低阈值单横模852nm半导体激光器

基于波导理论、等效折射率方法,设计并制备了非对称波导隔离双沟结构脊型边发射激光器,最终获得了低闽值单基侧模852 nm激光器.详细研究了不同脊型台深宽比参数设计对激光器侧向模式特性的影响规律,实现了腔面未镀膜情况下脊型波导边发射激光器的单基侧模稳定输出,同时激射波长可以精确调谐到852 nm;工作电流达到150 mA,工作温度30℃;斜率效率最高可达0.89 nW/mA,光谱半宽小于1 nm.研究结果为进一步实现超窄线宽激光器提供了参考和借鉴,并且为实现激光器稳定输出提供了实验基础.     

混合表面等离子体激元的纳米激光器设计

为了实现纳米激光器的性能优化,设计了一种基于纳米线、半圆形氟化镁、三角形空气槽和金属脊结构的纳米激光器模型。模型中耦合在低折射率电介质层中的SPP模式和纳米线波导可以在低折射率间隙下像电容器那样存储光能,从而使低折射率的空气槽场强明显增大。应用有限元法在COMSOL Multiphysics软件下,分析了该纳米激光器模型的电场分布、模式特性、品质因数和增益阈值随着设计结构几何参数变化的规律,通过各部分折线图的综合分析来得出模型性能的数据。分析表明：该模型的光场约束能力较强且传播损耗较低,其中归一化面积最小可达到0.004 8,有效传输损耗最小可达到0.002。波导模场区域和限制因素表明,该激光器模型可以实现输出光场的亚波长约束。该模型基本实现了低增益阈值、低传输损耗和高品质因数的要求。     

Thermally driven sensitive surface phonon polariton modes in thin-film SiC

The results of this work show that significant changes to the spectral properties of thermal emission may be accomplished by taking advantage of surface phonon polariton (SPP) modes that are very sensitive to small refractive index changes. Surface phonon polaritons are interface restricted wave modes that do not usually participate in thermal radiative energy exchange. In this work, the possibility of varying the spectral properties by using a thin-film surface active material, layered between dielectrics, is explored. Unlike surface gratings, the multilayered structure discussed in this work couples the surface modes into radiative modes using subtle changes in refractive index. The proposed multilayer effect is studied by first developing the SPP mode dispersion relation to identify the spectral location of the surface modes. The relationship between SPP coupling and refractive index change is then developed. The fluctuation-dissipation theorem and an impedance boundary condition is used to theoretically show how thermal radiation can excite SPP modes. Results are then presented that show how film thickness and substrate properties act to support SPP modes that are particularly sensitive to changes in refractive index and therefore offers opportunities for dramatic changes to the spectral properties.     

Semi-elliptical dielectric-loaded surface plasmon-polariton waveguides

Semi-elliptical dielectric-loaded surface plasmon-polariton waveguide (DLSPPW) is proposed. The mode effective index, field confinement, and propagation length of the fundamental mode supported by it are calculated at the telecom wavelength λ = 1.55 μm for different dimensions of a polymer ridge (with the refractive index of 1.535) placed on a gold film surface. The waveguide structure is found to exhibit 23% increase of the propagation length while showing similar confinement as compared to conventional rectangular DLSPPW when ridge thickness t < 450 nm (ridge width w = 600 nm) and ridge width w < 320 nm (ridge thickness t = 600 nm).     

Efficient directional excitation of surface plasmon polaritons by partial dielectric filling slit structure

In this paper, we investigate the excitation of surface plasmon polariton (SPP) in the metallic slit partly filled with dielectric by using the finite-difference time-domain method. It is found that the slit structure displays high asymmetry in the field distribution and SPP excitation due to the difference in matching degree of SPP wavevector on the two sides of slit exit. At certain incident wavelengths, the power flow carried by SPP modes on one side of slit exit is over three orders of magnitude greater than that on the other side, an efficient directional excitation is achieved. The SPP generation efficiencies on both sides of slit exit can be periodically adjusted by the dielectric width, but their changes are not synchronous, implying that such slit structure could be acted as a directional splitter/coupler. Moreover, the asymmetry degree of SPP excitation can also be modulated by the refractive index of dielectric layer.     

