强反馈光纤光栅外腔半导体激光器

在理论上对强外腔反馈情形的半导体激光器线宽压窄效应进行了分析，对消反膜剩余反射率，外腔反射率，外腔腔长对线宽压缩的影响进行了研究，在实验上采用光纤光栅作为反馈元件，与一端镀有消反膜的１．５μｍ波段的常规多纵模交导体激光器耦合，构成强反馈光纤光栅外腔半导体激光器，得到单频窄线宽的激光输出，静态下边模抑制比大于３０ｄＢ，线宽小于１２０ｋＨｚ。     

外腔任意反馈半导体激光器的频率调谐特性

根据半导体激光器外腔反射率的不同，系统地研究了外腔任意反馈半导体激光器的频率调谐特性，理论分析及数值模拟与实验结果基本一致。     

电光晶体调谐的外腔反馈半导体激光器

报道一种用电光晶体实现快速调谐和凋制激光频率的方法.在Littrow型外腔反馈半导体激光中插入LiNbO3晶体,利用LiNbO3晶体的电光效应,通过改变晶体电压来调节激光器的有效腔长,可以对激光频率进行快速的调谐和调制.采用该方法,自制外腔反馈半导体激光器的调谐频率可达到2 kHz,它的调谐范围为350 MHz,激光频率调谐系数约为1.06 MHz/V,用饱和吸收光谱观测频率调谐的效果.快速激光频率调制可以应用在稳频技术上,将外腔反馈半导体激光器调制在5～100 kHz频率下,均获得了87Rb原子D2线的饱和吸收光谱的色散信号,并实现了激光频率在饱和吸收峰上的长期稳定.     

闪耀光栅外腔反馈压窄半导体激光器线宽技术的研究

在讨论半导体激光线宽压窄理论的基础上,利用闪耀光栅作为外部反馈元件,介绍了由中心波长为949.6nm、原始线宽为1.2THz的单管半导体激光器构成的反馈外腔,它能够很好的改善半导体激光器的性能。实验得到了中心波长稳定的、单纵模的高质量激光输出,边模抑制比大于30dB,线宽优于1.2MHz(Δλ<3.6×10-6nm)。实验证实了强反馈能够很好地改善外腔半导体激光器的动态特性。     

外腔反馈对半导体激光器振荡特性的影响

通过有效反射系数的引入，根据激光谐振腔的自再现条件和对腔内光子密度、载流子密度方程的求解，分析了外腔反馈对半导体激光器的阈值增益、振荡频率和输出功率等振荡特性的影响，并通过实验进行了验证.外腔反馈后，半导体激光器的阈值电流从420mA降为370mA，输出功率的斜率效率获得了提高，理论计算的输出功率曲线与实验结果符合的很好. 关键词： 半导体激光器 外腔反馈 振荡特性     

基于降温技术的宽范围外腔光栅可调谐半导体激光器

使用半导体制冷块,通过优化设计两级制冷系统,并结合隔离、密封等措施,将LD的温度冷却到-20 ℃,使室温下输出波长为789 nm的激光器工作在780 nm附近,改变了约9 nm.结合外腔光栅反馈技术,可以使激光器的输出波长稳定在Rb原子的D2线上.自制了一个简单的电路,能够以适当的比例同时调谐光栅压电陶瓷的电压和激光器的驱动电流,使激光器可以连续调谐1O GHz以上而不跳模.     

反馈相位随机调制消除混沌半导体激光器的外腔长信息

提出并数值证实利用反馈相位的随机调制可消除外腔半导体激光器反馈引起的时延结构. 研究发现:当反馈相位随机调制信号的速率处在0.1—1 Gbit/s范围,随机调制信号的切换幅值个数达到5时,在半导体激光器偏置电流(1.2—2.8I_th)和反馈速率(8—26 GHz)构成的参数空间中,反馈时延结构对应的外腔长信息可被有效地消除. 关键词： 半导体激光器 外腔长 反馈相位 随机信号调制     

