Photonic Crystal Microstructures Research Articles

Investigation of wave propagation characteristics in photonic crystal micro-structure containing circular shape with varied nonlinearity

Investigation of wave propagation characteristics in photonic crystal micro-structure containing circular shape with varied nonlinearity

An electro-optic comparator based on photonic crystal ring resonators covered by graphene nanoshells

A logic comparator is a digital circuit comprised of numerous transistors on an integrated circuit that compares two binary numbers. Researchers have proposed various designs for implementing comparators using logic gates, but most are based on DC electrical signals, which suffer from slow switching speeds and high power consumption. This paper presents a novel design for a fast and tunable electro-optic single-bit comparator utilizing graphene-coated nanoshells (GNSs) in photonic crystal (PhC) ring resonators. The comparator's structure includes three inputs, three GNS-coated ring resonators, several waveguides for comparison, and three outputs created in a PhC microstructure in an area of 760 µm². A continuous-wave laser source centered at 1550 nm is applied to the first input to enable the proposed photonic chip. Two other inputs are utilized to apply electrical voltages, and the comparator's task is to compare them. The optical signal applied to the enable input port is directed to the corresponding output depending on the comparison result. We used the finite-difference time-domain method to study the light propagation inside the proposed structure to solve Maxwell's equations. Numerical simulations demonstrate that the designed structure has a very short delay time of 1.85 ps, faster than previously reported comparators, including electronic, optoelectronic, and all-optical comparators. The proposed comparator's rapid response, small area, and tunability make it an appropriate device for optical applications in photonic integrated circuits.

Numerical investigation on self-heating effect in 1.3 µm quantum dot photonic crystal microstructure VCSELs

Numerical investigation on self-heating effect in 1.3 µm quantum dot photonic crystal microstructure VCSELs

High-sensitivity biosensor for simultaneous detection of cancer and diabetes using photonic crystal microstructure

In this study, we propose a refractive index-based sensor to detect skin cancer (Basal, HeLa, MDA-MB-231) through human blood. It also can detect diabetes through human tear fluid based on photonic crystals (PhC) at the same time. The proposed PhC composed of silicon rods in the air bed arranged in a hexagonal lattice, forms the fundamental structure, and two tubes are used to place the cancerous or diabetic samples for measurement. The sensor's transmission characteristics are simulated and analyzed by solving Maxwell's electromagnetic equations using the finite-difference time-domain method for samples under study. The diagnosis of three types of cancer and diabetes is based on changing the samples' refractive index by applying the laser source centered at 1550 nm. Our results demonstrate that the proposed structure's quality factor and sensitivity can be adjusted by changing the sensor's geometry. They reveal that the transmission power is between 91–100%, depending on the sample. The sensitivity range is also between 1294 and 3080 nm/RIU. The maximum figure of merit is about 1550.11 RIU−1 with a detection range of 31 × 10–6 RIU. The small biosensor area of 61.56 µm2 makes it suitable for various applications in compact photonic integrated circuits.

The heterojunction between 3D ordered macroporous TiO2 and MoS2 nanosheets for enhancing visible-light driven CO2 reduction

The photocatalytic CO2 and H2O conversion into CO and hydrocarbons over the semiconductors catalysts is an effective way to alleviate environmental pollution and resource shortage currently. Herein, three-dimensional ordered macroporous (3DOM) TiO2-supported two-dimensional layered MoS2 (MoS2/3DOM-TiO2) as two isolated photochemical systems were proposed to form heterojunction structure. The diffuse reflection of photonic crystal microstructure can raise the adsorption efficiency of visible light. The formation of TiO2-MoS2 heterojunction is favorable to the enhancing separation efficiency of photoexcitation electron and hole pairs. The binary MoS2/3DOM-TiO2 photocatalyst shows the higher catalytic performance for visible-light driven reduction of CO2 in the range of 420−900 nm. MoS2/3DOM-TiO2-1.5 photocatalyst shows the highest maximum formation yields of CO (22.6 μmol g-1) as well as CH4 (11.6 μmol g-1) products during 8 h, then its apparent quantum efficiency value is 6.7 %, which is far higher than the photosynthesis efficiency of green plants. The heterojunction of MoS2/3DOM-TiO2 photocatalysts with enhancing light adsorption and electron-hole separation efficiency is expected to provide more extensive reference for the evolution of high-efficient photocatalyst for CO2 conversion.

