两步离子交换低损耗光波导功分器的研制

报道了在热扩散条件下两步离子交换玻璃光波导功分器的理论分析、样品制作和实验测试.为了便于定量分析,采用了一种上升反正弦S型分支光波导系统的物理模型,得到了在热扩散条件下两步离子交换光功分器波导区的归一化折射率分布和在不同交换时间所形成的玻璃波导折射率分布.在此基础上,设计和制作出第一步采用含Tl 纯熔盐Tl2SO4与玻璃含Na 进行离子交换形成表面下半圆形波导,再把该波导表面脱钛膜放入含Na 熔盐NaNO3中进行第二步离子交换形成掩埋式圆形波导光功分器,实现插入损耗为0.15 dB和分光比为50:50的上升反正弦S型玻璃光波导功分器.     

高斯折射率分布Cu+-Na+离子交换玻璃波导的制备

利用Cu+ Na+ 离子交换技术制备了玻璃平面光波导 ,在 6 32 8nm波长下 ,用棱镜耦合技术测量出所制备波导的有效折射率 ,利用反WKB方法确定了平面光波导的折射率分布 ,并对折射率分布进行了函数拟合 ,近似符合高斯分布。求出了所制备玻璃平面光波导在 5 80℃的扩散系数为De ≈ 2 2 2 3× 10 -15m2 /s。     

渐变折射率分布MMI型光功分器的研制

以离子交换玻璃波导为例详细分析了渐变折射率分布波导中的自镜像效应,并完成了1×8渐变折射率分布MMI光功分器的设计和特性分析。在理论分析和设计的基础上完成了器件的制作,包括在国产K9光学玻璃上利用K+-Na+离子交换技术和以苯甲酸为交换源在铌酸锂基片上利用质子交换工艺分别完成1×8MMI光功分器的制作。测试表明器件基本实现了光均分功能。     

铜离子交换单步掩埋BK7玻璃波导的制备与表征

利用Cu离子交换技术制备了BK7玻璃平面光波导,在6328nm波长下,用棱镜耦合技术测量出所制备波导的有效折射率,利用反WKB方法计算并确定了平面光波导的折射率分布,通过对折射率分布进行函数拟合,发现离子交换后的样品折射率分布近似符合改进后的高斯分布,样品的折射率分布似乎是一个掩埋波导的折射率分布,求出所制备玻璃平面光波导在570℃的扩散系数De≈12133×10-14m2s。同时,对所制备波导进行了电子显微镜(EMS)和次级离子质谱(SIMS)测试,得到了铜离子在玻璃表面的浓度分布,从而证明了实验所得到的BK7玻璃平面光波导是掩埋波导。这种掩埋平面波导是由单步Cu离子交换技术得到的。     

用Tl_2SO_4制造玻璃光波导

本文报道了用TI盐(TI_2SO_4)离子交换法制备玻璃光波导的实验结果。与用AgNO_3离子交换制备的光波导相比,波导损耗较低,折射率分布呈准阶跃型,拟合确定其折射率分布函数为费米函数,折射率增量Δn>0.13。     

离子交换玻璃波导的模型分析

对采用BK7玻璃并经过K+ Na+ 二次离子交换法制备的波导 ,用数值求解分析了一次和二次离子交换所形成的折射率分布 ,并分析了影响折射率变化的原因。     

一种带有锥形多模过渡区的Y分支光波导

为减小Y分支波导的分支损耗,提出在输入波导和两输出波导间引入锥形多模过渡波导.与已被用于减小Y分支波导分支损耗的矩形多模过渡波导相比,所引入的锥形多模过渡波导,不仅可以减小过渡波导的长度,还可进一步减小分支损耗.利用三维有限差分光束传播法,对具有锥形过渡波导的退火质子交换铌酸锂Y分支光波导进行了数值模拟.数值结果为该类Y分支光波导的设计和制备提供参考.     

