【作者】 刘涛；

【导师】 王雪林；

【作者基本信息】 山东大学 ， 凝聚态物理， 2014， 博士

【摘要】 光波导是信号传输的通道和元器件的连接装置,不仅是集成光电子器件的基础,也是光通信的基础。光波导结构可以把光束限制在比较小的区域内传输从而提高光密度,加强波导中的光学现象,有益于波导器件及集成光路的应用。因此,制备性能优良的波导结构并研究其性质是集成光学领域重要的研究课题。目前,红外技术在国防、国民经济和科学研究中得到广泛的应用,并受到商业领域的密切关注。红外光线在通讯、探测、医疗、军事等方面占有重要地位,如红外成像、红外侦察、红外跟踪、红外制导、红外预警、红外对抗等,在现代和未来战争中都是很重要的战略与战术手段；红外波段的光电子器件在大气检测与环境监测、自由空间光通讯、红外测试、清洁能源、煤矿安全、分子光谱测量、激光医疗和生物技术等领域也表现出巨大的应用潜力。波导结构用于光的传输和各元件之间的相互连接,是集成光电子器件的基础元件,其性能的优劣对红外波段光电子器件的性能起着决定性作用。鉴于波导结构重要的应用价值,人们已经研究出多种方法来制备波导结构,主要有离子注入、快重离子辐照、离子交换、离子扩散、薄膜沉积、聚焦质子束直写和飞秒激光直写等。其中,离子注入和快重离子辐照是其中两种载能离子束制备波导的方法,通过载能离子与光学材料发生作用,改变材料的折射率形成波导结构。该工艺中的离子能量、剂量和形成波导层的厚度可精确控制,对材料的选择性较少并且稳定可调,已经较为相对成熟。载能离子束辐照技术可与光刻等多种微加工方法相结合制备出不同特性的光电子器件。到目前为止,人们已经利用载能离子束辐照的方法在晶体、半导体、玻璃以及聚合物等多种光学材料上成功制备了波导结构。本论文的工作重点是利用离子注入和快重离子辐照的方法结合光刻工艺在光学材料上制备可见和红外波段的平面及条形光波导,研究光波导在可见和红外波段的光学传输特性、离子注入或辐照前后光学材料的损伤特性、光谱特性等变化。本文主要涉及的光学材料为红外波段透光材料,主要有单晶材料(铌酸锂、偏硼酸钡、硫化锌、硒化锌、硫化镉、掺钕硅酸铋)、多晶材料(硫化锌)和玻璃态材料(硫系玻璃、熔融石英)。波导特性主要包含波导模式的有效折射率、折射率分布、模场分布以及损耗特性等。表征波导特性的方法有很多种,本论文中主要采用的理论和实验表征方法有：基于Monte-Karlo的SRIM (The Stopping and Range of Ions in Matter)软件模拟离子辐照过程中离子的射程、分布、离散、电子和核能量损失分布等；反射计算方法(Reflectivity calculation method, RCM)或强度计算方法(Intensity Calculation Method, ICM)重构光波导结构的折射率分布；有限差分光束传输方法(finite difference beam propagation method, FD-BPM)用于模拟光波导的模场分布,其结果与实验结果进行比较,从而验证实验的可行性；棱镜耦合方法用于测试633nn和1539nm波长下衬底材料的有效折射率和离子辐照后光强随入射角度的变化曲线；端面耦合法用于测试平面和条形波导结构在可见和红外波段的光学传输情况,并结合背散射(Back-Reflection)法测试平面波导结构的传输损耗；退火处理可以优化波导特性,利于波导特性的测试。除此之外,为了更好的研究离子辐照对光学材料性质的影响,我们采用了拉曼光谱、吸收谱等谱线测试的方法表征离子辐照后光学材料的损伤特性。基于以上表征方法,我们所取得的研究结果如下：II-VI族化合物半导体材料由元素周期表中的ⅡA族与VIA族构成的。Ⅱ-VⅥ族化合物半导体材料具有离子键成分比较大,禁带宽度变化范围大以及直接跃迁的能带结构等优点,在固体发光、激光、红外和压电效应等器件方面有广泛的应用。论文中采用的Ⅱ-Ⅵ族化合物半导体材料包括硫化锌(ZnS)、硫化镉(CdS)和硒化锌(ZnSe)晶体。我们利用能量为6.0MeV的碳离子分别注入上述三种晶体形成平面光波导结构,并结合光刻工艺制备了条形波导结构。条形波导结构制备中光刻胶的周期均为50μm,光刻胶空白区域为7μm。利用金相显微镜观察了抛光后的平面和条形波导的端面形貌,棱镜耦合仪测试了平面光波导结构在633nm和1539nm波长下的导模特性,并采用端面耦合测试系统得到了可见和近红外波段的近场光强分布。此外,我们利用多晶硫化锌材料的色散关系方程计算该材料在1300nm波长下的衬底折射率值。结果表明,能量为6.0MeV的碳离子注入该类型材料制备的波导结构主要依靠光学位垒限制光的传输。由于离子注入的过程中形成色心会影响样品的透过率,因此我们采用分光光度计测量离子注入前后样品吸收谱线的变化。该研究结果为离子注入红外材料制备可见和红外波段光波导结构提供了可行性依据。铌酸锂(LiNbO3)不仅是最早被人们深入研究的人工晶体之一,而且是少数经久不衰、并源源不断开辟应用新领域的非常重要的功能材料。LiNbO3是一种集压电、铁电、电光、光弹、热释电、光折变、非线性等功能于一身的多功能晶体材料,有光学“硅”材料之称,其透光范围大,是制备可见和红外波段光学元器件的首选材料之一。到目前为止,离子注入或辐照LiNbO3晶体的研究已经相对成熟。本论文中采用同成分化学计量比铌酸锂晶体,同成分点一般在Li/Nb=48.3/51.7-48.6/51.4之间。本文中采用能量和剂量分别为1.7GeV和1×1011ion/cm2的氪离子辐照LiNbO3晶体,研究辐照后该晶体的光学性质,在633nm波长下测得辐照层的近场光强分布分为两层,具有明显的界限。在4μm波长的端面耦合测试系统上测得快重氪离子辐照LiNbO3晶体的近场光强分布图。利用显微共聚焦微拉曼仪测得离子辐照层不同深度位置的拉曼谱线显示拉曼峰的位置和展宽等几乎没有变化,而拉曼峰的强度随着离子遂穿路径发生变化。基于实验测试结果,根据色散关系方程计算得到铌酸锂晶体在红外波长(4μm)的有效折射率值,结合SRIM模拟的能量损失曲线,重构红外波段折射率分布曲线。硫系玻璃由相对原子质量较大的原子(S, Se,Te,Ge,As, Sb等)组成,结构稳定,具有较高的折射率和良好的红外透过性,在民用、医学和军事等领域都有重要的应用价值。本文中采用低剂量、高能量的氪离子辐照玻璃材料80(0.8GeS2-0.2Ga2S3)·20CdI2(简写为GGC20),实验结果表明利用快重离子辐照红外玻璃材料可以有效地制备红外波段波导结构。偏硼酸钡(BaB2O4, BBO)晶体是我国科学家在1984年研制成功的具有国际影响力的人工晶体,具有大的双折射率和非线性光学系数、高的抗光损伤阈值、较宽的位相匹配范围和透光波段(189nm-3500nm),是一种理想的紫外双折射晶体。我们用能量和剂量分别为(500+550)keV和(1+2)×1016ion/cm2的质子注入BBO晶体制备平面光波导。多能量离子注入制备波导结构能够加宽光学位垒,使得波导结构更好的限制光的传输。为防止注入过程中样品表面破损,我们采取注入前高温退火处理。端面耦合测试结果表明多能量质子注入在偏硼酸钡晶体上制备的平面波导结构在可见和近红外波段都能限制光的传输。熔融石英(Fused quartz)是氧化硅的非晶态,光学各向同性,具有化学稳定好、热膨胀系数小、导热率低和透光波段宽等一系列的特点,广泛应用于集成光电子器件的制备和生产。本文中采用能量为(5.0+5.5+6.0)MeV和剂量为(1+1+1.5)×1015ions/cm2的C离子注入并结合光刻工艺在熔融石英上制备平面和条形波导结构,分别研究了633nm和1539nm波长下传输特性以及退火过程对波导性质的影响。对离子注入后的样品进行连续退火处理,退火温度范围为260℃～500℃。连续退火的结果表明多能量C离子注入的波导结构具有较好的热稳定性。采用多能量C离子注入制备的波导结构在633nm和1539nm波长下折射率增加的最大值分别为0.013和0.0125。实验结果表明,用多能量C离子注入熔融石英制备的波导结构在633nm和1539nm波长下形成了折射率增加的波导结构,是典型“位垒+势阱”型折射率分布,可以更有效限制光的传输。端面耦合测试结果表明,多能量C离子注入在熔融石英上制备的平面和条形波导结构在可见和近红外波段都能很好的限制光的传输。掺钕硅酸铋(Nd:BSO)晶体具有良好压电、声光效应、旋光特性、线性光电和光电导效应等性质。我们分别利用能量为500keV的He离子和能量为6.0MeV的C离子注入Nd:BSO晶体制备平面波导结构。利用棱镜耦合仪分别测得了退火前后633nm波长下的导模特性曲线,并详细记录和比较了连续退火处理后TEo模的折射率值。实验结果表明用He离子和C离子注入的方式在掺钕硅酸铋晶体上形成的波导结构主要依靠光学位垒层来限制光的传输。更多还原

