GaAs半导体中的三光子吸收

本文从直接能隙半导体中三光子吸收跃迁速率的全量子理论表达式出发,在二能带和四能带理论模型下,分别就抛物线和非抛物线型能带,计算了GaAs半导体的三光子吸收系数。其结果与实验值作了比较。同时还给出了GaAs中三光子吸收系数的色散曲线。     

GaAs半导体中三光子吸收的研究

本文利用全量子理论推导了半导体中多光子吸收跃迁速率的一般表达式。对各种模型计算了本征GaAs在λ=2.06um下的三光子吸收系数。实验上采用非线性光电导和非线性光透射技术,测量了GaAs中三光子吸收系数。     

GaAs在光通讯波段的超快非线性光学研究

采用Z-扫描和泵浦-探测技术,在光通讯波段对砷化镓(GaAs)单晶进行了非线性动力学以及非线性光学的实验研究.飞秒泵浦-探测实验结果表明,三阶非线性光学效应源于砷化镓单晶对飞秒激光的瞬态双光子吸收,而五阶非线性光学效应源于砷化镓单晶双光子吸收诱导的自由载流子吸收效应.通过Z扫描实验,得到了关于GaAs单晶所有的非线性光学参数,包括双光子吸收系数、三阶非线性折射系数、双光子吸收诱导的自由载流子吸收截面以及双光子吸收诱导的自由载流子折射截面.结果表明,砷化镓单晶在制造光限幅器件和光电探测器方面具有良好的发展前景.

     

GaAs中与施工高激发态有关的共振极化子效应

报道了ｎ型ＧａＡｓ的杂持磁光电导谱，在相对低的磁场下观察到束缚电子高激发态与ＬＯ声子的共振相互作用；讨论了共振极化子光电导响应随磁场强度变化的行为，以及钉扎在ＬＯ声子能量处的光电导峰的物理起源。     

GaAs半导体激光器线宽展宽因子的理论计算

本文利用简单模型综合考虑了带间跃迁、自由载流子吸收和带隙收缩对半导体激光器线宽展宽因子的影响,给出了半导体激光器线宽展宽因子的一种较为简便的计算方法.首先从理论上推导出线宽展宽因子的计算公式,分析并计算了GaAs半导体激光器的增益特性,并使用MATLAB软件中的Mupad工具包求解费米积分的数值解.然后根据得到的增益拟合曲线峰值的变化计算了带间跃迁对线宽展宽因子的影响.最后,分别讨论和计算了自由载流子吸收和带隙收缩对线宽展宽因子的影响.结果表明,带间跃迁和带隙收缩对线宽展宽因子的影响较大（α因子值分别为22.562,－6.853）,而自由载流子吸收对线宽展宽因子的影响较小（只有－0.605）.     

GaAs与InP半导体光导开关特性实验研究

利用Ⅲ-Ⅴ族化合物半导体材料砷化镓(GaAs)和磷化铟(InP)及其掺杂材料制作的光导开关具有很好的时间响应及高功率输出特性.比较了这两种材料制作的不同电极间隙类型的光导开关的开关时间响应速度、导通光能与饱和触发激光能量、线性与非线性工作模式及触发稳定性等特性.结果表明,利用InP和GaAs两种材料制作的光导开关都具有达到皮秒级的超快时间响应,其对时间最佳响应与偏置电场有关.两种开关的多次触发时间抖动在几个皮秒范围,输出电压峰峰值抖动优于10%.GaAs开关的非线性工作电场阈值比InP开关低,更容易实现非线性输出.     

注氮GaAs中的深能级及其对自由载流子的补偿

详细研究了注氮n型GaAs中深的和浅的杂质缺陷的电学性质。深能级瞬态谱(DLTS)技术测量表明,能量为140keV和剂量为1×10¹³cm^-2的氮离子注入并经800℃退火30min的GaAs中存在四个电子陷阱,E₁(0.111),E₂(0.234),E₃(0.415),E₄(0.669)和一个空穴陷阱H(0.545),而在能量为20keV和剂量为5×10^{14关键词：}     

Steady-state analysis of three-photon absorption spectra via density-matrix method in a three-coupled-quantum-well nanostructure

We numerically simulate three-photon absorption spectra in a three-coupled-quantum-well nanostructure interacting with a pump field,a coherent coupling field,and a probe field.We find that the three-photon absorption spectra can be dramatically influenced due to the intensities of the coupling field and pump field changing under the three-photon resonance condition.The effect of the frequency detuning of the pump field on the three-photon absorption spectra is also discussed.The study in our case is much more practical than the study in the case of its atomic counterpart in the sense of flexible design and the wide adjustable parameters.Thus it may open up some new possibilities for technological applications in optoelectronics and solid-state quantum information science.     

Two-photon absorption coefficient dichroism in Ⅱ-Ⅵ semiconductor crystals

Considering two beams propagate in semiconductor crystal, this paper discusses the polarization dependence of pump beam-induced intensity attenuation of probe beam due to two-photon absorption (TPA). Numerical calculation and experimental measurement demonstrate that TPA coefficient is polarization dependent. For homogeneous materials, probe beam attenuation arises from the imaginary part of diagonal and off-diagonal components of third-order nonlinear susceptibilities.     

