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Dynamic topological photonics is a novel research field, combining the time-domain optics and topological physics. In this review, the recent progress and realization platforms of dynamic topological photonics have been well introduced. The definition, measurement methods and the evolution process of the dynamic topological photonics are demonstrated to better understand the physical diagram. This review is meant to bring the readers a different perspective on topological photonics, grasp the advanced progress of dynamic topology, and inspire ideas about future prospects. [ABSTRACT FROM AUTHOR]

We report the study on pulse compression using air-core photonic band-gap fibre filled with air. The distortion of the output pulse is minimised using a distortion compensating fibre (DCF) for different input and output pulse energies at different values of atomic gas pressure. In the present work, 110 m long DCF was used and the pulses from a picosecond / femtosecond pulse were linearly stretched and then recompressed in 12 m of the air-core fibre. With the band-pass filter, the output pulses were as short as 1.2 ps. The peak power obtained was 100 W with the use of the filter. The output peak power was generated using a filter by simulation and the dispersion characterisation shows that with increasing order of the input pulse, dispersion also changes in the output pulse. The simulation is done by finite difference time domain method in a soliton pulse. [ABSTRACT FROM AUTHOR]

Spatial frequency shift (SFS) microscopy with evanescent wave illumination shows intriguing advantages, including large field of view (FOV), high speed, and good modularity. However, a missing band in the spatial frequency domain hampers the SFS superresolution microscopy from achieving resolution better than 3 folds of the Abbe diffraction limit. Here, we propose a novel tunable large-SFS microscopy, making the resolution improvement of a linear system no longer restricted by the detection numerical aperture (NA). The complete wide-range detection in the spatial frequency domain is realized by tuning the illumination spatial frequency actively and broadly through an angle modulation between the azimuthal propagating directions of two evanescent waves. The vertical spatial frequency is tuned via a sectional saturation effect, and the reconstructed depth information can be added to the lateral superresolution mask for 3D imaging. A lateral resolution of λ/9, and a vertical localization precision of ∼λ/200 (detection objective NA = 0.9) are realized with a gallium phosphide (GaP) waveguide. Its unlimited resolution enhancing capability is demonstrated by introducing a designed metamaterial chip with an unusual large refractive index. Besides the great resolution enhancement, this method shows better anti-noise capability than classical structured illumination microscopy without SFS tunability. This method is chip-compatible and can potentially provide a mass-producible illumination chip module achieving the fast, large-FOV, and deep-subwavelength 3D nanoscopy. [ABSTRACT FROM AUTHOR]

With recent advances in silicon nanophotonics, optical crossbars based on CMOS-compatible microring resonators have emerged as viable on-chip optical interconnection networks to deliver high-bandwidth communication at low power dissipation with a small footprint. This paper describes the design, fabrication and evaluation of an arbitration-free passive crossbar based on a microring resonator matrix that can be used to route wavelength division multiplexing (WDM) signals across the chip. The salient feature of the proposed design is the ability to support multicasting and many-to-one communication efficiently (without arbitration), which makes it suitable for implementing cache coherency protocols and on-chip interconnect in future many-core processors.

This study is performed to investigate the temperature sensitivity of SU-8-based triple-arm Mach-Zehnder interferometer (MZI) and straight waveguide. The proposed SU-8 2000-based rib waveguides are fabricated on a silicon wafer with 1.5-μm SiO2 thermal oxide layer. SU-8 layer of desired thickness is spin-coated onto the silicon wafer followed by patterning of the SU-8 waveguides. Temperature sensitivity of both waveguides is evaluated using the same heating source and under the same environmental conditions. Measurement results show that complex triple-arm MZI having different arm lengths offers a less linear sensitivity compared to the simple straight waveguide. [ABSTRACT FROM AUTHOR]

