离子注入铌酸锂平面波导双折射特性的研究

为了获得折射率信息,采用UT00-FPD型椭偏仪对5mm×10mm×1mm铌酸锂晶体及注入镓的铌酸锂晶体波导的双折射特性进行了测量.首先对铌酸锂晶体测量结果进行建模及数据处理,得到晶体在190nm～1700nm之间的双折射特性;在此模型的基础上,进一步对注入镓的铌酸锂晶体波导进行了建模和数据处理,得到了波导层的双折射率的分布.所得表征结果为铌酸锂晶体波导在光子器件中的应用提供了有用的信息.     

铌酸锂波导调制器的相位漂移机理

铌酸锂波导调制器的相位漂移是其主要失效模式之一.分析了外电场、温度、机械应力等外场作用对铌酸锂波导调制器相位稳定性能的影响,并提出了相应的解决措施,以提高铌酸锂波导调制器的调制相位稳定性.     

质子交换铌酸锂波导的退火工艺

介绍了质子交换铌酸锂波导的制作工艺，比较分析了不同切向、不同退火温度、不同退火时间下铌酸锂波导的特性．     

质子交换铌酸锂波导的退火工艺

介绍了质子交换铌酸锂波导的制作工艺,比较分析了不同切向、不同退火温度、不同退火时间下铌酸锂波导的特性。     

铌钽酸锂固溶体光波导

未来光纤维通讯和集成光学信息处理系统需要宽带、高速和低功耗光波导器件。钽酸锂和铌酸锂具有电光和声光性能,并容易制成传播损耗低于1分贝/厘米的高质量光波导,也可以制成除了光源和检测器以外的单片集成光路和功能件,因而是重要的集成光学材料。我们在钽酸锂衬底上固态扩散铌金属,研制出铌钽酸锂固溶体光波导(以下简写为LNT波导),对此进行了初步测量和理论分析。     

H:LiNbO3光波导

铌酸锂晶体具有良好的光声和电光性质，因而基于铌酸锂的集成光学器件已引起人们的广泛关注。质子交换法是一种制备铌酸锂光波导的重要方法。质子交换铌酸锂光波导具有制作工艺简单，折射率增量大，抗光折变能力强及可实现单偏振激励等特点。本文对质子交换铌酸锂光波导的制作工艺、波导特性及其应用进行了讨论，并指出目前应加强质子交换光波导、质子交换生长动力学和交换工艺的研究。     

光电子技术

O43 2010020259铌酸锂电光长周期波导光栅/郑建成,金伟,刘晴(香港城市大学电子工程学系)//电子科技大学学报.―2009,38(5).―544～549.该文对用铌酸锂制作电光长周期波导光栅的研究进展进行了综述。讨论了用铌酸锂制作长周期光栅的难点,介绍了解决该难点所用的特殊铌酸     

铌酸锂光波导制作工艺进展

文章综述了几种常用的铌酸锂波导的制作工艺,包括表面外扩散、金属内扩散、离子交换和质子交换,并分析、比较和总结了在不同工艺制作的条件下对铌酸锂光波导的性能造成的不同影响。目前,获得高质量光波导的主要途径是Ti扩散和质子交换。同时,文章对逐渐建立起的铌酸锂波导光学特性和结构特性之间的理论关系也进行了介绍。     

LiNbO3电光调制器的优化设计与制作

铌酸锂晶体有良好的光声和电光性质,因而基于铌酸锂的集成光学器件已引起人们广泛关注。利用LiNbO3作为介质材料,设计M-Z干涉型强度调制器。选用低损耗的质子交换光工艺技术制备光波导。对质子交换铌酸锂光波导的制作工艺、波导特性及其应用进行了研究。对电极结构进行了优化设计。     

全息法研究LN和Mg:LN晶体波导基片的光损伤

本文报道了用全息法研究铌酸锂(LN)晶体和掺镁铌酸锂(Mg:LN)晶体波导基片光损伤的结果。分别采用钛扩散和质子交换工艺制作波导基片;其中Mg:LN晶体波导基片的抗光损伤能力高于LN基片,质子交换波导片的抗光损伤能力高于钛扩散波导片。     

Local normal-mode analysis of second harmonic generation in aperiodic waveguide

A new theoretical analysis method based on the local normal-mode expansion is proposed for analysis of optical second harmonic generation (SHG) under quasi-phase-matching in a waveguide with a periodic structure. Nonlinear coupled mode equations, SHG efficiency, and effective SHG coefficient are derived. In addition, SHG devices quasi-phase-matched with corrugation and with periodic domain inversion are studied analytically and numerically. The results are compared to those obtained by the conventional ideal normal-mode expansion. It is shown that in a corrugated waveguide the local normal-mode expansion method presents a different result from the ideal normal-mode expansion since the periodic variation of the modal field profile is dominant in the quasi-phase-matching process. On the other hand, in the periodically domain-inverted ferroelectric waveguide, it is shown that the variation of the modal field profile is sufficiently small and both expansion methods coincide with each other     

Broadening of the phase-matching bandwidth in quasi-phase-matchedsecond-harmonic generation

We report on theoretical analysis and experiments for bandwidth broadening in quasi-phase-matched (QPM) second-harmonic generation (SHG) in LiTaO₃. QPM waveguides consisting of segments, where each segment has a phase-matching condition different from the others, are proposed to obtain a broad bandwidth and simultaneously, a high SHG efficiency. The waveguides were fabricated by adjusting the phase-matching condition either by changing the grating period of the SHG coefficient or by controlling the width of the waveguide. Consequently, the bandwidth of QPM-SHG was broadened to 0.35 nm with an SHG efficiency of 57 percent/W by modulation of the waveguide width and to 1.12 nm with an SHG efficiency of 29 percent/W by modulation of the grating period. The SHG efficiency and phase-matching characteristics in both types of waveguides showed good agreement with theoretical results     

