Two-dimensional Photonic Crystals Research Articles

High-speed photonic decoder employing two-dimensional photonic crystals

High-speed photonic decoder employing two-dimensional photonic crystals

Highly sensitive l-lysine molecularly imprinted two-dimensional photonic crystal hydrogel sensor

Using polystyrene two-dimensional photonic crystal as template, l-lysine molecularly imprinted two-dimensional photonic crystal hydrogel (l-Lys MIPCH) sensor with highly sensitive response to l-lysine was prepared by photoinitiated polymerization. The response performance of the l-Lys MIPCH sensor was investigated by observing the change of the diameter of the Debye ring (ΔD) and the structural color of the sensor. In the process of recognizing l-Lys molecules by l-Lys MIPCH sensor, the volume of hydrogel swells, the diameter of Debye ring decreases, and the particle spacing of photonic crystal increases. As the l-Lys concentration increased from 0 to 10−4 mol/L, the diameter of Debye ring decreased by 15.7 mm, the particle spacing of photonic crystals increased by 75.1 mm, and the structural color of hydrogel changed from blue to red correspondingly. When the l-Lys concentration was in the range of 10−12–10−4 mol/L, there was a linear relationship between the change in the diameter of the Debye ring (ΔD) and the logarithm value of the l-Lys concentration (lgc), and the linear relationship was as follows: ΔD = 19.04 + 0.90 lgc, R 2=0.9962. In addition, the detection limit of the sensor is as low as 10−16 mol/L. The prepared sensor not only has high selectivity, but also can be used for chiral recognition of l-Lys, and the results of l-Lys in the actual sample of lysiinositol vitamin B12 oral solution were also satisfactory.

Implementation of all-optical tristate Pauli X, Y and Z gates based on two-dimensional photonic crystal

Implementation of all-optical tristate Pauli X, Y and Z gates based on two-dimensional photonic crystal

Multiple topological states within a common bandgap of two non-trivial photonic crystals.

Topological photonic crystals (PCs) provide an effective method for controlling how light propagates and concentrates through their topological states. However, it remains unclear whether topological states can be obtained by combining two different two-dimensional (2D) PCs with topological non-trivial states. In this Letter, two types of 2D Penrose-square (P-S) PCs are proposed. These PCs can generate topological edge states (TESs) and topological corner states (TCSs) within the low-frequency part of the bandgap. Moreover, by combining these two non-trivial PCs, a total of two groups of TESs and four groups of TCSs can be generated in both the high-frequency and low-frequency parts of the common bandgap. To the best of our knowledge, the two proposed P-S PCs offer a new platform for investigating topological photonics and related devices, providing novel approaches and perspectives for generating topological states in 2D PCs.

High-Q two-dimensional photonic crystal nanocavity on glass with an upper glass thin film.

We numerically analyze two-dimensional photonic crystal (PhC) nanocavities on glass with a thin glass film on top of the structure. We investigated a multistep heterostructure GaAs PhC nanocavity located on glass. We found that covering the structure even with a very thin glass film efficiently suppresses unwanted polarization mode conversion occurring due to the asymmetric refractive index environment around the PhC. We also uncovered that the glass-covered structure can exhibit a higher Q factor than that observed in the structure symmetrically cladded with thick glass. We point out that the mode mismatch between the PhC nanocavity and modes in the upper glass film largely contributed to the observed Q-factor enhancement. These observations were further analyzed through the comparison among different types of on-glass PhC nanocavities covered with thin glass films. We also discuss that the in-plane structure of the upper glass film is important for additionally enhancing the Q factor of the nanocavity.

