Photonic Crystal Research Articles

Hybrid one-dimensional photonic crystals containing anisotropic metamaterials: Angle-driven photonic band gaps and angle-driven Tamm plasmon polaritons

Hybrid one-dimensional photonic crystals containing anisotropic metamaterials: Angle-driven photonic band gaps and angle-driven Tamm plasmon polaritons

Rapid Construction of PVA@CDs/SiO2 Fluorescent/Structural Color Dual-Mode Anti-Counterfeiting Labels via Spray-Coating Method.

A method of sequential spraying of polyvinyl alcohol with carbon quantum dots (PVA@CDs) aqueous suspension and SiO2 aqueous suspension is proposed to rapidly prepare multicolor dual-mode anti-counterfeiting labels. With the optimization of the concentration (15%) of colloidal microspheres in the SiO2 aqueous suspension as well as the spraying process parameters (spray distance of 10 cm, spray duration of 3 s, and assembly temperature of 20 °C), different-sized SiO2 microspheres (168 nm, 228 nm, and 263 nm) were utilized to rapidly assemble red, green, and blue photonic crystals. Furthermore, the tunable fluorescence emission of carbon quantum dots endows the labels with yellow, green, and blue fluorescence. The constructed dual-mode labeling was used to develop an anti-counterfeiting code with dual-channel information storage capabilities and also to create dual-mode multicolor anti-counterfeiting labels on various packaging substrates. This work provides a novel solution for anti-counterfeiting packaging and information storage.

3D Printing Photonic Crystals: A Review.

Living organisms in nature possess diverse and vibrant structural colors generated from their intrinsic surface micro/nanostructures. These intricate micro/nanostructures can be harnessed to develop a new generation of colorful materials for various fields such as photonics, information storage, display, and sensing. Recent advancements in the fabrication of photonic crystals have enabled the preparation of structurally colored materials with customized geometries using 3D printing technologies. Here, a comprehensive review of the historical development of fabrication methods for photonic crystals is provided. Diverse 3D printing approaches along with the underlying mechanisms, as well as the regulation methods adopted to generate photonic crystals with structural color, are discussed. This review aims to offer the readers an overview of the state-of-the-art 3D printing techniques for photonic crystals, present a guide and considerations to fabricate photonic crystals leveraging different 3D printing methods.

A polyelectrolyte-induced highly processable pigment-like photonic crystal ink

Developing a straightforward strategy for constructing highly processable photonic crystals (PCs) is crucial for various applications, yet remains a challenge. Here, we present a simple polyelectrolyte-induced self-assembly strategy for producing novel photonic crystal (PC) inks with outstanding processing flexibility by adding the polyelectrolytes into the ultralow concentration of colloidal nanoparticle solution. The polyelectrolyte can cover the nanoparticles through the hydrogen bond interaction to induce the aggregation and mutual repulsion of them simultaneously, enabling the self-assembly of ultralow concentration (0.01–1.0 v/v%) of nanoparticles into short-range ordered arrays with angle-independent structural colors. The resulting PC inks present unprecedented pigment-like color modulation capacity, as well as ultrahigh freedom in processing methods due to the fact that the rheological behaviors of PC inks can be widely adjusted by varying the properties of polyelectrolytes. Consequently, the PC inks can be easily shaped into complex and exquisite multicolor patterns/3D structures using various techniques, including injection molding, writing, drawing, and 3D printing. This general approach paves the way for quick and scalable production of advanced PC materials deeply required in practical applications.

High Q factor of photonic cavity with SU-8 photoresist micro-disk for electromagnetic wave control

How to control electromagnetic wave effectively is the key to the realization of applicable filters in many optics technologies. In our work, a SU-8 photoresist micro-disk is written onto a photonic crystal waveguide to control electromagnetic wave. Corresponding simulation and experiment shows that, the quality Q increases as the thickness of SU-8 smaller. When the thickness exceeds 400 nm, the change of thickness has little influence on electromagnetic waves. Besides, the increase of the radius of disc-shaped SU-8 can also increase the Q value. By optimizing the simulation and experimental data, we can successfully create a SU-8 photoresist micro-disk cavity with the thickness of 5 µm and height of 20 nm, the quality factor of Q can reach 8200. However, longer exposure time and more stable experimental equipment is needed if we want to get a larger radius. The method in our work by using SU-8 photoresist micro-disk on photonic crystals to control electromagnetic wave is more practical and flexible, which can provide new significance for research into optical filter.

