Experimental Research on Single-Pass SHG from Periodically Poled LiNbO_3 Crystal

Quasi phase matching (QPM) periodical poled LiNbO 3(PPLN) is designed and successfully fabricated to enable second harmonic generation(SHG).The samples were Z cut 0.5 mm thick and grating period is Λ=6.8 μm for the first order QPM of continual wave λ=1.064 μm which is emitted by Nd∶YAG laser at room temperature 27 ℃. The output single pass SHG power was tested by an authorized optical system. The normalized max conversion efficiency is calculated to be 0.25 0 0(W·cm) -1 .The fabrication and parameters calculated method are introduced, and testing scheme is described in this paper. Even some ideas to improve conversion efficiency are offered.

周期极化的LiNbO_3中二次谐波的产生与偏振控制

在同一块LiNbO3晶体中,实现二次谐波的产生(SHG)及偏振控制.具体设计方法是,将一块z切的LiNbO3极化成周期不同的两个部分,在第一部分利用非线性光学效应产生二次谐波;在第二部分利用电光效应对二次谐波进行偏振控制.

1-W,high-repetition-rate room temperature operation of mid-infrared optical parametric oscillator based on periodically poled MgO-doped LiNbO

In this paper a high-repetition-rate mid-infrared （mid-IR） optical parametric oscillator based on periodically poled MgO-doped LiNbO3 （PPMgLN） at room temperature was demonstrated. The maximum average mid-IR output power at 3.63μm was 1.02 W with the repetition rate of 60kHz and corresponding efficiency from the pump to the idler was 26.7%. The temperature tuning and the period tuning characteristics were also discussed.

Nonlinear Talbot self-healing in periodically poled LiNbO_3 crystal [Invited]

The nonlinear Talbot effect is a near-field nonlinear diffraction phenomenon in which the self-imaging of periodic objects is formed by the second harmonics of the incident laser beam. We demonstrate the first, to the best of our knowledge, example of nonlinear Talbot self-healing, i.e., the capability of creating defect-free images from faulty nonlinear optical structures. In particular, we employ the tightly focused femtosecond infrared optical pulses to fabricate LiNbO_(3) nonlinear photonic crystals and show that the defects in the form of the missing points of two-dimensional square and hexagonal periodic structures are restored in the second harmonic images at the first nonlinear Talbot plane. The observed nonlinear Talbot self-healing opens up new possibilities for defect-tolerant optical lithography and printing.

Theoretical analysis of periodically poled LiNbO_(3) nonlinear mirror and its application in a passively mode-locked Nd:YSAG laser

In this paper, we report a passively mode-locked Nd∶Y3Sc2Al3O12(Nd:YSAG) laser using a periodically poled Li Nb O3(PPLN)superlattice. Nonlinear mirror mode locking based on PPLN intracavity frequency doubling was theoretically analyzed. The modulation depth of nonlinear reflectivity of the nonlinear mirror is approximately 8.8%. Optical performances of the modelocked laser including output power, radio frequency spectrum, and optical spectrum were experimentally investigated. An average output power of 710 m W with a slope efficiency of 14.6% was obtained at the pump power of 6.5 W. The repetition rate is 101.7 MHz, and the signal-to-noise ratio of the mode-locked pulse is 45 d B. The mode-locked pulse width was approximately 9 ps.

A periodically poled LiNbO_3 optical parametric generator in wavelength conversion from 2 to 3.88——4.34 μm

A periodically poled lithium niobate （PPLN） optical parametric generator （OPG） pumped by a laser diode （LD）-pumped Q-switched Tm,Ho：GdVO4 laser operated at 2.048 μm with pump pulse of 25 ns and repetition rate of 10 kHz is reported. A continuous tunable middle-infrared （mid-IR） spectrum of 3.88 - 4.34 μm is obtained by changing the crystal temperature from 50 to 124℃. When the incident pump power is 3 W, the total OPG output power is 95 mW, corresponding to optical conversion efficiency of 3.2%.