反馈强度对外腔反馈半导体激光器混沌熵源生成的随机数序列性能的影响

外腔反馈半导体激光器在合适的反馈强度下将呈现混沌态, 其输出的激光混沌信号可作为物理熵源获取物理随机数序列. 着重研究了外腔反馈强度对最后获取的二元码序列的随机性的影响. 数值仿真结果表明, 随着反馈强度的增加, 外腔反馈半导体激光器输出的混沌信号的延时时间特征峰值呈现先逐渐减小再逐渐增大的过程, 而对应的排列熵特征值呈现先增大、后缓慢降低的过程, 即存在一个优化的反馈强度可使输出的混沌信号的延时特征得到有效抑制且复杂度高. 利用NIST Special Publication 800-22软件对基于不同反馈强度下外腔半导体激光器输出的混沌信号所产生的二元码序列的随机性进行了相关测试, 并讨论了反馈强度的大小对测试结果的影响.     

光注入下外光反馈半导体激光器输出自相关特性研究

基于半导体激光器(SL)受到外部扰动(光反馈和光注入)下的速率方程组,研究了反馈系数、延迟时间、注入强度和频率失谐对半导体激光器输出混沌信号自相关特性的影响.研究表明：上述四个参量对SL输出混沌信号的自相关函数曲线的半高全宽(FWHM)以及边峰抑制比都有影响;通过合理选择各参量,可以使SL输出的混沌信号具有尖锐的自相关函数曲线分布,其FWHM可降到0.02 ns,比已有相关报道提高了一个数量级. 关键词： 半导体激光器 光反馈 光注入 自相关函数     

920 nm光抽运垂直外腔面发射半导体激光器结构设计

设计并优化了一种用808nm的大功率激光二极管为抽运光源,In_0.09Ga_0.91As量子阱结构为增益介质的920nm光抽运半导体垂直外腔面发射激光器。运用有限元方法,对激光器的电特性方程和光特性方程求自洽解,计算了器件各种特性参量。分析了单个周期内不同阱的个数(1,2和3)、不同阱深、不同垒宽、不同非吸收层组分、不同非吸收层尺寸条件下,器件性能的改变,特别是模式、阈值和光-光转换效率的改变,从而选择一个最佳的结构。     

A new approach to asymmetric feedback in a segmented broad area diode laser

We present the demonstration of a non-critical setup for asymmetric feedback in a segmented broad area diode laser. We compare the dependence of the beam quality on the position of the dispersive element for standard spectral beam combining and our new non-critical setup. We find that our new approach is significantly less critical to the position of the dispersive element. It is shown that we can displace the dispersive element by at least 50% of the focal length of the collimating lens away from the Fourier plane without compromising performance. Furthermore, our approach provides the same high beam quality as is possible using off-axis spectral beam combining. This provides the possibility of achieving a high beam quality in a more compact setup than previously possible.     

一种实现光纤激光器高功率输出的方法

介绍了一种实现光纤激光器高功率输出的新方法——采用螺旋芯光纤，这种光纤是在光纤制作过程中按照一定的弯曲半径使纤芯呈螺旋状排布在光纤包层中。介绍了这种螺旋芯光纤的原理和其提高输出功率的能力，以及目前的理论与实验研究现状。基于该光纤，提出了一种光纤激光器相干合成新思想。     

高边模抑制比窄线宽的光纤光栅外腔半导体激光器

本文从耦合腔理论出发分析了光纤光栅外腔半导体激光器的模式选择,得到了为达到稳定的高主边模抑制比所需的短外腔、短光纤光栅的器件设计原则.制作了两只光纤光栅外腔半导体激光器,     

Experimental investigations on the external cavity time signature in chaotic output of an incoherent optical feedback external cavity semiconductor laser

Chaotic dynamics of a semiconductor laser subject to incoherent optical feedback (IOF) are experimentally investigated, and the external cavity time are retrieved and measured from intensity time series of the laser output by using self-correlation function and the mutual information. Through moderating feedback strength and injection current of the laser, the external cavity time signature of the laser chaotic output is effectively attenuated, and then the security of such chaos encryption system can be assured to a certain degree.     