Design and analysis of a novel four‐channel optical filter using ring resonators and line defects in photonic crystal microstructure

In this paper, we report a new design of an all-optical filter using photonic crystal microstructure. Ring resonators, line defects, scatterer rods, microcavities, and coupling rods are used to form the filter in order to extract specific wavelengths at the output channels. The well-known plane wave expansion method is used to calculate the photonic band diagram. The widely used finite-difference time-domain method is also applied to study the light propagation inside the filter. Our numerical results demonstrate that the proposed structure has high transmission power, high-quality factor, and low cross-talk. They reveal an optical signal centered at 1522 nm exits the first output channel, which has an output-to-input ratio (OIR) of 95 % with a bandwidth (FWHM) of 0.4 nm, and an optical signal centered at 1520.8 nm exits the second output channel with an OIR of 98 % and an FWHM of 0.5 nm. The third output channel can exit the optical signal centered at 1518.2 nm with an OIR of 78 % and an FWHM of 0.4 nm. Furthermore, the fourth channel will exit the optical signal at 1519.3 nm with an OIR of 56 % and an FWHM of 0.4 nm. Therefore, the quality factors of the first to fourth outputs of the filter are equal to 3805, 3041, 3795, and 3798, respectively. The first to fourth outputs’ cross-talk values are also − 37 dB, − 36 dB, − 41 dB, and − 38 dB, respectively, which confirm the least interference between output channels. Besides, linear dielectric rods form the filter design that leads to the filter’s appropriate performance at a low input power that is the most important benefit of this work compared to other recently published articles. The maximum rise time of the proposed filter for all output ports is less than 8 ps. The structure also has ​​375.84 µm2, which makes the filter easy to use in photonic integrated circuits.

A Novel All-Optical Sensor Design Based on a Tunable Resonant Nanocavity in Photonic Crystal Microstructure Applicable in MEMS Accelerometers

In view of the large scientific and technical interest in the MEMS accelerometer sensor and the limitations of capacitive, resistive piezo, and piezoelectric methods, we focus on the measurement of the seismic mass displacement using a novel design of the all-optical sensor (AOS). The proposed AOS consists of two waveguides and a ring resonator in a two-dimensional rod-based photonic crystal (PhC) microstructure, and a holder which connects the central rod of a nanocavity to a proof mass. The photonic band structure of the AOS is calculated with the plane-wave expansion approach for TE and TM polarization modes, and the light wave propagation inside the sensor is analyzed by solving Maxwell’s equations using the finite-difference time-domain method. The results of our simulations demonstrate that the fundamental PhC has a free spectral range of about 730 nm covering the optical communication wavelength-bands. Simulations also show that the AOS has the resonant peak of 0.8 at 1.644µm, quality factor of 3288, full width at half maximum of 0.5nm, and figure of merit of 0.97. Furthermore, for the maximum 200nm nanocavity displacements in the x- or y-direction, the resonant wavelengths shift to 1.618µm and 1.547µm, respectively. We also calculate all characteristics of the nanocavity displacement in positive and negative directions of the x-axis and y-axis. The small area of 104.35 µm2 and short propagation time of the AOS make it an interesting sensor for various applications, especially in the vehicle navigation systems and aviation safety tools.

Three-Dimensional Photonic Crystal Bulks with Outstanding Mechanical Performance Assembled by Thermoforming-Etching Cross-linked Polymer Microspheres.

