One-dimensional Photonic Crystal Structure Research Articles

Angular and polarization dependence of all optical diode in one-dimensional photonic crystal

The effect of the incident angle on all-optical diode (AOD) efficiency in a one-dimensional photonic crystal structure (1DPC) for TE and TM polarizations was studied. An asymmetric hybrid Fabry Perot resonator type 1DPC structure composed of linear and nonlinear materials was considered in this communication. The nonlinear transmission curves around the defect mode resonant frequency inside the photonic band gap for both TE and TM polarizations at different incident angles, from left to right (L-R) and right to left (R-L) incidences, are illustrated. Results showed that with increasing the incident angle, AOD performance efficiency increases only for TM polarization. The AOD efficiency increased to 80% for an incident angle of 60 degrees because of the dynamical shifting of the defect mode peak frequency caused by the intensity-dependency of the nonlinear layer refractive index along the z-axes. For TE polarization, the z-component of the electric field remained constant for all incident angles. The results of this study can be important in optical data communications and information analysis in all-optical integrated circuits.

Optimal design of one-dimensional photonic crystal filters using minimax optimization approach.

In this paper, we introduce a simulation-driven optimization approach for achieving the optimal design of electromagnetic wave (EMW) filters consisting of one-dimensional (1D) multilayer photonic crystal (PC) structures. The PC layers' thicknesses and/or material types are considered as designable parameters. The optimal design problem is formulated as a minimax optimization problem that is entirely solved by making use of readily available software tools. The proposed approach allows for the consideration of problems of higher dimension than usually treated before. In addition, it can proceed starting from bad initial design points. The validity, flexibility, and efficiency of the proposed approach is demonstrated by applying it to obtain the optimal design of two practical examples. The first is (SiC/Ag/SiO(2))(N) wide bandpass optical filter operating in the visible range. Contrarily, the second example is (Ag/SiO(2))(N) EMW low pass spectral filter, working in the infrared range, which is used for enhancing the efficiency of thermophotovoltaic systems. The approach shows a good ability to converge to the optimal solution, for different design specifications, regardless of the starting design point. This ensures that the approach is robust and general enough to be applied for obtaining the optimal design of all 1D photonic crystals promising applications.

Analysis of Asymmetric Cantor Set Multi-Layered Structure

The word fractal is derived from the latin word fractus , meaning broken. In more scienti c terms, fractal is used to describe geometries that present selfsimilar patterns, such as the small patterns are replicas of the large ones [1]. Fractal theory is applied to a wide range of areas including chemistry, biology, physics and engineering. In electromagnetics, fractals have been used to produce antennas [2], optical devices [3 5] and nanoparticles [6]. In particular, one-dimensional structures such as the Cantor set can be easily constructed and has been used to create broadband devices and enhancing nonlinear effects. The Cantor set has a Hausdor dimension of log (2)/log (3) [1]. A standard Cantor set is created by initially removing the middle third of a segment, creating a Cantor set of order 1. The next order is obtained by removing the middle third of the rst and third remaining segments the procedure could be, in principle, repeated at exhaustion. On the other hand, photonic crystals have been used in a wide variety of applications in ltering, sensors, lasers and multiplexing [7 17]. Photonic crystals are periodic structures of high refractive index contrast (e.g. GaAs and air): in a certain wavelength range (photonic bandgap region), light cannot propagate through the structure. In addition to producing re ectors that are used in lasers [10] and optical lters, defects introduced in the photonic crystal lattice can be used to create microcavities and waveguides. In fact, photonic crystal waveguides can exhibit very interesting properties such as very low group velocities. In this paper, we analyze one-dimensional photonic crystal structures that are based on the Cantor set structures: we modify the traditional Cantor set structure by adding asymmetries in the formation of the Cantor set and study the re ectivity properties of these photonic

Enhanced fluorescence from CdSe/ZnS quantum dot nanophosphors embedded in a one-dimensional photonic crystal backbone structure.

