一维缺陷光子晶体温度的测量

采用Si和SiO₂两种介质材料构造一维缺陷光子晶体，缺陷层介质为Si，利用传输矩阵法对带有缺陷的一维光子晶体的传光特性进行了理论分析，并得到其带隙特性.由于缺陷的存在，使得光子晶体的透射谱中产生缺陷峰.当被测温度变化时，根据两种介质的热光效应和热膨胀效应，光子晶体介质和缺陷层的光学厚度和折射率发生变化，透射谱缺陷峰产生漂移，由缺陷峰的中心波长漂移量得到被测温度的大小.构建了一维缺陷光子晶体测量温度的实验系统，实验结果表明缺陷峰中心波长与光子晶体所受的温度呈线性关系，测量灵敏度为0—2     

A new design of tunable four-port wavelength demultiplexer by photonic crystal ring resonators

A four-channel wavelength demultiplexer based on photonic crystal ring resonators (PCRR), which can be used for photonic integrated circuits, is designed. Dropping efficiency and Q factor of single improved ring are 100% and 842, respectively. In order to achieve the structure of demultiplexer, three improved rings have been used, that every ring has an individual inner rod radius; it means that each ring has a varying resonant wavelength. The results of simulation using finite-difference time-domain (FDTD) method in our proposed structure reveals an average transmitted power higher than 90% for each output port, Channel spacing is about 8 nm and bandwidth for each individual channel is about 2.8 nm. The mean value of the crosstalk between output channels and the area of the proposed structure are about −29 dB and 317 μm², respectively. By changing the radius of inner rods, various wavelengths can be chosen, therefore this device is tunable.     

Properties of defect modes in one-dimensional photonic crystals containing two nonlinear defects

Transmission properties of one-dimensional photonic crystal with two nonlinear defects were investigated based on the nonlinear transfer matrix method. From the inspection of the optical bistabilities around different defect modes, it was found that the threshold of bistability for the bonding mode is always lower than that for the anti-bonding mode. When intensity of the incident wave increases bistability could happen at any wavelength larger than the resonance wavelength of the linear anti-bonding mode in the gap. The threshold of bistability increases initially with the wavelength, then decreases sharply in reaching the resonance wavelength of the linear bonding mode. The coupling behavior of the two defects was also discussed, and it was found that the threshold of bistability increases with the distance between the two defects. A flat spectrum similar to that formed in the photonic crystal molecules was obtained under certain incident intensity.     

Analysis of defect mode in a dielectric photonic crystal containing ITO defect

In this work, based on the use of ITO as a defect, we study the infrared defect mode in defective photonic crystal made of SiO₂ and InP. Due to the dispersion in the dielectric function of ITO, it is found that the defect mode is sensitive to the ITO thickness. The defect frequency is shown to be blue-shifted as the thickness of ITO decreases. In the angular dependence of defect mode, it is seen that the defect frequency is also blue-shifted when the angle of incidence increases for both TE and TM polarizations. However, the shifting feature is appeared to be nearly polarization-independent. The shift in the defect frequency enables us to employ ITO as a tunable agent in order to design a tunable photonic crystal filter in the infrared region.     

Nonlinear transmission and reflection characteristics of plasma/polystyrene one dimensional photonic crystal

Reflection and transmission properties of one-dimensional plasma/polystyrene nonlinear photonic crystal have been investigated theoretically. Reflectance and transmitted amplitude of electromagnetic waves through these periodic multilayered structures are calculated for different intensities of controlling wave. It is found that the reflectance of the proposed structures depends on the intensity of the controlling wave and this property can be exploited in the design of WDM coupler, filter, optical logic gates, etc.     

Kerr nonlinear switch based on ultra-compact photonic crystal directional coupler

In this paper, an all optical switch based on nonlinear photonic crystal directional coupler has been simulated and analyzed by the finite difference time domain (FDTD) method. The lunched pump signal increases the refractive indices of the central row of the coupler, due to nonlinear Kerr effect, hence the coupler works in the nonlinear conditions and lightwave guides to the other output port. We have tried to increase the coupling efficiency and reduce the required power in the nonlinear status by optimizing the bends structure and increasing the interaction between dielectric and lightwave signal. Therefore, the input signal beam can be controlled to be exchanged between two output ports to earn the highest output power ratio and the smallest amount of power required for nonlinear performance, the physical length of the coupler is determined to be 20a, where a is the structure lattice constant.     