Theoretical model of a planar waveguide refractive index sensor assisted by a corrugated long period metal grating

A theoretical model of a novel planar integrated refractive index sensor based on surface plasmon-polariton (SPP) excitation with a corrugated metal long period grating (LPG) is presented and comprehensively investigated. The main principle of the operation this device is based on co-directional energy transfer by means of a corrugated metal LPG between a p-polarized guided mode propagating in a waveguide layer and the SPP propagating a metal layer separated from the waveguide layer by a buffer. The corrugated LPG is engraved in the metal layer in contact with the sensed medium. The power transmitted through the LPG in the guided mode serves as an input signal for an interrogation unit. This device is free from any moving parts and can be simply integrated into any planar waveguide system. Our sensor simulations are based on the local-normal-mode transfer matrix method and performed in telecom wavelength range.     

Theoretical model of a planar integrated refractive index sensor based on surface plasmon-polariton excitation

A theoretical model of a new integrated planar surface plasmon-polariton (SPP) refractive index sensor is presented and comprehensively investigated. The main principle of operation of this device is based on high efficiency energy transfer between a p-polarized guided mode propagating in a waveguide layer of the structure and the SPP propagating in the opposite direction in a metal layer separated from the waveguide layer by a dielectric buffer. The high efficiency energy transfer is realised by means of a properly designed Bragg grating imprinted in the waveguide layer. This device is compact, free from any moving parts and can easily be integrated into any planar scheme. Our simulations for the sensor operating at the well developed and commercialised telecom wavelengths are based on coupled mode theory.     

聚合物电光调制器中M-Z波导TM模分析

M-Z光波导是聚合物电光调制器的重要结构单元。利用有效折射率法计算聚合物脊形波导的横向折射率分布，将三维光波场传播简化为二维传播。从导模满足的标量波动方程出发，结合透明边界条件，采用Crank-Nicholson差分格式，得出有限差分束传播法的基本计算格式。通过对M Z型波导结构中TM模的传播及损耗特性进行理论分析，系统地研究了脊宽、分支角等结构参数对损耗的影响。研究表明，有效折射率法与二维有限差分束传播法的结合可以较好地解决脊形M Z波导的设计问题。该方法具有精度高、计算量小及效率高等优点，为聚合物电光调制器的制备提供了理论依据。     

Disposable and compact integrated plasmonic sensor using a long-period grating

This Letter theoretically proposes and investigates an integrated plasmonic sensor that is based on a grating-assisted coupling between a surface plasmon polariton (SPP) and a dielectric waveguide (DW) mode. It consists of a glass slide with a gold film for the propagation of an SPP and a separate DW with a long-period grating. For sensing, the two parts are temporarily combined. After sensing, the former is replaceable, and so the sensor has disposability. The design procedure and analysis method for the sensor are explained. The designed sensor is shown to be very compact. Its characteristics of sensing a change of the refractive index of liquid are analyzed and discussed.     

Polarization detection analysis of dual-channel surface plasmon resonance sensing for silicone oils based on the D-shaped fiber with a central hole

We present and numerically characterize a dual channel surface plasmon resonance (SPR) sensor based on a D-shaped fiber with a central hole for silicone oil detections. The proposed design incorporates two metalized channels to facilitate the simultaneous detection of one group of silicone oils, which can consist of two different species. It has been demonstrated that the p-polarized input light can induce two peaks among surface plasmon resonance places, which come from the coupling between the core-guided mode and the fundamental surface plasmon polariton (SPP) modes at the D-shaped surface and around the central hole surface. However, the s-polarized input light can only induce one peak among surface plasmon resonance places, which comes from the coupling between the core-guided mode and the fundamental SPP mode around the central hole surface. The simulation results show that the characteristic responses of two channels independently correspond to the refractive index variations in the silicone oils with which they are in contact. A maximum sensitivity of 3500 nm/RIU (refractive index unit) and 4400 nm/RIU are achieved for channel A and B, respectively. This kind of sensor structure and polarization related demodulation method is promising in the simultaneous multi-analytes sensing applications in the future.     