Lithium Niobate (LiNbO 3 ) nano and micro structures are deposited on glass substrates by sol-gel method. The nanostructures are deposited at 3000 RPM for 30 s, and annealed at different temperatures, 400, 500 and 600 °C. These samples are characterized and analyzed by Scanning Electron Microscope (SEM), Atomic Force Microscopy (AFM), X-ray diffraction (XRD) and Ultra-Violet visible (UV–vis) spectrophotometer, respectively. The results show an importance of increasing the annealing temperatures, which indicate that the structure will be enhanced and more crystallize to become more regular. The measured lattice constants, energy gaps and refractive index give good accordance with the experimental results. [ABSTRACT FROM AUTHOR]

A novel plasmonic waveguide composed of graphene-coated dielectric bow-tie type nanowire pair is designed in this paper. The finite element method ( F E M ) is used to study the dependences of the modal performances on the geometry and electromagnetic parameters. Simulation results show that strong enhancement of the optical field can be confined in the gap region formed by the bow-tie type nanowire pair coated by graphene. The minimum value of normalized mode area approaches to an order of 10 −7 magnitude. Moreover, it has a good tolerance to practical fabrication errors. Thanks to these excellent optical characteristics, this kind of graphene-based plasmonic waveguide can be used to fabricate various functional optoelectronic devices for the future nanoscale photonic integrated circuits and biosensors. [ABSTRACT FROM AUTHOR]

Ultrafast laser photoinscription and laser-based refractive index engineering develop towards a unique way for three-dimensional optical design inside bulk materials for the conception of embedded photonic applications. The specific optical functions for the light guiding elements, notably their single mode characteristics and the accessible spectral domains, depend on the achieved refractive index contrast in the material transparency window and on the characteristic dimensions of the optical modification. We give here an overview of several laser processing options, developed to increase the effective index area and contrast using pulse engineering methods in space and time, and optical design involving focal shaping, tubular concepts, evanescently coupled waveguide arrays, or structured waveguides. [ABSTRACT FROM AUTHOR]

We present a study on analytical solutions of coupled-mode equations for microring resonators with an emphasis on occurrence of all-optical EIT phenomenon, obtained by using a cofactor. As concrete examples, analytical solutions for a 3×3 linearly distributed coupler and a circularly distributed coupler are obtained. The former corresponds to a non-degenerate eigenvalue problem and the latter corresponds to a degenerate eigenvalue problem. For comparison and without loss of generality, analytical solution for a 4×4 linearly distributed coupler is also obtained. This paper may be of interest to optical physics and integrated photonics communities. [ABSTRACT FROM AUTHOR]

A novel approach is presented for waveguide mode selection by using thin-film spatial filters embedded in multimode waveguides. The waveguide modes are allowed to pass through the spatial filters if and when their mode angles fall within the angle-domain bandwidth of the filters. Consequently the waveguide modes are selectable with varied angle-domain bandwidth of the spatial filters. This approach is relatively simple, cost-effective and features good suppression effect of high-order modes, and is suitable for high-power laser systems. [ABSTRACT FROM AUTHOR]

This work explores the production and characterization of pedestal-type active waveguides based on PbO-GeO2 (PGO) thin films codoped with Tm3+/Yb3+ rare earth ions. Silicon wafers containing around 1.7 μm of SiO2 thickness were used as substrate, and the pedestal structure was obtained by conventional photolithography and plasma etching in a reactive ion etching reactor. Plasma etching procedures were made in steps to reduce roughness at the laterals and sidewalls of waveguides. Around 0.5 μm of Tm3+/Yb3+ codoped PGO thin film was obtained by radio frequency magnetron sputtering deposition after etching procedures. Results of scanning electron microscopy confirmed the waveguide pedestal profile. Optical propagation losses around 4, 5, and 20 dB/cm were observed at 1050, 633, and 543 nm, respectively, for waveguide width in the 30-100 μm range. Near field profiles at these wavelengths and also at 980 nm are also reported and confirmed the multimode coupling behavior. The present results corroborate the possibility of using Tm3+/Yb3+ codoped PGO thin films as active waveguides for photonic applications. [ABSTRACT FROM AUTHOR]