Influence of defect mode displacement in photonic crystal band gap over light group velocity

The light group velocity of defect mode in photonic crystal is active controlled in order to gain controllable light delay by using thermo-optic effect to change the reflective index of material or changing the geometry structure of photonic crystal. From former research we know that the position of defect mode in band gap is changed with light group velocity. Our research further finds that the position of defect mode can be kept by changing more than one parameter correspondingly, and meanwhile the group velocity is not changed too. It comes to the relationship between position of defect mode in photonic band gap and light group velocity, and it is proved theoretically using the principle of plane wave expand method.     

Bending insensitive large mode area photonic crystal fiber

A novel kind of large mode area photonic crystal fibers (PCFs) are proposed in this paper. In order to achieve large effective mode area, a novel technique is applied to seven missing air hole PCF structures. The modal characteristics of PCF structures such as effective mode area, confinement loss, chromatic dispersion properties with doped cores, are investigated by employing the full vectorial finite element method (FEM). Simulation results demonstrate that effective mode area and confinement losses of fundamental mode simultaneously improved by applying our novel technique to proposed structures. The effects of bending on confinement losses of the proposed PCFs have been thoroughly investigated. Additionally, confinement losses of first higher order modes are presented and the possibility of stripping them in a simple way is discussed.     

An ultra compact photonic crystal wavelength division demultiplexer using resonance cavities in a modified Y-branch structure

An ultra small size 4-channel wavelength division demultiplexer based on 2D photonic crystal modified Y-Branch, suitable for integration, is proposed in this paper. The output wavelengths of designed structure can be tuned for communication applications (around 1550 nm) by choosing suitable defect parameters in the corner of each resonance cavity and output waveguides. The cross section of the structure is 313.28 μm² (17.8 μm × 17.6 μm) and desirable for integration based on popular planar technology. The bandwidth of each channel is near to 1 nm and the channel spacing is approximately 3.5 nm and wavelengths of demultiplexer channels are 1548.8 nm, 1551.9 nm, 1555.4 nm and 1559.3 nm respectively. Also, the crosstalk is between −33.1855 dB and −10.4947 dB. Furthermore, the mean values of the crosstalk and quality factor are −22.54 dB and 1496.7 respectively.     

Tunable characteristics of one dimensional magnetic photonic crystal composed with single-negative materials

In this paper, we present the study of dispersion and transmittance characteristics of one dimensional magnetic photonic crystal composed by single negative indexed materials. For this structure, we have considered magnetic negative (MNG) with ? = 1 and μ < 0 and electric negative (ENG) with ? < 0 and μ = 4. We used simple transfer matrix method and Bloch's theorem for its analytical explanations. Analyzing transmittance characteristics of the proposed structure, we obtain the tunneling of certain frequency range where as the dispersion characteristic shows total forbidden for the same range for TM mode. The tunable property is found inside the band structure due to zero-?, zero-μ and magnetic behavior of the material. To identify zero-? and zero-μ of the structure, we have calculated the dispersion and the transmittance of the magnetic structure of MNG–ENG on different angles of incidence and thickness of layers.     

Dense wavelength division demultiplexing using photonic crystal waveguides based on cavity resonance

We demonstrated a photonic crystal waveguide based dense wavelength division multiplexing device using the resonances in the cavities. The demultiplexing is achieved through filtering. This filtering is achieved by varying the radii of the surrounding holes of the cavity, which in turn changes the resonant wavelength of the cavity. The four wavelengths demultiplexed in the design are 0.8 nm apart in the optical region centered on 1.55 and 1.56 μm. The device designed and simulated has easy to realize structure as well as high quality factor. Two-dimensional Finite Difference Time Domain (FDTD) is chosen to do the simulation of this work.     

Calculation of optical properties of hollow-core photonic crystal fibers

We propose a method for calculation of the bandgaps in the cladding of hollow-core photonic crystal fibers, based on the Floquet theorem. The effectiveness of the approach is confirmed by estimates of the effect of the number of air channels in the cladding on attenuation of the fiber modes due to mode energy leakage from the core. We have studied the conditions for the existence of eigenmodes in the indicated fibers. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 311–320, March–April, 2009.     

Widely tunable dual-pump parametric amplifiers with photonic crystal fibres

This paper theoretically studies the double-pumped fibre-optical parametric amplifiers （FOPAs） in photonic crystal fibres. Two distinct working regimes of FOPAs are researched, which depend on the dispersion at the central wavelength of the two pumps. Extremely broad tuning range can be obtained when the central pump wavelength is in the normal dispersion regime and is insensitive to the wavelength separation between the two pumps, while the tuning range is narrow in the anomalous dispersion regime and can be significantly enhanced by increasing the wavelength separation. Impacts of higher-order dispersions and temporal walk-off on the gain spectra are also discussed.     