Floquet modeling of surface-wave amplification in two-dimensional photonic time crystals

Floquet modeling of surface-wave amplification in two-dimensional photonic time crystals

Vertical coupling to photonic crystal waveguide using chiral plasmonic lenses

Manipulating surface plasmon polariton waves for the development of micro-nano devices has been widely studied in recent years. Two-dimensional artificial photonic crystals have bandstructure characteristics like semiconductors. However, the requirement for light to be incident along the structural periodic direction poses a challenge in coupling light into the photonic crystal, thereby impeding its integrations and applications. In this work, we proposed coupling vertically incident left-circularly polarized light into a photonic crystal waveguide using a chiral plasmonic lens. Linearly-polarized light can also generate surface plasmon polariton waves and couple them into photonic crystal waveguides, but the intensity is lower. In contrast, right-circularly polarized light propagates in the opposite direction and exhibits minimal propagation into the photonic crystal waveguide. The results indicate that the proposed structure can operate broadband within the wavelength range of 620–670 nm. This method provides a simple and easily integrated coupling method for photonic crystal devices.

Two-dimensional photonic crystal sensor enabled by hydrophobic hydrogen-bonded organic Frameworks@Metal-Organic frameworks for trace nerve agents detection

The development of fast and accurate sensors for nerve agents holds immense significance for homeland security and public health. However, the humidity interference from ambient environments and poor sensitivity for trace nerve agents are largely unsolved problems. To overcome the problems, a humidity-independent two-dimensional photonic crystal (2-D PC) sensor is developed by exploiting UiO-66-NH2 2-D PC with excellent sensitivity coupled to a hydrophobic hydrogen-bonded organic framework (HOFs) for detection sarin simulant dimethyl methyl phosphonate (DMMP). Selective sensing results show that the HOFs@UiO-66-NH2 2-D PC sensor presents the outstanding DMMP specificity, and the limit of detection (LOD) for DMMP response of the sensor can reach 508 ± 68 ppb at room temperature. Water-resistant experiments demonstrate that the HOFs@UiO-66-NH2 2-D PC sensor shows excellent stability even under 80% relative humidity (RH). Moreover, the sensor also exhibits a rapid response/recovery time of 1 s/3 s and can maintain excellent sensing performance under heat-treatment of 200 °C and in the long-term storage (30 days). The adsorption kinetics and the hydrogen bond interaction are conducted to elucidate the mechanism of enhanced sensing DMMP properties. These results indicate the potential application of the sensor in the trace nerve agent's detection, especially in humidity environment.

Two-dimensional silicon-based dielectric column photonic crystal point defect microcavity Neural network modelling

In order to solve the problem that it is difficult to predict the microcavity photonic energy bands of point defects in two-dimensional silicon-based dielectric column photonic crystals, this paper proposes a method to predict the microcavity photonic energy bands of point defects in two-dimensional silicon-based photonic crystals by using an artificial neural network model. In this paper, the energy band structure of triangular lattice point defects at different radii is calculated using MPB, and a neural network model is established based on this data and the accuracy of the established model is verified.

Wavelength division multiplexing based on the coupling effect of helical edge states in two-dimensional dielectric photonic crystals.

Photonic topological insulators with topologically protected edge states featuring one-way, robustness and backscattering-immunity possess extraordinary abilities to steer and manipulate light. In this work, we construct a topological heterostructure (TH) consisting of a domain of nontrivial pseudospin-type topological photonic crystals (PCs) sandwiched between two domains of trivial PCs based on two-dimensional all-dielectric core-shell PCs in triangle lattice. We consider three THs with different number of layers in the middle nontrivial domain (i.e., one-layer, two-layer, three-layer) and demonstrate that the projected band diagrams of the three THs host interesting topological waveguide states (TWSs) with properties of one-way, large-area, broad-bandwidth and robustness due to coupling effect of the helical edge states associated with the two domain-wall interfaces. Moreover, taking advantage of the tunable bandgap between the TWSs by the layer number of the middle domain due to the coupling effect, a topological Y-splitter with functionality of wavelength division multiplexing is explicitly demonstrated exploiting the unique feature of the dispersion curves of TWSs in the three THs. Our work not only offers a new method to realize pseudospin-polarized large-area TWSs with tunable mode-width, but also could provide new opportunities for practical applications in on-chip multifunctional (i.e., wavelength division multiplexing) photonic devices with topological protection and information processing with pseudospin-dependent transport.

