Laser diode beam shaping by optical interference

We recently proposed a novel beam shaping technique that employs Lloyd’s mirror interference. In this study, we apply this technique to three commercial laser diodes: laser diodes used for optical pumping of solid-state lasers, for laser beam printers, and for laser displays. The elliptical output beams from these laser diodes could be transformed into nearly circular beams by inserting a mirror-polished GaAs substrate below the active layer of each laser diode and adjusting its height. The experimentally observed far-field patterns were predicted fairly well by numerical calculations based on Huygens’ integral. We confirmed that our beam shaping technique is applicable to laser diodes with various wavelengths and vertical beam divergence angles. We also describe the monolithic configuration of the beam shaping system, which can be fabricated by dry etching.     

角锥棱镜腔激光二极管抽运被动调Q激光器

为了提高传导冷却条件下激光二极管(LD)侧向抽运被动调Q激光器的光束质量和输出稳定性,采用了两组半圆柱面激光二极管阵列侧向交错抽运两根串接的激光棒,实现了均匀抽运和散热。通过实验分析了横模结构对被动调Q稳定性的影响,设计了角锥棱镜-高斯输出镜非稳腔,在显著提高器件光束质量的同时,明显改善了被动调Q的稳定性,并保证了谐振腔的机械稳定性。在此基础上研制了一台重复频率20 Hz、单脉冲能量64 mJ、脉冲宽度7 ns、稳定性优于±5%、光束发散角0.6 mrad、光-光效率9.1%,且光轴指向稳定的工程实用器件。     

切削用量对铝靶表面质量的影响

采用单点金刚石切削技术，完成了对ICF实验用铝靶的切削加工，重点研究了切削用量对加工表面质量的影响。实验结果表明:采用较小的进给速度，较大的主轴转速能够获得较低的表面粗糙度，切削深度对表面质量影响较小。通过Form Talysurf 表面轮廓仪测量，结果表明表面粗糙度小于50 nm。     

折返式激光二极管侧抽运Nd∶YAG激光器

提出一种明显改善激光二极管侧面直接抽运固体激光器输出光束质量的新型谐振腔――折返式谐振腔,它由三部分组成     

Study on the Beam Quality of Uncoupled Laser Diode Arrays

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Study on the Beam Quality of Uncoupled Laser Diode Arrays

The beam quality of uncoupled laser diode array is studied theoretically and experimentally. By calculating the second order moments of the beam emitted from the laser diode array, the dependence of the M2-factor of the laser diode array on the M2-factor of the single emitter, the ratio of the emitting region to the non-emitting space, and the number of emitters, has been deduced. From the measurement of the beam propagation the M2-factor of a laser diode bar is experimentally determined. The measured M2-factor of the laser diode bar agrees with the theoretical prediction.     

Nanometer-scale displacement sensing using self-mixing interferometry with a correlation-based signal processing technique

A self-mixing interferometer is proposed to measure nanometre-scale optical path length changes in the interferometer’s external cavity. As light source, the developed technique uses a blue emitting GaN laser diode. An external reflector, a silicon mirror, driven by a piezo nanopositioner is used to produce an interference signal which is detected with the monitor photodiode of the laser diode. Changing the optical path length of the external cavity introduces a phase difference to the interference signal. This phase difference is detected using a signal processing algorithm based on Pearson’s correlation coefficient and cubic spline interpolation techniques. The results show that the average deviation between the measured and actual displacements of the silicon mirror is 3.1 nm in the 0–110 nm displacement range. Moreover, the measured displacements follow linearly the actual displacement of the silicon mirror. Finally, the paper considers the effects produced by the temperature and current stability of the laser diode as well as dispersion effects in the external cavity of the interferometer. These reduce the sensor’s measurement accuracy especially in long-term measurements.     