Design, analysis and optimization of silicon-on-insulator photonic crystal dual band wavelength demultiplexer

A highly efficient photonic crystal dual band wavelength demultiplexer (DBWD) using silicon-on-insulator (SOI) substrates is proposed for demultiplexing two optical communication wavelengths, 1.31 μm and 1.55 μm. Demultiplexing of two wavelength channels is obtained by modifying the propagation properties of guided modes in two arms of Y type photonic crystal structure. Propagation characteristics of proposed DBWD are analyzed utilizing 3D finite difference time domain (FDTD) method. Enhancement in spectral response is further obtained by optimizing the Y junction of demultiplexer giving rise to high transmission and extinction ratio for the wavelengths, 1.31 μm and 1.55 μm. Hence it validates the efficiency of proposed optimized DBWD design for separating two optical communication wavelengths, 1.31 μm and 1.55 μm. Tolerance analysis was also performed to check the effect of variation of air hole radius, etch depth and refractive index on the transmission characteristics of the proposed design of SOI based photonic crystal DBWD.     

Defect mode properties in a one-dimensional photonic crystal

Based on the transfer matrix method (TMM), the interaction of electromagnetic waves with one-dimensional (1D) defective photonic crystal in ultraviolet (UV) frequency region had been studied. With the calculated transmittance characteristics in the wavelength domain, it can be found that the defect mode can be generated within the photonic band gap (PBG) at the central wavelength. Also the effects of many parameters such as the angle of incidence, the state of polarization and the defect layer thickness have been taken in account. A significant effect in generating multiple defect peaks within the PBG has been illustrated.     

Low threshold laser cavities of two-dimensional photonic crystal line defect mode

Two-dimensional (2D) rod-type photonic crystal (PC) line defect waveguide (LDW) laser cavities based on three types of line defect modes with zero group velocity are studied by using finite-difference time-domain (FDTD) method. These laser cavities have high quality (Q) factor, better localization of light, non-uniform gain distribution and small overlap between gain medium and light field. Therefore, they have the advantages over conventional and air-bridge PC cavities with uniform gain, such as low threshold, single mode lasing and effectively avoiding thermal effect. From their comparison, one can find the mode at middle Brillouin zones (BZ) is the best one to be used as lasing mode. Its dynamic lasing process and lasing features are demonstrated by the numerical experiment where the FDTD method coupling Maxwell's equations with the rate equations of electronic population is used.     

Lateral shifting in one dimensional chiral photonic crystal

We report the lateral shifts of the transmitted waves in a one dimensional chiral photonic crystal by using the stationary-phase approach. It is revealed that two kinds of lateral shifts are observed due to the existence of cross coupling in chiral materials, which is different from what has been observed in previous non-chiral photonic crystals. Unlike the chiral slab, the positions of lateral shift peaks are closely related to the band edges of band gap characteristics of periodic structure and lateral shifts can be positive as well as negative. Besides, the lateral shifts show a strong dependence on the chiral factor, which varies the lateral shift peaks in both magnitudes and positions. These features are desirable for future device applications.     

圆柱形光子晶体中电磁波的模式和带隙

利用电磁波在一维圆柱光子晶体中径向受限的条件,推导出电磁波在一维圆柱光子晶体中各个模式满足的关系式。研究了各个模式的特征。计算出TE波和TM波各模式的禁带随模式量子数、圆柱半径以及入射角的变化规律。得出了一些不同于一维非受限光子晶体带隙的新结构。     

Single mode lasers based on monolithic integration of ridge waveguides with 2D photonic crystal waveguides

The monolithic combination of active light sources with photonic crystal (PC) waveguide components is a key building block for future highly integrated photonic circuits. We demonstrate the coupling of light from an InGaAs/AlGaAs ridge waveguide laser to a monolithically integrated 2D PC waveguide. The PC guide is formed by removing three or five rows in a triangular lattice of air rods etched into the semiconductor. A tapered ridge waveguide geometry is demonstrated to improve coupling efficiency, so that maximum output powers of up to 10 mW from the PC waveguide are achieved. The resulting coupled cavity laser shows single mode emission with side mode suppression ratios > 35 dB over a broad range of injection currents.