参量振荡器化学计量比钽酸锂室温极化技术

采用助熔剂籽晶提拉法成功生长了近化学计量比钽酸锂单晶.采用自行研制的极化设备,研究了大面积且厚度达到1.8 mm的近化学计量比钽酸锂晶体的电场室温极化过程,针对在极化过程中外部施加高电压时产生的回流现象,采用改变极化时间和相应的极化电压来抑制的方法,取得了较好的效果.利用化学腐蚀法,成功地观察了钽酸锂晶体的大面积畴反转.发现近化学计量比钽酸锂反向矫顽场较正向矫顽场低,并利用这一性质,进一步研究了近化学计量比钽酸锂的极化特性.     

近化学计量比掺镁铌酸锂晶体周期极化特性研究

采用汽相输运平衡技术制备出了高质量近化学计量比掺镁铌酸锂晶体 ,系统研究了晶体中的 [Li]/ [Nb]比含量对其畴极化电场的影响 .实验结果表明 :随着晶体中 [Li]/ [Nb]比的提高 ,畴极化反转电场呈明显下降趋势 ,使用近化学计量比掺镁铌酸锂晶体 ,我们在 3.5± 0 .1kV/mm大小的外加极化电场条件下 ,成功地实现了 1.0mm厚度的周期极化畴反转 .我们用铌酸锂晶体的缺陷模型对实验结果给出了合理的解释 .     

近化学计量比LiTaO_3反转畴运动特性研究

通过添加助熔剂,生长了掺Mg近化学计量比LiTaO3(SLT)晶体,晶体的居里温度为684±1℃。对厚度1.8 mm的晶片进行外加单脉冲电场室温极化,得到了完全反转的畴结构。利用化学腐蚀的方法,观察极化过程中反转畴成核、运动及合并的过程。结果表明,室温极化时,反转畴的运动是非匀速的,实现完全反转至多需要50 s,极化初始阶段反转畴的平均横向扩展速率为0.012 mm/s。     

基于非周期极化铌酸锂晶体产生任意频率太赫兹辐射

理论上研究并论证了飞秒激光在非周期性极化畴反转的铌酸锂晶体(LN)中由光整流效应产生任意频率、窄带的太赫兹(THz)波辐射的可行性.为实现对THz波谱的整形,文中利用模拟退火(SA)算法设计出铌酸锂晶体的极化畴反转结构的最佳模型,由此可产生任意预置时间波形的THz辐射场.结果表明,SA算法是一种有效的通过设计晶体极化畴...     

准速度匹配相位调制器钽酸锂晶体的室温电场极化技术

利用准速度匹配技术可以实现大调制度的电光相位调制器,从而可以用来展宽激光频谱,它在光谱学、激光变频以及改善激光均匀性等方面有重要应用。当大功率激光通过调制器时,要求晶体的通光面积越大越好,所以大面积并且具有较大厚度的铁电晶体的室温极化技术成为准速度匹配实现的关键技术。详细研究了大面积并且厚度达到1 mm的钽酸锂晶体的电场室温极化过程,针对在极化过程中外部施加高电压时产生的回流现象,采用了改变极化时间来抑制,取得了较好的效果。利用热释电和化学腐蚀方法,成功地实现了钽酸锂晶体的大面积畴反转。该种技术同样可以用于其他大面积铁电晶体的极化。     

近化学计量比掺镁铌酸锂晶体特性研究

采用气相输运平衡技术,对同成分掺镁铌酸锂晶体薄片进行了近化学计量比处理.对处理后晶体的吸收特性、极化电场、抗光折变性能等进行了系统研究.实验结果表明,与同成分样品相比,近化学计量比掺镁铌酸锂晶体吸收边发生蓝移,光折变阈值提高4个量级,周期极化电场降低近1个量级.     

光纤激光器泵浦PPKTP晶体倍频连续绿光输出

用离子交换法降低了磷酸氧钛钾(KTP)晶体的电导率,用高压电场极化反转成功获得了体积为4mm×6mm×1mm,周期为Λ=9.0μm的周期极化KTP(PPKTP)晶体。在倍频(SHG)光学系统中用包层泵浦的光纤激光器输出的1064nm激光作为泵浦光,在室温下得到PPKTP器件的最高SHG转换效率为0.32%,归一化SHG效率为2 4%。化学蚀刻表面显示这种方法获得的PPKTP晶体反转畴边缘整齐,没有明显的畴壁扩展现象。     