Fabrication of ZnO–Al2O3 inverse opals with atomic layer deposited Amorphous-Al2O3 for enhanced photocatalysis

Zinc oxide inverse opal (IO) has excellent photocatalytic properties, while Al2O3 has high chemical stability and negligible photocatalytic activity. However, combining these materials creates a crystalline ZnO-amorphous Al2O3 composite IO photonic crystal material with improved photocatalytic performance. In this study, ZnO IO and ZnO–Al2O3 combined structures were grown on self-assembled polystyrene (PS) nanosphere templates. ZnO layer was coated by thermal atomic layer deposition (TALD) in the pores of the template, and the template was then removed by annealing to yield a self-standing ZnO IO nanostructure. An ultra-thin film of Al2O3 was coated on the top of ZnO IO by TALD or plasma-enhanced ALD (PEALD). SEM imaging, Raman spectroscopy, and XRD analysis confirmed the presence of a periodically arranged, and wurtzite ZnO IO structure, with an amorphous Al2O3 layer on top. The UV–Vis results demonstrated distinctive absorption bands in both regions, with a notable increase in visible light absorption attributed to the slow photon effect within the near-bandgap region of the photonic materials. The ZnO/Al2O3-TALD photocatalyst exhibited enhanced photocatalytic performance in degrading various pollutants including methylene blue, rhodamine 6G, and 4-nitrophenol under visible light illumination compared to its pristine IO and PEALD composite counterparts. This is attributed to its periodic arrangement of the IO structure that acts as a photonic crystal, precisely controlling light interaction through photonic band gap manipulation and the slow photon effect. This tailored light manipulation within the visible spectrum significantly enhances photodegradation efficiency.

Bio-Inspired Photoelectric Dual-Mode Sensor Based on Photonic Crystals for Human Motion Sensing and Monitoring.

Photoelectric dual-mode sensors, which respond to strain signal through photoelectric dual-signals, hold great promise as wearable sensors in human motion monitoring. In this work, a photoelectric dual-mode sensor based on photonic crystals hydrogel was developed for human joint motion detection. The optical signal of the sensor originated from the structural color of photonic crystals, which was achieved by tuning the polymethyl methacrylate (PMMA) microspheres diameter. The reflective peak of the sensor, based on 250 nm PMMA PCs, shifted from 623 nm to 492 nm with 100% strain. Graphene was employed to enhance the electrical signal of the sensor, resulting in a conductivity increase from 9.33 × 10-4 S/m to 2 × 10-3 S/m with an increase in graphene from 0 to 8 mg·mL-1. Concurrently, the resistance of the hydrogel with 8 mg·mL-1 graphene increased from 160 kΩ to 485 kΩ with a gauge factor (GF) = 0.02 under 100% strain, while maintaining a good cyclic stability. The results of the sensing and monitoring of finger joint bending revealed a significant shift in the reflective peak of the photoelectric dual-mode sensor from 624 nm to 526 nm. Additionally, its resistance change rate was measured at 1.72 with a 90° bending angle. These findings suggest that the photoelectric dual-mode sensor had the capability to detect the strain signal with photoelectric dual-mode signals, and indicates its great potential for the sensing and monitoring of joint motion.

