InGaAs/GaAs应变量子阱激光器线宽展宽因子的理论研究

详细地介绍了计算线宽展宽因子(α因子)的理论基础及推导过程, 建立了α因子的简便模型. 该模型分别考虑了带间跃迁、带隙收缩和自由载流子效应对α因子的影响, 利用不同载流子浓度下的增益曲线得到光子能量随载流子浓度的变化速率以及微分增益, 进而对α因子进行近似计算. 模拟计算了InGaAs/GaAs量子阱激光器的增益曲线及α 因子的大小, 计算结果与文献报道的实验值相符. 进一步讨论了InGaAs/GaAs量子阱阱宽及In组分对α 因子的影响. 结果表明, α 因子随In组分和阱宽的增加而增加.     

硅基支撑系统的光刻工艺

为提高硅基支持系统制备中光刻过程的线宽精度,用正交试验分析了前烘、曝光、显影主要步骤中一些主要参数对制备结果的影响,得到了它们的影响程度的规律以及较优的参数组合。在此基础上设计和训练了合适的前向误差反向传播神经网络,对主要工艺参数进行了进一步的分析、预测和优选,并用实验加以验证。最终得到在胶厚约1.55 m时,前烘温度100 ℃,时间90 s; 曝光时间5 s; 显影温度15 ℃,时间90 s时,光刻后图形的线宽偏差最小,达到了0.3 m以下。     

减反膜外腔半导体激光器特性的研究

研究了镀减反膜GaAs半导体激光器在Littrow 式外腔结构中的输出特性.采用电流补偿技术,得到了约30 GHz的连续无跳模调谐范围.利用外差拍探测技术获得激光器输出线宽约为120 kHz.还研究了激光器的强度噪声分别随着电流与波长变化的特点并对此进行了分析.该类激光器可以广泛应用在冷原子物理、激光光谱以及量子光学等许多领域. 关键词： 减反膜 半导体激光器 线宽 强度噪声     

Influence of laser linewidth on external-cavity frequency doubling efficiency of a 1.56μm master oscillator fiber power amplifier

By using an external-cavity frequency-doubling master oscillator fiber power amplifier (MOPA), a 700~mW continuous-wave single-frequency laser source at 780~nm is produced. It is shown that the frequency doubling efficiency is improved when the seed diode laser is optically locked to a resonant frequency of a confocal Fabry--Perot (F-P) cavity. This phenomenon can be attributed to the narrowing of the 1.56~μ m laser linewidth and explained by our presented theoretical model. The experimental results are found to be in good agreement with the theoretical predictions.     

相位调制信号对窄线宽光纤放大器线宽特性和受激布里渊散射阈值的影响

高功率窄线宽光纤放大器的输出功率主要受限于受激布里渊散射(SBS)效应,通过相位调制进行线宽展宽可以有效抑制SBS效应.基于窄线宽光纤放大器中的SBS动力学模型,研究了正弦信号、白噪声信号和伪随机编码信号(PRBS)对窄线宽光纤放大器光谱特性与SBS阈值的影响.研究发现,采用不同信号进行相位调制时,调制频率和调制深度等参数对调制后激光光谱的谱线间隔、谱线数目与光谱平整度的影响存在较大差异,进而影响放大器的线宽特性和SBS阈值.通过对比分析,给出了调制信号的类型选择和参数优化原则,能够为窄线宽光纤放大器的相位调制系统设计提供参考.     

Cavity linewidth narrowing with dark-state polaritons

We present a quantum-theoretical treatment of cavity linewidth narrowing with intracavity electromagnetically induced transparency(EIT). By means of intracavity EIT, the photons in the cavity are in the form of cavity polaritons:bright-state polariton and dark-state polariton. Strong coupling of the bright-state polariton to the excited state induces an effect known as vacuum Rabi splitting, whereas the dark-state polariton decoupled from the excited state induces a narrow cavity transmission window. Our analysis would provide a quantum theory of linewidth narrowing with a quantum field pulse.     

激光场线宽对四能级原子系统相干效应的影响

采用密度矩阵方程,在引入激光场线宽的条件下,计算了N型四能级原子系统中介质对探测场的吸收。结果表明:耦合场线宽的引入,消弱了四能级原子相干,对抑制吸收有增强作用,对增强吸收有抑制作用,即耦合场线宽的引入导致了退相干。控制场线宽的引入,在电磁感应透明中削弱了四能级原子相干性,降低了共振吸收,增强了光透明;在电磁感应吸收中,控制场线宽的增加使谱线中心两侧的吸收增强,削弱了谱线中心的吸收增强,从而使四能级系统的电磁感应吸收转换为电磁感应透明。     

半导体激光器的线宽压窄及频率连续调谐

我们利用共焦F—P腔光学弱反馈技术，实现了单模GaAlAs半导体激光器线宽压窄、频率锁定及连续调谐。其线宽从自由运转时的10MHz被压窄到45kHz，并可将频率锁定于共焦F—P腔。实验证明，在弱反馈情况下，激光器的频率连续调谐范围与共焦FP腔的光强反馈量近似成正比，实现了在铷原子D2线附近1．2GHz的频率连续调谐，     

Electron spin resonance studies on deuterated nitroxyl spin probes used in Overhauser‐enhanced magnetic resonance imaging

The electron spin resonance studies were carried out for 2 mm concentration of ¹⁴N‐labeled and ¹⁵N‐labeled 3‐carbamoyl‐2,2,5,5‐tetramethyl‐pyrrolidine‐1‐oxyl, 3‐carboxy‐2,2,5,5‐tetramethyl‐pyrrolidine‐1‐oxyl, 3‐methoxycarbonyl‐2,2,5,5‐tetramethyl‐pyrrolidine‐1‐oxyl and their deuterated nitroxyl radicals using X‐band electron spin resonance spectrometer. The electron spin resonance line shape analysis was carried out. The electron spin resonance parameters such as linewidth, Lorentzian component, signal intensity ratio, rotational correlation time, hyperfine coupling constant and g‐factor were estimated. The deuterated nitroxyl radicals have narrow linewidth and an increase in Lorentzian component, compared with undeuterated nitroxyl radicals. The dynamic nuclear polarization factor was observed for all nitroxyl radicals. Upon ²H labeling, about 70% and 40% increase in dynamic nuclear polarization factor were observed for ¹⁴N‐labeled and ¹⁵N‐labeled nitroxyl radicals, respectively. The signal intensity ratio and g‐value indicate the isotropic nature of the nitroxyl radicals in pure water. Therefore, the deuterated nitroxyl radicals are suitable spin probes for in vivo/in vitro electron spin resonance and Overhauser‐enhanced magnetic resonance imaging modalities. Copyright © 2017 John Wiley & Sons, Ltd.