Advanced Photonics Research最新文献

Coupled microring lattices are versatile photonic systems that can be used to realize various topological phases of matter. In two-dimensional (2D) microring lattices, the periodic and unidirectional circulation of light in each microring gives rise to a time-like dimension, so that the lattice emulates a (2 + 1)D system with much richer topological behaviors than static 2D lattices. Accurate treatment of these systems requires a departure from the static tight-binding model of coupled resonators and take into account the periodic coupling sequence of light in the lattice network. This article provides an overview of the theory and design of (2 + 1)D microring lattices for realizing Floquet topological photonic insulators (TPIs). Particular focus is placed on the microring Lieb lattice with perfect couplings, which emulates an anomalous Floquet insulator with all flat bands. Such a system exhibits some unique properties, including wide edge mode continuum exceeding a Floquet–Brillouin zone, super-robustness to lattice disorder, Aharonov–Bohm (AB) caging and compact localized flat-band states that can be used to realize high-quality factor topological resonators. All-bands-flat Floquet–Lieb microring lattices provide a versatile platform for investigating topological physics as well as potential applications in realizing topologically-protected photonic devices.

Miura origami's reconfigurable characteristic and structural asymmetry, combined with electromagnetic (EM) wave manipulation, crashed a unique spark. However, the complexity of the three-dimensional (3D) origami structure after folding makes it challenging to study the phase regulation mechanism. Here, we propose a reconfigurable phase gradient metasurface based on Miura origami and derive the underlying mechanism of phase modulation in detail under linearly and circularly polarized (LP and CP) incidence. We adopt the one-dimensional (1D) gradient design along the x direction to verify the idea. The phase calculation formulas are given under LP and CP incidence through the Jones matrix's derivation. The beam deflector angles corresponding to LP and CP waves are identical in the planar state. As the folding angle increases, the phase evolution rules corresponding to the LP and CP waves are discrepant, leading to differential beam steering. Finally, the origami sample is processed for verification, and the experimental data are consistent with the simulation and theoretically calculated values. We believe this work can help analyze the EM behavior of complex 3D origami structures and lay a foundation for designing a multifunctional EM origami metasurface.

Symmetry-protected bound states in the continuum (BICs), emerging at the $��{\Gamma }_0�$ point in the Brillouin zone of periodic lattices of scatters, are robust optical modes under modifications in the lattice if the C₂ symmetry (two fold rotational symmetry) is preserved. In this study, the manipulation of these symmetry-protected BIC and quasi-BIC modes in a system comprising two metallic rods per unit cell by adjusting their lateral separation and displacement is focused on. With non-symmetric systems under 180° rotation, two distinct coupling mechanisms resulting from changes in the lateral separation are investigated: the coupling of two half-wavelength (λ/2) resonances and the coupling of two surface lattice resonances (SLRs). Notably, symmetric structures with minimal lateral separation cannot sustain BIC modes owing to the near-field coupling between the rods. However, when the lateral separation is sufficiently large, the existence of a BIC mode supported by an SLR remains robust even with positional shifts. Furthermore, increasing the lateral separation and the shift displacement between the rods in asymmetric systems induces a redshift and a blueshift in the quasi-BIC mode, respectively. This shift is attributed to the near-field coupling effect between two rods, enabling the tunability of the resonance frequency with a high-quality factor.

Halide perovskites have attracted increasingly attention as “rising star” materials for advanced photonics and optoelectronics. Construction micro-/nano-architecture of perovskites will provide a good platform to investigate and optimize the fundamental photon–matter–structure interaction. It will also improve the properties, pixelate and miniaturize the integration of versatile optoelectronic devices for emerging applications. In this regard, femtosecond (fs) laser processing technique has been widely used to fabricate micro-/nano-architecture with high spatial resolution, limitless flexibility, and unrestricted three-dimensional structuring capability at a large-scale, low-cost way. Concurrently, it is reported that the high refractive index, low thermal conductivity and ultrafast thermalization rate of perovskites are beneficial for the processing by fs laser into micro-/nano-architecture without the degradation of their optoelectronic properties. This review systematically summarizes the interaction of fs laser with perovskites, including the mechanisms, and phenomena. Besides the traditional optoelectronics and applications of halide perovskites, the novel properties and applications from optical structures generated by fs laser processing of perovskites are also discussed. The challenges and outlooks for fs laser processed perovskite materials and devices are highlighted. This review will promote the relevant fundamental research on light–matter–structure interaction, and facilitate the integration of perovskite micro-/nano-architecture-based optoelectronic devices.