Traditional self-assembly methods for photonic crystals (PCs) limited by poor mechanical performance and microstructure defects make it hard to be directly applied to optical devices, whose performance strongly rely on mechanical performance and microstructure of PCs. Here, a thermoforming-etching strategy combining both traditional processing and nanofabrication is reported to develop cross-linked polystyrene microsphere-based PC bulks with outstanding mechanical performance. It illustrates scientific principles, where surface molecular chains of PS microspheres were activated and entangled with each other under thermoforming conditions (200 °C; 220 MPa), resulting in applicable mechanical strength (hardness and modulus reach 0.12 and 4.12 GPa, respectively). The optimum optical reflectivity of the PS microsphere-based (180 nm) PC bulk is 49.4% at 381 nm. Furthermore, these PC bulks have been successfully written in anti-counterfeiting and realized colorful pattern printing. The innovative method opens a new route for the rapid and simple fabrication of the nanoparticle structure which can be used as various functional devices and directly promotes the industrialization of bulk PC devices, such as optical and display devices, and so forth.

An ultra-narrowband all-optical filter based on the resonant cavities in rod-based photonic crystal microstructure

In view of the large scientific and technical interest in the frequency-selective all-optical devices, and some optical filters limitations, we focus on the design and analysis of a novel ultra-narrowband all-optical filter. The proposed structure consists of input/output waveguides and a resonator in a microstructured photonic crystal that encompasses silicon rods. We study the effects of the variations of rod radius, the lattice constant, and the refractive index of the filter on the resonance wavelength, quality factor, transmission, and full width at half maximum (FWHM) by solving Maxwell’s equations using the finite-difference time-domain method. The numerical results show that the proposed filter with a lattice constant of a = 540 nm, central resonant rod radius of 216 nm, and the rod radius of r = 0.2a has a resonant wavelength of λr = 1253 nm, the quality factor of Qf = 3288, FWHM of 0.26 nm and broad free spectral range of FSR = 790 nm while this filter for r = 0.26a has λr = 1552 nm, Qf = 5542, FWHM of 0.28 nm, and FSR = 720 nm. Some promising characteristics, such as its short propagation time and a small area of 102.6 µm2 make this optical filter an interesting candidate for use in photonic integrated chips.

High sensitivity sensing system theoretical research base on waveguide-nano DBRs one dimensional photonic crystal microstructure

In this paper, we propose a novel wavelength modulation system dedicated to improve the performance of the integrated silicon microsensor. This system includes light source, waveguide, distributed Bragg reflectors (DBRs) and optical spectrum analyzer. Here, the silicon waveguide and two nano DBRs were designed to be one dimensional photonic crystal structure, which can implement wider modulation range in the photonic band gap. The rigorous coupled wave analysis (RCWA) method was used to quantitatively calculate transmissivity of each wavelength photon, and then spectral data in different displacement were obtained. By analyzing the defect modes in the spectrum, typical performance indicators of this modulation system are demonstrated as follows: The wavelength defect mode can be modulated from 1.2μm to 2.7μm, corresponding displacement is from 0 to 1.5μm; System sensitivity is up to 1.23-1.41, linearity ranges from 0.99 to 0.9999 for order 1 defect mode; The minimum peak transmittance of defect mode is greater than 0.68 based on 1 pm wavelength calculated step. Compared with the same type of system reported, the performance indicators have obvious advantages, and it is expected to directly improve the sensor performance by combining with the existing micro-mechanical structure.

An ultrafast all-optical half adder using nonlinear ring resonators in photonic crystal microstructure

Half adder and half subtractor are the basic building blocks of an arithmetic logic unit used in every optical central processing unit (CPU) to provide computational operators. In this paper, we aim to design an ultrafast all-optical half adder based on nonlinear ring resonators. The proposed structure consists of the concurrent designs of the AND and XOR logic gates inside a rod-based photonic crystal microstructure. The linear dielectric rods made of silicon and nonlinear dielectric rods composed of doped glass are used to design the nonlinear ring resonators as the fundamental blocks of a half adder. We demonstrate as the intensity of the incoming light increases, the nonlinear Kerr effect appears, and the total refractive index increases. It diverts the direction of light propagation to the desired nonlinear ring resonator depending on the signal wavelength, the radius of rods and lattice constant. Finally, after several resonances, the light is coupled to the output. Our numerical simulations using a two-dimensional finite-difference time-domain method reveal depending on the light intensity, the maximum and minimum transmissions of the half adder are 100% and 96%, respectively. The calculations also show the delay of the designed half adder is 3.6 ps. Due to the small area of 249.75 µm2, the proposed half adder is an appropriate candidate for photonic integrated circuits used in the next generation of all-optical CPUs.