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We used LCR transmission lines to model right-handed (conventional material) and left-handed (electromagnetic metamaterial) systems. Both systems are perturbed by an electric field and expressions for the electrical conductivity are obtained. An expression that relates both conductivities is obtained, a numerical analysis shows explicitly the parameter range for the occurrence of a window of conductivity. [ABSTRACT FROM PUBLISHER]

Expressions that relates the dissipated electric energy between the right-handed (conventional material) and the left-handed (electromagnetic metamaterial) systems are obtained from generic spectra for external electric and magnetic perturbations. Also when the perturbations are electromagnetic waves. In this case, an expression is obtained that depends only on frequency of these perturbations. Both systems are modeled by direct LCR transmission lines and their dual, respectively. An numeric study shows that design parameters of both systems and the frequency range of the external perturbation define the relationship between the dissipated electric powers. [ABSTRACT FROM AUTHOR]

We propose the realization of a grating assisted tunneling scheme for tunable synthetic magnetic fields in optically induced one- and two-dimensional dielectric photonic lattices. As a signature of the synthetic magnetic fields, we demonstrate conical diffraction patterns in particular realization of these lattices, which possess Dirac points in k -space. We compare the light propagation in these realistic (continuous) systems with the evolution in discrete models representing the Harper–Hofstadter Hamiltonian, and obtain excellent agreement.

Abstract: Proton beam writing (PBW) is a powerful tool for prototyping microphotonic structures in a wide variety of materials including polymers, insulators, semiconductors and metals. Prototyping is achieved either through direct fabrication with the proton beam, or by the fabrication of a master that can be used for replication. In recent times we have explored the use of PBW for various advanced optical applications including fabrication of subwavelength metallic structures and metamaterials, direct write of silicon waveguides for mid IR applications and integrated waveguides for lab-on-a-chip devices. This paper will review the recent progress made in these areas with particular emphasis on the main advantages of using the PBW technique for these novel applications. [Copyright &y& Elsevier]

Azobenzene polymer surface relief diffraction gratings were inscribed on relaxor ferroelectric Lead Lanthanum Zirconate Titanate (PLZT) thin films having a (9/65/35) composition. Resonance structures were observed in the reflected intensity spectra of a laser light beam onto these films, indicating coupling of the incident light. An ac electric field was then applied along the thickness of the PLZT films and an electro-optic modulation signal was measured as a function of the incidence angle of the laser beam. It was found that the resonance structures increased the modulation signal of the PLZT thin films at constant field amplitude. [ABSTRACT FROM AUTHOR]

Abstract: The integration of optical waveguides within biological assay chips seems to be an interesting solution to increase their functionality as it will allow local optical probing of the samples. However, the techniques proposed to build such chips are generally complex requiring multiple steps to fabricate waveguides and channels, and at the same time losing the capacity to use cost-effective fabrication technique like injection moulding. We propose a techniques where the waveguides are actually built as empty channel in the optical chip and later filled with special liquid to be used as waveguide. In this way, the chip only necessitates the fabrication of channels, some carrying the biological samples and others used as waveguides. To simplify further the fabrication, we developed a standard holder that allows to address the issue of filling the waveguide channel with the special liquid and at the same time provide connection for the sample testing. The chip was fabricated in PDMS and it was tested together with the standard holder using different liquids. Although the optical loss is still high due to scattering, this type of system was able to easily detect the bubbles appearing in a bi-phasic flow, opening the way for further improvements in the technology. [Copyright &y& Elsevier]