The finite penetration depth of light in biological tissues is a practical constraint in light-induced therapies, such as antimicrobial light therapy, photothermal therapy, and photodynamic cancer therapy. Herein, a biocompatible and implantable device, termed hydrogel planar waveguide with lens-microneedles, for light delivery in deep tissue is demonstrated. The prototype device, integrated planar waveguide and lens-microneedles, is fabricated by press-molding polyethylene glycol diacrylate polymers. The optical beams through the lens-microneedles are focused at a specific point to realize the optimal intensity profile in the tissue. The adequate treatment depth and region for the hydrogel planar waveguide with five lens-microneedles are extended to 24 mm and 3.1 cm². The photoswitchable chemotherapeutic against colorectal cancer cells is switched by using different hydrogel waveguides. The performances of hydrogel-waveguide-enabled photoswitching are characterized by the dose responses from the optical microscope, crystal violet staining, and MTT assays. The anticancer drug activated by the hydrogel planar waveguide with five lens-microneedles is shown to be twice as effective as the other fibers and waveguides in causing cancer cell death. The proposed biodegradable waveguide can be utilized for long-term light delivery and does not require to be removed as it is gradually resorbed by the tissue. The results point to a new paradigm for widespread use in photomedicine.

Herein, a YAG/10 at% Yb:YAG/YAG transparent ceramic planar waveguide (PWG) gain medium has been molded via inkjet printing and dry pressing molding. The composition and rheological property of ink are optimized along with the printing process to enhance the printing accuracy and quality. The PWG has dimensions of 13.5 × 8.0 × 1.8 mm³, while the thickness of the core Yb:YAG layer is ≈190 μm. The in-line transmittance of the PWG reaches 81.7% at 1030 nm, and the average grain size is ≈2.3 μm. The diffusion characteristics of Yb ions across the interface between the cladding YAG layer and the core Yb:YAG layer are investigated by calculating the diffusion coefficient and the mean diffusion distance of ¹⁷²Yb ions. The Yb:YAG PWG oscillator, which is pumped from a single end by a 940 nm laser diode, produces continuous wave laser at a wavelength of 1030 nm and exhibits the highest power (3.8 W) and highest absorbed–output slope efficiency (64.6%).

Herein, the lasing action of fabricated bulged CH₃NH₃PbBr₃ microwires is demonstrated with features of a low threshold, narrow linewidth, single-mode operation, and high intensity. Benefiting from the bulged end facets, the CH₃NH₃PbBr₃ microwires are feasible for constructing a high-brightness, whispering-gallery-mode(WGM)-type, and single-mode laser while suppressing Fabry–Pérot-type multi-mode lasing. Numerical simulation unveils that the bulged end facets result in the significantly reduced reflectivity of fundamental waveguided modes. The obtained microlasers require neither complex structures (such as distributed Bragg reflector) nor careful pumping adjustment, suggesting the practical feasibility of a higher single-mode lasing intensity than conventional WGM perovskite microlasers. The results provide new routes to realize high-performance perovskite microlasers and their potential application in sensing refractive index.

Photonic switches play a vital role in optical communications and computer networks for establishing and releasing connections of optical signals. With the growing demand for ultra-compact switches in high-speed optical computing and communications, thermally reconfigurable optical switches have gained significant attention. These switches offer simplicity, ease of fabrication, and leverage a wide range of thermo-optic materials. Silicon remains an ideal platform for making photonic devices including the switches due to its compatibility with complementary metal-oxide-semiconductor (CMOS) technology and cost-effectiveness. The article presents a drop cast sub-stoichiometric vanadium oxide (VO_2−x) nanoparticles combined with a silicon ridge waveguide to make a compact thermally reconfigurable optical switch with low transition temperature and accelerated phase transition. Furthermore, the design achieves high modulation depth in addition to its scalability and simplicity. This study demonstrates the potential of solution-based VO_2−x nanoparticles in combination with silicon waveguides for efficient optical switch design for various applications.