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In this paper, tunable plasmon-induced transparency (PIT) is achieved in a novel and compact plasmonic system which consists of dual hexagonal resonators with rotatable rectangular bar embedded in resonators and a metal-insulator-metal (MIM) waveguide. The proposed structure is numerically investigated by finite-difference time-domain (FDTD) method. The numerical simulation results reveal that by rotating the embedded bar to different angles, PIT can realize in different wavelengths. Tunability in transparency peak wavelength, transmission, and optical delay are also obtained when the angle of embedded bars are changed. In addition, the influences of other structural parameters on transmission and optical delay are analyzed in detail. This proposed structure may provide a novel manipulation for tunable PIT and potentially be applied in highly integrated optical storage and switch devices.

An optical phase shifter based on narrow-core hollow waveguide is proposed. The light is guided in an air core between the top and bottom reflectors made up of silicon and indium tin oxide (ITO) gratings. The proposed narrow-core hollow structure is able to guide slow light mode with a low loss of 0.2 dB/cm and a high group index of 64 in 0.8 μm thick air core. The presence of ITO enables electrically controlled phase shifting. In order to realize phase shifting, a p-i-n junction in ITO is used around the air core and in the top and bottom gratings. The geometry is optimized for enhanced interaction between the free charge carriers injected in the intrinsic region of ITO and the propagating optical mode. The proposed device shows a phase shifting of 180° for a 71-μm long device resulting from the slow-light effect.

Densely interconnected, nonlinear, and reconfigurable optical networks represent a route to high-performance optical computing, communications, and sensing technologies. Dielectric nanoantennas are promising building blocks for such architectures since they can precisely control optical diffraction. However, they are traditionally limited in their nonlinear and reconfigurable responses owing to their relatively low-quality factor (Q-factor). Here, we highlight new and emerging design strategies to increase the Q-factor while maintaining control of optical diffraction, enabling unprecedented spatial and temporal control of light. We describe how multipolar modes and bound states in the continuum increase Q and show how these high-Q nanoantennas can be cascaded to create almost limitless resonant optical transfer functions. With high-Q nanoantennas, new paradigms in reconfigurable wavefront-shaping, low-noise, multiplexed biosensors and quantum transduction are possible. [ABSTRACT FROM AUTHOR]

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In this paper, we theoretically and numerically reported a dual plasmon-induced transparency and the relevant sensing property in a multi-cross metasurface by the coupled mode analysis. A phase coupling model was established to characterize the optical response of this plasmonic sensor. It was found that the transparency windows were sensitive to the resonance mode of each metal strip, which was well demonstrated by the theoretical model. Both the sensing property and the slow light in this structure were discussed. A high figure of merit of 223 and sensitivity of 850 nm/RIU were achieved. In addition, the 1170-nm near-infrared light can be slowed down by nearly two order of magnitude with group delay of 0.45 ps in this sensor. These results may provide guidance for light-matter interaction-enhanced slow-light sensor and integrated optical circuit design. [ABSTRACT FROM AUTHOR]

We implement slow-light under electromagnetically induced transparency condition to measure the motion of cold atoms in an optical lattice undergoing Bloch oscillation. The motion of atoms is mapped out through the phase shift of light without perturbing the external and internal state of the atoms. Our results can be used to construct a continuous motional sensor of cold atoms. [ABSTRACT FROM AUTHOR]

A novel electromagnetically induced transparency (EIT) effect analogue based on metamaterials is proposed, which is composed of metal-based H shaped cut wires (MH) and parallel cut wires (MPW) on F4BM substrate. Distinct EIT-like window can be observed under irradiation of plane wave with y polarised direction through the coupling of bright element MH and dark element MPW. In addition, relative position of MH and MPW can influence the EIT-like effect which can be validated by experimental test and expressed by damping rate of bright mode and coupling coefficient of bright-dark mode on the basis of two particles mode. The work exhibits guiding function in EIT designs and realizations. [ABSTRACT FROM AUTHOR]

In this paper, we study the optical properties and surface plasmon resonance of a bimetallic core-shell spherical nanoparticle exhibiting monolayer graphene coatings. The extinction cross section (Qex) and slow light factor of this structure are investigated. The effect of coated graphene, host medium, and geometrical parameters such as the core radius and thickness of the shell on the Qex and the slow light factor are studied. The results show that the monolayer of graphene enhances the absorption and also leads to a redshift in the Qex and the slow light spectrums. These unique optical properties of bimetallic nanoparticles render them attractive for a broad range of applications such as biological sensors and optical communication devices. [ABSTRACT FROM AUTHOR]