A nano-engineered phosphor structure that produces enhanced fluorescence is reported. Two kinds of polymer materials with different refractive indices are spin-coated alternately to realize a one-dimensional (1D) photonic crystal (PC) phosphor platform, in which CdSe/ZnS core-shell quantum dots (QDs) were embedded as a fluorescence agent. The 1D PC phosphor structure is designed to match the pump photon energy with one of the photonic band-edges (PBEs), where the photon group velocity becomes zero, and thus the interaction between pump photons and fluorescent centres strengthened. A reference phosphor structure is also designed and fabricated; however, it has no PBE and exhibited bulk-like photonic properties. The fluorescence intensity from the 1D PC phosphors is examined during the pump photon energy scanning across the PBE. It is found that fluorescence from the 1D PC phosphor reaches its maximum when the pump photon energy coincides with the PBE, which is consistent with the theoretical prediction. In comparison with the reference phosphor, the fluorescence from the 1D PC phosphor is measured to be enhanced by a factor of 1.36.

Fluorescence excitation enhancement by Bloch surface wave in all-polymer one-dimensional photonic structure

We demonstrate photoluminescence excitation enhancement in an all-polymer flexible one-dimensional photonic crystal structure capped with a fluorescent organic ultrathin film. When optical matching conditions between the excitation beam and the Bloch Surface Wave mode supported by the photonic structure are achieved, a ten times enhancement of the photoluminescence is observed. We notice that in these systems luminescence signal reinforcement is achieved by increasing the pump efficiency with no need of spectral resonance to the emission of the chosen fluorophore. All these features make these systems suitable candidates for easy, flexible, and cheap fluorescent sensing.

Plasma photonic crystals numerical and filter characteristics analysis based on symplectic algorithm

From the Maxwell equation, the method of symplectic finite-difference time-domain is applied in analyzing one-dimensional plasma photonic crystal. The propagation process of electromagnetic pulse in one-dimensional vacuum plasma photonic crystal structure is simulated by symplectic algorithm discrete in 2nd order time 2nd order space (T2S2), and 2nd order time 4th order space (T2S4) respectively. Then, from the perspective of frequency domain, the reflection coefficient of the plasma–vacuum photonic crystals is analyzed. The results show that the symplectic finite-difference time-domain method is accuracy and correctness. In the end, the filter characteristics of the plasma photonic crystals (PPCs) are analyzed in different thickness of plasma.

Third-harmonic pulse generation in one-dimensional photonic crystal structures

Enhanced third-harmonic generation in a one-dimensional photonic crystal doped with third-order nonlinear medium was numerically investigated using the multiple-scale method and the split-step Fourier transform. The optimal fundamental frequency for third-harmonic wave generation was determined from the transmission spectrum. The third-harmonic pulse intensities grow, depending on the structure thickness and the fundamental-frequency detuning parameter, which determines the band-edge phase matching condition. Furthermore, the total energy output of third-harmonic pulses, depending on the fundamental-frequency pulse width, may be more than 1000 times the energy produced by a phase-matched bulk medium. A narrow pulse with bandwidth less than the band-edge transmission peak enables high conversion efficiency. The maximum conversion efficiency of the forward component may be 12 to 13 orders of magnitude greater than that of the backward component.

INVESTIGATION OF ULTRA-WIDE REFLECTION BANDS IN UV REGION BY USING ONE-DIMENSIONAL MULTI QUANTUM WELL PHOTONIC CRYSTAL

Enhancement of the reflection bands in ultraviolet region by using one-dimensional multi quantum well (MQW) photonic crystal (PC) structure has been investigated theoretically. The proposed structure is composed of three MgF2/SrTiO3 MQWs. The range of reflection band is investigated from the reflectance spectra of the one-dimensional MQW photonic crystal structure obtained by Transfer Matrix Method (TMM). From the numerical analysis it is observed that a range of reflection band for a single MQW PC is very narrow though it increases as the thickness of layers increases. But when three MQWs of MgF2/SrTiO3 are used we get much enlarged reflection band covering the range 119.8 nm- 311.3 nm (reflectivity > 99%) with bandwidth 191.5 nm, for normal incidence. Further, we see that when the angle of incidence is increased, the width of reflection band increases in case of TE wave with a decrease for TM wave, because this omnidirectional reflection (ODR) band is very much narrow in UV region. We have computed ODR band upto incidence angle 50 ◦ for single as well as combined MQW PC. Analyzing the reflectance curve for incidence angle up to 50 ◦ for both TE and TM polarizations we find that by applying the combined MQW PC, omnidirectional reflection band increases significantly in comparison to single MQW structure. The proposed MQW photonic crystal structure is very useful in designing ultraviolet shielding for drugs, ultraviolet reflector for protecting damage of DNA and in skin diseases especially for skin cancer.

