微加工获得的F-P半导体激光器的光谱特性分析

利用微加工法可以在FP半导体激光器中引入具有反射功能的缺欠点或面来改进激光器的光谱特性。作者导出了含有多个缺欠点的微加工获得的FP半导体激光器(MMLD)的输出谱表达式,并对MMLD振荡模的边模被抑制的情况作了简要的说明。     

60GHz毫米波ROF系统的光源研究

提出了把通过注入锁定方法得到的FP单模输出光源应用到60GHz毫米波ROF系统中的方法.通过利用窄带放大自发辐射(ASE)光源插入FP半导体激光器以实现波长锁定,改变FP激光器的多模输出,得到单模输出的廉价光源的方法,成功地为ROF系统的基站提供了激光器.     

高温CW半导体激光器的阈值电流

用载流子速率方程分析了高温CW半导体激光器(LD)阈值电流(I_(th))与温度(T)的关系.数值计算结果分别给出了与T有关的腔内损耗、双分子复合和俄歇过程以及载流子泄漏效应对I_(th)的贡献大小.     

垂直耦合腔面发射激光器阈值特性研究

为了研究垂直耦合腔面发射激光器(CC-VCSELs)阈值特性,利用传输矩阵法计算了其阈值载流子浓度,在此基础上结合载流子速率方程讨论了阈值电流,得到了CC-VCSELs的双阈值点(1mA,0.75mA)与阈值电流关系曲线.数值计算结果比较表明,利用传输矩阵与载流子速率方程相结合的方法研究CC-VCSELs的阈值特性优于速率方程法,且数值计算结果与实验结果相吻合.     

增益非线性参数对半导体激光器调制特性的影响

本文用小信号分析法建立了半导体激光器调制的数学模拟，用这个模型研究了增益与载流子密度的非线性依赖关系对半导体激光器的功率调制、波长调制和ＣＰＲ值的影响。     

非制冷980 nm半导体激光器封装设计与热特性分析

针对非制冷980 nm半导体激光器组件的封装结构,对采用倒装贴片封装的激光器模块内部芯片外延层、热沉和焊料层进行了优化设计,运用有限元法(FEM)对微型双列直插(mini-DIL)非制冷980 nm半导体激光器在连续波(CW)驱动条件下的热场分布进行了模拟计算.对比了倒装贴片和正装贴片的激光器热特性,并对实际封装的激光器光电性能进行了测试.倒装贴片型非制冷980 nm半导体激光器的输出光谱在0～70℃时中心波长漂移仅为0.2 nm,半峰全宽(FWHM)小于1.6 nm,边模抑制比(SMSR)保持在45 dB以上,最大出纤功率达200 mW.研究结果表明,倒装贴片的非制冷980 nm半导体激光器在热稳定性和光电性能方面都有较大提高,能够满足高性能小型化掺铒光纤放大器对非制冷980 nm半导体激光器的性能要求.     

(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.     

AlGaAs/GaAs-MQW激光器光增益谱理论和实验

本文简明地描述了由载流子带内弛豫加宽的半经典的密度矩阵理论.根据该理论计算了AlGaAs/GaAs多量子阱激光器的线性偏振光增益及量子阱宽L_x、Al_xGa_(1-x)As势垒层x值和带内弛豫时间τ_(in)对TE增益的影响.实验测量了多量子阱激光器的偏振光增益谱.理论与实验进行了比较.     

新型无本振毫米波光纤无线通信上变频系统

基于低速信号注入法-珀(FP)激光器可实现无微波本振光纤无线通信(RoF)上变频技术,但是得到的微波本振频率受到FP激光器中四波混频效率的限制,难以直接实现毫米波载波的RoF上变频。在注入锁定FP激光器的基础上提出了一种新型的、低成本的在光域直接产生毫米波载波的RoF上变频方案。由于注入锁定FP激光器过程中的动态载流子特性,上变频得到的载波信号带有正啁啾,故可用负色散介质对载波信号进行脉冲压缩,从而增强高阶谐波分量以完成毫米波载波的无本振RoF上变频。实验中采用2 Gb/s非归零码注入实现了载波为13.9 GHz,用2.5 Gb/s注入实现了载波分别为13.9 GHz和15.4 GHz的RoF上变频,并采用上述方案分别实现27.8 GHz和30.8 GHz的倍频载波分量的增强。进一步实验验证了用本方案实现载波频率约60 GHz可调谐毫米波的无本振RoF上变频的可行性。     

本征碲镉汞光电导体中响应率对阻挡接触结构的依赖关系

本文导出了本征光电导体的低频响应率与阻挡接触结构相关的分析表达式。8～12μm碲镉汞(HgCdTe)光导探测器的数值计算结果表明:最佳的阻挡接触结构由金属-半导体界面处的载流子复合速率决定。     

Strong increase of the derivative of the carrier-induced indexchange of semiconductor lasers at low injected carrier density

The carrier-induced index change of a semiconductor laser was measured for injected carrier density ranging from 3 × 10¹⁶ cm^-3 to 2 × 10¹⁸ cm^-3. A strong nonlinear behavior between index change and carrier density is observed. The derivative of the index change versus carrier density at low carrier density can be 15 times larger than the derivative of the index change at high carrier density     

