II-VI多量子阱中局域化激子的受激发射

通过对ＺｎｘＣｄ１－ｘＴｅ－ＺｎＴｅ多量子阱样品的光泵受激发射研究讨论了材料中激子局域态对受激发射激子过程以及受激发射特性的影响。两块不同组份和不同局域态密度的ＺｎＣｄＴｅ－ＺｎＴｅ多量子阱样品受激发射过程都是ｎ＝１重空穴激子参与的一系列过程，但在Ｚｎ０．６７Ｃｄ０．３３Ｔｅ－ＺｎＴｅ中发现了激子－激子散射的受激发射过程，而在Ｚｎ０．７８Ｃｄ０．２２Ｔｅ－ＺｎＴｅ中没有发现这一受激发射的激子过程。ｘ＝０．６７的样品中具有较高的局域化激子密度，其受激发射具有较高的阈值。     

钕激活玻璃激射光谱成分随时间的变化

本文指出了钕激活的玻璃光受激发射在闪光过程中振荡光谱线的数目以及它们的波长随时间的变化。斯奈泽(E. Sixitzer)的文章曾经指出钕激活玻璃受激光发射,由分布在1.061~1.062微米波段的光谱线组成。     

新颖激光器的物理机制

论述了电激励远红外激光器、光泵远红外激光器和自由电子激光器产生远红外受激发射的物理机制。以氰化氢激光器和甲基氟激光器为例,分析了HCN分子和CH_3F分子产生受激发射的物理过程和受激发射特性。用三能级二光场的密度矩阵方程     

简讯

第三次受激光发射会议开会期间,曾举行名词统一小组会议,讨论光受激发射领域中几个最常用而又较为混乱的译名。     

掺Yb3+硅酸盐玻璃的制备和光谱特性

为了研究用于高功率激光器的掺Yb3+激光玻璃的制备和光谱特性,采用高温熔融工艺制备了两块碱金属元素含量不同的掺Yb3+硅酸盐激光玻璃,利用相应的光谱仪器测试了两块玻璃样品的吸收光谱和荧光光谱;分析了不同碱金属离子对吸收系数和荧光强度的影响;比较了倒易法和Fuchtbauer-Ladenburg(F-L)法两种不同方法得到的受激发射截面图,得到了Yb3+掺杂玻璃的各个光谱参量和激光参量。结果表明,随着碱金属离子半径的增大,吸收系数和荧光强度减小;样品的吸收截面图与倒易法计算所得的受激发射截面图相似,而与F-L法计算所得的受激发射截面图差别较大,并且倒易法发射截面图中主峰波长较F-L法发射截面图的主峰波长蓝移;最终样品1的增益性能比较好。     

325毫微米紫外固体Ce:YLF激光器

本文首次报导三价稀土离子掺杂晶体中5d-4f跃迁的受激发射的研究。用249亳微米光泵LiYF4(YLF)晶体中Ce3+离子，获得325.5毫微米的激光发射，这是波长最短的光泵固体激光器。宽的激光跃迁荧光线宽使Ce:YLF激光器成为305~325亳微米波段的一个可调谐相干近紫外辊射光源。     

电子束控CO激光器发射特性的理论研究

对发射长脉冲（10^-4~10^-3秒）电子束控CO激光器的光谱、阈值及能量特性作了研究，该研究建立在速率方程的数值解上，这个速率方程组描述了：CO分子振动能级的粒子数；由在CO分子振动级间的跃迁引起的受激发射；及在这种气体转动-平动温度中的变化。     

近二十年来激光发展概况

1917年，爱因斯坦从用统计平衡的观点研究黑体辐射的工作中，得到激发态原子可有两种释放能量的发射方式一是自发发射，一是受激发射。对于受激发射这一重要概念的意义没有被人们立刻认识。1940年前后，有人曾观察到能级粒子数反转现象。     

麻省理工学院制成单原子激光器

当主持G．R．Harrison光谱实验室的M．Feld告诉我他们已制成一台单原子激光器时，我心存疑惑。听了KgungwonAn──在此完成博士论文的一位韩国学生──叙述该工作后，所有疑惑都烟消云散。该技术不仅采用了空间孤立自由原子，也省去受激发射，即把原子的瞬时激发态变为发射自然产生光子的爱因斯坦链式反应原理。迄今受激发射是激光物理的基石，所有商用激光器都依此生产。Feld小组不仅超越了激光技术的这方面，也示出在处理局限于“箱”内的单光子、单原子相互作用时量子效应也是重要的。他们采用了什么方法呢？象维多利亚烹任书上说的…     

用串级能量转移进行有机薄膜的光放大

现在，对开发使用固体有机材料和聚合物材料作增益介质的激光器已有新兴趣。这些有机材料具有许多特性，很适合作增益介质激光器的侯选应用，比如，它们的发射带（经斯托克斯频移）偏离吸收带，发射（光的）物质很易嵌在合适基质材料中［‘－‘j。但尽管有这些优点，为进行光放大所需的阈值功率密度迄今报导仍很高［’－‘］。本文介绍一种基于分子间能量转移的方法，它可降低受激发射和激光作用的阈值，同时又能显著改善激活介质和波导特性。在我们材料中，分子的初始激发态是由基质化合物通过吸收光能而产生的。然后，这种态通过一步或多…     