Tunable terahertz filter based on graphene photonic crystals with defective layers

In this paper, we design a high-precision tunable terahertz filter by using transfer matrix method. The filter structure mainly consists of graphene embedded photonic crystals (GPCs). The front part of the GPCs contains artificial synthetic material and air layer, the back part of the GPCs is composed by and periodic stack of isotropic dielectric slabs (MgF2) embedded with graphene sheets, where air defect layer is located in the middle of the GPC as a central layer. Our simulation reveals that graphene layer and air defective layer strongly affect the filter performance. And we can get a relatively pure transmission peak in a wide frequency region. Additionally, the influence of incidence angle of terahertz wave, thickness of air layer, the unit number of front periodic structure and chemical potential of the graphene sheets can also modulate the function of the filter. And the filter has strong stability when the temperature changes from 150 K to 350 K.The results indicate that single channel, dual and multiple channels filter in a narrow frequency can be obtained by optimizing the structure parameter.

Topology-optimized photonic topological crystalline insulators with multiband helical edge states

Abstract Photonic topological crystalline insulators (PTCIs) with helical edge states provide an alternative way to achieve robust electromagnetic wave transport and processing. However, most existing PTCIs only involve a single topological bandgap, and generally support a pair of gapped helical edge states, restricting the scope of applications in various fields such as multiband waveguides, filters, and communication systems. Here, we design dual-band PTCIs, in which multiple helical edge modes appear within two distinct bulk gaps, for transverse electric (TE) and transverse magnetic (TM) modes, respectively, by introducing the topology optimization method into the photonic crystals with glide symmetry. For PTCIs with TE modes, the mismatched frequency ranges of edge modes hosted by two orthometric boundaries offer an opportunity to realize a photonic demultiplexer. For PTCIs with TM modes, we show the enhanced second harmonic (SH) generation through the coupling of multiband edge modes by matching the frequency ranges of edge modes within the first and second bandgaps to fundamental and SH waves, respectively. This work provides a new way for designing multiband PTCIs with helical edge states, having promising potentials in developing multiband topological photonic devices for both linear and nonlinear applications.

The effect of singularities and damping on the spectra of photonic crystals

Understanding the dispersive properties of photonic crystals is a fundamental and well-studied problem. However, the introduction of singular permittivities and damping complicates the otherwise straightforward theory. In this paper, we study photonic crystals with a Drude–Lorentz model for the permittivity, motivated by halide perovskites. We demonstrate how the introduction of singularities and damping affects the spectral band structure and show how to interpret the notion of a “band gap” in this setting. We study a one-dimensional model for which we present explicit solutions.

Splice Loss Investigation of Single-Mode Fiber and Photonic Crystal Fibers and Its Potential Refractometric Sensing Applications

Splice Loss Investigation of Single-Mode Fiber and Photonic Crystal Fibers and Its Potential Refractometric Sensing Applications

Photonic crystal-connected bidirectional micro-ring resonator array for duplex mode and wavelength channel (de)multiplexing

The progress of on-chip optical communication relies on integrated multi-dimensional mode (de)multiplexers to enhance communication capacity and establish comprehensive networks. However, existing multi-dimensional (de)multiplexers, involving modes and wavelengths, face limitations due to their reliance on single-directional total internal reflection and multi-level mode conversion based on directional coupling principles. These constraints restrict their potential for full-duplex functionality and highly integrated communication. We solve these problems by introducing a photonic-like crystal-connected bidirectional micro-ring resonator array (PBMRA) and apply it to duplex mode-wavelength multiplexing communication. The directional independence of total internal reflection and the cumulative effect of the subwavelength-scale pillar within the single-level photonic crystal enable bidirectional mode and wavelength multiplexed signals to transmit among multi-pair nodes without interference, improving on-chip integration in single-level mode conversion. As a proof of concept, we fabricated a nine-channel bidirectional multi-dimensional (de)multiplexer, featuring three wavelengths and three TE modes, compactly housed within a footprint of 80 μm×80 μm, which efficiently transmits QPSK-OFDM signals at a rate of 216 Gbit/s, achieving a bit error rate lower than 10−4. Leveraging the co-ring transmission characteristic and the orthogonality of the mode-wavelength channel, this (de)multiplexer also enables a doubling of communication capacity using two physical transmission channels.