Holography with guided optical waves

Waveguide holograms are recorded in a storage material layer covering a planar dielectric waveguide with a guided mode as reference wave. They are also read-out with a guided mode. In the storage material, assumed to have a lower refractive index than the waveguiding film, the fields of the reference and of the read-out wave are evanescent waves. We describe the preparation of the epoxy resin (Araldit) waveguides on glass substrates, their coating with a dichromated gelatin (DCG) layer as storage material, the processing of the DCG, and the recording and reconstruction techniques. Waveguide holograms of good quality with a size of several square centimeters have been realized for the first time. The holograms were recorded and read-out with wavelength λ=488 nm. They have a length of about 25 mm and a width of 17 mm. To obtain holograms that wide a special prism coupler had to be used which allowed to couple in a laser beam of elliptical cross section, and thus to excite a guided reference or read-out mode with a width of 17 mm.     

Numerical analysis of plasmon polarition refractive index fiber sensors with hollow core and a long period grating

The main principle of this design is based on the efficient energy transfer between the waveguide mode (WM) and the co-directional SPP provided by a properly designed fiber long period grating (LPG). This LPG is imprinted into a waveguide fiber layer of a specially designed hollow core optical fiber. The simulations are based on the finite element method (FEM) algorithm in electromagnetics and coupled mode theory for gratings. Compared to the previous proposed structure using a fiber Bragg grating (FBG), this novel kind of sensor can greatly enhance the refractive index sensitivity, e.g., from 5.93 nm/RIU (with FBG) to 817 nm/RIU (with LPG) at the sensing refractive index of 1.40. The other advantage is that the working conditions can be performed for the well-developed telecom wavelength windows 1500-1600 nm.     

Refractive index sensor based on high-order surface plasmon resonance in gold nanofilm coated photonic crystal fiber

We propose a novel kind of wide-range refractive index optical sensor based on photonic crystal fiber(PCF) covered with nano-ring gold film.The refractive index sensing performance of the PCF sensor is analyzed and simulated by the finite element method(FEM).The refractive index liquid is infiltrated into the cladding air hole of the PCF.By comparing the sensing performance of two kinds of photonic crystal fiber structures, a wide range and high sensitivity structure is optimized.The surface plasmon resonance(SPR) excitation material is chose as gold, and large gold nanorings are embedded around the first cladding air hole of the PCF.The higher order surface plasmon modes are generated in this designed optical fiber structure.The resonance coupling between the fundamental mode and the 5 th order surface plasmon polariton(SPP)modes is excited when the phase matching condition is matched.Therefore, the 3 rd loss peaks appear obvious red-shift with the increase of the analyte refractive index, which shows a remarkable polynomial fitting law.The fitnesses of two structures are 0.99 and 0.98, respectively.When the range of refractive indices is from 1.40 to 1.43, the two kinds of sensors have high linear sensitivities of 1604 nm/RIU and 3978 nm/RIU, respectively.     

双带通啁啾光纤光栅光谱特性仿真及分析

针对啁啾光纤光栅的带通滤波特性,设计了纤芯/包层复合结构的啁啾光纤光栅滤波器.基于光纤耦合模和传输矩阵理论及坐标变换方法,对其光谱特性进行仿真分析,验证了该光栅的双带通滤波特性;对周期为536、537、538nm,长度为8、10、12mm,折射率调试深度为0.0002、0.0003、0.0004,啁啾系数为0.05、0...     