An optical modulator is designed and fabricated based on a Si0.75Ge0.25/Si/Si0.5Ge0.5 asymmetrical superlattice structure. The device comprises a p-i-n diode made on the asymmetrical superlattice integrated with a 920-μm-long Fabry-Perot (F-P) cavity. Parameters of the rib waveguide are designed to satisfy only the fundamental-TE mode transmission. Here, 65 and 40-pm red shifts of the peak resonant were measured under the applied bias of 2.5 and −32.0 V, respectively. The analysis shows that, besides the thermal-optical and plasma dispersion effects, the Pockels effect also contributes to such a peak shift. The corresponding calculated effective Pockels coefficient is about 0.158 pm/V. [ABSTRACT FROM AUTHOR]

Abstract: We discuss the discrete Talbot effect in one- and two-dimensional waveguide lattices under the influence of an external potential. It is shown that the field recovery can be precisely tuned by changing the gradient of the potential. In a two-dimensional configuration, the diagonal coupling does not affect the period of recovery. [Copyright &y& Elsevier]

Abstract: Self-imaging theory is widely accepted as a good method in designing 1× N multimode interference (MMI) couplers, but it is also true that self-imaging theory is not suitable for low-contrast structures. An improved self-imaging theory is proposed in this paper for the optimal design of low-contrast 1× N MMI couplers. The average effective width of MMI waveguide and the average effective propagation constant of MMI waveguide are used as the basis to modify the conventional self-imaging theory. A direct calculation of the average effective width of low-contrast MMIs is presented. We use this approach in the optimal design of a 1×4 silica MMI coupler, and the results show that the improved self-imaging theory is more accurate than conventional self-imaging theory for low-contrast structures, the results also show that if the material parameters and the width of an MMI waveguide are fixed, the average effective width of the MMI waveguide will increase with the decrease of the height of the core layer. [Copyright &y& Elsevier]

Abstract: Fields in subwavelength-diameter terahertz hollow optical fiber (STHOF) can be intensified by large discontinuity of the electric field at high index contrast interfaces. The influences of fiber geometry and refractive index of the dielectric region on the fiber characteristics, such as power distribution, enhancement factor, have been discussed in detail. By appropriate design, the intensity in the central region of STHOF may be enhanced by a factor of greater than 1.5 compared with subwavelength-diameter terahertz fiber without the central hole and the loss can be reduced. For its compact structure and simple fabrication process, the fiber may be very useful in many miniaturized high performance and novel terahertz photonic devices. [Copyright &y& Elsevier]

Abstract: We study self-collimation and beam splitting in low-refractive-index photonic crystals created within chalcogenide glass. We propose a beam splitter structure that allows direct experimental verification of photonic-crystal effects at optical wavelengths in a straightforward and definitive manner. The beam splitter provides angular separation of 90° using a highly compact spatial footprint, thus delivering direct application in highly integrated photonic devices. [Copyright &y& Elsevier]

We present a robust practical scheme for measuring the topological invariants of non-interacting tight-binding models realized in arrays of coupled photonic cavities. More specifically, we aim to focus on the implementation of a single unit cell with tunable twisted boundary conditions in order to access the bulk topological properties of much larger systems experimentally. We illustrate our method in a two-dimensional integer quantum Hall model, demonstrating that the associated topological invariants can be measured to a high degree of accuracy despite the driven-dissipative bosonic nature of the system, and discuss the robustness of our scheme against various sources of disorder.

We predict that two correlated particles hopping on a one-dimensional Hubbard lattice can show transient self-acceleration and self-induced Bloch oscillations as a result of anti-Newtonian dynamics. Self-propulsion occurs for two particles with opposite effective mass on the lattice and requires long-range particle interaction. A photonic simulator of the two-particle Hubbard model with controllable long-range interaction, where self-propulsion can be observed, is discussed.

Abstract: We demonstrate that porous fibers in addition to low loss and high confinement, have near zero dispersion for 0.5–1THz resulting in reduced terahertz signal degradation compared to microwires. We also show for the first time that these new fibers can be designed, introducing asymmetrical sub-wavelength airholes within the core, to achieve high birefringence 0.026. This opens up the potential for realization of novel polarization preserving fibers in the terahertz regime. [Copyright &y& Elsevier]