Near-stoichiometric Ti:LiNbO3 strip waveguide with varied substrate refractive index in waveguide layer

We report the near-stoichiometric Ti：LiNbO3 strip waveguides fabricated by vapour transport equilibration （VTE） at 1060~^{／circ}C for 12 h and co-diffusion of 4--8~／mu m wide, 115-nm thick Ti-strips. Optical studies show that these waveguides are monomode at 1.5~／mu m and have losses of 1.3 and 1.1~dB/cm for the TM and TE modes, respectively. In the waveguide width/depth direction, the mode field follows a Gauss/Hermite--Gauss profile. A secondary ion mass spectrometry study reveals that the Ti profile follows a sum of two error functions along the width direction and a complementary error function in the depth direction. Micro-Raman analysis shows that the Li-composition in the depth direction also follows a complementary error function. The mean Li/Nb ratio in the waveguide layer is about 0.98. The inhomogeneous Li-composition profile results in a varied substrate index in the guiding layer, and the refractive index profile in the guiding layer is given.

Greatly enhanced electro-optic modulation efficiency in titanium in-diffusion PIN-PMN-PT waveguide

Electro-optic modulators,which convert electrical signals onto the transmission light,are key devices in electro-optic modulating systems.Modulation efficiency is one of the most important parameters of an electro-optic modulator,which directly determines the footprint and power consumption of the device.Generally,modulation efficiency strongly depends on the electro-optic response of the crystal.The Pb(In_(1/2)Nb_(1/2))O_(3)-Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)(PIN-PMN-PT)single crystal with giant electro-optic coefficient(λ_(c))and high transparency indicates the potential to achieve greatly enhanced modulation efficiency.In this study,a prototype PIN-PMN-PT phase modulator was fabricated based on a titanium(Ti)in-diffusion waveguide,which is reported for the first time.The influences of titanium in-diffusion on the composition and domain structure of the PIN-PMN-PT single crystal were studied by transmission electron microscopy(TEM)and piezoelectric force microscopy(PFM),respectively.Finally,a half-wave voltage(V_(π))of 2.3 V was obtained using a device with 6-mm-long(L)electrodes.Furthermore,the electro-optic modulation efficiency(V_(π)L)was calculated as 1.38 V-cm,which was approximately one order of magnitude lower than that of commercial lithium niobate(LiNbO_(3),LN)phase modulators.Such enhanced modulation efficiency indicates more compact device and lower power consumption,which is of great significance for electro-optic modulation systems used in micro-fiber gyroscope,integrated photonic devices,etc.

Reactive ion etching of Ti-diffused LiNbO_3 slab waveguides

Reactive ion etching（RIE） of LiNbO_3（LN） in SF_6 plasma atmosphere was studied for optimizing the preparation conditions for LN ridge waveguides.The samples to be etched are Ti-diffused LN slab waveguides overlaid with a chromium film mask that has a Mach-Zehnder interferometer（MZI） array pattern.The experimental results indicate that the LN-etching rate（R_（LN）） and the Cr-etching rate（R_（Cr）） as well as the rate ratio R_（LN）/R_（Cr） increase with either increasing the radio-frequency（RF） power at a given SF_6 flow rate or increasing the SF_6 flow rate at a fixed RF power.The maximum values of R_（LN） = 43.2 nm/min and R_（LN）/R_（Cr） = 3.27 were achieved with 300 W RF power and 40 sccm SF_6 flow.When the SF_6 flow rate exceeds 40 sccm,an increase in the flow rate causes the etching rates and the rate ratio to decrease.The scanning electron microscope images of the LN ridge prepared after～20 min etching show that the ridge height is 680 nm and the sidewall slope angle is about 60°.

质子交换LiNbO_(3)光波导

本文全面系统地综述了质子交换LiNbO3光波导的机理、结构特征和光学性质。描述了掺杂LiNbO3质子交换波导的特征 。

掺铒铌酸锂波导激光器的发展

本文主要讨论掺铒铌酸锂波导激光器的特点、光谱特性、物理模型和结构与制作，并介绍了国内外最新研究进展状况。

Variational analysis of eigenmodes of integrated optical waveguides and applications

An iterative procedure is proposed for the variational analysis of Ti:LiNbO3 optical waveguides. A trial solution for the dominant electric field profile of arbitrary-order eigenmodes in strip waveguides and two coupled waveguides is proposed and its parameters are determined using the variational method. The results calculated using this method agree well with those obtained using the finite-element method. The present method has been used to check the accuracy of the effective index method as well as a quasi-analytical technique based on the effective index method. The results show that the effective index method is generally accurate for the fundamental mode and becomes less accurate for higher-order vertical modes.

Z切LiNbO_(3)晶体中退火质子交换光波导特性的研究

系统地研究 Z切 L i Nb O3晶体中质子交换波导和退火质子交换波导的特性 ,得到了质子交换过程中的扩散常数和激活能 ,发现了质子交换波导的折射率呈线性阶跃型的折射率分布。通过连续退火 ,波导的折射率分布由线性阶跃型向高斯型过渡。退火可分为两个阶段 ,波导深度的增加在第一阶段随退火时间成指数关系 ,第二阶段与退火时间的平方根成线性关系。

铌酸锂波导中折射率改变的物理机制研究

本文结合构成铌酸锂波导的两种方法对影响折射率的因素做了较详尽的探讨 ,从微观机理上解释了两种方法中折射率改变的不同现象 ,给出了折射率改变的不同原因。扩 Ti中引起折射率改变的主要机理是弹光效应 。