High-sensitivity sensing based on intensity-interrogated Bloch surface wave sensors

A high-sensitivity sensing scheme based on Bloch surface wave is presented with the simple intensity interrogation configuration. The p-polarized electromagnetic surface wave is designed to be excited in a one-dimensional photonic crystal band-gap structure, and support a rather steep resonance dip, much sharper than that of the well-known surface plasmon resonance (SPR). Although the angular shift of this Bloch-surface-wave-based sensor is not as sensitive, the intensity measurement proves to be a more suitable scheme for Bloch surface wave based sensors, thanks to the sharpness of their resonance. Through detection of glycerol in water solution for different concentrations, the intensity sensitivity of our Bloch-surface-wave-based sensor significantly surpasses that of the conventional SPR-based sensors. Experimental results show that the sensor could achieve a detection limit as low as 7.5×10−7 refractive index units in a simple lab setup, which is much simpler than many of the much more complicated SPR-based platforms.

Enhanced nonlinear optical effects due to the excitation of optical Tamm plasmon polaritons in one-dimensional photonic crystal structures

We suggest optimally designed one-dimensional metal/photonic crystal structures for the excitation of optical Tamm plasmon polaritons, which show strongly enhanced electromagnetic field intensities compared to those due to conventional surface plasmon excitations. We assume that the photonic crystal is made of weakly nonlinear optical materials and calculate the reflectance and the electromagnetic field distribution precisely, using the invariant imbedding method generalized to nonlinear media. We find field intensity enhancement factors as large as 3,000 at the metal/photonic crystal interface. We verify that due to this strong enhancement, nonlinear optical effects such as optical bistability can be observed for very small values of the incident wave power. Our results imply that using our structure, very strong surface enhanced Raman scattering signals can be achieved and optical switching devices can be operated in much lower threshold light intensities.

Design of omnidirectional reflectors based on a cascaded one-dimensional photonic crystal structure

The omnidirectional transmission properties of photonic heterostructures composed of cascaded one-dimensional photonic crystals (1DPCs) with the same materials and different thickness ratios of the alternate high- and low-refractive index layers were studied theoretically. A criterion for designing omnidirectional reflectors with a maximum bandgap width is presented for heterostructures with an arbitrary number of cascaded 1DPCs. Omnidirectional reflectors based on two and three cascaded 1DPCs are designed according to the criterion.

A low-cost high-efficiency crystalline silicon solar cell based on one-dimensional photonic crystal front surface textures

In this paper we analyze the influence of active layer thickness on the light absorption processes of c-Si solar cells by the finite-difference frequency-domain (FDFD) method and show that the ideal c-Si active layer thickness range is from 10 to 20 μm. By evaluating the absorption enhancement factor, we find that c-Si solar cells with thicknesses within this range can give full play to the synergistic effects of back reflectors and antireflection coatings. By using a simple light trapping scheme, which is composed of a Ag back reflector, a bilayer antireflection coating and a one-dimensional photonic crystal front surface texture structure with rectangular profile, a c-Si solar cell with an active layer thickness of 12 μm can obtain a higher photocurrent density of 32.6 mA cm−2 for normally incident sunlight and a broader acceptance angle range of −60°–60° for obliquely incident sunlight.

Electro-Optical Tuning in Photonic Crystals – Dispersed Liquid Crystalline Metamaterials

Two different metamaterial-liquid crystal structures are fabricated with the metamaterials as liquid crystal (LC) and semiconductor nanorods doped LC alignment layers. E-beam lithography was used to pattern the electron-sensitive polymer one-dimensional photonic crystal (PC) structures. The nanostructured aligning surfaces have been characterized by scanning electron microscopy. The PCs-Dispersed Liquid Crystalline Metamaterials have been investigated through polarized optical microscopy. The threshold voltage and response times for the undoped and doped nematic LCs in the glass cells are measured as a function of the applied external electric field.