基于无芯光纤的多参数测量传感器

设计并制作了一种基于单模-无芯-单模-无芯-单模光纤结构的马赫-曾德尔传感器,可用来同时测量折射率和温度.该传感器中,两处无芯光纤充当输入、输出耦合器,中间单模光纤作为传感臂.利用有限元仿真和理论分析,确定耦合器和传感臂的最优长度为15 mm.在无芯光纤中激发出的高阶模进入单模光纤的包层传输,由于倏逝场的作用,受到环境折射率和温度的影响.选取透射谱不同干涉级次的波谷作为研究对象,实现了折射率和温度的同步测量.实验结果表明:1545 nm附近干涉谷的折射率和温度灵敏度分别为–153.89 nm/RIU(refractive index unit)和0.166 nm/℃;1570 nm附近干涉谷的折射率和温度灵敏度分别为–202.74 nm/RIU和0.183 nm/℃.该传感器在实现折射率和温度同步测量的同时,仍能保持较高灵敏度,在生物医疗等方面有着较好的应用前景.     

Numerical study on lateral mode behavior of 660-nm InGaP/AlGaInP multiple-quantum-well laser diodes

Theoretical analysis for InGaP/AlGaInP laser diodes with different ridge waveguide structures is performed to investigate the lateral mode behavior using advanced device simulation. The internal physical mechanisms including temperature-induced changes in the refractive index profile, spatial hole burning effect, lateral carrier distribution, and gain profile variation with increasing input current are discussed by theoretical calculation to analyze the effects of different ridge structures on the lateral mode behavior of 660-nm AlGaInP laser diodes. The simulation results show that the use of narrow and shallow ridge geometry is the approach to obtaining single mode operation. Furthermore, it is found that the different values of the ridge height cause the lateral carrier distribution within the active region to be varied, which is also an important factor in determining the emergence of the first order lateral mode in addition to the geometry-dependent waveguide cutoff condition.     

半导体激光器列阵的有限元分析

本文利用有限元法对四种半导体激光器列阵进行了分析,得到了超模的近场强度分布,为实现最低阶超模的均匀强度分布提供了一些可能的结构.     

Propagation length of surface plasmon polaritons excited by a 1D plasmonic grating

The propagation length of surface plasmon polaritons (SPPs) is investigated experimentally using a 1D metallic grating fabricated on a higher refractive index substrate (Gallium Phosphide, GaP). The experimentally measured value propagation length of the SPP (L_SPP) at 785 nm wavelength is 13.33 ± 0.13 μm, which is close to the theoretical value of the L_SPP on an ideal Au-thin film. The SPP resonance observed in far-field measurements confirms the underlying process and the related effects on the L_SPP measured by scanning near field optical microscope (SNOM). Far-field measurements shows that L_SPP is associated with the full width at half maximum (FWHM) of the SPP resonance which in-turn associated with in-plane directional scattering of the SPP.     

带有增益介质层的混合脊状等离子体波导的传输特性

在传统脊状等离子体波导的基础上设计了一种带有增益介质层的新型混合脊状等离子体波导,其结构中的介质层部分包含两个区域:前区为单一介质,后区的脊是由2种介质构成的双层脊区。采用二维时域有限差分方法分析了波导结构的传输特性,得到了TM模下的电场分布图,并对输出功率以及传输损耗与结构参数和介质折射率的变化规律进行了讨论。结果表明,在波导中引入的增益介质材料磷化铟后其损耗达到-6 dB/μm。此种波导结构对于光集成芯片的研究与制作具有重要意义。     

聚合物波导M-Z调制器TM模的泰勒级数展开法研究

根据聚合物脊型波导的结构特点,利用有效折射率法求出其横向折射率分布,将三维传播转化为二维传播,并从标量波动方程出发,在傍轴近似的情况下,采用Crank-Nicholson差分格式,得到了泰勒级数展开法基本计算格式,并对算法进行了适当优化;通过对Mach-Zehnder光波导TM模的模拟,分析了各种参数对损耗的影响。结果表明：泰勒级数展开法具有精度高、稳定性好、算法简单、易于编程等优点,是一种比较理想的光波导数值分析方法,可为聚合物电光调制器的设计制作提供理论参考。