Black phosphorus (BP) offers unique opportunities for mid‐infrared (MIR) waveguide photodetectors due to its narrow direct bandgap and layered lattice structure. Further miniaturization of the photodetector will improve operation speed, signal‐to‐noise ratio, and internal quantum efficiency. However, it is challenging to maintain high responsivities in miniaturized BP waveguide photodetectors because of reduced light–matter interaction lengths. To address this issue, a method utilizing the slow light effect in photonic crystal waveguides (PhCWGs) is proposed and experimentally demonstrated. A shared‐BP photonic system is proposed and utilized to fairly and precisely characterize the slow light enhancement. Close to the band edge around 3.8 µm, the responsivity is enhanced by more than tenfold in the BP photodetector on a 10 µm long PhCWG as compared with the counterpart on a subwavelength grating waveguide. At a 0.5 V bias, the BP PhCWG photodetector achieves a 11.31 A W−1 responsivity and a 0.012 nW Hz−1/2 noise equivalent power. The trap‐induced photoconductive gain is validated as both the dominant photoresponse mechanism and the major limiting factor of the response speed. The BP slow light waveguide photodetector is envisioned to realize miniaturized high‐performance on‐chip MIR systems for widespread applications including environmental monitoring, industrial process control, and medical diagnostics. [ABSTRACT FROM AUTHOR]

We have theoretically investigated a plasmonic metal-dielectric-metal (MDM) resonant system with water-based dielectric, which allow easy implementation of up to eight Fano resonant channels. The reported plasmonic MDM system is composed by an end-coupled square ring and three reversed L-shape cavities, which can support bright modes or dark modes that will interact with each other to generate sharp and asymmetric Fano profiles in transmission spectra. Finite-difference time-domain (FDTD) method and multiple interference coupled mode theory (MICMT) are employed to investigate high performances of those Fano resonances, of which sensitivity and figure of merit are high as ~1813 nm/RIU and ~57.77 dB, respectively. The proposed plasmonic MDM resonant system may promote the development of integrated photonic devices for applications in nanoscale optical sensing and optical communications. [ABSTRACT FROM AUTHOR]

We theoretically, demonstrate a high delay bandwidth product (DBP) and zero group velocity dispersion (GVD) in a two-dimensional one-way slow light waveguide. The waveguide consists of gyromagnetic photonic crystal (GMPC) and a cladding formed by silicon photonic crystal. At the edge of the band, weak interactions ("semi-anticrossing") between the chiral edge state (CES) mode and the mode localized at the surface of cladding are observed. The group velocity of CES wave can be tuned by adjusting the modal field distribution. As a result, an extraordinarily large value of normalized DBP of 0.63 with a group index of 10.32 and a bandwidth ranging from 0. 5 2 9 (2 π c / a) to 0. 5 6 2 (2 π c / a) is obtained. This result may contribute to one-way slow light applications in information communication systems. [ABSTRACT FROM AUTHOR]

In this work, an optical switch based on electro-optic effect is reported. We used defect mode in two-dimensional photonic crystal made of Lithium Niobate. Under an applied voltage of 3 V, a refractive index change of −0.0702 is obtained which has led to a transmittance contrast about 60% for the ON state and a high extinction ratio of about 20 dB. Moreover, Slow light structure performance is investigated to optimize proposed optic switch. Due to elliptic shape of holes, the applied voltage is decreased to 0.5 V. Also, a refractive index change decrease around −0.0481, a transmittance contrast increase 65 %, and an extinction ratio increase by 5 dB have been observed. We used plan wave expansion and finite difference time domain methods to analyze the structures performances. It is seen that a defect mode shift about 40 nm and a switching length of 6.48 μm are obtained with drive voltage of 3 V for simple structure and only 0.5 V for slow light structure. [ABSTRACT FROM AUTHOR]

Dispersion engineering, such as the design of slow light waveguide systems, is an effective tool for a wide range of photonic applications, but presents a difficult optical design challenge. Most applications require a slow light waveguide design that mitigates group velocity dispersion, and efficient coupling solutions over the slow light operating bandwidth. In this work, we optimize the slow light dispersion relation of a photonic crystal waveguide with three dimensional (3D) inverse design methods. In addition, we design mode couplers for the photonic crystal waveguide. The optimized waveguide supports a slow light mode with a group index of $\mathbf {n_g = 25}$ and a normalized bandwidth group index product of $\mathbf {0.38}$. A compact mode coupler to a strip waveguide is designed with an average efficiency of 92.7% within the slow light operating bandwidth. Lastly, we design a fully etched grating which couples directly to the slow light mode with a 32.5% average efficiency. [ABSTRACT FROM AUTHOR]

