A novel technique to measure the sucrose concentration in hydrogel sucrose solution using two dimensional photonic crystal structures

We propose a novel technique to measure the concentration of sucrose in PAm-hydrogel sucrose solution using two dimensional photonic crystal structures consists of air holes. PAm-hydrogel is an organic hydrogels, which is used as biomedical applications. The principle of measurement is based on the linear variation of photonic band gap with the change of dielectric constant of the solution infiltrated in air holes of photonic crystal structure. Plane wave expansion method is used to find the band gap and linear variation (R² = 0.9949) of photonic band gap with respect to sucrose concentration is observed. Besides this, an excellent linear variation (R² = 0.9949) of transmitted intensity of light with respect to sucrose concentration is also seen. Since the simulation is based on optical principle, it gives accurate results. This suggests the possible use of 2-D photonic crystal structure as a sucrose sensor. Experimental procedure for measuring the concentration of sucrose is also mentioned.     

Slight disorder effects in two dimensional photonic crystal structures

In the actual manufacturing process of photonic crystal structure, unavoidable error can generate slight disorder which may influence the performance of photonic crystal based device. In this work, randomly distributional disorders are applied to the air holes in the photonic crystal structure. Based on this, we investigate the influence of the slight disorder on the photonic crystal band structure and the performance of photonic crystal based devices (waveguide and slab cavity). The studies indicate that the slight disorder provides small influence on the band structure of the photonic crystal. But, the random disorder in photonic crystal waveguide may increase transmission loss obviously when the wavelength of the light and the distribution of disorder break the balance of multiple interferences. Also, the slight disorder can reduce the Q factor of the photonic crystal cavity at a certain degree. The studies may provide some useful guides for further photonic crystal device research.     

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 关键词： 温度测量 一维光子晶体 传输矩阵法 缺陷峰     

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     

2维光子晶体谐振腔的分析与模拟

为指导光子晶体谐振腔的设计,运用3维电磁场仿真软件HFSS模拟了2维光子晶体谐振腔,分析了影响2维光子晶体谐振腔的主要特性参数,主要包括所插介质杆的排列结构、介电常数及其半径和间距。研究表明,在其它条件保持不变时,若增大介质杆半径,则同一模式频率没有同一的变化规律;若增大介质杆介电常数,则出现的规则模式减少,并且没有基模出现,同一个模式,频率明显降低;若增大介质杆间距,则计算的频率间隔减小,对其它参数影响不大,只是同一模式的频率略有减小。     

2维光子晶体谐振腔的分析与模拟

 为指导光子晶体谐振腔的设计,运用3维电磁场仿真软件HFSS模拟了2维光子晶体谐振腔,分析了影响2维光子晶体谐振腔的主要特性参数,主要包括所插介质杆的排列结构、介电常数及其半径和间距。研究表明,在其它条件保持不变时,若增大介质杆半径,则同一模式频率没有同一的变化规律;若增大介质杆介电常数,则出现的规则模式减少,并且没有基模出现,同一个模式,频率明显降低;若增大介质杆间距,则计算的频率间隔减小,对其它参数影响不大,只是同一模式的频率略有减小。     

Lightwave splitting in two dimensional photonic crystal analogue of coupler

Two bent channels are created in an otherwise periodically arrayed photonic crystal structure by removing some dielectric pillars. If lightwave is introduced into one channel, a part of it would couple into the second channel and propagate down the guide. Factors deciding the amount of light couple from the first channel into the second channel are discussed thoroughly. This coupling scheme could be an important part for photonic integrated devices.     

Visual device for pressure measurement using photonic crystal slabs

We propose and demonstrate a visual, all-optical pressure-measuring device composed of a flexible membrane dilating toward a photonic crystal slab. Due to its transparency and capability to be miniaturized, it may be integrated on the inner side of an artificial lens and directly measure the eye's intraocular pressure. Using crossed polarization filters for the readout process, we obtain a contrast enhancement for the circular contact area of the membrane with the photonic crystal slab. We demonstrate that the visible circle increases as a function of pressure.     

