激光不稳定性的平均场理论分析

我们将单模驻波腔激光器的Maxwell-Bloch方程取平均场近似,在腔和原子完全共振情况下,对连续输出的激光系统以合作参数C作判据,讨论了出现不稳定性的条件。当取三次特征方程近似时,得到了通常出现不稳定性的坏腔条件,并且给出了出现不稳定性的阈值。     

均匀加宽激光器不稳定性的单模平均场理论

在均匀加宽驻波腔激光器中,我们采用考虑光谱线函数的Maxwell-Bloch方程,对单模情况进行了线性稳定性分析,给出了出现不稳定性的阈值C_(thr)(C为合作参数)。结果表明:只有满足η>4(r+1)条件,才能出现不稳定性;并且分析了各个参数对不稳定性的影响。在γ、η取定后,对不     

光纤光栅外腔半导体激光器理论模型分析与选取

为了讨论三腔镜近似或耦合腔近似两种等效腔模型对计算光纤光栅外腔半导体激光器等效反射率等参量的近似程度,挑选出最优的理论模型,采用数值计算的方法进行模拟仿真,得到了两种模型在采用切趾光纤Bragg光栅和非切趾光纤Bragg光栅情况下的阈值增益等特性曲线。结果表明,在采用切趾光纤Bragg光栅,特别是切趾深度较大的情况下,采用三腔镜近似模型更加符合实际情况。此研究结果对分析和设计单纵模光纤光栅外腔半导体激光器具有一定的参考价值。     

带注入信号的双光子激光器的双稳性质

对于带注入信号、原子均匀展宽的单模环形腔双光子激光器,给出半经典的Maxwell-Bloch方程,论证了该系统在调谐情况下会出现双稳态,并通过绝热消除描述了双稳性导致的输出光的瞬态行为和滞后循环。所得结果表明:在输出场不连续变化之处,出现临界慢化现象。“坏腔”极限下,在     

(双稳外腔)LD分析中扰动近似的有效性研究

在两种不同调制(增益和损耗调制)情况下,对半导体激光器(LD)速率方程组的扰动近似处理有效性进行了分析.结果表明,在电流(或增益)调制情况下,扰动近似法所忽略的二阶小量在量级上确实与保留的一阶小量的平方相当;在损耗调制的情况下,系统变化前后的阈值载流子密度不同,被忽略的二阶小量可能会达到与一阶小量可比拟的程度.以可调谐双稳外腔半导体激光器(ECLD)为例,指明了在损耗调制下,扰动近似分析可能会失效.     

半导体激光器调制响应的速率方程小信号近似法研究

速率方程是研究半导体激光器瞬态过程的理论工具。为了能对实际中各种调制响应进行分析,采用小信号近似法求解了在任意调制信号下半导体激光器的速率方程。得到了任意调制信号下半导体激光器的速率方程的实值解析解,并根据得出的实值解析解分析了半导体激光器的一些调制响应特性,给出了一个调制信号为矩形脉冲电流的具体实例。最后研究并得出了小信号近似法准确的严格条件。根据一些半导体激光器的实际参数,给出了该条件在某些情况下的近似表达。     

环形染料激光器不稳定性的实验研究

用环形染料激光器观察并记录了腔内激光功率和激光频率随泵浦功率的变化。激光器在第一次达到阈值并建立激光振荡后,随着泵浦功率的增加先后出现第二、第三个阈值,激光功率出现两次不连续突变;同时激光器两次出现由单频工作到双频工作的跃变。     

布里渊单模光纤环形腔激光器实验研究

实验研究了布里渊单模光纤环形腔激光器(BSFRL)的输出功率、输出光谱和输出时域特性。通过对激光输出功率和光谱特性与构建激光器的光纤长度和输出耦合器的反馈耦合比关系的研究与分析发现,当构建的BSFRL的输出耦合器反馈耦合比为0.4、光纤长度为1.5 km时,BSFRL具有低泵浦阈值、高转换效率和稳定的单模激光输出,此时激光器的泵浦阈值约为3 mW,光-光转化效率为65%。通过调节偏振控制器,得到稳定的锁模脉冲输出。讨论了BSFRL的时域不稳定性并给出了相应解释。     

波导激光器的几个问题及波导式介质壁封闭腔的理论

考虑到无波导管中混合气体的导电性,或其它损耗因素,重新推导出相应于TE、TM、HE三种模式的特征方程,并求解出相应于各种模式的衰减常数C'nm,Marca-tili的结果是我们的近似情况。提出了波导式介质壁封闭光腔的理论,求出了腔的共振模式,共振频率和Q值的解析式并与开放腔作了比较。由于波导式介质壁封闭光腔对最低阶模式有相当高的Q和强的模式选择性能,因而建议运用于固体激光器中并给出了原理图。     

基于偏振测量的VCSEL激光器阈值行为研究

设计构建了垂直腔面发射激光器偏振测试系统,利用该测试系统研究了激光器不同偏振模式的阈值行为特点。激光器的输出光随着驱动电流的增大将会出现P偏振以及S偏振两种相互正交的偏振分量,并且两者具有不同的工作阈值;进一步依据测得的阈值点将激光器分为三个工作区域,通过对非偏振及偏振测试结果的比较分析得出:垂直腔面发射激光器的非偏振测量中观测到的工作阈值点体现的是P偏振分量的阈值点;激光器S偏振分量的阈值需要通过偏振测量才能明显观测到;P偏振与S偏振分量阈值电流之间的工作区域具有最好的线偏振度。本文的研究为垂直腔面发射激光器的未来研制测试工作和更好应用夯实了基础。     