Structural slow light is the dispersion engineering process by which the group velocity of light can be drastically reduced in a periodic waveguide structure. Enabling large group delay and enhancing the light-matter interaction on a subwavelength scale, on-chip slow light is of great interest in a vast array of fields such as non-linear optic, sensing, laser physics, telecommunication and computing. In this work, we experimentally demonstrate, for the first time, slow light in subwavelength grating waveguides on the silicon-on-insulator platform. We present a comprehensive numerical study in analytical modelling and 3-D FDTD. Multiple waveguides variations were fabricated using an electron-beam lithography process. Figures of merit such as group index, bandwidth and loss-per-delay are examined in both theory and experiment. A maximum measured group index of 47.74 with a loss-per-delay of 103.37 dB/ns has been achieved near the wavelength of 1550 nm. A broad bandwidth of 8.82 nm was measured, in which the group index remains larger than 10. We also show that the region of slow light operation can be shifted over a large wavelength span by controlling a single design parameter. [ABSTRACT FROM AUTHOR]

High-quality (high-Q) resonators play a crucial role in optical-wave manipulation. It is challenging to excite guide modes in 1-D photonic crystals (PhC guided modes (PCGMs)) because of their high Q factors and complex patterns. To address this, a hybrid cavity Tamm plasmon (HCTP) structure composed of a metal film, cavity, and 1-D photonic crystal (1-D PhC) was designed. Subsequently, a grating was incorporated into the HCTP structure to diffract the electric fields of the HCTP resonance mode. This efficiently excited the PCGMs. When the detuning between the PCGM and HCTP modes approached zero, a plasmon-induced transparency (PIT)-like effect occurred. Under normal incidence, the PIT-like effect exhibited an impressively high Q factor (5015.5). The physical properties of the PIT-like effect were analyzed using the coupling mode theory. The results show that there is a strong phase coupling between PCGM and HCTP modes. This resulted in a modulation depth of 97.4 %. Under an oblique incidence, the degenerated PCGMs split into two modes. Both these were coupled with the HCTP mode. This resulted in a double PIT-like effect with a high modulation depth. The Q factor was enhanced further to 8957.7. Active modulation of the PIT-like spectra was achieved by modifying the incident or polarization angle. The coupling also exhibited slow-light properties, with a group delay of 17.54 ps under inclined incidence. The strong coupling between PCGM and HCTP resulted in the generation of high-Q and deep-modulation PIT-like effect. These hold high potential for various applications such as nanosensing, slow-light devices, nanolasers, and angle detectors. • A hybrid cavity Tamm plasmon (HCTP) structure was designed to allow the presence of a PIT-like transparent window with an increased Q factor of 8957.7. • The structure can be actively modulated by adjusting the incidence angle and polarization angle. • The study shows that the structure can be used for slow light with a group delay of 17.54 ps. [ABSTRACT FROM AUTHOR]

We theoretically investigate Fano resonance in the absorption spectrum of a quantum dot (QD) based on a hybrid QD-nanomechanical resonator (QD–NR) system mediated by Majorana fermions (MFs) in superconducting iron (Fe) chains. The absorption spectra exhibit a series of asymmetric Fano line shapes, which are accompanied by the rapid normal phase dispersion and induce the optical propagation properties such as the slow light effect under suitable parametric regimes. The results indicated that the slow light induced by MFs can be obtained under different coupling regimes and different detuning regimes. Moreover, we also investigated the role of the NR, and the NR behaving as a phonon cavity enhances the slow light effect.

Slow light propagation through photonic crystal (PhC) slab devices has great potential to reduce the size and power consumption of silicon photonic optical circuits. Most commonly, slow light routing through photonic crystals is achieved by using W1 waveguide bends operating near their cutoff frequencies. Unfortunately, this leads to optical pulse distortion due the high group velocity dispersion (GVD) associated with these designs. In this letter, however, we study the coupling between slow light waveguides optimized for near-zero GVD and 60° PhC bends. Using numerical methods and the temporal coupled mode theory, we assess the performance of single bends coupled to input/output waveguides, and S-bends composed of two cascaded bends. In this latter, we observe that the bend-waveguide quality factor has great impact over transmission and dispersion. We propose a novel 60° PhC bend design for routing optical modes while maintained reduced dispersion. This is achieved over a -3 dB bandwidth of around 50 nm in devices with slowdown factor up to 40. We show that this 60° PhC bend has good stability under changes in S-bend length and fabrication induced disorder. These results can lead to great improvements in the design of monolithically integrated modulators, switches, (de)multiplexers, and filters based on photonic crystals, as well as on the routing of long optical buffers and delay lines.