36 W侧面抽运腔内倍频Nd:YAG/KTP连续绿光激光器

通过优化平-凹-平三镜折叠腔结构设计,利用大功率半导体激光器侧面抽运、Ⅱ类相位匹配KTP晶体腔内倍频,获得高效高功率连续绿色激光输出.当抽运电流约为36 A时,得到最高36.6 W的连续绿光激光输出,对应的光—光转换效率为8.71％.在输出功率33 W时测量激光功率稳定性,其功率不稳定度为0.27%.用刀口法测量了激光器高输出功率时的光束质量,光束质量因子小于8.对高功率抽运情况下三镜折叠腔的像散补偿、失调灵敏度和基模在腔内分布情况做了数值模拟. 关键词： 侧面抽运 腔内倍频 连续波     

基于激光自混合干涉的物体旋转中心确定方法

在被测物体上设置一低反射率反射镜,激光器输出的激光束入射到反射镜上,激光束经反射镜反射反馈回激光器内.入射光线若偏离被测物体的旋转中心,当被测物体旋转时,将引起激光器的输出功率随角度变化的自混合干涉信号.当入射光线通过被侧物体的旋转中心时,被测物体的角度变化将不会导致回馈光的光程变化,被侧物体旋转时也就观测不到自混合干...     

Compact beam collimator for laser diode bar

A compact beam collimator for a laser diode (LD) bar fabricated by a simple method is presented. It consists of a single set of microlenses and a cylindrical lens, which are fabricated from SiO₂ rods using a fiber-drawing tower. The principle and parameter optimization of this device are investigated numerically using ZEMAX software and illustrated experimentally for a specific LD bar. It is shown that the output beam is well collimated in both the fast-axis and slow-axis directions; the beam quality is greatly enhanced via the redistribution of intensity in the two directions and by eliminating the fill factor for the LD bar.     

体布拉格光栅外腔实现激光二极管阵列同相模输出

 采用体布拉格光栅作为商用二极管激光阵列外腔,通过将每个单元发出的光反馈回相邻单元实现了外腔锁相。采用这种方法对发光单元宽度为100 μm、周期为200 μm,由49个单元构成的二极管阵列进行了外腔锁相实验,在远场获得了高光束质量、窄带宽的稳定输出。二极管激光阵列自由运转下功率为15 W,经外腔锁相后输出功率为3.67 W,对应光束远场发散角1.47 mrad, 光谱的峰值半宽由1.7 nm压窄到0.17 nm。     

基于外腔反馈二极管线阵列的smile效应测量方法

采用外建激光谐振腔,在低于原芯片阈值的电流激励下对LDA的每个发光点进行单独测量,从而分析整个半导体激光阵列(LDA)的smile效应。实验中利用镀膜反射率大于半导体前腔面的外腔镜形成外腔半导体激光器。在外腔中插入曲面平行于p-n结的柱面镜,使只在光轴上的发光点与外腔镜形成外腔激光器,降低该发光点的激光阈值,从而使其在正常的阈值以下的电流激励下输出激光,在平行于p-n结的方向移动柱面镜,可以逐个对半导体激光器中的发光点进行选择测量,从而获得LDA smile效应的测量值。测量中的低电流激励产生的热量对芯片寿命没有影响,对LDA的发光点的单个测量也避免了其他发光点对CCD的影响。     

采用多波长光束组合改善二极管激光阵列的光束质量

 基于多波长光束组合技术，利用光栅的衍射和外腔的反馈，将二极管阵列的发光单元锁定在不同的波长上，相邻单元的出射光波长有微小的差异。从外腔耦合镜输出近似平行的光束，其光束质量等同于单个发光单元的光束质量,而组合光束亮度随着组合光束个数定标放大。实验中采用发光单元宽度为100 μm、填充因子为0.5、由49个单元构成的1 cm 阵列获得功率为2.39 W的输出光束，其光谱宽度为27 nm，远场光斑的直径为0.08 mm，对应的远场发散角为1.2 mrad，其光束质量因子约为28，与单个发光单元的光束质量相当。     

Fast quasi-optical phase shifter based on the effect of induced photo conductivity in silicon

We study, both numerically and experimentally, a microwave commutator (phase shifter), whose active element comprises a metal plane mirror with a semiconductor plate on it. Phase shifting of the reflected microwave beam is attained by creating a conducting layer in the semiconductor by a laser with quantum energy approximately equal to the forbidden band width. Using a disk of high-purity silicon and a titatnium-sapphire pulsed laser, we study experimentally a 180° phase shifter operated with a Gaussian wave beam at a frequency of 30 GHz. Efficient phase shifting of the wave beam over a time of several nanoseconds is shown at a low power level.     