Polarization-independent dislocation modes in photonic crystals

Recently, gapless dislocation modes along the synthetic translation dimensions are proposed in two-dimensional photonic crystals. However, gapless dislocation modes are specific to either transverse magnetic or transverse electric polarization, hindering their utility in polarization-independent optics. In this work, we achieve polarization-independent dislocation modes in the crossing of gapless dislocation modes of two polarizations. The frequencies of TM and TE polarized dislocation modes change with the translation parameter. By selecting suitable translation parameter, we realize TM and TE polarized dislocation modes at the same frequency within a single dislocation. We not only realize dual-polarization gapless dislocation modes but also investigate their eigen field characteristics with different frequencies. Our work offers a novel strategy for developing polarization-independent topological photonic devices.

Ultra-fast and compact optical Galois field adder based on the LPhC structure and phase shift keying.

In this study, we propose a novel, to the best of our knowledge, all-optical Galois field (AOGF) adder that utilizes logic all-optical XOR gates. The design is founded on optical beams' constructive and destructive interference phenomenon and incorporates the phase shift keying technique within a two-dimensional linear photonic crystal (2D-LPhC) structure. The suggested AOGF adder comprises eight input ports and four output ports. We employ the finite difference time domain (FDTD) procedure to obtain the electric field distribution in this structure. The FDTD simulation results of the proposed AOGF adder demonstrate that the minimum and maximum values of the normalized power at ON and OFF states (P 1,min, P 0,max) for the output ports are 95% and 1.7%, respectively. Additionally, we obtain different functional parameters, including the ON-OFF contrast ratio, rise time, fall time, and total footprint, which are measured at 17.47dB, 0.1ps, 0.05ps, and 147µm 2, respectively.

A tunable flat terahertz lens using Dirac semimetals: a simulation study

We propose and design a flat and tunable terahertz lens achieved through a two-dimensional photonic crystal composed of an array of rods made of a Dirac semimetal placed in air as the background medium. The structure of interest is a graded index photonic crystal, made possible by the slight variations in the rods’ radii in a direction perpendicular to the direction of the light propagation. Dirac semimetals' ability to respond to variations in their Fermi energy level manifested as a change in the refractive index provides the tunability of our proposed lens. The interaction of electromagnetic waves with the designed structure is investigated for both transverse magnetic and transverse electric polarizations using two-dimensional finite-difference time-domain method.

Fabrication of large-area photonic crystal-modified X-ray scintillator imager for optical coding imaging.

The limited pattern area of periodic nanostructures limits the development of practical devices. This study introduces an X-ray interference lithography (XIL) stitching technique to fabricate a large-area (1.5 cm × 1.5 cm) two-dimensional photonic crystal (PhC) on the YAG: Ce scintillator, which functions as an encoder in a high numerical aperture optical encoding imaging system to effectively capture high-frequency information. An X-ray imaging experiment revealed a substantial 7.64 dB improvement in the signal-to-noise ratio (SNR) across a large field of view (2.6 mm × 2.6 mm) and achieved comparable or superior image quality with half the exposure dose. These findings have significant implications for advancing practical applications of X-ray imaging.

Flat Landau levels and interface states in two-dimensional photonic crystals with a nodal ring

Flat Landau levels and interface states in two-dimensional photonic crystals with a nodal ring

Design and analysis of optically sensitive biosensor using two-dimensional photonic crystal for oral cancerous cell detection

Design and analysis of optically sensitive biosensor using two-dimensional photonic crystal for oral cancerous cell detection

Transmissible topological edge states based on Su–Schrieffer–Heeger photonic crystals with defect cavities