A bifunctional tunable metamaterial composed of pattern metal structure, graphene, and strontium titanate (STO) film is proposed and studied numerically and theoretically. The dual plasmon-induced transparency (PIT) window is obtained by coupling the bright state cut wire (CW) and two pairs of dark state dual symmetric semiring resonators (DSSRs) with different parameters. Correspondingly, slow light effect can also be realized. When shifting independently, the Fermi level of the graphene strips, the amplitudes of the two PIT transparency windows and slow light effect can be tuned, respectively. In addition, when independently tuning the temperature of the metamaterial, the frequency of the dual PIT windows and slow light effect can be tuned. The physical mechanism of the dual-PIT was analyzed theoretically by using a three-harmonic oscillator model. The results show that the regulation function of the PIT peak results from the change of the oscillation damping at the dark state DSSRs by tuning conductivity of graphene. Our design presents a new structure to realize the bifunctional optical switch and slow light.

We theoretically investigate the optical output fields of a photonic-molecule optomechanical system in an optomechanically induced transparency (OMIT) regime, in which the optomechanical cavity is optically driven by a strong pump laser field and a weak probe laser field and the mechanical mode is driven by weak coherent phonon driving. The numerical simulations indicate that when the driven frequency of the phonon pump equals the frequency difference of the two laser fields, we show an enhancement OMIT where the probe transmission can exceed unity via controlling the driving amplitude and pump phase of the phonon driving. In addition, the phase dispersion of the transmitted probe field can be modified for different parametric regimes, which leads to a tunable delayed probe light transmission. We further study the group delay of the output probe field with numerical simulations, which can reach a tunable conversion from slow to fast light with the manipulation of the pump laser power, the ratio parameter of the two cavities, and the driving amplitude and phase of the weak phonon pump.

In this paper, tunable plasmon-induced transparency (PIT) is achieved in a novel and compact plasmonic system which consists of dual hexagonal resonators with rotatable rectangular bar embedded in resonators and a metal-insulator-metal (MIM) waveguide. The proposed structure is numerically investigated by finite-difference time-domain (FDTD) method. The numerical simulation results reveal that by rotating the embedded bar to different angles, PIT can realize in different wavelengths. Tunability in transparency peak wavelength, transmission, and optical delay are also obtained when the angle of embedded bars are changed. In addition, the influences of other structural parameters on transmission and optical delay are analyzed in detail. This proposed structure may provide a novel manipulation for tunable PIT and potentially be applied in highly integrated optical storage and switch devices. [ABSTRACT FROM AUTHOR]

Active manipulation of group delay of electromagnetic waves is highly desirable for telecommunications and information processing. However, most control means of the group delay currently demonstrated experimentally in the artificial metamaterials require different external excitations necessitating complex setups. Here, electrical manipulation of resonance strength of electromagnetically induced reflectance (EIR) are theoretically and numerically demonstrated in a hybrid metal-graphene complementary metamaterial for actively tunable slow light applications. Combining a monolayer graphene with a metal-based complementary metamaterial composed of a dipole slot and a quadrupole slot, a sharp EIR window in the complementary structure is excited due to strong coupling between two resonators. As shifting the Fermi energy of graphene implanted under the dark mode resonator via electrostatic doping, the EIR window can realize an on-to-off switch, and the modulation depth of 73.3% for the EIR resonance strength is achieved with actively switchable group delay of 6.44 ps. Further investigations show that the active modulation can be attributed to the change in the damping rate of the dark mode caused by the tunable conductivity of graphene. This work provides an alternative way for innovative design and realization of dynamically controllable terahertz slow light devices, which may show potential applications in future terahertz wireless communications. [ABSTRACT FROM AUTHOR]

Graphene nanomaterials exhibit excellent optical properties when interacting with electromagnetical fields, which plays an important role in a wide range of applications such as optical communications, optical storage and other fields. Based on the electromagnetically induced transparency (EIT) effect, we investigate control of slow light in the Landau quantized graphene system with different three-level and four-level coupling schemes. Utilizing the EIT effect, group velocity of the probe fields can be significantly reduced and well controlled by manipulating Rabi frequencies and detunings of the coupling lasers as well as probe detuning. Furthermore, probe light with different frequencies can even be controlled in different EIT windows in the graphene system with the four-level scheme, which may find applications in signal selection and discrimination. This work can provide reference for the design of graphene-based quantum devices and have potential applications in optical communications and optical quantum information processing, etc. [ABSTRACT FROM AUTHOR]