基于周期性极化钽酸锂晶体的连续激光倍频技术研究

针对连续激光倍频的需求,对比分析了周期性极化钽酸锂晶体和铌酸锂晶体的非线性光学特性,从技术研究角度确定了周期性极化钽酸锂晶体更适合用于连续激光倍频。依据非线性转换效率和晶体结构安装尺寸,确定了基频激光压缩及倍频激光准直的参数,从保证工程应用的角度选择了81μm极化周期的钽酸锂晶体,设计并实现了双光路倍频,获得了超过5W的540nm连续倍频激光输出。     

钽酸锂晶体滤波器的离子束刻蚀技术研究

以钽酸锂晶体作为晶体滤波器压电材料。通过优化离子束刻蚀工艺参数,采用间歇式离子束刻蚀方法,解决了刻蚀区微裂纹工艺问题,使厚度为60μm钽酸锂晶片减薄至30μm。利用反台阶结构晶片制作出了中心频率为70MHz、3dB带宽为1 109kHz的高基频宽带钽酸锂晶体滤波器。     

高掺镁铌酸锂晶体周期极化及倍频特性研究

研究了掺镁(5mol％)铌酸锂晶体的周期极化特性,发现晶体的极化矫顽场仅为3kV／mm,根据镁掺杂对晶体本征缺陷的影响解释了极化矫顽场降低的原因．采用短脉冲极化电场,对极化电流的热效应进行抑制从而消除了晶体均匀性对制备周期极化光栅的影响,在1mm厚的掺镁(5mol％)铌酸锂晶体上成功制备出了均匀的周期极化光栅．在室温下,利用1．064μm的Nd：YAG调Q激光器对得到的周期极化掺镁铌酸锂晶体进行了倍频实验,在输入功率为75mW时,得到3．5mW的532nm倍频绿光输出,转换效率为4．6％．     

Guided-wave acousto-optic interaction on proton-exchanged lithium tantalate

A guided-wave acoustic-optic Bragg cell has been fabricated for the first time, to our knowledge, on lithium tantalate. The waveguide is fabricated by dilute melt proton-exchange, and without electrical tuning a maximum diffraction efficiency of 22% has been demonstrated. In addition, the thermo-optic behaviour of the lithium tantalate waveguide has been shown to be similar to that previously demonstrated on titaniumindiffused and proton-exchange lithium niobate waveguides     

Deformation Anisotropy of <Emphasis Type="Italic">Y</Emphasis> + 128°-Cut Single Crystalline Bidomain Wafers of Lithium Niobate

Bidomain single crystals of lithium niobate (LiNbO₃) and lithium tantalate (LiTaO₃) are promising materials for use as actuators, mechanoelectrical transducers, and sensors capable of working in a wide temperature range. One need to take into account the anisotropy of the properties of the crystalline material when such devices are designed. In this study we investigated deformations of bidomain round shaped Y + 128°-cut wafers of lithium niobate in an external electric field. The dependences of the piezoelectric coefficients on the rotation angles were calculated for lithium niobate and lithium tantalate and plotted for the crystal cuts which are used for the formation of a bidomain ferroelectric structure. In the experiment, we utilized an external heating method and long-time annealing with the lithium out-diffusion method in order to create round bidomain lithium niobate wafers. Optical microscopy was used to obtain the dependences of the bidomain crystals’ movements on the rotation angle with central fastening and the application of an external electric field. We also modelled the shape of the deformed bidomain wafer with the suggestion that the edge movement depends on the radial distance to the fastening point quadratically. In conclusion, we revealed that the bidomain Y + 128°-cut lithium niobate wafer exhibits a saddle-like deformation when a DC electric field is applied.     

Proton-exchanged periodically segmented channel waveguides inlithium niobate

Annealed proton-exchanged periodically segmented channel waveguides were fabricated in Z-cut lithium niobate. The propagation losses as a function of the duty cycle and the segmentation period are reported. Waveguiding was observed at large segmentation periods, up to 100 μm. For duty cycles >0.5, the propagation losses are nearly the same as measured for a continuous waveguide with the same width, namely ~1.45 dB/cm. With decreasing duty cycle, the mode expands in the transverse directions     

稳定占空比高速SSTL_2 I/O缓冲器的实现

应对时钟上升沿和下降沿均采集数据的芯片间高速接口,提出了一种输出占空比在50%左右、偏差范围±5%的支持SSTL_2标准的I/O缓冲器.利用互补有源电流镜差动对,实现在不同温度和工艺角下输出信号稳定的占空比偏差范围的输入接收器.为了验证电路实际工作性能,测试芯片在SMIC 0.18 μm 1P6M混合信号工艺下流片.测试结果显示,333 MHz时,输出占空比为47%;200 MHz时,输出占空比为48%;与已报道的支持SSTL_2标准的接收器相比,工作在333 MHz时,输出占空比仍保持在45%到55%间,偏差范围减小约72%.     

