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Effect of Conduction Band Non-Parabolicity on the Nonlinear Optical Properties in GaAs/Ga1?xAlxAs Double Semi-V-shaped Quantum Wells
摘要： In this paper, we investigate the effect of conduction band non-parabolicity (NPBE) on the third harmonic generation(THG), the linear and nonlinear intersub-band optical absorption coefficients (OACs) related with electronic states of double semi-V-shaped GaAs/Ga1?x Alx As quantum wells(QWs) by using the compact-density-matrix approach. Simultaneously, the work is performed in the position dependent effective mass in order to compute the electronic structure for the system by the finite difference and self-consistent techniques. We also compare the results with and without considering NPBE. It is found that: (1) the NPBE has a significant influence on the sub-band energy levels of double semi-V-shaped QWs, and (2) the amplitude and position of the resonant peaks of the THG and nonlinear OACs in the case of considering NPBE show complicated behavior due to the energy dependent effective mass m*(E) where the energy value was chosen self-consistently.
关键词： finite difference method,non-parabolicity effect,double quantum wells,optical properties
更新于2025-09-23 15:22:29
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PRECISE FINITE DIFFERENCE ANALYSIS OF LORENTZ FORCE ACTING ON METAL NANOPARTICLE IRRADIATED WITH LIGHT
摘要： A ?nite di?erence method in the frequency domain is evaluated to clarify characteristics of the Lorentz force exerted on a metal nanoscale particle by light irradiation. Numerical results are compared with exact values obtained from Mie theory to show that applying a smoothing algorithm to the surface of a nanoparticle increases the accuracy of the simulation. Analysis of the Lorentz force exerted between two spheres aligned closely indicates that strong forces cause the spheres to attract each other at the plasmon resonant frequency. It was also noticed that application of the smoothing algorithm was indispensable in order to achieve the above result.
关键词： plasmon resonance,finite difference method,Lorentz force,light irradiation,metal nanoparticle,Mie theory
更新于2025-09-23 15:21:01
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Gain characteristics of the hybrid slot waveguide amplifiers integrated with NaYF <sub/>4</sub> :Er <sup>3+</sup> NPs-PMMA covalently linked nanocomposites
摘要： Waveguide amplifiers based on slot waveguide have enormous capacity due to their ability to confine light strongly to a narrow slot waveguide. NaYF4:Er3+ nanoparticles-polymeric methyl methacrylate covalently linked nanocomposites were synthesized and filled into the slot. The stability and the Er3+ concentration doped in this novel material were improved. The slot waveguide was designed accurately. The rigorous numerical method, full-vector finite difference method, was used to analyze the modal characteristics and optimize the slot combined with the maximum power confinement in the slot and the minimum effective mode area of the slot. A four-level spectroscopic model pumped at 1480 nm was presented. The rate equations and propagation equations were solved and the gain characteristics of the slot waveguide amplifier were numerically simulated. The primary parameters were optimized. A net gain of 5.78 dB was achieved when the signal power was 0.001 mW at 1530 nm, pump power was 20 mW, Er3+ concentration was 1.3 (cid:1) 1027 m(cid:3)3, and the waveguide length was 1.5 cm.
关键词： NaYF4:Er3+ NPs-PMMA,slot waveguide,erbium-doped polymer waveguide amplifier,full-vector finite difference method,gain characteristics
更新于2025-09-23 15:19:57
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The effects of close packing and electric fields on the optical properties of three-dimensionally stacked quantum dots
摘要： An algorithm to evaluate the position of spherical quantum dots in a closely packed state inside a cube is presented and its accuracy confirmed numerically. A finite-difference method to solve the corresponding three-dimensional Schr?dinger equation in the presence of an external electric field is then described. The Arnoldi factorization method is used to diagonalize the resulting huge sparse matrix. The results reveal that both the intensity and direction of the electric field can significantly change the height of the absorption peak and are thus both important. Two different semiconducting structures, viz. GaAs/AlxGa1?xAs and InSb/GaSb, are investigated, revealing that the latter exhibits a more tunable absorption coefficient. The effect of the composition parameter x on the mentioned optical properties is also studied. The combination of this and earlier work indicates that photodetection in the wide range of 1.2–8.4 THz is possible. The proposed structure can thus be regarded as a possible candidate for use in photodetection devices in different fields of industries such as imaging, medicine, and materials characterization.
关键词： Close packing effect,Electric field,Finite difference method,Absorption coefficient,Three-dimensionally stacked quantum dots
更新于2025-09-16 10:30:52
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Applications of Silicon Photonics in Sensors and Waveguides || New Approach to Mach-Zehnder Interferometer (MZI) Cell Based on Silicon Waveguides for Nanophotonic Circuits
摘要： In this chapter, we present a new scheme for Mach-Zehnder Interferometer (MZI) structure based on only one 4×4 multimode interference (MMI) coupler. We design the new MZI cell on the silicon on insulator (SOI) platform. The MZI based on directional coupler and 2×2 MMI coupler is also investigated in detail. The new MZI cell is a basic building block for photonic applications such as optical quantum gate, optical computing and reconfigurable processors. The numerical simulations show that our approach has advantages of compact size, ease of fabrication with the current complementary metal oxide semiconductor (CMOS) circuitry.
关键词： multimode interference,finite difference time difference,directional coupler,modified effective index method,multimode waveguide,finite difference method,silicon on insulator
更新于2025-09-11 14:15:04
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DESIGN AND SIMULATION OF ARBITRARILY-SHAPED TRANSFORMATION OPTIC DEVICES USING A SIMPLE FINITE-DIFFERENCE METHOD
摘要： A fast and simple design methodology for transformation optics (TO) is described for devices having completely arbitrary geometries. An intuitive approach to the design of arbitrary devices is presented which enables possibilities not available through analytical coordinate transformations. Laplace’s equation is solved using the ?nite-di?erence method to generate the arbitrary spatial transforms. Simple techniques are presented for enforcing boundary conditions and for isolating the solution of Laplace’s equation to just the device itself. It is then described how to calculate the permittivity and permeability functions via TO from the numerical spatial transforms. Last, a modi?cation is made to the standard anisotropic ?nite-di?erence frequency-domain (AFDFD) method for much faster and more e?cient simulations. Several examples are given at the end to benchmark and to demonstrate the versatility of the approach. This work provides the basis for a complete set of tools to design and simulate TO devices of any shape and size.
关键词： transformation optics,finite-difference method,Laplace’s equation,electromagnetic simulation,anisotropic materials
更新于2025-09-10 09:29:36