The origin of non-dispersive flat band modes for a quasi-one dimensional square-kagomé ladder network is explored analytically by virtue of the real space renormalization group (RSRG) technique. A section of the eigenstates is non-diffusive i.e., localized within a cluster of sub-lattice sites partly by the destructive type of quantum interference and partly by the physical boundary created by the site with zero wave function amplitude. By making the amplitude vanish at the selective sites it becomes possible to confine the incoming excitation within the trapping cell leading to the formation of compact localized states. The effective mass of the particle becomes infinitely large corresponding to those self-localized modes and hence the mobility of the wave train becomes vanishingly small. This quenched kinetic energy leads to a momentum independent contribution to a dispersion curve. The present analysis is corroborated by numerical calculation of spectral landscape and the corresponding dispersion profile. The application of uniform magnetic flux may lead to a comprehensive engineering of the position as well as the curvature of the band. Also, one-to-one mapping between electronic case and photonic case within the tight-binding framework helps us to study the photonic localization in an analogous single mode wave guide system. The concept of slow light eventually introduces the possibility of spatial compression of light energy. • Analytical study of flat band states for square kagomé ladder network is reported. • The dispersionless nature is also justified within tight binding description. • Flux sensitivity of the compact localized states is also discussed elaborately. • The analogous slow light case may throw achievable challenge to the experimentalists. [ABSTRACT FROM AUTHOR]

Abstract Slow-light performance based on photonic-crystal coupled-cavity waveguide (PC-CCW) is investigated with low-dispersion pulse transmission. A chain of periodically arranged specific defect cavities of air holes are created along the axis of the waveguide and each of the cavities looks like an irregular hexagon with arrow-like left and right sides to form the PC-CCW. By changing the radius and position of certain defects, slow light modes are achieved. Through optimization, we obtained a highest compromise value for an operating bandwidth of 12.9 nm with an average group index of 70.75 and a normalized delay-bandwidth product (NDBP) of 0.5873. This value of NDBP with low group velocity dispersion is higher than that in other structures based on waveguides or coupled cavities reported previously. The arrow-like shape of the cavity sides is shown to be perfect for reducing the transmission loss of the waveguide. The proposed structure with high NDBP is beneficial for buffering applications and slow light devices. [ABSTRACT FROM AUTHOR]

The performance of on-chip gas sensors using absorption spectroscopy are currently limited by the small overlap and reduced interaction length between the light and the analyte. Here, the use of slow-light in subwavelength grating (SWG) waveguide integrated on a silicon photonic chip is proposed to improve methane sensing by tunable diode laser absorption spectroscopy in the near infrared. Such SWG waveguide increases the interaction by two means. First, close to the photonic bandgap edge, a SWG waveguide no longer acts as a metamaterial with a homogeneous index, but rather as a 1D photonic crystal in which slow-light effect enhances the light-analyte interaction. Second, the subwavelength segmentation of the waveguide increases the modal overlap with the air. These two enhancement mechanisms results in a six-fold improvement of the interaction with respect to strip waveguides. In this paper, we discuss how to engineer the group index of SWG waveguides to exploit slow-light effect for the first time. Design guidelines for minimizing propagation loss and disorder effect are discussed considering limitations of typical fabrication processes. SWG waveguides could improve the sensitivity and the limit of detection of on-chip trace-gas sensors that provide a compact, fabrication tolerant, inexpensive, and selective sensing technology. [ABSTRACT FROM AUTHOR]

In this paper, rectangular and triangular photonic crystal (PC) delay lines are designed using PTS (p-toluene sulfonate) at 1550 nm. PTS possesses a high nonlinear refractive index; consequently, when it interacts with an incident light, it provides slow light propagation in a PTS-based device due to the Kerr effect. First, a PC waveguide (PCW) is designed by introducing a line defect made of PTS bars. Such a defect, by using PTS, provides two significant advantages; these include slow group velocity and extremely high optical confinement for a propagating wave through the PCW. Then, two similar PCWs are placed next to each other to investigate the crosstalk phenomenon between them. By choosing an appropriate distance between them, the rectangular and triangular PC reflective meandering delay lines are realized. The rectangular lattice PC reflective meandering delay line exhibits lower propagation losses because this lattice shows a higher transmission coefficient at the corners in comparison with the triangular one. On the other hand, the triangular lattice PC reflective meandering delay line provides very low group velocity for a propagating light wave at the wavelength of 1550 nm; as a consequence, a higher slowing factor is achieved for the triangular lattice PC reflective meandering delay line due to the stronger light-PTS interactions. Simulations are performed using LUMERICAL FDTD SOLUTION v8.15. [ABSTRACT FROM AUTHOR]