Structural Color Colloidal Photonic Crystals for Biomedical Applications.

Photonic crystals are a new class of optical microstructure materials characterized by a dielectric constant that varies periodically with space and features a photonic bandgap. Inspired by natural photonic crystals such as butterfly scales, a series of artificial photonic crystals are developed for use in integrated photonic platforms, biosensing, communication, and other fields. Among them, colloidal photonic crystals (CPCs) have gained widespread attention due to their excellent optical properties and advantages, such as ease of preparation and functionalization. This work reviews the classification and self-assembly principles of CPCs, details some of the latest biomedical applications of large-area, high-quality CPCs prepared using advanced self-assembly methods, summarizes the existing challenges in CPC construction and application, and anticipates future development directions and optimization strategy. With further advancements, CPCs are expected to play a more critical role in biosensors, drug delivery, cell research, and other fields, bringing significant benefits to biomedical research and clinical practice.

Topologically Protected Single Edge Mode Lasing in Photonic Crystal Su–Schrieffer–Heeger Lattice with Directional Loss Control

AbstractTopological photonics is considered to be a robust and flexible platform for the design of nanophotonic devices against structural imperfections and performance degradation. Combining with parity‐time (PT) symmetry systems based on spatially distributed gain and loss, photonic crystal (PhC) lasers with micron‐size carrier reservoirs offer an ideal test bed for lasing mode competition and topological protection in nanophotonic structures. In this study, single topological edge mode (TEM) lasing is demonstrated in PhC lasers with a Su–Schrieffer–Heeger lattice comprised of coupled nanoresonators. By inducing directional loss control, a mode selection strategy is implemented, that achieves single TEM lasing with a side‐mode‐suppression ratio exceeding 30 dB. One of the TEMs exhibits remarkable robustness against local potential variation introduced by additional loss channels. This strategy integrating both topological protection and PT symmetry in nanophotonics would open up new prospects for the development of on‐chip single‐mode topological lasers unperturbed by output channels in nanophotonic integrated circuits.

Unidirectional self-imaging in multiple shifted photonic crystal interfaces.

In this study, we investigate the unidirectional self-imaging phenomenon in the shifted photonic crystal (PC) heterostructure. A spin-locked topological edge state, which originates from the mismatch of the Wannier center positions, can propagate along the shifted PC interface without backscattering. When the neighboring shifted PC interfaces are close enough, the coupling between the edge states happens, and coupled edge states (CES) can be found. Based on the finite element method (FEM) simulation, the spin-locked multimode interference (MMI) and self-imaging phenomenon of CES, including paired and symmetrical interference, are achieved in multiple shifted PC interfaces. To illustrate the application of the frequency splitters, the T-shaped and double cross-shaped structures with backscattering immunity and spin-locked characteristics are proposed. Our work provides an alternative way toward the design of a topological splitter by utilizing the photonic frequency and spin degrees of freedom at the same time.

Fluorescent Nanowires from Dual‐State Emitting Fluorophores Directed by Molecular Motors and Aggregation‐Induced Emission: Produce Quantized Light Spectrum

AbstractLuminescent materials require systems that exhibit both dual‐state emission (DSE) and aggregation‐induced emission (AIE) to overcome the limitation of aggregation‐caused quenching (ACQ). Herein, a molecular assembler capable of crafting nanowires that exhibit programmable fluorescence across a broad spectrum of colors in a precisely quantized manner is reported. Because it is a starburst dendritic box made of PAMAM dendrimer (P), controller (C) molecules, and motor (M) molecules, the assembler is called PCM. Here, Nile red is chosen as C and placed into the hollow core of the dendrimer; a double ratchet motor (DRM) is chosen as M and is connected to the N‐terminals of the PAMAM dendrimer. While aqueous dispersed PCM assemblers have broad fluorescence bands beyond 300 nm, their crafted nanowires produce quantized cyan‐green, yellow, and orange‐red light emission in the spectra. These PCM assemblers are shown to hold long‐term memory, rapid switching, and energy harvesting by modulating photonic bandgaps, causing a longer redshift in the solid phase. The DSE of PCM can yield versatile photonics applications like bioimaging and energy harvesting. As PCM nanowires can modulate photonic bandgaps to cause a longer redshift, PCM fluorophores hold promise for drug delivery and cell separation like infrared‐sensitive operations.