Tunable rectangular array illuminator in periodically poled LiNbO_3 crystal

An electro-optic tunable rectangular array illuminator in one-dimensional periodically poled LiNbO3 （PPLN） crystal is presented experimentally which result is in good agreement with results from simu- lation. The illuminator is formed based on the Talbot self-imaging effect by applying an electric field on PPLN. The intensi~.y distribution of rectangular array could be precisely modulated. Compared with other array illuminators, this tunable illuminator uses a lower voltage and could get a more concentrated intensity distribution. The influence of the incident angle to the self-imaging patterns is studied for the first time.

Sodium guide star laser generation by single-pass frequency doubling in a periodically poled near-stoichiometric LiTaO_3 crystal

We report in this work a continuous wave(CW) narrowband 589 nm light generation for the purpose of laser guide assisted adaptive optics.A 39 mm long 1 mm thick periodically poled near stoichiometric LiTaO3 crystal with duty cycle near 50% was fabricated using electrical poling at room temperature and pumped by a Raman fiber amplifier.We tested two temperature control ovens,and a maximum conversion efficiency of about 14.3%,corresponding to 4 W of yellow light with 28 W of fundamental power,and bandwidth less than 0.18 GHz was achieved.

周期极化掺镁不同组分LiNbO_3晶体的研究

利用气相平衡扩散法研制出掺镁不同组分的LiNbO3晶体 ,并对其极化特性进行了研究 .研究表明晶体的开关电场和自发极化不仅与晶体组分 [Li] [Nb]比有关而且与掺镁量有关 ,[Li] [Nb]比为 0 973掺入 2mol%MgO的近化学比LiNbO3晶体的开关电场仅为 1 8kV mm ,是同成分晶体的 1 12 ,且其极化结构的质量要远好于同成分LiNbO3晶体和近化学比LiNbO3晶体 .

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%.

准相位匹配周期极化掺镁铌酸锂490nm倍频连续输出

在室温下通过外加电场极化法 ,首次用较低的极化开关电场～ 5 .5kV/mm ,在厚为 1mm、长为 2 0mm、宽为 18mm的掺镁铌酸锂基片上成功的制备了周期为 4 .8～ 5 .2 μm的一阶准相位匹配倍频光学微结构 ;并在室温下 ,以波长为 980nm的半导体激光器为基频光源 ,对所研制的微结构样品进行倍频通光实验 ,在入射基频光为 80 0mW时 ,产生约 4 0mW的 4 90nm的倍频光 ,其对应转换效率为 5 % 。

准相位匹配LiNbO_3蓝光倍频器的研究

采用外加电场极化法 ,实现了 Li Nb O3 晶体的周期性极化 ,并制备出周期为 9.5μm的三阶准相位匹配周期性极化 Li Nb O3 晶体 (PPLN) ;用准连续钛宝石激光器作基频光源 ,对准相位匹配周期性极化 Li Nb O3 进行了光学倍频实验 ,得到了 1 2μW的蓝光输出。

周期极化近化学计量掺镁铌酸锂晶体倍频研究

采用气相输运平衡技术 ,对不同掺镁浓度的铌酸锂进行了近化学计量处理 ,并检验了其抗光折变性能。实验结果表明 ,掺摩尔分数为 2 %的镁的近化学计量铌酸锂晶体 ,光折变阈值比同成分晶体提高了 4个量级。通过施加 4 .5kV/mm的脉冲电场 ,在上述 1.0mm厚z切晶体上制备出了周期为 6 .8μm的均匀畴结构。采用声光调QNd∶YAG激光器作抽运光源 ,基频光波波长为 1.0 6 4 μm ,平均输入功率为 2 30mW ,在室温条件下 ,得到波长为0 .5 32 μm,输出功率为 2 .8mW的倍频绿光输出 ,倍频转换效率为 1.2 2 %。

外电场周期极化LiNbO_3的高压电源设计

分析了周期极化LiNbO3的极化反转过程和特性,进而提出了一种用于外加电场极化法制作周期极化LiNbO3的极化波形,并完成了相应的高压极化电源的设计与制作。电源可产生梯形波、序列脉冲方波以及由两者组合的多种波形,其最高输出电压为15kV,最大输出电流可达到300μA。用其在LiN bO3晶体上进行了多次极化反转实验,取得了很好的效果。