A photonic crystal beam splitter used for light path multiplexing: synergy of TIR and PBG light guiding

Optical sensors, such as fiber interferometers transmit along light paths and perform measurements based on optical path difference. These types of sensors can reduce device volume and improve sensing performance using optical multiplexing. A beam splitter for optical path multiplexing in an optical fiber ring is proposed. A photonic crystal was used to design the beam splitter. By optimizing and improving the photonic crystal microstructure, the beam splitting function can be realized while taking into account the cycling capability. Therefore, the light can recirculate multiple times in the fiber ring to realize light path multiplexing. The finite difference time domain method is used to analyze and evaluate the performance of the beam splitter.

Multicolored Photonic Crystal Carbon Fiber Yarns and Fabrics with Mechanical Robustness for Thermal Management.

Multicolored photonic crystal carbon fiber (CF) yarns and fabrics with mechanical robustness in a full spectrum are reported. By facilely controlling the thickness of the periodic layer, a series of photonic CF yarns and fabrics with vivid structural colors ranging from purple, green, yellow, orange, to red are obtained. Interestingly, the prepared multicolored CF yarns show anisotropic optical reflection properties because of their unique axisymmetric geometry, while the plain-woven fabrics exhibit vivid colors even under ambient scattering light. Most importantly, they can withstand cyclical mechanical rubbing, laundering, and accelerated light aging, indicating great potential for practical uses. Finally, considering such impressive characteristics as well as reflection in the visible and near-infrared regions, the above photonic crystal microstructure is further used as a new material for the application of outdoor reflective cooling of the textile surface, demonstrating a superior temperature reduction up to ∼12 °C with respect to the control sample.

Tri‐core photonic crystal fiber based refractive index dual sensor for salinity and temperature detection

AbstractThis article discusses the tri‐core photonic crystal microstructure fiber for the process of simultaneous sensing for salinity and temperature of water substances. This kind of microstructure is preferred in many sensing application to scale the detection process in micrometer range. In this novel sensor, the sensitivity is calculated through coupling mechanism by tracking wavelength shift of various concentrations of salinity and temperature using finite element method. The sensible samples are in liquid and are infiltrated into the framed hollow cavity. Based on the coupling principle between silica substrate and the analyte material, the sense of the salt as well as temperature is obtained. Finally, it is noted that sensitivity of the salt level in water as 5404.9 nm/RIU for x polarization direction and 5674 nm/RIU for y polarization direction have been calculated with the temperature sensitivity of 4 nm/°C in the same water substances.

Preparation and self-assembly of photonic crystals on polyester fabrics

Photonic crystals play the vital role in structural color appearance, and they can be fabricated on polymer substrates. In this paper, monodispersed SiO2 microspheres with the average diameter ranging from 150 to 300 nm were prepared by classical Stober method. The spherical size of SiO2 microspheres was regulated by controlling concentrations of ammonia. The tunable structural colors could be changed by modulating the diameters of SiO2 microspheres or viewing angles, which adhered to the law of the Bragg diffraction. As a kind of polymer fabric, the polyester fabrics, smoother than natural fiber fabrics, exhibited bright structural colors from the well-ordered photonic crystal microstructure by vertical deposition self-assembly of SiO2 photonic crystals. Moreover, the result indicated that the difference of fabric-woven structure could affect the lightness of structure color, and the lightness on satin fabric was duller than that of plain fabric. Besides, we have also discussed the influence of fabric structure on the lightness of structure color using the theory of thin film interference. It is believed that the structural color could provide a new strategy for related polymer product coloration without chemical dyes and pigments, and has a potential to reduce the pollution in related polymer materials dyeing and printing processes.