【Abstract】 Optical waveguide is the basis of the devices in integrated optics and optical telecommunication field, as signal propagation channels and equipments connected some devices with others. Optical waveguide structures allow confinement of the light in small volumes with dimensions of micrometer, which can improve the optical density and enhance many optical performances in the wave-guiding structures. Such a configuration is a promising feature for the practical application of waveguide devices as well as integrated optical circuits. So, the fabrication waveguide structure with high performance and the investigation of properties of waveguide are both important topic in integrated optics.At present, the infrared technology has been widely used in national defense, national economy and scientific research, and pays close attention to in the field of business. Infrared light in such aspects as communication, detection, medical and military have a wide range of applications, such as infrared imaging, infrared detection, infrared tracking, infrared guidance, infrared warning, and infrared countermeasures, which is an important strategic and tactical means in the modern and future war. Infrared optoelectronic devices show great potential application in the atmosphere of the testing and environmental monitoring, free space optical communication, infrared testing, clean energy, coal mine safety, molecular spectroscopy measurement, laser medical and biological technology. As the basis of integrated optoelectronic devices components, the performance of the optical waveguide structure plays a decisive role in the infrared optoelectronic devices.In view of the important application value of optical waveguide structure, several methods have been employed to manufacture optical waveguides, including ion implantation, swift heavy ion irradiation, ion exchange, diffusion, thin film deposition, focused ion beam writing and femtosecond laser inscription. As two kinds of energentic ion beam irradiation, the waveguide structure formed by ion implantation and swift heavy ion irradiation methods through the incident ion colliding with the target ions and changing the refractive index of the layer. The energentic ion beam irradiation has developed into a relatively mature method for waveguide fabrication due to the controllable energy and doses of the implanted ions and the depth of the waveguide layer etc.. Combined with the micromaching technology, such as photolithography technique, energentic ion beam irradiation technology can fabricate optoelectronic devices with different performances. So far, energentic ion beam irradiation technology has been successfully fabricated waveguide in several optical materials including crystals, insulators, glasses and polymer and so on.In this dissertation, we report the fabrication and optical properties of planar or channel waveguide structures formed by energentic ion beam irradiation technology in visible and infrared band. In this paper, we focus on the optical materials with transmitting infrared band, including LiNbO3, BBO, ZnSe, CdS, Nd:BSO, ZnS, glass and fused silica.The effective refractive index of modes, the refractive index distribution, mode field distribution and loss are the main characteristics of waveguide structures. There are many ways for representing the waveguide characteristics and the theoretical and experimental methods in our work are as follows:The Stopping and Range of Ions in Matter (SRIM) is used to simulate the process ion implantation; Reflectivity calculation method (RCM) or Intensity Calculation Method (ICM) is used