离子交换单模玻璃平面波导折射率分布的确定

用Ag-Na离子交换技术制备了玻璃平面波导.求解扩散方程得到Ag离子在玻璃内部浓度分布.使用一次多项式模拟的方法求解折射率变化与Ag离子浓度变化之间的关系,从而得到了单模平面波导的折射率分布,并验证其与同等实验条件(离子交换时间除外)的多模波导获得的折射率分布函数基本一致.     

双M-Z干涉仪中Y分支波导设计与分析

介绍了分支波导和S形弯曲波导,设计了对称双Y分支S形弯曲波导的结构,并计算了其弯曲损耗。对1/2Y和1/4Y分支波导的传输及弯曲损耗随长度的变化进行了模拟仿真,结果表明,设计的双Y分支波导达到了低损耗的要求。最后对双M-Z干涉仪的光场传输进行了二维各向同性仿真,得到其光场传输图和折射率分布图。结果表明,设计的双M-Z干涉仪的分光比可达1∶1∶1∶1。     

电场辅助离子交换制备玻璃光波导

使用电场辅助离子交换和热离子交换技术在玻璃基片上制作了平板波导。实验结果表明,这两种方法制作的波导的有效折射率分布不同,电场辅助离子交换技术制作的波导有效折射率呈近似阶跃型分布,而热离子交换制作的波导有效折射率分布为渐变型。经数值计算发现,近似阶跃型折射率分布的波导对光场限制得更好,更适用于制作有源光器件和集成光器件。     

Optical waveguides in fluoride lead silicate glasses fabricated by carbon ion implantation

The carbon ion implantation with energy of 4.0 MeV and a dose of 4.0×1014 ions/cm2 is employed for fabricating the optical waveguide in fluoride lead silicate glasses. The optical modes as well as the effective refractive indices are measured by the prism coupling method. The refractive index distribution in the fluoride lead silicate glass waveguide is simulated by the reflectivity calculation method (RCM). The light intensity profile and the energy losses are calculated by the ?nite-difference beam propagation method (FD-BPM) and the program of stopping and range of ions in matter (SRIM), respectively. The propagation properties indicate that the C2+ ion-implanted fluoride lead silicate glass waveguide is a candidate for fabricating optical devices.     

多模掩埋式平面玻璃波导的制作及测试

利用加电场的离子交换和热处理等方法制作膜厚深的多模玻璃波导,并采用二步法制作了多模掩埋式平面玻璃波导,测试了m线谱,用White法计算了波导的折射率分布。     

Index profiles: TE mode solutions

This letter presents a novel method to study one-dimensional waveguide problems in which the profiles of the refractive index are arbitrary. In the proposed method, distributions of both the refractive index and electric field are expanded into finite-term Fourier cosine series. A particular matrix is then formed by the Fourier spectral amplitudes that correspond to the refractive-index distribution. The eigenvalues and the eigenvectors of such a matrix correspond to the mode indices and the electric field distribution, respectively, in the waveguide considered herein. TE mode solutions are obtained for a step-index structure and an inhomogeneous structure. It is found that quite accurate results can be obtained by this proposed method     

Design of ideal structures for lossless bends in optical waveguidesby conformal mapping

We propose an ideal structure for lossless bends in optical waveguides for the first time. The ideal structure is obtained by applying a series of conformal mappings to transform a single-mode straight waveguide into the equivalent bend configuration. The expressions used to determine the waveguide path and the refractive index are derived for the lossless bends with arbitrary bend angles, even up to 90°. Also, variations in the waveguide path and the refractive index are illustrated by adopting lossless bends with six different bend angles (4, 10, 30, 45, 60, and 90°). The simulated results show that the refractive-index distribution can be controlled within the range of interest for the practical bend structure. Moreover, the characteristics of the phase front for the modal field in a lossless bend are thoroughly discussed to verify that no transmitted power would be lost by conversion to radiation modes     

Planar silica-glass optical waveguides with thermally inducedlateral mode confinement