Modelocking and multimode instability in laser intracavity frequency modulation

Using the Maxwell-Bloch equations, we have studied dynamics associated with an electro-optically tunable laser modulated by a sinusoidal signal with a frequency near the cavity free spectral range. We find that frequency modulation (FM) modelocking may occur when a higher order FM mode acquires the lowest threshold. For short-cavity lasers, the pulse waveform in modelocking is complicated, and unlike the simple Gaussian shape suggested by previous studies. In order to explain instability observed in laser FM operation, we develop a linear stability analysis for the lasing FM mode. Our analysis shows that this type of instability is attributed to mode competition and to laser relaxation dynamics. We then confirm the analytic results with numerical simulations.     

Analysis of gain and saturation characteristics of a semiconductorlaser optical amplifier using transfer matrices

The transfer matrix method (TMM) has been applied to analyze the gain and saturation characteristics of semiconductor laser optical amplifiers. This method approximates the amplifier cavity by dividing it into M discrete subsections, and TMM has been applied to analyze the stepwise longitudinal field distribution at each subsection along the amplifier cavity. By incorporating also the carrier rate equations into the analysis, it has been shown that the approximation can accurately describe the carrier density and longitudinal field distribution along the amplifier cavity if M is sufficiently large (i.e., the size of each subsection is about an order of magnitude of one wavelength of the input signal). By assuming that the amplifier is biased below oscillation threshold such that the contribution of spontaneous emissions to the gain characteristics can be neglected, we have shown that our proposed method yields a fast and efficient algorithm in analyzing the gain and saturation characteristics of laser amplifiers. We have compared the results produced by our method to those analyzed using the average photon density (AVPD) approximation technique, as well as to experimental results on a 1.5-μm buried heterostructure semiconductor laser amplifier     

掺钕激光晶体双波长振荡条件的理论研究

阐述了具有双下能级四能级结构的激光介质产生双波长激光的原理,介绍了二镜腔内两个波长同时振荡所要满足的阈值公式,数值计算发现空间烧孔效应的存在使阈值条件从一条曲线拓宽为一个区域,使两个波长更容易同时起振。然后,计算了激光晶体长度和泵浦功率对双波长阈值条件的影响,结果发现在增益饱和前晶体越长,泵浦功率越高,越容易出现双波长激光。最后,计算了几种常用掺钕激光晶体的双波长阈值曲线,对比发现Nd:YAP晶体由于具有两个相近的发射截面而更适合于产生双波长激光。     

外腔反馈半导体激光器的损耗和阈值特性研究

通过对半导体激光器(LD)的损耗和阈值电流特性的分析，引入等效反射系数的概念，根据多光束干涉的原理，导出了在外腔反馈作用下LD的阈值电流公式。从等效反射系数的推导可以看出，外腔的反馈相当于增大了LD一个端面的反射率，减小了损耗，从而使LD激光振荡的阈值降低。该公式在外腔长度和激光波长可以比拟的情况下能够准确地分析反馈注入对阈值电流的影响，但是在外腔长度远大于激光波长情况下不再适用。针对实验中外腔长度较大的情况，使用光功率的分析简化了理论模型，得出了与实验结果相吻合的结论，即外腔反馈注入使LD出光阈值电流明显降低。     

V型无反转激光的非绝热线宽

应用c数量子朗之万方法在激光场的低阶近似下讨论了强相干驱动场下V型三能级系统无反转激光的非绝热线宽,证明了在强驱动场下,不管激光腔是“好腔”还是“坏腔”,系统的非绝热效应消,了系统均可作绝热近似。     

Temperature dependence of the threshold current for InGaAlP visiblelaser diodes

The temperature dependence of the threshold current for InGaAlP visible-light laser diodes was investigated from the standpoint of gain-current characteristics. The dependence of the light output power versus the current characteristic on the cavity length was evaluated for a 40-μm-wide InGaP-InGaAlP broad-stripe laser in the temperature range between -70 and 90°C. The threshold-current density dependence on the cavity length shows that a linear-gain approximation is suitable for this system. A minimum threshold-current density of 860 A/cm² was achieved at room temperature with a cavity length of 1160 μm. The internal quantum efficiency decreased in the temperature range higher than -10°C, which affected the excess threshold-current increase and the decrease in the characteristic temperature at this temperature range     

高损伤阈值氟化氘腔镜研制

报道了氟化氘(DF)激光器腔镜的膜系设计、材料选取、制备工艺及其损伤阈值和热畸变测试结果。实验结果表明，镜面在21kW／cm^2功率密度下的热畸变为0．32左右(λ=632．8nm)，腔镜的损伤阈值大于40kW／cm^2。     

Dynamics of optically switched bistable diode laser amplifiers

Measurements of the switch-off time of an optically switched Fabry-Perot InGaAsP/InP laser amplifier indicate that the device can turn off in less than the spontaneous carrier lifetime. The switching dynamics of the amplifier are numerically modeled using the van der Pol equation with optical injection and the rate equation for the carrier density. The simulations show that the device switches off faster as its injection current is increased toward the threshold level. A qualitative analytical analysis is presented which shows that this fast switch off is due to the very large cavity finesse of the amplifier when biased near its lasing threshold.