to reconstruct the refractive index distribution; the plots of the light propagation is simulated by finite difference beam propagation method (FD-BPM); the effective refractive indices of the planar waveguide at633nm and1539nm are measured by the prism-coupling methods; the end-face coupling arrangement is used to measure the near-field intensity distribution of the guided light and the propagation loss the waveguide; annealing treatment can improve the optical properties. In addition, we measured the Raman spectrum and absorption spectrum to represent the damage properties of ion irradiation. Based on the above methods, we do the results are as follows:Compound semiconductor materials of Ⅱ-Ⅵ family is consisted by the family elements of ⅡA and ⅥA in the periodic table, which posses large ionic bond component, large range of forbidden band width and direct transition band structure and presents widely application in the devices of solid light, laser, infrared and piezoelectric effect etc. We have fabricated planar waveguide structure with an energy of6.0MeV on the polycrystal ZnS, CdS and ZnSe crystals and channel waveguide structure on the CdS and ZnSe crystals. The photoresist mask consisted of narrow strips with a period of50μm and a width of7μm. The microscope images of the planar or channel waveguide cross section are collected by a metallographic microscope. We measure the effective refractive indices of the guided modes at the wavelength of633nm and1539nm by prim-coupling measurements. The near-field intensity distribution of the guided light in visible and infrared band is measured by end-face coupling methods. According to the Sellmeier equation for Cleartran ZnS, the refractive index of the substrate at1300nm is estimated. The results show that the waveguide implanted by C ions with energy of6.0MeV can confine light by the barrier layer. The optical absorption spectra before and after implantation are measured by using a Jasco U570spectrophotometer. Our data shows that the ion implantation technique could be of interest for optical waveguide in optical materials in the visible and near-infrared bands.LiNbO3has been one of the most attractive materials due to its outstanding piezoelectric, ferroelectric, electro-optical, photoelastic, pyroelectric, photorefractive and nonlinear properties. The Li/Nb concentration ratio of the LiNbO3in our work is about48.3/51.7-48.6/51.4. Swift heavy ion with high energy and low fluences is used to irradiated on the LiNbO3crystal. A70-μm-thick Al foil is placed before the sample to slow down the incident Kr ions and reduce the ion energy to approximately1.7GeV. The incident Kr ion beam vertically irradiates the Al foil and the surface of the sample. The ion beam fluence is1×1011ions/cm2. The near-field intensity image of the light coupled out of the waveguide at633nm is recorded on the screen. The thickness of the irradiated layer is approximately150μm. There are two dark lines: one line in the irradiated layer and the other line at the end of the ion track in the LN crystal. The near-field intensity profiles at the wavelengths of633nm and4μm are obtained using end-face coupling setups. The Raman spectra at different depths in the Kr-ion-irradiated LN crystal and a virgin LN crystal are measured. The refractive index ne at the wavelength of4Μm in LN crystal is calculated according to the Sellmeier equation. The refractive index profile at a4μm wavelength is then estimated based on the refractive index (ne) profiles at633nm.Chalcogenide glasses are stable because of the relatively large atomic mass of their constituent atoms, including the chalcogen elements S, Se, Te, Ge, As, and