Abstract Topological photonic crystals have great potential in the application of on-chip integrated optical communication devices. Here, we successfully construct the on-chip transmissible topological edge states using one-dimensional Su–Schrieffer–Heeger (SSH) photonic crystals with defect cavities on silicon-on-insulator slab. Different coupling strengths between the lateral modes and diagonal modes in photonic crystal defect cavities are used to construct the SSH model. Furthermore, two photonic SSH-cavity configurations, called α and β configurations, are designed to demonstrate the topological edge states. Leveraging the capabilities of photonic crystal transverse electric modes with on-chip transmission, we introduced a waveguide to excite a boundary defect cavity and found that the transmission peak of light, corresponding to the topological edge state, can be received in another boundary defect cavity, which is caused by the tunnel effect. Moreover, the position of this peak experiences a blue shift as the defect cavity size increases. Therefore, by tuning the size of the SSH defect cavity, on-chip wavelength division multiplexing function can be achieved, which is demonstrated in experiments. The ultrafast response time of one operation can be less than 20 fs. This work harmonizes the simplicity of one-dimensional SSH model with the transmissibility of two-dimensional photonic crystals, realizing transmissible on-chip zero-dimensional topological edge states. Since transmission peaks are highly sensitive to defect cavity size, this configuration can also serve as a wavelength sensor and a reconfigurable optical device, which is of substantial practical value to on-chip applications of topological photonics.

Effective enhancement of the non-Hermitian corner skin effect in reciprocal photonic crystals.

With the rich physical phenomena arising from non-Hermitian systems, the non-Hermitian skin effect (NHSE) has become a current research hotspot. Nowadays, the corner skin effect based on non-reciprocal photonic crystals has been proposed. Considering the complexity of realizing non-reciprocity, the corner skin effect based on reciprocal photonic crystals is well worth investigating. In this Letter, a non-Hermitian reciprocal geometry-dependent corner skin effect based on two-dimensional photonic crystals is presented, which is manifested as the distribution of eigenstates on the corners of a particular geometry by applying open boundary conditions in both directions of photonic crystals. For the better application of the NHSE in the future, such as highly sensitive sensors and lasers, a new, to the best of our knowledge, method that can effectively enhance the performance of the NHSE in photonic crystals is proposed. The method introduces both gain and loss in an ideal photonic crystal to enhance the non-Hermitian specificity of the system, which improves the performance of the non-Hermitian corner skin effect of photonic crystals by 64.5%. Furthermore, this geometry-dependent corner skin effect is corroborated with the spectral topology.

Argon metastable density and temperature of a 94 GHz microplasma

Laser diode absorption spectroscopy is used to experimentally measure Ar(1s5) metastable density and translational gas temperature within a 94 GHz microplasma. A square two-dimensional photonic crystal (PhC) at this resonance frequency serves to ignite and sustain the plasma from 20 to 200 Torr (2.7 × 103–2.7 × 104 Pa) by using millimeter wave power from 300 to 1000 mW. Metastable density within the plasma is estimated from the absorption line shape of the laser traversing the PhC. The metastable density reaches an order of 1019 m−3 at lower pressure and decreases as pressure increases. From the Lorentzian line shape of the absorption profile at 811.53 nm, the gas temperature is extracted and found to increase from 500 K at 20 Torr to 1300 K at 200 Torr. These data are analyzed and compared with a zero-dimensional plasma model and with previous experimental plasma results at 43 GHz.

High Field Confinement Enhancement in Silicon-based Photonic Crystal with Different Point Defects

Two-dimensional silicon-based photonic crystals as optical analogs to electronic semiconductors are presented in this paper, emphasizing the design and analysis of two-dimensional structures. Employing the Lumerical FDTD solver, we initially crafted defect-free photonic crystals within a hexagonal lattice of air holes on a silicon slab (6.57 μm along x, 6.57 μm along y, 0.75 μm along z). The lattice parameters (a = 0.365 μm, r = 0.1095 μm, with r = 0.3a) established a target resonant wavelength of 1.5 μm. Utilizing Finite Difference Time-Domain (FDTD), we evaluated electric field decay, resonant modes, and the Q factor. The defect-free structure exhibited a peak Q factor of 736.004 at a resonant wavelength of 1262.87 nm. Removal of a central hole enhanced the Q factor to 1286.96 at 1391.07 nm. Introducing various line defects, the structure with three holes removed from vertical positions emerged as the optimal candidate for silicon-based photonic crystal cavity resonators, displaying the highest Q factor near the target resonant wavelength. Additionally, the structure with seven holes removed showed stable linear decays at both resonant wavelengths, suggesting its potential as a cavity resonator design candidate.