光纤端面耦合周期极化铌酸锂(PPLN)薄膜波导器件的研究

通过有限元模拟器从理论上分析了在理想光学系统中实现光纤与周期性极化铌酸锂(PPLN)波导之间高效耦合的可行性。仿真模拟了单模保偏光纤和透镜光纤在空间中的发散情况。针对截面尺寸为10μm×10μm、长度为20 mm的PPLN脊形波导,进行了与两种不同光纤的直接端面耦合模拟分析。分析发现,尽管透镜光纤的耦合效率高达95%,但其基模占比却不足5%。鉴于PPLN倍频器件主要依赖于激光的基模进行工作,这使透镜光纤的耦合效率在实际应用中显得相对较低。相比之下,单模保偏光纤的基模占比高达93.8%,显示出更为优越的性能。因此,本文选择了单模保偏光纤与PPLN脊形波导进行封装测试。实验结果表明:当温度为24.8℃,从光纤放大器输出的泵浦功率最大为1.6 W时,计算扣除输入端光纤与波导的耦合损耗后的输入泵浦功率为1.2 W,光纤到波导的耦合效率为75%,略高于当前已知的最高效率72%。1 560 nm基频光的输入功率为1.2 W时,最大输出653 mW的倍频光,光光转换效率达到了54.4%,归一化转换效率为20.2%/(W·cm^(2))。

Fabrication and characterization of high-damage resistance Zn-diffused MgO:PPLN ridge waveguides

This study investigates the fabrication process of Zn-diffused ridge waveguides in periodically poled magnesium-doped lithium niobate(PPMgO:LN).A controlled variable method is used to study the effects of diffusion temperature,diffusion time,ZnO film thickness,and barrier layer thickness on the surface domain depolarization and waveguide quality of PPMgO:LN.A special barrier layer is proposed that can automatically lift off from the sample surface,which increases the depth of Zn doping and reduces the surface loss of the waveguide.By optimizing the process parameters,we fabricate Zn-diffused PPMgO:LN ridge waveguides with a length of 22.80 mm and a period of 18.0μm.The above waveguides can make a second harmonic generation(SHG)at 775 nm with an output power of 90.20 mW by a pump power of 741 mW at 1550 nm.The corresponding conversion efficiency is 3.160%/W·cm2,and the waveguide loss is approximately 0.81 dB/cm.These results demonstrate that high-efficiency devices can be obtained through the fabrication process described in this paper.

Simulation design of thin film lithium niobate electro-optic modulator with bimetallic layer electrodes

Thin-film lithium niobate electro-optical modulator will become the key device in the future optical communication,which has the advantages of high modulation rate,low half-wave voltage,large bandwidth,and easy integration compared with conventional bulk lithium niobate modulator.However,because the electrode gap of the lithium niobate film modulator is very narrow,when the microwave frequency gets higher,it leads to higher microwave loss,and the electro-optical performance of the modulator will be greatly reduced.Here,we propose a thin film lithium niobate electro-optic modulator with a bimetallic layer electrode structure to achieve microwave loss less than 8 dB/cm in the range of 200 GHz,exhibiting a voltage-length product of 1.1 V·cm and a 3 dB electro-optic bandwidth greater than 160 GHz.High-speed data transmission test has been performed,showing good performance.

Compact yellow-orange Nd:YVO_(4)/PPMgLN laser at 589 nm

We propose and make a compact yellow-orange laser of the Nd-doped yttrium vanadate(Nd:YVO_(4))/periodically poled Mg-doped lithium niobate(PPMgLN)module by Raman frequency-doubling at 589 nm.By reasonably designing the size of the Nd:YVO_(4)and 5 mol%PPMgLN crystals,cavity length and coating parameter,a compact 589 nm laser module with a total size of 3 mm×10 mm×1.5 mm is fabricated.In the laser module,the input surface of Nd:YVO_(4)crystal is end-pumped by an 808 nm laser diode(LD).Under the effect of linear resonant cavity structure,the output surface of PPMgLN crystal with a period of 9.48μm generates 589 nm yellow-orange light.The experimental results show that the maximum output power at 589 nm is 390 mW at the pump power of 3 W with the optical-optical conversion efficiency of 13%and the stability of the output power is less than 2%within 3 h.