A novel proposal for DWDM demultiplexer design using modified-T photonic crystal structure

We propose an ultra compact structure to realize demultiplexing operation for Dense Wavelength Division Multiplexing (DWDM) communication systems using resonant cavity in modified-T Photonic Crystal (PC) structure. To the best of our knowledge, this is for the first time that a PC-based demultiplexer has been achieved with 1 nm channel spacing and 0.45 nm mean value of bandwidth without using either specific materials or complexities in fabrication process. Designs offering improvement of channel spacing and bandwidth of the proposed demultiplexer is our aim in this work. The attained characteristics are approximately in the range of the DWDM communication systems. Accurate resonant cavities have been used in terms of location and size of holes in the proposed structure in order for them to capture desired wavelengths in optical telecommunication range. Our simulations indicate the average amount of crosstalk (Xt) and the average quality factor (Q) to be ?21.1 dB and 3488, respectively. Two-dimensional (2D) Finite-Difference-Time-Domain (FDTD) is chosen for simulation of the proposed structure. The footprint of the structure is approximately 536 μm² and can be fabricated and integrated densely and easily.     

Differential transfer matrix method for photonic band structure of one dimensional non-uniform distribution plasma photonic crystal

An approach of analytical calculation for photonic band gap structure (PBGS) of one-dimensional periodic media, such as non-uniform distribution plasma photonic crystal (PPC), is given on the basis of the recently reported differential transfer matrix method. The dispersion equation of electromagnetic wave propagating in one dimensional non-uniform distribution PPC is derived and the PBGSs for several numerical cases, such as linear distribution, exponential distribution and Epstein distribution, are calculated and discussed.     

Investigation on two dimensional photonic crystal resonant cavity based bandpass filter

In this paper, different cavities, namely quasi square, tri-quarter square, square, hexagonal, circular, elliptical, diamond and annular ring based photonic crystal bandpass filters (PCBPFs) are proposed and investigated by exploiting coupling between two in-line quasi waveguides and a resonant cavity. The resonant wavelength, output efficiency and bandwidth of designed PCBPFs are studied by varying the size of the cavity. The normalized transmission spectra of PCBPF are observed using 2D finite difference time domain (FDTD) method. The photonic band gap (PBG) is calculated by plane wave expansion (PWE) method. The circular cavity based PCBPF gives better performance than others because of its circular resonating modes. The number of passbands is increased linearly while increasing the size of the cavity. The overall size of the PCBPF chip is about 11.4 μm × 11.4 μm, which is more suitable for photonic integrated circuits (PIC), wavelength division multiplexing (WDM) systems and sensing applications.     

Fabrication and measurement of optical characterization of one dimensional photonic crystal with defect

Numerical calculations based on the transfer matrix method are carried out, and the results of band gap with resonance peaks are obtained. The electron beam lithography technology （EBL） and induction coupling plasma （ICP） etching are used to make the photonic crystal （PC） structures, and from several scanning electron microscope images, the PC structures are observed with features closing to the design. In order to create the tiny PC structures in the right places of the waveguide by the EBL technology at different time, some alignment markers are deposited on the chip, which are made of gold that deposited on titanium for its good adhesion to the underlying Si. An optical testing bed is designed for measurement of the optical characterization of PC structures. Through the analysis of the measured data, a △λ value of 0.8 nm is obtained and for the centre frequency of 1547 nm, a very high quality factor value of 1933 can be obtained. The 3-rim difference represents only a 0.2% error from the theoretical centre.     

新型抗弯曲大模场面积光子晶体光纤

研制出一种新型抗弯曲大模场面积石英光子晶体光纤. 利用光子晶体光纤结构设计的灵活性, 通过规划缺陷的位置及空气孔的尺寸, 实现了大模场面积单模及低弯曲损耗特性.应用建立的实际光子晶体光纤特性分析模型, 研究了研制光纤的模式特性和弯曲特性, 在波长1064 nm处, 平直状态下光纤的模场面积可以达到2812 μm², 基模限制损耗为0.00024 dB/m, 高阶模限制损耗高于1.248 dB/m. 基模和高阶模之间的高传输损耗差, 保证了在获得大模场面积的同时实现单模传输. 弯曲半径和弯曲方向角所带来弯曲损耗变化的研究结果显示, 即使在弯曲半径小到5 cm时, 弯曲损耗也在10^-3 dB/m量级以下, 而且在弯曲半径为30 cm时光纤可承受的弯曲方向角范围扩展至-60°–60°. 研制的光纤具有良好的低弯曲损耗特性, 可有效解决非对称结构所带来的光纤弯曲特性对弯曲方向角敏感的问题. 该光纤在高功率光纤激光器、放大器及高功率传输等技术领域具有重要的应用价值. 关键词： 光子晶体光纤 大模场面积 低弯曲损耗 弯曲方向角     