2DPSK modulator based on the transmission phase properties of photonic crystals with coupled cavities

The phase properties of the transmitted light from one-dimensional coupled-cavity photonic crystal structures with the form (HL)kA(LH)k, where A contains N micro-cavities, are studied. It is found, for k ≥ 1, that the transmission phase changes drastically around each transmitted peak and the corresponding phase shift is approximately equal to π. Moreover, the transmitted power is almost zero during the π phase transition between neighboring transmission maxima. These properties show great promise for inverse phase devices, optical switches, and, in particular, binary differential phase-shift-keying (2DPSK) format data transmission, where a π phase transition is required. As an example, a 2DPSK modulator is demonstrated.

Position dependence of extraction efficiency in organic light-emitting diodes with photonic crystal structure

We demonstrate by finite-difference time-domain simulations that a one-dimensional (1D) photonic crystal (PC) structure between glass substrate and indium tin oxide layer can improve the light extraction efficiency of organic light-emitting diodes. The extraction efficiency depends on the emitters' positions varying laterally in a unit cell of PC. The highest efficiency is obtained when the emitters are under higher refractive index strips. Efficiency decreases when the emitters shift to lower refractive index strips. Simulations for both transverse magnetic and transverse electric modes indicate that when emitters are close to the middle of the higher refractive index strips, the guided wave transmits with less divergence and inhibited reflection because of the guiding effect of higher refractive index strips. A modified method that considers the position effects is proposed to calculate the extraction efficiency more precisely.

Investigation of one-dimensional photonic crystal structures with two sublattices in microwaves

The behavior of eigenfrequencies of an irregular microstrip resonator, being an integral part of the one-dimensional photonic crystal (PC) with two sublattices, is investigated as a function of its design parameters. The possibility of a significant increase of the second band gap of the PC with two sublattices is demonstrated that essentially improves the frequency selection properties of the bandpass filters designed on its basis. Good agreement between the calculated results and measurements with the prototype of the original filter built around the microstrip photonic crystal of new design comprising 19 layers is demonstrated.

Defect mode suppression in a photonic crystal with a magnetic defect in the ferromagnetic resonance region

The specific features of the transmission and reflection spectra of a one-dimensional photonic crystal structure with a magnetically active layer placed between dielectric Bragg mirrors have been investigated. If the magnetic resonance frequency coincides with the frequency of the defect mode in one of the photonic bands, the defect mode in the photonic crystal can be completely suppressed, which makes it possible to effectively control the spectrum of such a structure by an external magnetic field.

All-Optical Switches Based on Multiple Cascaded Resonators With Reduced Switching Intensity-Response Time Products

The general nonlinear behavior of multiple cascaded resonators is analyzed by using the coupled-mode theory in time and then compared to a single resonator from the viewpoint of optical bistable operation. Our analysis reveals that from the perspective of switching intensity, the multiple resonator structure is more advantageous than the single resonator with an equivalently increasing quality factor. It is also shown that a switching intensity-response time product, suggested as a performance metric for optical bistable devices, decreases linearly as the number of cascaded resonators increases. The effect of coupling n resonators is equivalent to a single resonator device with n-time increased quality factor in terms of the performance metric. The coupled-mode theory analysis is confirmed by a numerical study of the bistable operation of one-dimensional photonic crystal resonator structures using the finite-difference time-domain method.

Design of a wavelength division demultiplexer using Si-based one-dimensional photonic crystal with a defect

Transmission characteristics of one-dimensional photonic crystal structure with a defect have been studied. We consider a Si/air multilayer system. We also consider the refractive index of Si layer to be dependent on temperature and wavelength simultaneously. Central wavelength of the defect mode depends on the width of the defect layer, so we can change the central wavelength of defect mode by changing the width of defect layer. This property can be exploited in the designing of wavelength division demultiplexer for optical communication.

Wide Range Temperature Sensors Based on One-Dimensional Photonic Crystal with a Single Defect

Transmission characteristics of one-dimensional photonic crystal structure with a defect have been studied. Transfer matrix method has been employed to find the transmission spectra of the proposed structure. We consider a Si/air multilayer system and refractive index of Si layer has been taken as temperature dependent. As the refractive index of Si layer is a function of temperature of medium, so the central wavelength of the defect mode is a function of temperature. Variation in temperature causes the shifting of defect modes. It is found that the average change or shift in central wavelength of defect modes is 0.064 nm/K. This property can be exploited in the design of a temperature sensor.