Thiophene-fluorene derivatives with high three-photon absorption activities and their application to optical power limiting

The three-photon absorption (3PA) properties of two thiophene-fluorene derivatives (abbreviated as MOTFTBr and {ATFTBr}) have been determined by using a Q-switched Nd:YAG laser pumped with 38ps pulses at 1064nm in DMF. The measured 3PA cross-sections are 152\times 10^-78cm⁶s² and 139\times 10^-78cm⁶s², respectively. The optimized structures were obtained by AM1 calculations and the results indicate that these two molecules show nonplanar structures, and attaching different donors has different effects on the molecular structure. The charge density distributions during the excitation were also systematically studied by using AM1 method. In addition, an obvious optical power limiting effect induced by 3PA has been demonstrated for both derivatives.     

Optical absorption in a semiconductor cylindrical nanolayer

In the effective-mass approximation the single-electron states in a semiconductor cylindrical nanolayer in the regime of strong quantization are considered. The explicit form of the energy spectrum and envelope wave functions of single-electron states is obtained in the case of large and moderate radii of the system. The corresponding absorption bands of dipole and quadrupole optical transitions in the layer are calculated.     

两种新型芴类衍生物的三光子吸收特性研究

研究了两种新型芴类衍生物9,9_二（2_乙基已基）_2,7_二咔唑_9H_芴（简记为DCZF）和9 ,9_二（2_乙基已基）_2,7_二（2_（4_甲氧基）苯_2,1_乙烯基）芴（简记为BMOSF）在N ,N_二甲基甲酰胺（DMF）中的线性吸收和单光子荧光行为,并用脉冲宽度为38ps,重复 频率为10 Hz的1064 nm Nd：YAG脉冲激光研究了两种化合物的三光子吸收性质.结果表明： 两种新材料的最大线性吸收峰分别位于330和380nm,吸收区域覆盖了270—420 nm波段. 两种化合物的荧光带位于蓝_紫区,中心波长为369和442 nm,都具有较小的斯托克斯位移. 化合物DCZF和BMOSF的三光子吸收系数分别为γ_DCZF=678×10^{- 20} cm3/W²和γ_BMOSF=592×10^-20 cm³/W². 同时, 两种新材料还表现出明显的三光子吸收光限幅效应,当入射光强分别为8和6GW/cm²时,非线性透过率分别达到30%和45%.关键词：芴类衍生物三光子吸收光限幅非线性透过率     

两种三光子吸收染料光限幅性能的实验研究

研究了两种新型D-π-D结构的芴类衍生物4-{7-[4-（二甲基胺）苯基]-9,9-二（2-乙基己基）-9H-芴-2-}-N,N-二甲基苯胺[缩写为B（DMAP）F]和4-{2-[7-（4-氨基苯乙烯基）-9,9-二（2-乙基己基）-9H-芴-2-]乙烯基}苯胺（缩写为BASF）在四氢呋喃（THF）和N,N-二甲基甲酰胺（DMF）中的线性吸收和单光子荧光行为,用脉冲宽度为38ps,重复频率为10Hz的1064nmNd;YAG脉冲激光研究了两种化合物的三光子吸收性质,结果表明：受溶剂效应的影响,两种化合物在极性较大的四氢呋喃溶剂中的最大线性吸收峰和荧光发射峰都有所红移;在极性较大溶剂中三光子吸收截面的数值较大,最高达到10^ -76cm^6S^2数量级。两种新材料还表现出明显的三光子吸收光限幅效应,当入射光强为8GW／cm^2时,B（DMAP）F和BASF的非线性透过率分别达到35％和39％。     

Two-photon absorption coefficient in relation to the typical pulse models of laser

The two-photon absorption (TPA) coefficient (β) relating to pulse models of laser is theoretically studied based on the nonlinear absorption equation. An expression of nonlinear energy transmission is obtained, in which a factor (g) is introduced to describe the β deviation resulting from the pulse profile of laser. The relative deviation can be then expressed as (1/g − 1)% for comparing β obtained based on other pulse models of laser with β₀ based on the rectangular one. The values of g factor and the deviation of some typical ultra-short pulse models used nowadays are also calculated and presented. Our results suggest that the β deviations from the temporal pulse shapes should not be neglected in usual nonlinear transmission measurement. The g factor may become a useful parameter in taking account of this deviation.     

Fractional photon model of three-photon mixing in the non-linear interaction process

In this paper, a fractional photon model is proposed by considering the photon-exchange interaction in the reverse process of the non-linear three-photon mixing interaction. The phase matching condition for various types of uniaxial crystals can be simplified and classified by this model with the consideration of the unequal fractional photon-exchange of the two generated waves in the reverse manner. This also leads to the explanation of observing the phase mismatch and output bandwidth of the resonant and non-resonant waves in a cavity. Finally, a quantitative approach to this model, with experimental results, is also demonstrated.     

Optical absorption in dendrimers

Dendrimers are highly branched molecules, which are expected to be useful, for example, as efficient artificial light harvesting systems in nano-technological applications. There are two different classes of dendrimers: compact dendrimers with constant distance between neighboring branching points throughout the macromolecule and extended dendrimers, where this distance increases from the system periphery to the center. We investigate the linear absorption spectra of these dendrimer types using the Frenkel exciton concept. The electron–phonon interaction is taken into account by introducing a heat bath that interacts with the exciton in a stochastic manner.     

用共振多光子电离技术测量分子动力学参数

理论上推导了央三光子共振四光子电离过程中，电离流与多光子动力学参数的关系。首次提出用共振多光子离技术获得三光子吸收截面，四光子电离截面以及无辐射弛豫速率参数法。实验测量了气相甲苯分子里德堡态的上述动力学参数。结果在理论预期的数量级范围内。