A novel method of rapidly modeling optical properties of actual photonic crystal fibres

<正>The flexible structure of photonic crystal fibre not only offers novel optical properties but also brings some difficulties in keeping the fibre structure in the fabrication process which inevitably cause the optical properties of the resulting fibre to deviate from the designed properties.Therefore,a method of evaluating the optical properties of the actual fibre is necessary for the purpose of application.Up to now,the methods employed to measure the properties of the actual photonic crystal fibre often require long fibre samples or complex expensive equipments.To our knowledge, there are few studies of modeling an actual photonic crystal fibre and evaluating its properties rapidly.In this paper,a novel method,based on the combination model of digital image processing and the finite element method,is proposed to rapidly model the optical properties of the actual photonic crystal fibre.Two kinds of photonic crystal fibres made by Crystal Fiber A/S are modeled.It is confirmed from numerical results that the proposed method is simple,rapid and accurate for evaluating the optical properties of the actual photonic crystal fibre without requiring complex equipment.     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.     

A novel proposal for enhancement of light extraction efficiency in WOLEDs based on optimized photonic crystal structures

In this paper we propose a framework to enhance light extraction efficiency in white organic light emitting diodes (WOLED) using photonic crystal (PhC) structures sandwiched between indium tin oxide (ITO, n_ITO = 1.8+0.01i) and glass (n_glass = 1.51) substrate, according to the high refractive index contrast of these two layers almost 50% of the generated light inside WOLED gets trapped in the mentioned interface. The main purpose of this article is to suggest a method to intentionally optimize PhC structures to reduce total internal reflections (TIR) happening at ITO/glass interface. Here three different patterns are considered including rectangular, hexagonal and circular lattices. Using Finite Difference Time Domain (FDTD) method and the presented framework for choosing structural parameters the portion of 50% trapped light in ITO was reduced to 20% which is a large enhancement in extraction efficiency of WOLED. Also far-field results before and after adding PhCs are investigated.     

Multichannel W3 Y-branch filter in a two dimensional triangular-lattice photonic crystal slab

We demonstrate the design, fabrication and characterization of a highly efficient multichannel W3 Y-branch filter in a two dimensional triangular-lattice photonic crystal slab. The coupling properties between high-order waveguide modes and fundamental resonant modes are investigated. By finely adjusting the size of resonant cavities, four higher-order mode channels with different output wavelengths are experimentally realized, which is in agreement with the theoretical simulations. The results show that this kind of filter may be useful in optical integrated circuits with high coupling and transmission efficiency.     

Low dimensional silicon structures for photonic and sensor applications

We review here our work on the photonic and sensor applications of nanostructured silicon. As we change the dimensionality of silicon very fascinating and new optical properties of the material appear. Light sources, modulators, waveguides, logical gates are a few examples of the various photonic devices which have been developed based on silicon nanocrystals. Needless to say, all these devices rely on quantum confinement and on the interplay between bulk and surface properties. Size effects and surface reconstructions are two critical issues which one has to master to employ silicon nanocrystals. Finally the use of silicon nanocrystals to develop innovative sensing mechanisms to reveal biomolecules or poisoning gasses will be discussed.     

Determination of glucose concentration in biological liquids using photonic crystal waveguides

The possibility of using hollow-core photonic crystal waveguides as biological sensors is shown. The influence of the glucose concentration in solutions introduced into the waveguide core on the transmission spectrum of photonic crystal waveguides is shown. Two possible methods of determining the glucose concentration in liquids are considered, refractometric and photometric.