Excitation/emission-enhanced heterostructure photonic crystal array synergizing with "DD-A" FRET entropy-driven circuit for high-resolution and ultrasensitive analysis of ctDNA

Circulating tumor DNA (ctDNA) is an emerging biomarker of liquid biopsy for cancer. But it remains a challenge to achieve simple, sensitive and specific detection of ctDNA because of low abundance and single-base mutation. In this work, an excitation/emission-enhanced heterostructure photonic crystal (PC) array synergizing with entropy-driven circuit (EDC) was developed for high-resolution and ultrasensitive analysis of ctDNA. The donor donor−acceptor FÖrster resonance energy transfer ("DD-A" FRET) was integrated in EDC based on the introduction of simple auxiliary strand, which exhibited higher sensitivity than that of traditional EDC. The heterostructure PC array was constructed with the bilayer periodic nanostructures of nanospheres. Because the heterostructure PC has the adjustable dual photonic band gaps (PBGs) by changing nanosphere sizes, and the "DD-A" FRET can offer the excitation and emission peak with enough distance, it helps the successful matches between the dual PBGs of heterostructure PC and the excitation/emission peaks of "DD-A" FRET; thus, the fluorescence from EDC can be enhanced effectively from both of excitation and emission processes on heterostructure PC array. Besides, high-resolution of single-base mutation was obtained through the strict recognition of EDC. Benefiting from the specific spectrum-matched and synergetic amplification of heterostructure PC and EDC with "DD-A" FRET, the proposed array obtained ultrasensitive detection of ctDNA with LOD of 12.9 fM, and achieved the analysis of mutation frequency as low as 0.01%. Therefore, the proposed strategy has the advantages of simple operation, mild conditions (enzyme-free and isothermal), high-sensitivity, high-resolution and high-throughput analysis, showing potential in bioassay and clinical application.

Improvement of Luminous Efficiency of Micro Ultraviolet LightEmitting Diodes with Photonic Crystals

Improvement of Luminous Efficiency of Micro Ultraviolet LightEmitting Diodes with Photonic Crystals

Design of a breath analyzer by using double defect layered 1D quaternary photonic band gap structure

Design of a breath analyzer by using double defect layered 1D quaternary photonic band gap structure

Photothermally Reconfigurable Biomimetic Photonic Structures Prepared via Crystallization of Polydopamine‐Incorporated Core–Shell Nanoparticles

AbstractSome creatures have periodic nanostructures and chromophores in their flexible organs that allow them to control the color and shape of their skin. Artificial photonic structures that can mimic the aforementioned ability of these natural structures are researched extensively. In this study, polydopamine‐incorporated core–interlayer–shell (CIS‐PDA) nanoparticles capable of shape reconfiguration and expressing vivid structural colors are designed. These nanoparticles can be readily assembled to produce colloidal photonic crystals (CPhCs) and can exhibit vivid structural colors by virtue of their light‐absorbing capability. Soft CPhC films prepared with these nanoparticles undergo stable elastic deformation at 15% strain and exhibit mechanochromic properties. Specifically, the PDA in the CIS nanoparticles can absorb broadband light and exhibit a photothermal effect resembling that of melanosomes in living organisms, which enables self‐healing between multiple CPhC films. Due to their favorable properties, the CPhC films prepared in this study represent promising photothermally reconfigurable photonic materials. Moreover, arbitrarily shaped 2D or 3D surfaces are conformally coated with the films via microimprinting or vacuum wrapping, courtesy of the reconfigurability of these films. These findings suggest that CPhC films prepared with CIS‐PDA nanoparticles can be used as form‐free mechanochromic strain sensors and nonfading optical films for industrial products.