A new type of planar silica-glass optical waveguide is proposed utilizing the thermo-optic effect of glass. The vertical mode-field confinement is defined by the core slab sandwiched between the upper and lower claddings while the lateral confinement is achieved due to localized increase of refractive index induced by the thin-film heater placed on the upper cladding. An analytical expression of the steady-state temperature distribution across the waveguide cross-section is derived and the induced mode-field characteristics are analyzed by solving the vector-wave equation using the mode-matching method. Mode propagation losses due to the metallic heater and the leakage into the silicon substrate are both calculated. The bending loss of this thermally induced waveguide is also analyzed for future device implementation using this waveguide     

Optical properties of an Er3+-doped phosphate glass waveguide formed by single-energy H+ ion implantation

In this work, we report the fabrication of an optical waveguide by single-energy H+ ion implantation in the Er3+-doped phosphate glass. The ion implantation conditions are with energy of 0.4 MeV and a fluence of 8.0×1016 ions/cm2. The dark mode spectrum of the waveguide structure was measured by the prism coupling experiment. The refractive index change along with the penetration depth was fitted by using the reflectivity calculation method (RCM). Finally, the calculated near-field light intensity distribution shows superior waveguide properties, which demonstrates its promising potentials for compact optical integrated devices.     

New design method for low-loss Y-branch waveguides

We propose a new method to design low-loss Y-branch waveguides. In conventional design methods, a specific geometry of branching structure is given first, and then structural parameters describing the details of the proposed geometry (for example, location, sizes, and refractive index of microprisms or phase-adjusting elements) are determined by ray optics or other means. In this paper, we take quite a different approach. Given a complex field distribution, one complex refractive index distribution that supports it is determined uniquely, according to the scalar Helmholtz equation. Using this relation, we first make up an ideal field distribution for dividing optical waves smoothly in the branching region. Next, we calculate the refractive index distribution corresponding to the ideal field. Finally, the imaginary part of the refractive index is set to be zero and its real part is discretized into three levels from the practical viewpoint. Numerical simulations show that the present design method offers extremely low-loss Y-branch waveguides     

Direct index measurements of diffused channel waveguides

A nondestructive method is described for obtaining information about the refractive index profiles of diffused channel waveguides of the type used in integrated optics. The method assumes that the index profile can be approximated as a product of two functions each of which depends on one of the two transverse coordinates. By observing the focusing effect, which the waveguide has on collimated light passing through it transversely to its axis, the shape of the index profile in a direction parallel to the surface of the substrate can be obtained. From measurements of the reflection coefficients we obtain the refractive index at the upper surface of the waveguide. By combining the two measurements the effective depth of the waveguide can be calculated. Results of measurements on multimode and single-mode waveguides formed in glass and lithium niobate are presented.     

Radiation pattern of light scattering from the core region of dielectric-slab-optical waveguides

The scattering from dielectric-slab-optical waveguides having refractive-index inhomogeneities in the core region has been studied by solving the Maxwell equations together with the use of a stationary phase method. The scattering phenomenon is of interest since it provides the radiation pattern in the far-field region which is characterized by the statistical scale of inhomogeneities in a waveguide. The anisotropic fluctuations of the refractive index in the directions parallel and perpendicular to the axis of light propagation have been assumed in the analysis. It is found that the strong multiple peaks in the forward direction occur in the substrate region when the correlation length of refractive-index inhomogeneities in the axial direction is much greater than the wavelength of light.     

Characterization of refractive index profiles in silver-sodiumion-exchanged glass waveguides for homogeneous refracting waveguidestructures

The refractive index profiles are investigated for Ag⁺-Na⁺ ion-exchanged waveguides in soda-lime glass. The waveguides with the highest index change, used to design homogeneous refracting waveguide lenses and prisms, are fabricated at 350°C using concentrated melt with composition of 10 mol.% AgNO₃ and 90 mol.% NaNO₃. The profiles of two- and three-mode waveguides are reconstructed from the measured mode refractive indexes. The linear correlation between the index change and the silver concentration in glass is experimentally confirmed. The concentration profiles are numerically simulated on the base of diffusion-exchange theory. It is established that the values of the maximum in index profile near the glass surface tend to a saturation value after a long exchange time