An optical phase shifter based on narrow-core hollow waveguide is proposed. The light is guided in an air core between the top and bottom reflectors made up of silicon and indium tin oxide (ITO) gratings. The proposed narrow-core hollow structure is able to guide slow light mode with a low loss of 0.2 dB/cm and a high group index of 64 in 0.8 μm thick air core. The presence of ITO enables electrically controlled phase shifting. In order to realize phase shifting, a p-i-n junction in ITO is used around the air core and in the top and bottom gratings. The geometry is optimized for enhanced interaction between the free charge carriers injected in the intrinsic region of ITO and the propagating optical mode. The proposed device shows a phase shifting of 180° for a 71-μm long device resulting from the slow-light effect. [ABSTRACT FROM AUTHOR]

We design a novel slow-light silicon photonic crystal waveguide which can operate over an extremely wide flat band for ultrafast integrated nonlinear photonics. By conveniently adjusting the radii and positions of the second air-holes rows, a flat slow-light low-dispersion band of 50 nm is achieved numerically. Such a slow-light photonic crystal waveguide with large flat low-dispersion wideband will pave the way for governing the femtosecond pulses in integrated nonlinear photonic platforms based on CMOS technology.

We theoretically report an approach to support multispectral ultranarrow Fano resonances (FRs) from ultraviolet (UV) to visible region in a 3D metamaterial composed of aluminium vertical split-ring resonators with a nanogap (Al VSRRG). The plasmonic hybridization between the 1st order broad localized surface plasmon (LSP) resonance of the Al VSRRG and the 1st order narrow optical diffraction mode propagated in the dielectric substrate caused by the Wood anomaly, and the plasmonic hybridization between the 2nd order LSP resonance and the 2nd order optical diffraction mode produce the dual ultranarrow FRs with quality (Q) factors of 118 and 437 in the visible and UV regions, respectively. The simulated dual FRs phenomenon of the proposed Al VSRRG array is well explained by the coupled oscillator theory. In comparison with the Al VSRR without a gap, both the Q -factors of the double FR peaks and the localized electromagnetic field intensities of the Al VSRRG are further increased. The positions and line shapes of the ultrahigh- Q double FRs tuned by different geometric parameters are also investigated. Our designed simple 3D gap metamaterial has large group indexes of 210 and 240 in visible and UV regions, suggesting promising applications in slow light nanodevices. [ABSTRACT FROM AUTHOR]

The electromagnetically induced transparent-like metamaterials have received much attention because of their excellent slow-light properties and strong nonlinear effects. They have many promising applications in novel terahertz functional devices, high-sensitivity sensors, and optical storages. In this paper, a flexible terahertz switching device based on the electromagnetically induced transparent-like effect was proposed. The device exhibited a significant slow light phenomenon without pumped laser. Meanwhile, it is demonstrated that the device has a large modulation depth and excellent tunable slow light performance with low-power pumped laser. Its amplitude modulation depth can reach 60.4% and the group delay modulation can reach 32.5 ps. And the minimum group velocity of the device in slow terahertz light can reach 0.69 × 105 m/s. Moreover, the flexible substrate of the proposed device is not easily damaged. It makes the device suited for more complex environments well. Therefore, the device will have great potential for future research on high-performance terahertz switching devices. • A terahertz device based on the EIT-like effect was proposed. • The WTE2 material enables the device to have significant modulation capability. • A small group velocity of the device in slow terahertz light was obtained. [ABSTRACT FROM AUTHOR]

Plasmon-induced transparency (PIT) in a compact plasmonic resonator structure, which consists of a metal- dielectric-metal waveguide with an aperture-coupled square cavity and a slot resonator, is investigated theoretically and numerically. We find the transparency window and the delay of slow light in this structure can be controlled at a fixed wavelength by carefully adjusting the geometrical parameters of the aperture-coupled square cavity. By introducing gain medium into the slot resonator, the transmittance and the group index in transparency window both are dramatically enhanced with optically pumping the medium, and the group delay time can reach to 0.93 ps. In addition, triple PIT effects are also achieved by adding another aperture-coupled cavity and slot cavity, and corresponding slow light also can be dynamically tuned. This study paves a new route toward the realization of highly integrated all-optical circuits and networks, especially for ultrafast switches, optical buffers, lasers, and nanosensors.