Pulsewidth control loop with a frequency detector for wide frequency range operation

A pulsewidth control loop (PWCL) with a frequency detector for wide frequency range operation is presented. The proposed PWCL is implemented with a duty cycle controlled circuit and frequency detector to correct the wide range frequency and duty cycle of the input clock. The duty cycle controlled circuit is able to modify the gain with different frequency and duty cycle ranges. The frequency and duty cycle of the input clock are detected by the frequency detector. The frequency detector is based on a ring oscillator and the input clock duty cycle and frequency are detected within two input clock cycles. The proposed circuit has been fabricated in a 0.35 μm CMOS technology. The proposed circuit generates the output clock of 50% duty cycle with the input range from 20% to 80% and frequency range 50–800 MHz. The measured duty cycle error is less than 1% within the frequency range from 50 MHz to 800 MHz.     

钽酸锂晶体及其应用分析

钽酸锂作为一种优良的多功能晶体材料,具有良好的压电、电光和热释电等性能,已被广泛应用于通信、电子等行业。该文介绍了钽酸锂晶体的结构、缺陷及性能调控方式,总结了钽酸锂晶体的制备方法及优缺点,分析了钽酸锂晶体在各应用领域的国内外研究进展,并对钽酸锂晶体的发展进行了展望,以期对钽酸锂晶体的应用及研究提供帮助。     

Clock buffer with duty cycle corrector

A clock buffer with duty cycle corrector circuit is presented. The proposed circuit can generate either 50% duty cycle or conserve the duty cycle as input clock. It corrects the input duty cycle of 10-90% for generated 50% duty cycle of output clock with error less than 0.9%. Moreover, it enhances the input clock signal driving ability and keeps the same duty cycle as input clock within range from 20% to 80% with a maximum duty error of 0.5%. The proposed circuit operation frequency range is from 100 MHz to 1 GHz. The proposed circuit has been fabricated in a 0.18 μm CMOS technology.     

Characteristics of a micromachined piezovalve combined with a multilayer ceramic actuator

This paper describes the design, fabrication and characteristics of a micromachined piezoelectric valve utilizing a multilayer ceramic actuator (MCA). The micromachined MCA valve, which uses a buckling effect, consists of three separate structures: the MCA, the valve actuator die and the seat die. The valve seat die with six trenches was made, and the actuator die, which is driven by the MCA under optimized conditions, was also fabricated. After Si wafer direct bonding between the seat die and the actuator die, the MCA was also anodically bonded to the seat/actuator die structure. A polydimethylsiloxane (PDMS) sealing pad was fabricated to minimize the leak rate. Finally, the PDMS sealing pad was also bonded to the seat die and the stainless steel package. The MCA valve shows a flow rate of 9.13 sccm at an applied DC voltage of 100 V with a 50% duty cycle and a maximum non-linearity of 2.24% FS. Therefore, the fabricated MCA valve is suitable for a variety of flow control equipment, as a medical bio-system and in the automobile industry.     

Distributed PMD Compensator in Lithium–Niobate–Tantalate: Performance Modeling Toward Highest Bit Rates

Polarization mode dispersion (PMD) is caused by noncircular fiber cores and poses a serious threat for transmitting 10-Gb/s optical signals over older fibers and 40-Gb/s optical signals over any type of fiber. We study the architecture of a PMD compensator (PMDC) capable of 40-Gb/s operation in X-cut Y-propagation lithium niobate (LiNbO₃) based on cascaded integrated optical TE-TM mode converters with endlessly adjustable coupling phases and propose several improvements in its architecture to tailor its performance toward highest bit rates. The performance of such distributed PMDCs can be pushed toward highest bit rates of 160 and 640 Gb/s if they are implemented in mixed ferroelectric crystals such as lithium niobate tantalate (LiNb_1-y/Ta_y/O₃) or lithium tantalate (LiTaO₃) crystals, respectively. A tantalum (Ta) content y of up to 0.5 is good to realize a distributed PMDC for about 160-Gb/s operation. Two- and three-phase TE-TM mode converters for integrated optical PMD compensation are compared, and the latter are found to have slightly better electrooptic efficiency. For Z-cut lithium tantalate, four-phase electrodes which need only two independent operation voltages are found to be more attractive.