect ratios (>1) with relatively high fidelity and precision. Spectroscopic characterization at visible and near‐infrared frequencies demonstrate that the resonant properties of these dielectric pillar arrays allow for a drastic reduction of light transmission (cutting more than 50% on glass) and reduced reflection (reflecting less than 3% on glass and 16% on bulk silicon), accounting for an efficient light trapping. These results provide a guideline for the fabrication of Mie resonators using a fast, versatile, low‐cost, low‐temperature technique for efficient light manipulation at the nanoscale.

Partially hollowed ultra-thin dielectric meta-surface for transmission manipulation.

Impressive optical properties are numerically demonstrated in the partially hollowed dielectric meta-surface (p-HDMS), which consists of an air cavity array intercalated in an ultra-thin (~λ/6) high-index dielectric film. Multispectral transmission band-stop response with near-perfect spectral modulation depth is achieved. The spectral slop is up to 80%/nm, indicating the sharp and narrowband transmission behavior. Classical Malus law is confirmed by this sub-wavelength platform. Moreover, the multispectral light propagation manipulation can be perfectly reproduced by using the actual dielectric with absorption loss. In this all-dielectric meta-surface, conduction loss is avoided compared to its metallic plasmonic counterpart. Such configurations can therefore serve as excellent alternatives for plasmonic meta-surfaces and constitute an important step in nanophotonics.

Self-collimation-based photonic crystal Mach–Zehnder demultiplexer

A photonic crystal Mach–Zehnder demultiplexer (PC-MZDmux) with four output ports based on the self-collimation phenomenon in a two-dimensional (2D) PC is proposed and numerically studied using finite-difference time-domain simulations. The PC-MZDmux is composed of three Mach–Zehnder interferometers (MZIs) and each MZI consists of two 50:50 beam splitters and two perfect mirrors. Employed as the design parameters to achieve the demultiplexing functionality are the radius of phase control rods (PCRs) in the mirrors and the distance between the beam spitter and the mirror in the three MZIs. From spatial electric field distributions and transmission spectra, it is demonstrated that an incident self-collimated beam with four different frequencies can be demultiplexed to four output ports of the PC-MZDmux with proper design parameters. Our results indicate that this device design may constitute an efficient approach to light propagation manipulation and increase the application range of self-collimated beams.