The fabrication of full color P(St‐MAA) photonic crystal structure on polyester fabrics by vertical deposition self‐assembly

ABSTRACTThree‐dimensional (3D) photonic crystals with face‐centered cubic structure were successfully fabricated on soft polyester fabrics via vertical deposition self‐assembly, with monodisperse P(St‐MAA) microspheres prepared by soap‐free emulsion copolymerization. The resultant polyester fabrics exhibited bright structural colors through the well‐ordered photonic crystal microstructure without any chemical dyes and pigments. The tunable structural colors across the whole visible region confirmed by reflectance spectra could be adjusted by controlling the diameters of the microspheres and viewing angles, and this was consistent with the law of the Bragg diffraction. The resultant polyester fabrics also presented some favorable properties including double‐sided coloration effect, clear fabric texture, and soft fabric handle. The structural coloration by vertical deposition self‐assembly of P(St‐MAA) photonic crystals may provide a new strategy for textile coloration without using chemical colorants, and have a potential to reduce the pollution in the current textile dyeing and printing processes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41750.

The Effect of Anisotropy on Light Extraction of Organic Light‐Emitting Diodes with Photonic Crystal Structure

The light extraction efficiency of organic light‐emitting diodes (OLED) is greatly limited due to the difference in refractive indexes between materials of OLED. We fabricated OLED with photonic crystal microstructures in the interface between the glass substrate and the ITO anode. The light extraction efficiency can be improved by utilizing photonic crystals; however, the anisotropy effect of light extraction was clearly observed in experiment. To optimize the device performance, the effect of photonic crystal on both light extraction and angular distribution was investigated using finite‐difference time domain (FDTD) method. We simulated the photonic crystals with the structure of square lattice and triangle lattice. We analyzed the improvement of these structures in the light extraction efficiency of the OLED and the influence of arrangement, depth, period, and diameter on anisotropy. The optimized geometric parameters were provided, which will provide the theoretical support for designing the high performance OLED.

Colloidal photonic crystal microstructure fiber:propagation characteristics analysis

In the paper, we describe the structure of colloidal photonic crystal microstructure fiber and investigate the propagation characteristics using the finite-difference time-domain method. A structure model is eastablished to simulate the transmission spectra and propagation field distributions under different wavelengths. Experimental system is built to measure the transmission spectrum of fabricated colloidal photonic crystal microstructure fiber. Experimental result is in good agreement with numerical result. The propagation field distribution result shows that the colloidal crystal changes the propagation mode of optical fiber under different wavelengths.

Self-Organized Colloidal Crystals in a Capillary with a Fiber Junction

We present a facile approach to fabricating colloidal photonic crystal microstructures in a capillary. Typical procedures for fabricating such microstructures are demonstrated. A fiber-capillary butt-joint was constructed with self-organized colloidal photonic crystals in a capillary through evaporation-induced nucleation and crystallization. Silica colloidal microspheres with a diameter of 320 nm self-organized in a glass capillary were investigated. Colloidal crystal samples were characterized by optical microscopy and scanning electronic microscopey (SEM), and the SEM images show that these crystals favor an fcc lattice with a longitudinal (111) crystallographic axis. With the use of a fiber junction, the resulting high-quality colloidal crystals may be implemented in sensor applications, for example, as an ideal template for a porous microstructure that can be used for biochemical sensors.

Replication of butterfly wing microstructures using molding lithography

This study employed a soft lithography technique to fabricate a polydimethylsiloxane (PDMS) replica of the multi-layered scales on the upper surface of a Morpho butterfly. The bionic photonic crystal microstructure of the replicated scales was examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The absorptivity, reflectivity and fluorescent characteristics of the wing were measured. The results showed that the microstructural and optical characteristics of the replicated wing qualitatively agree with those of the actual wing. The contact angle for the natural wing structure and the replicated wing were about 143° and 120°, respectively. As a result, it can be inferred that the soft lithography technique employed in this study represents a viable approach for the mass production of artificial photonic crystal structures for a variety of commercial applications, including optical elements for computing and communications purposes, photonic integrated circuits, anti-counterfeiting mechanisms, and so forth.