Sb. Because of the relatively large atomic mass of their constituent atoms, chalcogenide glasses have low phonon energies. And the low phonon energies of250～450cm-1result in low non-radiative decay rates of rare-earth energy levels. Chalcogenide glasses are attractive because they have high refractive indices and enhanced IR transmission with low phonon energy. Chalcogenide glass has numerous potential applications in civil, medical, and military fields, among others. Planar waveguide structures have been fabricated in chalcogenide glass using swift heavy Kr ions with energies of17MeV or150MeV. These results demonstrate that swift Kr ion irradiation is a promising method for fabricating waveguide structures in chalcogenide glass.Fused quartz is pure SiO2and exhibits low coefficient of thermal expansion, low electrical conductivity, and excellent chemical stability. Fused quartz is a key material in fabrication of integrated devices, which transmits extends from ultraviolet to infrared. We report the fabrication of planar and channel waveguides in fused quartz using multi-energy C ion at energies of (5.0+5.5+6.0) MeV and fluences of (1+1+1.5)×1015ions/cm2. The guiding modes at the wavelength of633nm (He-Ne laser) and1539nm (diode laser) were detected using the prism-coupling method, and the modes were stable after annealing in air. The refractive index profiles of planar and channel waveguides at the wavelength of633nm and1539nm were typical "well+barrier" distributions, which were reconstructed using the reflectivity calculation method (RCM) software and intensity calculation method (ICM), respectively. For comparison to the experimental results, the finite difference beam propagation method (FD-BPM) was used to simulate the guiding modes of the waveguides. We measured the near-filed intensity distributions for the visible (633nm) and near-infrared (1300 nm,1539nm and1620nm) wavelength regions, suggesting that the modes can be effective transmission in the wavelength range for optical fiber communications.BBO is an abbreviation for beta barium borate (β-BaB2O4), which has been considered an attractive nonlinear crystal since it was discovered in1984. BBO exhibits a large second harmonic generation (SHG) coefficient (d22≈2.2pm/V), a wide range of transparency from190nm to3500nm, a high damage threshold, a wide phase matching angle and high nonlinear optical coefficients, as well as a high birefringence; all these qualities make BBO very attractive for nonlinear optical applications, especially UV applications. We report on z-cut P-BBO planar waveguide produced by multi-energy proton implantation in total of3×1016ion/cm2at room temperature. Multi-energy ion implantation can increase the damage range, broadening the optical barrier and reducing the leakage of light from the substrate through the barrier wall. Annealing at600℃for5hours prior to the implantation process is used to decrease the influence of the stress induced during the ion implantation process. Multi-energy proton implantation could be an effective method for waveguide formation in β-BBO crystal.Bismuth oxide crystals of the type Bi12M02o (M=Ge, Si, Ti), which have body-centered cubic structures and belong to the space group123, exhibit a number of remarkable properties, such as photorefractivity, photoconductivity, optical activity, and the electro-optic, piezoelectric, elasto-optic and electrogration effects and so on. Planar optical waveguides in Nd:BSO crystals were fabricated by the implantation of500keV He ions and6.0MeV C ions at two different substrate temperatures. The guiding modes were measured by the prism-coupling method with a He-Ne beam at633nm.更多还原