In present study, the effect of different defect layer refractive indices and thicknesses on group velocity has been studied in one-dimensional photonic crystal. It is found that the increase of refractive index, number of defects and defect layer thickness will induce the decrease of group velocity. Taking advantage of these results, a novel technique has been introduced to tune and control the slowing light in photonic crystal

Increasing development of nano-technology in optics and photonics by using modern methods of light control in waveguide devices and requiring miniaturization and electromagnetic devices such as antennas, transmission and storage as well as improvement in the electromagnetic tool, have led researchers to use the phenomenon of electromagnetically induced transparency (EIT) and similar phenomena in metamaterials. In this work, we introduce a metamaterial structure in nanometer dimensions and THz frequency region. Moreover, by broking the geometrical symmetry structure, we offer EIT with high transmittance and more Q-factor in comparison, to our knowledge, with previous studies of two-dimensional structure, in the infrared region. These achievements can be a good choice for slow light applications and can be used to amplify light in nanostructure and also to detect the infrared light. Finally, we study the effect of changing the metal on the proposed metamaterial. Moreover, in this study, numerical calculations and simulations are done by FDTD methodphenomenon of electromagnetically induced transparency (EIT) and similar phenomena in metamaterials. In this work, we introduce a metamaterial structure in nanometer dimensions and THz frequency region. Moreover, by broking the geometrical symmetry structure, we offer EIT with high transmittance and more Q-factor in comparison, to our knowledge, with previous studies of two-dimensional structure, in the infrared region. These achievements can be a good choice for slow light applications and can be used to amplify light in nanostructure and also to detect the infrared light. Finally, we study the effect of changing the metal on the proposed metamaterial. Moreover, in this study, numerical calculations and simulations are done by FDTD method.

Active control of the electromagnetically induced transparency (EIT) is highly desirable for advanced terahertz (THz) device applications. Currently, the EIT peak positions in the graphene-based metamaterials have been actively controlled by tailoring Fermi energy of graphene via electric doping. However, there is still a considerable challenge to realize active strength modulation of the EIT peak without frequency shifting. Here, a hybrid metal-graphene structure, consisting of the metal-based EIT metamaterial and patterning graphenes, is proposed at the THz frequencies. Through changing Fermi energy of graphene, the EIT peak strength can exhibit both active modulation and on-to-off switch without frequency shifting. Moreover, theoretical model and field distributions discover that the active response can be attributed to the increasing damping rate of the dark mode caused by the controllable conductivity of graphene. In addition, the controllable group delay is also achieved for the slow light applications. Therefore, this work provides the possibility for designing compact slow light devices in the information processing and telecommunication applications.

Slow light with adequate low group velocity and wide bandwidth with a flat band of the zero-dispersion area were investigated. High buffering capabilities were obtained in a silicon-polymer coupled-slot slab photonic crystal waveguide (SP-CS-SPCW) with infiltrating slots by ionic liquid. A figure of merit (FoM) around 0.663 with the lowest physical bit length Lbit of 4.6748 µm for each stored bit in the optical communication waveband was gained by appropriately modifying the square air slot length. Posteriorly, by filling the slots with ionic liquid, the Lbit was enhanced to be 4.2817 μm with the highest FoM of 0.72402 in wider transmission bandwidth and ultra-high bit rate in terabit range, which may become useful for the future 6G mobile communication network. Ionic liquids have had a noticeable effect in altering the optical properties of photonic crystals. A polymer was used for the future incorporation of an electro-optic effect in buffers to realize the dynamic controlling of optical properties. Ionic liquids enhanced the transmission rate through optical materials. Additionally, the delay time in the ns-range was achieved, providing longer delay and ultra-low group velocity, which is important for light-matter interaction in light amplifiers and nonlinear devices.

Active photonics based on graphene has attracted wide attention for developing tunable and compact optical devices with excellent performances. In this paper, the dynamic manipulation of electromagnetically induced transparency (EIT) with high quality factors (Q-factors) is realized in the optical telecommunication range via the graphene-loaded all-dielectric metasurface. The all-dielectric metasurface is composed of split Si nanocuboids, and high Q-factor EIT resonance stems from the destructive interference between the toroidal dipole resonance and the magnetic dipole resonance. As graphene is integrated on the all-dielectric metasurface, the modulation of the EIT window is realized by tuning the Fermi level of graphene, engendering an appreciable modulation depth of 88%. Moreover, the group velocity can be tuned from c/1120 to c/3390. Our proposed metasurface has the potential for optical filters, modulators, and switches.