Measurements and analysis of antireflection coatings reflectivity related to external cavity lasers

Facets of semiconductor optical amplifiers (SOA) designed for external cavity lasers must be coated with an antireflection (AR) film of high quality and extremely low reflectance. Therefore measurements of facet reflectance play a crucial role in the fabrication of such AR coating. The reflectance can be estimated by studying the optical power reflected from the Fabry-Perot cavity formed for that purpose by the examined SOA facet and the end of a single-mode fibre. We have made analysis of practical suitability of such measurement method. Theoretical calculations show that, for the low reflectance coatings, losses due to light coupling into optical fibre cannot be omitted in the analysis of the experimental results. To verify this conclusion a theoretical model was tested for a low reflectance surface and we have found that the relative error of the measurements supported by the theoretical model is on the order of 8%.     

带调谐光纤F-P腔的光纤环腔半导体激光器的频偏特性研究

本文由速率方程出发分析了带调谐光纤F-P腔的光纤环形腔半导体激光器的频偏特性,结果表明在低频时的频偏功率比自由运转激光器低,而在高频时则趋于一致。改变调制频率和F-P腔的腔长可以改变激光器的频偏功率比,选择适当的调制频率和F-P腔参数就能获得不同的频偏特性。     

Fabrication and characterization of 1.55 μm single transverse mode large diameter electrically pumped VECSEL

We report on the design, fabrication, and characterization of InP-based 1.55 μm wavelength large diameter (50 μm) electrically pumped vertical external cavity surface emitting lasers (EP-VECSELs). The hybrid device consists of a half vertical cavity surface emitting laser (1/2-VCSEL) structure assembled with a concave dielectric external mirror. The 1/2-VCSEL is monolithically grown on InP substrate and includes a semiconductor Bragg mirror and a tunnel junction for electrical injection. Buried (BTJ) and ion implanted (ITJ) tunnel junction electrical confinement schemes are compared in terms of their thermal and electrical characteristics. Lower thermal resistance values are measured for BJT, but reduced current crowding effects and uniform current injection are evidenced for ITJ. Using the ITJ technique, we demonstrate Room-Temperature (RT) continuous-wave (CW) single transverse mode laser operation from 50-μm diameter EP-VECSEL devices. We show that the experimental laser optical output versus injected current (L–I) curves are well-reproduced by a simple analytical thermal model, consistent with the thermal resistance measurements performed on the 1/2-VCSEL structure. Our results indicate that thermal heating is the main mechanism limiting the maximum CW output power of 50-μm diameter VECSELs, rather than current injection inhomogeneity.     

Study on a broad-area laser diode with external cavity feedback

The external cavity feedback of a broad-area laser diode is investigated. In Fourier optic methods, the inserted prism in an external cavity can be interpreted as a spatial filter in the Fourier plane of the laser diode. The transverse mode can be selected by changing the position of the filter. As the result of a self-consistency theoretical analysis, the output beam of the external cavity has a single-lobed far-field profile. It agrees well with the experiment result. The beam times-diffraction-limit-factor M² is measured to be 1.16.     

V型槽衬底内条形大光腔可见光半导体激光器

采用一种新的液相外延工艺，研制出具有大光腔结构的Ｖ型槽衬底内条形可见光发射半导体激光器，其光谱波长为７７９－７８４ｎｍ，室温连续工作阈值电流为６０ｍＡ，具有２倍阈值的基模工作时，线性输出光功率可达８ｍＷ，４ｍＷ下工作寿命已超过３０００小时。     

光栅耦合外谐振腔调谐的半导体量子级连激光器

本文研究了由InGaAs/InAlAs材料组成,波长为4.6和5.1微米的量子级连中红外半导体激光器的光栅外耦合谐振腔的特性。在温度是80K时波长可调制宽度是激光中心波长的1.5%左右。对于这两个激光器而言,它们的波长可调制宽度随温度升高而减低。被调制的单模激光器的输出光功率是几个毫瓦,激光的谱线宽度是1到2个微米。激光阈值电流随波长缓慢变化,然而激光输出效率在短波长时更加优化。