Coupled-mode analysis of second harmonic generation in the form ofCerenkov radiation from a channel optical waveguide

Optical second-harmonic generation (SHG) in the form of Cerenkov radiation from a channel waveguide is analyzed by a coupled-mode theory. A simple formula is given which expresses the SHG efficiency in terms of waveguide and optical nonlinear parameters and by which one can simulate the radiation pattern of SHG. Computational examples are plotted for LiNbO₃ crystals and reasonably agree with reported results. The analysis shows that the efficiency could be increased significantly if the sign of a d-constant in a substrate were modulated with a proper period     

Variations of optical M-waveguides for direct phase matching inAlGaAs

Two variations of an optical indexwise M-shaped waveguide structure in AlGaAs are presented as results of numerical simulations. The principal differences of the waveguiding aspects are discussed. The impact of the optical layer thicknesses is investigated with respect to phase matching and conversion efficiency for second-harmonic generation (SHG). Despite large differences in the interacting mode distributions, both waveguide configurations yield comparable nonlinear normalized conversion efficiencies. The technologically simple waveguide designs represent an attractive alternative for phase matched SHG     

Broadband quasi-phase-matched second-harmonic generation in MgO:LiNbO3 waveguide

The quasi-phase-matched(QPM) condition of broadband second harmonic generation(SHG) in Ti-diffused MgO:LiNbO3 waveguide is theoretically simulated.The results show that the center wavelength of broadband SHG dependent on the waveguide width is around 1550 nm and the bandwidth is 50 nm.     

High-Power, Highly Efficient Second-Harmonic Generation in a Periodically Poled ${hbox {MgO}}{:}{hbox {LiNbO}}_{3}$ Planar Waveguide

We designed a single-pass quasi-phase-matched second-harmonic generation (SHG) device with a planar waveguide; the device comprised a Y-cut 5 mol% MgO-doped LiNbO₃ (MgO:LiNbO₃)crystal core that was 3 mum thick and SiO₂ cladding. The waveguide provided a high coupling efficiency of 95% between an incident Gaussian beam and the fundamental guided mode of a fundamental wave; it also provided high electric-field confinement in the case of both the fundamental and SHG waves in the core. Thus, a high overlap between nonlinear polarization and an SHG-guided mode was attained. The bonding of the device with the waveguide side positioned downward to a heat sink provided a large heat radiation area when pumping with a near-collimated Gaussian beam, which reduced the temperature rise and its gradient along the waveguide to minimize the phase mismatch. We demonstrated the green light generation of 1.6 W with 40% conversion efficiency using a 7-mm-long sample and 1.2-W SHG with 60% efficiency using an 18-mm-long sample.     

Broadband second-harmonic generation in a tapered PPLN waveguide

We demonstrate a period poled tapered lithium niobate waveguide and study second harmonic generation (SHG) in this device for the purpose of broadening the quasi-phase matching (QPM) acceptance bandwidth. The finite-difference beam-propagation method is used to simulate the guided modes and calculate the effective indices. The simulation results show that by tapering the width of the cross section linearly, the phase mismatch between a specific input wavelength and its SHG signal can be varied along the propagation length. Ideal SHG phase-matching conditions for a wide range of input wavelengths in communication band from 1 542.5 nm to 1 553.5 nm can be satisfied in different positions of the waveguide.     

Theory on phase-matched second-harmonic generation in biaxialplanar waveguides

A theoretical study on the optimization of second harmonic generation (SHG) in a planar waveguide in a biaxial nonlinear material is presented. Numerically computed curves show the dependence of the SHG efficiency on the condition of lateral focusing in the planar waveguide, of double refraction and of phase matching. The calculations take full account of double refraction and diffraction in the paraxial approximation in the planar guide. It is shown that in the absence of double refraction and under optimum focusing conditions the generated second harmonic power increases in proportion to L^3/2, where L is the length of the planar waveguide     

40-GHz picosecond-pulse second-harmonic generation in an MgO-doped PPLN waveguide

Second-harmonic generation (SHG) of 40-GHz picosecond optical pulses with different pulsewidths, pulse energies, and central wavelengths in a MgO-doped periodically poled lithium niobate (PPLN) waveguide is studied experimentally and theoretically. In the experiments, the picosecond pulses are generated from a 40-GHz mode-locked fiber laser and two tunable filters, with which the lasing wavelength can be tuned from 1530 to 1570 nm, and the pulsewidth can be tuned from 2 to 7 ps. The second-harmonic (SH) pulses are generated when the picosecond pump pulses pass through the MgO-doped PPLN waveguide. Dependences of SHG on pump pulsewidth, average pump power, and pump central wavelength are then investigated systematically. Meanwhile, dynamic behaviors of both pump and SH pulses in propagation are simulated numerically. Based on the temporal and spectral characteristics of SHG, a quantitative and systematic analysis on SHG efficiencies in terms of both pulse energy and spectral peak is presented. The simulation results are in good agreement with the measured data.     

LiNbO/sub 3/ waveguide SHG device with ferroelectric-domain-inverted grating formed by electron-beam scanning

A ferroelectric-domain-inverted grating was fabricated by electron beam scanning in LiNbO/sub 3/. A waveguide second harmonic generation (SHG) device with the grating was fabricated and demonstrated for the first time. The experiments were performed using a CW-Nd:YAG laser, and normalised SHG conversion efficiency of 50%/W was obtained.<>