皮秒和纳秒脉冲激光作用于半导体材料的加热机理研究

从半导体材料的吸收机制出发,分析研究了激光能量在半导体材料中的传输过程,并采用双温模型分别模拟计算了在人射激光能量相同的情况下,皮秒和纳秒激光脉冲作用于硅半导体材料的加热过程,结果表明在纳秒脉冲作用下,可以忽略载流子效应,用单纯的单温热传导方程来模拟。而在皮秒脉冲作用下,应该考虑载流子效应,采用包括晶格温度和载流子温度的双温模型来模拟硅半导体材料的加热过程。     

基于半导体光放大器的可调谐环形腔激光器的激光建立过程

基于半导体光放大器(SOA)的环形腔激光器可实现高达兆赫兹的高速调谐,在光纤通信和光纤传感领域有广泛应用。采用稳态模型和分段算法研究SOA自发辐射特性,并基于此分别讨论了使用高斯型滤波器和法布里-珀罗(F-P)滤波器的两种可调谐环形腔激光器,研究了激光建立过程的特性,包括输出光谱和输出光功率随绕行圈数的变化,讨论了波长调谐的速度。结果表明,F-P滤波器的环形腔可以更快建立激光振荡,便于实际高速调谐应用。     

60 GHz millimeter-wave source using two-mode injection-locking of aFabry-Perot slave laser

We demonstrate 60 GHz carrier generation and transmission using a two-mode injection-locked Fabry-Perot (F-P) slave laser. The relationship between the power of the generated carriers and the frequency of the reference signal for the injection-locking is also investigated. The RF power-penalty caused by fiber dispersion was within 2.0 dB when the locked modes were transmitted at a distance of 0.5-48 km. Accordingly, the two-mode locked F-P laser can be used in fiber-based millimeter-wave systems     

半导体激光器的光谱及参数测量

半导体激光器的输出光谱,反映了激光器本身的基本工作特性。本文从实验上研究了半导体激光器的输出光谱特性随偏置电流而变化的关系,并对其进行了理论分析。在此基础上,进一步测得了半导体激光器的热阻,增益峰值波长和纵模波长对载流子密度的相对变化率等基本参量。     

Temperature dependence of the threshold current density in semiconductor lasers (λ = 1050–1070 nm)

The temperature dependences of the threshold current density and threshold concentration in semiconductor lasers based on MOVPE-grown asymmetric separate-confinement heterostructures with an extended waveguide have been studied (wavelengths ?? = 1050?C1070). It is shown that the temperature dependence of the threshold current density in semiconductor lasers becomes markedly stronger at above-room temperatures, which is due to temperature-induced carrier delocalization into the waveguide layers of a laser heterostructure. It was found that the sharp decrease in the thermal stability of the threshold current density with increasing temperature correlates with the coincidence of the Fermi level with the conduction-band bottom of the waveguide layer in the laser heterostructure. It is experimentally demonstrated that an increase in the energy depth and number of quantum wells in the active region of a semiconductor laser improves the thermal stability of the threshold current density. It is demonstrated that the characteristic parameter T ₀ attains a value of 220 K in the temperature range from ?20 to +70°C.     

Predicting shapes of hysteresis loops on the output of tunableexternal-cavity semiconductor lasers

Studies have been made of the nonlinear characteristics of grating tuned external-cavity semiconductor lasers with the aid of the analytical expression of the threshold carrier density required for the laser to oscillate at different frequencies. After connecting refractive index with carrier density through the spectral broadening factor and choosing an appropriate reference carrier density, the key points defining hysteresis loops on the N-ν (carrier density-frequency) curves have been determined analytically. Consequently, different shapes of hysteresis loops on P-ν (power-frequency) curves have been predicted. The validity of the theory has been examined using the data provided by different papers     

激光相位调制法布里-珀罗腔精细度法测定反射率

谐振腔精细度法是通过测量光学谐振腔透射谱线宽度来实现对光学反射镜反射率的测定。由于此谱线宽度数值通常在射频范围,采用光谱仪难以精确测量,而在谐振腔精细度方法的基础上引入激光相位调制技术,提出激光相位调制法布里-珀罗(F-P)腔精细度法测定反射率。利用电光调制器对激光进行射频相位调制,以产生的调制边带与激光载波的频率间隔作为“射频标尺”,精确测量了法布里-珀罗腔透射光谱的谱线宽度。利用腔精细度与腔透射光谱的谱线宽度及反射率的关系公式,获得了反射镜的反射率,测量精度可达到10-4。     

Concept of linewidth enhancement factor in semiconductor lasers:its usefulness and limitations

The usefulness and the limitations of the concept of the linewidth enhancement factor α in semiconductor lasers are examined by considering the laser dynamics without the rate-equation approximation. The rate equations with a constant value of α can be used for semiconductor lasers operating continuously or modulated directly such that the carrier density does not change significantly during each modulation cycle. A new set of generalized Bloch equations should be used whenever subpicosecond optical pulses are involved