Enhanced 1.32 µm fluorescence and broadband amplifying for O-band optical amplifier in Nd3+-doped tellurite glass

WO3 oxides with relatively high phonon energy and different concentrations were introduced into the Nd3+-doped tellurite-based glasses of TeO2-ZnO-Na2O to improve the 1.32 µm band fluorescence emission. The absorption spectra, Raman spectra, 1.32 µm band fluorescence spectra and differential scanning calorimeter (DSC) curves were measured, together with the Judd-Ofelt intensity parameters, stimulated emission and gain parameters were calculated to evaluate the effects of WO3 amount on the glass structure and spectroscopic properties of 1.32 µm band fluorescence. It is shown that the introduction of an appropriate amount of WO3 oxide can effectively improve the 1.32 µm band fluorescence intensity through the enhanced multi-phonon relaxation (MPR) processes between the excited levels of Nd3+. The results indicate that the prepared Nd3+-doped tellurite glass with an appropriate amount of WO3 oxide is a potential gain medium applied for the O-band broad and high-gain fiber amplifier.     

Valence band mixing and optical emission in modulation-doped GaAs-(AlGa)As heterostructures

Unexpected optical emission spectra from electrons confined in GaAs quantum layers reveal a strong component with polarization normal to the plane of the layers. For elementary electron-hole recombination processes, this suggests surprisingly large band mixing in the ground valence subband. Effective mass theories that include conventional symmetry breaking mechanisms do not satisfactorily account for this phenomenon. The stress dependence of the spectra confirm that many body shake-up processes in the Fermi sea are important in describing emission associated with the 2D electron plasma.     

基于二能级系统的广义吸收定律

传统Beer定律只有在入射功率密度小于几个kW时才能准确描述介质内部的光学吸收,而对于较大入射功率密度情形,由于存在受激发射和自发发射过程,使得该定律不再适用。目前已有的能够分析含有吸收、受激发射和自发发射三种过程的模型都没有得出关于吸收定律的解析表达式。为此,本文在二能级系统模型中,利用Lambert W函数解速率方程,推导出了吸收定律的广义解析表达式,并分析得出该广义定律的应用判据。在入射功率密度较低的情况下,该广义吸收定律可转化为传统Beer定律。通过实验测量与数值计算的对比分析,表明该广义定律能够快速准确地描述复杂介质内部的光学吸收。     

Spectroscopic study of Ga-doped Ge under uniaxial pressure

To identify the optical transitions responsible for the excitation of long-wavelength stimulated emission in uniaxially compressed Ga-doped Ge, the optical absorption and photoconductivity spectra of the material were investigated at a wide range of pressures in directions [111] and [001]. The dependence of the valence band splitting between the light-and heavy-hole subbands in Ge as a function of the applied pressure was found. As determined from this dependence, the deformation potential constants for the valence band appeared to be less than the presently accepted values. It is shown that, as pressure increases, some of the excited states of the Ga impurity levels reach the light-hole band, enter it, and remain close to its edge (the resonant states). It is possible that a population inversion of these resonant states gives rise to the excitation of stimulated emission at a photon energy of about 10 meV. No specific features confirming the existence of resonant impurity states near the edge of the heavy-hole band were found in the spectra.     

Semiconductor lasers with internal wavelength selection

Laser diodes with a deep built-in trapezoidal large-period diffraction grating have been developed on the basis of InGaAs/GaAs/AlGaAs heterostructures. The electroluminescence and stimulated emission spectra and light-current characteristics of diffraction-grating laser diodes have been studied. A substantial narrowing of both the luminescence and stimulated emission spectra was achieved due to the spectral selectivity of the grating. The maximum output optical power was 1 W at a drive current of 4 A. At the highest power, the lasing spectrum had a FWHM of ～2 Å. A narrowing of the lasing spectrum of the diffraction-grating laser by tens of times was demonstrated, compared with that of a laser with a Fabry-Perot cavity.     

Lasing and stimulated emission in π-conjugated polymers

Recent studies of lasing and stimulated emission in luminescent π-conjugated polymers performed by our group are presented. Optical properties of cylindrical high-Q polymer microcavities are discussed. The emission spectra of plastic microring and microdisk lasers are measured and analyzed. Light-emitting polymer microdiodes are demonstrated as possible candidates for electrically driven plastic lasers. In addition, two unusual regimes of stimulated emission characterized by narrow laser-like spectral lines are demonstrated in thin waveguiding polymer films. These regimes may be associated with random optical feedback introduced by light scattering inside the polymer films and amplified Raman scattering, respectively     

Stimulated and spontaneous emission of Cd<Subscript>x</Subscript>Hg<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Te structures in the range 3.2–3.7 µm at 77 K

Stimulated emission of radiation from Cd_xHg_1?xTe samples pumped by a Nd:YAG laser at temperature T≈77 K is obtained. Both spontaneous and stimulated emission is observed for the wavelengths λ in the range 3300–3600 nm. Experimental emission spectra are presented. The special features of the spectra and the possible applications of the structures are discussed.