脉冲激光二极管侧面抽运Nd∶YAG激光器晶体时变热效应

采用数值计算的方法,对脉冲激光二极管三向侧面抽运固体激光器中,激光晶体的温度场时变分布进行了计算. 分析了三向侧面抽运情况下晶体内光强分布,在此基础上,采用有限元法,以脉冲激光二极管侧面抽运Nd∶YAG激光器为例,对单脉冲过程中晶体温度分布及其影响因素进行分析. 结果表明,晶体升温过程受到抽运条件以及散热条件的影响,但是主要受到抽运条件即抽运光强度和光束半径的影响,降温过程受到晶体热物性参数和晶体半径以及散热条件的影响. 当晶体温度达到周期性分布后,由于晶体径向温度梯度的周期性变化,引起通过晶体的平面光波的中心和边缘光线相对光程差也随时间作周期性变化. 关键词： 激光二极管侧面抽运固体激光器 热效应 有限元法 时变过程     

激光二极管列阵泵浦的位相共轭板条YAG激光放大系统

采用新型的微通道冷却半导体激光二极管列阵泵浦ＹＡＧ激光振荡器及板条ＹＡＧ放大器，文中用ＣＣｌ４受激布里渊散射作位相共轭镜，使激光在板条放大器中作多通放大，获得了高重复率下小于１．５倍衍射极限的高质量１．０６μｍ的激光输出，其脉冲宽度为１５ｎｓ，平均功率为１８０Ｗ。     

Coherent beam combination of broad-area laser diode array using off-axis external cavity with double feedback

In this letter, we demonstrate coherent beam combination of laser diode array using the external Talbot cavity with double feedback. The double feedback elements consist of grating and high-reflection plane mirror. Compared with single high-reflection plane mirror feedback, the external Talbot cavity with double feedback reduce the number of interference strips in the far-field pattern and narrow spectral line-width of the laser diode array. The results indicate that the application of the external Talbot cavity with double feedback produces a clear far-field interference pattern. In addition, line-width is reduced to 0.15 nm full-width at half-maximum (FWHM).     

洛埃镜干涉微小尺度测量系统的研究

设计了一款利用洛埃镜干涉进行微小尺度测量的系统。该系统利用机械的杠杆原理,将微小尺度的改变反映在镜面与光源的垂直距离上,相当于改变洛埃镜干涉系统中光源与虚光源之间的间距,从而干涉条纹的宽度将相应的发生变化。利用光电池将光信号转化为电信号,并通过信号的放大和模数转化,最终在计算机上显示干涉条纹。通过相应的测量公式就可以得知待测物体的微小尺度。对标准塞尺的测量结果显示,该系统具有精度高,操作简便,测量迅速等优点。     

LBO晶体和频产生589 nm激光的数值模拟及实验研究

 基于非线性光学理论，分析了1 064 nm和1 319 nm和频产生589 nm激光源的理论基础。针对LBO晶体的I类相位匹配条件及最佳晶体长度的选择进行了计算机数值模拟，给出了最佳晶体长度与总入射功率的关系曲线。当波矢量与光轴夹角为90°，波矢量方位角为3.39°时，计算出相应的有效和频系数为0.952×10^-12 m/V。设计了一种简便高效的实验和频方案，二极管泵浦Nd:YAG激光器经腔镜镀膜及腔内可倾斜标准具调谐，分别输出了波长为1 064 nm和1 319 nm的准连续激光，然后通过脉冲同步调节，实现了589 nm黄光输出，平均功率达到500 mW，光束质量因子M2约2.1，和频效率18%。     

二极管面阵侧泵浦Nd:YAG双板条激光器

 叙述了二极管面阵侧泵浦双板条耦合单横模 Q 开关激光器的研制。泵浦源为二极管面阵激光器,使用梯形波导板耦合系统,耦合效率达90%,谐振腔为凸凹腔,全反射镜的曲率半径为 3.0m的凹面镜,输出镜为曲率半径3.0m的可变反射率超高斯镜。激光器在 100Hz 重复频率下,输出单脉冲能量18.23mJ,脉宽为15.25ns,光束质量M²<1.5具有平顶分布的超高斯光束。