Over the last two decades, breakthrough works in the field of non-linear phononics have revealed that high-frequency lattice vibrations, when driven to high amplitude by mid- to far-infrared optical pulses, can bolster the light-matter interaction and thereby lend control over a variety of spontaneous orderings. This approach fundamentally relies on the resonant excitation of infrared-active transverse optical phonon modes, which are characterized by a maximum in the imaginary part of the medium's permittivity. Here, in this Perspective article, we discuss an alternative strategy where the light pulses are instead tailored to match the frequency at which the real part of the medium's permittivity goes to zero. This so-called epsilon-near-zero regime, popularly studied in the context of metamaterials, naturally emerges to some extent in all dielectric crystals in the infrared spectral range. We find that the light-matter interaction in the phononic epsilon-near-zero regime becomes strongly enhanced, yielding even the possibility of permanently switching both spin and polarization order parameters. We provide our perspective on how this hitherto-neglected yet fertile research area can be explored in future, with the aim to outline and highlight the exciting challenges and opportunities ahead., Competing Interests: Competing interestsThe authors declare no competing interests., (© The Author(s) 2024.)

Layered materials, such as graphene, transition metal dichacogenides and black phosphorus have attracted lots of attention recently. They are emerging novel materials in electronics and photonics, with tremendous potential in revolutionizing the traditional electronics and photonics industry. Marrying layered material to the nanophotonics is being proved fruitful. With the recent emphasis and development of metasurfaces in nanophotonics, atomically thin materials can find their unique position and strength in this field. In this article, I will focus on one specific two dimensional material: bilayer graphene. Basic physics will be reviewed, such as band-gap opening, electron-phonon interaction, phonon-plasmon interaction and Fano resonances in the optical response. Moreover, I will review the application of bilayer graphene as a sensitive and fast photodetector. An outlook will be given in the final part of the paper.

Üçgen örgülü GaAs fotonik kristal yapısı kullanılarak sayısal ortamda bir sıcaklık algılayıcısı önerilmiş ve algılayıcının duyarlılığı kavite çevresinde yapısal değişimler yapılarak ve yavaş ışık özelliği kullanılarak iyileştirilmiştir. Fotonik kristal dalga kılavuzunun bir sıra ilerisinde bir noktasal kusur oluşturularak kavite rezonans frekanslarındaki ışık bu noktasal boşluğa bağlaştırılmış ve sıcaklığa bağlı olarak rezonans frekansın değişimi incelenmiştir. Duyarlılığın artırılması için kavitenin yanlarındaki deliklerin yarıçapı ve kavite alanı değiştirilmiştir. 0.1001 nm/ºC olan sıcaklık algılayıcısının duyarlılığı yapısal iyileştirmeler ile 1.4%±0.1% artırılmıştır. Dalga kılavuzu çevresindeki ilk sıra deliklerin yarıçapı değiştirilerek ve dalga kılavuzuna paralel doğrultuda kaydırılarak kavite rezonans dalga boyunu da içeren 20.23 nm'lik aralıkta ışık 14 kat yavaşlatılmıştır. Yavaş ışık etkisi ile kipin kavite ile daha fazla optiksel olarak örtüşmesi sonucu algılayıcının duyarlılığı %2.8±%0.1 artmıştır.

A temperature sensor is proposed in the computational environment using triangular lattice GaAs photonic crystal structure and the sensitivity of the sensor is enhanced by employing structural improvements around the cavity and by using slow light feature. By creating a point defect one row ahead from the photonic crystal waveguide, light in the cavity resonance frequencies is coupled to this point defect and the change of the resonance frequency related to the temperature is investigated. The radius of the holes around the cavity and the cavity area are changed to enhance the sensitivity. 0.1001 nm/ºC sensitivity of the temperature sensor is increased by 1.4%±0.1% with structural optimizations. Light is slowed down by 14 times in a 20.23 nm range including the cavity resonance wavelength by changing the radius of the first rows of holes surrounding the waveguide and shifting them in a direction parallel to the waveguide. The sensitivity of the sensor is increased by 2.8%±0.1% as a result of increasing optical overlap of the mode with the cavity by slow light effect.