周期性极化掺镁铌酸锂晶体光参量振荡研究

为了实现高转化率3μm红外激光光参量振荡输出,采用外加脉冲电场法在厚度为1mm、掺摩尔分数为0.05的镁铌酸锂晶体上成功制备了周期为31.2μm的极化光栅,理论计算并模拟了1064nm激光抽运周期极化铌酸锂晶体时,闲频光波长随温度的对应关系,并进行了实验验证。利用1064nm声光调Q Nd∶YAG激光器作为抽运源对样品进行了光学参量振荡实验,其中,脉冲激光脉宽为200ns,重复频率是20k Hz。在控制温度为80℃、输入抽运光功率为5.567W时,光参量振荡输出波长3μm的闲频光功率为1.141W,光光转换效率达到20.1%。结果表明,通过此方法制备的周期性极化铌酸锂晶体光参量振荡,具有较高的光光转换效率。

Performance of Optical Sampling Based on SHG in CPPLN Waveguide

Sampling efficiency and bandwidth of the optical sampling system based on second harmonic generation （SHG） in chirped periodically poled LiNbO3 （CPPLN） are numerically researched. A broad sampling bandwidth can be obtained by adjusting chirp coefficient and waveguide length of CPPLN, and sampling efficiency can be improved by using higher pump power, increasing waveguide length and choosing appropriate chirp coefficient. Results show that both sampling bandwidth and efficiency in CPPLN waveguides are controllable and that CPPLN waveguides are more suitable for multiwavelength optical sampling systems.

准相位匹配周期极化高掺镁铌酸锂532nm倍频准连续输出研究

对周期性极化高掺镁铌酸锂倍频过程进行了准相位匹配倍频理论研究.在室温下通过外加电场极化法,用较低的极化开关电场～5.5 kV/mm,在厚为1 mm、长为10 mm、宽为10 mm的掺镁铌酸锂基片上成功地制备了周期为5.8～7.3 μm(间隔0.3 μm)的一阶准相位匹配倍频周期性极化光学微结构.将温度控制在70℃左右,以波长为1.064 μm的Nd:YAG激光为基频光源,对所研制的光学微结构样品进行倍频通光实验验证.当入射基频光为920 mW时,可以获得约15 mW的532 nm准连续倍频蓝光输出,其归一化转换效率高达1.77%/W.

近化学计量比铌酸锂晶体周期极化畴反转特性研究

采用K2 O作助熔剂直接拉晶法和气相输运平衡技术制备出了高质量近化学计量比铌酸锂晶体 ,研究了铌酸锂晶体中的 [Li] [Nb]比含量对其畴反转结构和极化电场的影响 .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 ,使用近化学计量比铌酸锂晶体 ,在 4 .0± 0 .5kV mm大小极化电场条件下 ,成功地实现了 1.0mm厚度的周期极化畴反转 .并用铌酸锂晶体的Li空位缺陷模型对上述实验结果给出了合理的解释 .

全固态激光器抽运的PPLN光参变振荡

用全固态 10 6 4nm调Q激光输出 ,抽运多周期PPLN ,实现了宽调谐的准相位匹配光参变振荡。振荡阈值10 .3μJ(脉宽 2 2ns) ,信号光最高输出平均功率为 42 .5mW ,斜率效率为 12 .5 %

一阶准相位匹配周期性极化铌酸锂倍频产生18mW绿光连续输出

通过高压脉冲电场极化 ,制备了周期为 6 5 μm、长为 12mm、宽为 10mm、厚为 0 5mm的一阶准相位匹配周期性极化铌酸锂 ;由 1 1W连续 1 0 6 μmNd∶YAG激光器抽运 ,在 5°时产生了约 18mW、0 .5 32 μm的倍频连续绿光 ,其对应的二次谐波转换效率约为 1 6 % ,二次谐波的归一化转换效率约为 1 5 %cm- 1 W- 1 ,相当于 79%的周期性极化铌酸锂的理想非线性系数。