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 共查询到20条相似文献,搜索用时 703 毫秒
1.
We introduce a new technique to excite multiple waveguides in fs laser written waveguide arrays. Using a microstructured grating, we were able to couple almost all of the power of the laser beam into multiple waveguides in one- and two-dimensional lattices. Tilting the sample a defined phase shift between adjacent waveguides can be obtained, which allows anomalous diffraction and refraction to be studied. PACS 42.79.-e; 42.79.Gn; 42.82.Et; 42.25.Kb  相似文献   

2.
We present a fully planar integrated optical approach to single-molecule detection based on microfabricated planar networks of intersecting solid and liquid-core waveguides. We study fluorescence from dye molecules in liquid-core antiresonant reflecting optical waveguides, and demonstrate subpicoliter excitation volumes, parallel excitation through multiple pump waveguides, and single-molecule detection sensitivity. Integrated silicon photonics combined with single-molecule detection in solution create a compact, robust, and sensitive platform that has applications in numerous fields ranging from atomic physics to the life sciences.  相似文献   

3.
Transmission properties of photonic crystal (PC) waveguides with discretely modulated exit surfaces are investigated numerically using the finite-difference time-domain (FDTD) method. Unlike the case of periodically modulated surfaces, where the transmission beam tends to be a single and directional beam, when the exit surfaces are modulated only at several discrete points, the emission power tends to split into multiple and directional beams. We explain this phenomenon using a multiple point source interference model. Based on these results, we propose a 1-to-N beam splitter, and numerically realized high efficiency coupling between a PC sub-wavelength waveguide and three traditional dielectric waveguides with a total efficiency larger than 92%. This simple, easy fabrication, and controllable mechanism may find more potential applications in integrated optical circuits.  相似文献   

4.
We present results on the fabrication and characterization of ridge waveguides in zinc-substituted lithium niobate. High-quality waveguides were fabricated by a combination of liquid-phase epitaxy and multiple applications of ion-beam enhanced etching. The two major demands on ridge waveguides, a very low side-wall roughness and a rectangle shape with side-wall angles close to 90 degrees , were realized simultaneously by using this technique. Single-mode waveguiding at a wavelength of 1064 nm was demonstrated with attenuation values of 0.9 dB/cm.  相似文献   

5.
Enhanced second-harmonic generation (SHG) conversion efficiency was theoretically predicted in waveguide geometry with coupling to a one-dimensional grating photonic band gap (PBG). We report a series of experiments using samples made with lithium niobate. A waveguide was fabricated near the surface by applying the proton-exchange technique. The characteristics of waveguide modes were determined by several techniques: prism coupling, diffraction, and Cherenkov radiation. The WKB method was used to analyze the results. Ultraviolet laser lithography was applied to make PBG gratings on the sample. We further investigated Cherenkov second-harmonic generation (CSHG), i.e., SHG radiated into the substrate, under the condition of a band-edge PBG resonance in the waveguides. The SHG inside planar waveguides was also experimentally investigated. We fabricated waveguides with multiple pump modes and found that the second mode was more efficient in enhancing the second harmonic signal. This result is explained by our model. Several samples were investigated in detail; the highest conversion efficiency of CSHG with a PBG was enhanced around 50 times above the CSHG signal without a PBG. A numerical model was constructed with parameters calculated from our sample characterization data to interpret the experimental results.  相似文献   

6.
Xu Y  Lee RK  Yariv A 《Optics letters》2000,25(10):755-757
We study adiabatic transformation in optical waveguides with discrete translational symmetry. We calculate the reflection and transmission coefficient for a structure consisting of a slab waveguide that is adiabatically transformed into a photonic crystal waveguide and then back into a slab waveguide. The calculation yields high transmission over a wide frequency range of the photonic crystal waveguide band and indicates efficient coupling between the slab waveguide and the photonic crystal waveguide. Other applications of adiabatic mode transformation in photonic crystal waveguides and the coupled-resonator optical waveguides are also discussed.  相似文献   

7.
We report difference frequency generation-based wavelength converters with multiple phase-matching wavelengths that use engineered quasi-phase-matching structures in LiNbO(3) waveguides. Multiple-channel wavelength conversion is demonstrated within the 1.5-mum band and between the 1.3- and 1.5-mum bands. With simultaneous use of M pump wavelengths, these devices can also be used to perform wavelength broadcasting, in which each of N input signals is converted into M output wavelengths.  相似文献   

8.
Watanabe W  Note Y  Itoh K 《Optics letters》2005,30(21):2888-2890
We report on the fabrication of multimode interference (MMI) waveguides that split single-mode light into multimode light in synthesized silica by use of femtosecond laser pulses. The number of modes at the output facet is dependent on both the width and the length of the MMI waveguides. The output spectral responses of the MMI waveguides in the visible region were examined. The fabricated MMI waveguides can be used as compact power splitters with large fan-outs.  相似文献   

9.
A rigorous analysis and design of efficient coupling from photonic crystal (PhC) waveguides into conventional dielectric waveguides is reported. Closed-form expressions for the reflection and transmission matrices that completely characterize the scattering that occurs at the interface are derived based on an eigenmode expansion technique and a Bloch basis. Analytic expressions are used to analyze the reflection into PhC waveguides. We obtain that negligible reflection can be achieved by choosing a certain interface within a PhC unit cell. Furthermore, analytic expressions are used to design a novel and compact coupler structure in order to achieve high coupling efficiency when broad dielectric waveguides are considered. Thereby, transmission efficiencies near 100 from the fundamental guided Bloch mode into the fundamental waveguide mode are achieved.  相似文献   

10.
潘文峰  李卓球 《计算物理》2008,25(2):191-196
研究三维海洋波导中多障碍物的声散射问题.基于Galerkin变分原理和DtN映射方法,发展一种自然边界元与有限元耦合的求解方法,提出有效的数值实现方法,避免常规有限元中需要采用吸收边界的缺点.对多种形状多障碍物的数值计算结果表明,所建立的理论方法是有效的.  相似文献   

11.
《Physics letters. A》2005,335(4):316-326
We present numerical calculations of the energy dispersion of spin-polarized electrons in quasi-one-dimensional electronic waveguides in the presence of Rashba spin–orbit interaction (SOI), by using an efficient expanded basis method. Within this model, the general mixing between any two subbands is taken into account. We investigate the properties of spin-polarized transport in the nonuniform SOI system. It is found that the multi-band mixing brings significant effects on the properties of multiple subbands transport in the regime of high energy, especially for the cases of the wide waveguide, the strong SOI and the long extension of the SOI region.  相似文献   

12.
A. Bahrami  A. Rostami  F. Nazari 《Optik》2011,122(20):1787-1790
We propose an all-optical switch (AOS) based on Mach-Zehnder (MZ) and Multi-mode interference (MMI) using nonlinear closely coupled waveguides. The device operates by switching between two states of coupled waveguides. In first state the refractive index of waveguides are same and light field will completely couple to nonlinear waveguide in half length of coupler and will back in the second half. We will have π phase difference in this procedure and the input field will appear in Bar-state output. In the second state the refractive index of nonlinear waveguide increase with high intensity control field. In this case, we have lower coupling and change in phase. But, we choose the best refractive index change to obtain the phase change of multiple of 2π necessary for Cross-state in output. The beam propagation method is used to simulate the device operation.  相似文献   

13.
《Infrared physics》1989,29(2-4):607-630
We propose a scheme of particle accelerators driven by far-infrared free-electron lasers on the basis of oversized periodically or helically corrugated hollow waveguides with cooled walls of high-Tc superconductors. In this context, we discuss the basic principles of particle acceleration in periodic and helical hollow waveguides, the relevant modes and fields of these waveguides, attenuation and damage threshold in the waveguides assuming walls made of standard metals as well as high-Tc superconductors, and the energy gain of particles for two modes of coupling laser radiation into the waveguides.  相似文献   

14.
We demonstrate the design, fabrication, and characterization of single-mode low-loss waveguides for mid-infrared (MIR) wavelengths. Planar waveguide structures were fabricated from multilayer thin films of arsenic-based chalcogenide glasses followed by the creation of channel waveguides by using the photodarkening effect. Propagation losses as low as 0.5 dB/cm were measured for a quantum cascade laser end-fire coupled into the waveguides. This is a first step toward the design and fabrication of integrated optical components for MIR applications.  相似文献   

15.
The optical guided modes in the plane array of metallic cylindrical waveguides are considered. The case of the arbitrary propagation constant β is studied. Thus far, only the case β = 0 has been investigated in literature. We have revealed that just for β ≠ 0, the new branch of guided modes appears. The case of silver waveguides is investigated in details. It is found that, for sufficiently small β, the dispersion curve for the guided mode is located below the transmission window. We found the conditions for which the dispersion curve with β ≠ 0 is located completely within the transmission window. The multiple scattering formalism based on the expansion in the vector cylinder harmonics is employed. The cases of copper and gold waveguides are discussed briefly.  相似文献   

16.
We report room-temperature quantum-confined Stark effect in Ge/SiGe multiple quantum wells (MQWs) with light propagating parallel to the plane of the Ge/SiGe MQWs for applications in integrated photonics. Planar waveguides embedded in a p-i-n diode are fabricated in order to investigate the absorption spectra at different reverse bias voltages from optical transmission measurements for both TE and TM polarizations. Polarization dependence of the absorption spectra of the Ge/SiGe MQWs is clearly observed. The planar waveguides exhibit a high extinction ratio and low insertion loss over a wide spectral range for TE polarization.  相似文献   

17.
梯形截面多量子阱脊形波导模式特性   总被引:1,自引:0,他引:1  
本文根据多量子阱双折射率的性质,运用有效折射率法和WKB法对具有梯形截面多量子阱脊形波导的模式特性作了分析,导出了Emnx模和Emny模的本征值方程.  相似文献   

18.
We study efficient injectors for coupling light from z-invariant ridge waveguides into slow Bloch modes of single-row defect photonic crystal waveguides. Two-dimensional vectorial computations performed with a Bloch mode theory approach predict that very high efficiencies (>90%) can be achieved for injector lengths of only a few wavelengths in length, even for small group velocities in the range of c/100-c/400. This result suggests that photonic crystal devices operating with slow waves can be interfaced with classical waveguides without sacrificing compactness.  相似文献   

19.
We compare coupling between parallel waveguides within one-dimensional photonic crystals and coupling between conventional waveguides. We consider the situation in which coupling between the waveguides is minimized, so that light in the waveguides propagates essentially independently. Subject to this condition, we compare the minimum mutual distance between conventional planar waveguides and waveguides in one-dimensional photonic crystals. We find that the packing densities of the conventional and periodic structures are comparable.  相似文献   

20.
We propose a wavelength router design to improve insertion loss uniformity. Branched waveguides are placed at junctions between the waveguide array and a planar waveguide. The diffracted light injected into planar waveguides is forwarded in different directions. At the image plane of the planar waveguide, a flat top envelope is attained to ensure loss uniformity among output ports.  相似文献   

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