Absorption of light by a ferromagnetic semiconductor

The coefficient of absorption of light by a ferromagnetic semiconductor is calculated for indirect transitions with allowance for the electron-magnon interaction. The absorption coefficient is obtained as a function of the external magnetic field. The magnetic red shift of the absorption edge is considered.     

金属微粒-半导体薄膜中小胶粒的光吸收和散射

金属微粒-半导体薄膜具有特殊的电学、光学及光电特性。本文讨论了埋藏于半导体基体中金属小胶粒光吸收和光散射公式。这些胶粉可以是球形,也可以是长球或扁球形。本文以银胶粒-氧化铯半导体为例,讨论了胶粒大小、椭球的偏心率对相对光吸收系数和光散射系数的影响,并给出这些系数随波长改变的曲线。 关键词：     

Optical absorption caused by the transitions between donor-acceptor pairs in a parabolic quantum well

The interimpurity optical absorption in a parabolic quantum well is studied theoretically. Under the assumption of a lightly doped semiconductor, the probabilities of acceptor-to-donor transitions are determined and the corresponding coefficient of light absorption is calculated. Within the framework of the nearest neighbor model, the broadening of impurity levels connected with the spatial distribution of donor-acceptor pairs is taken into account. The dependence of the absorption coefficient on the impurity concentration is determined and the blueshift in the absorption spectrum is studied.     

Free carrier modulation of a sub-bandgap CW laser beam: A Si optoelectronic chopper

In this work we introduced two beam photocarrier cross-modulation for creation of an optically driven photonic laser beam modulator using a semiconductor wafer as the active medium. Unlike other laser beam modulators, the process of modulation of an unmodulated sub-bandgap laser beam was made possible by generating a spatially- and free-carrier density-wave-dependent infrared absorption coefficient in the bulk of the semiconductor, following absorption of a collinear super-bandgap modulated laser beam. The experimental results showed that the modulation efficiency strongly depends on the transport parameters of the semiconductor material and on the power of the super-bandgap laser beam.     

Optical absorption in a heavily doped semiconductor with a narrow forbidden band

The coefficient of interband absorption in a heavily doped, strongly compensated semiconductor with a narrow forbidden band was calculated for emission frequencies ?ω which are smaller than the width? _g of the forbidden band. If the width of the forbidden band is smaller than the characteristic energy w₀ of the random field produced by randomly distributed impurities, the optical absorption gap is missing and the coefficient of absorption increases with the frequency, with the increase being basically proportional toω.     

一维半导体的光学吸收

研究一维半导体在外电磁场中的光吸收、涉及电子带间的直接跃迁与间接跃迁，考虑了电子－空穴相互作用的激子光吸收，导出一维半导体的光吸收系数公式。     

Influence of the Coulomb gap on the impurity absorption in AIIIBV semiconductors

Using the interpolation formula, which adequately describes the impurity band structure in a broad energy range regardless of the degree of compensation, an explicit expression is obtained for the light absorption coefficient related to the transitions from the impurity band to the conduction band. It is shown that at low temperatures the absorption coefficient has a clearly expressed absorption threshold. The explicit frequency dependence of the absorption coefficient is derived for a wide frequency range of the incident radiation. The absorption coefficient dependence on the degree of doping of a semiconductor is also studied.     

用光声技术研究半导体TiO2,ZnO纳米晶粉的光学特性

应用新型的光声光谱技术,研究了不同种类和不同制备工艺条件的半导体纳米晶粉的光学特性,测量了半导体TiO2、ZnO和掺铝ZnO纳米晶粉的光声光谱,获得了这些半导体纳米晶粉的带隙和光谱吸收系数.研究结果表明,相同种类和相同颗粒形状的半导体纳米晶粉的粒径越小,光学吸收系数越大.半导体纳米晶粉的带隙与相同种类纳米颗粒形状(圆球...     

Oscillations of the free electron concentration in a semiconductor under the action of a femtosecond pulse

The interaction of a femtosecond light pulse with a semiconductor is studied in the approximation of an optically thin layer taking into account the dependence of the absorption coefficient on the light-induced electric field. A possibility of the development of spatial oscillations of semiconductor characteristics (concentrations of free electrons and ionized donors and the strength of the light-induced electric field) under the action of a Gaussian beam is demonstrated on the basis of computer simulation and linear analysis.     

Interzone light absorption with consideration of multiphonon transitions in semiconductors with a Coulomb-like random field

The method of calculating the interzone light absorption coefficient in a semiconductor with Coulomb-like random field developed by Bonch-Bruevich is generalized by inclusion of multiphonon processes. A formula is obtained for the frequency dependence of the absorption coefficient in the optical tail range in the Condon approximation with neglect of frequency effect.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 64–67, July, 1981.In conclusion, the author expresses his gratitude to V. L. Bonch-Bruevich for his interest in the study.     

Optical absorption in unordered systems

The coefficient of interzone absorption is calculated for the tail region in an unordered semiconductor at low temperatures with consideration of spin-orbital interaction. Together with the exponential portion, the absorption coefficient contains a Gaussian addition, which under certain circumstances may be comparable to the exponential term.     

Absorption of light by deep traps in a quasiclassical random field

The low frequency portions of the impurity optical absorption coefficient, produced by the presence of a quasiclassical, i.e., slowly changing over space, Gaussian random force field, are calculated by the Green function method. In the rigid (undeformed by electron transition) lattice approximation, the tail of the absorption coefficient for an isotropic nondegenerate semiconductor will have an exponential form. It is shown that under certain conditions consideration of multiphonon processes has no significant effect on the form of the absorption coefficient curve, but leads only to a certain shift in the threshold frequencies.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 96–102, February, 1973.The author expresses his deep gratitude to V. L. Bonch-Bruevich for his constant interest in the work and valuable advice.     

Linearly and circular dichroism in a semiconductor with a complex valence band with allowance for four-photon absorption of light

This paper presents a theoretical study of the linear and circular dichroism of multiphoton absorption of light in semiconductors with a complex valence band. Matrix elements of optical transitions between subbands of the valence bands of a p-GaAs semiconductor are calculated. Transitions connected with both nonsimultaneous absorption of single photons and simultaneous absorption of two photons are taken into account. An expression for the temperature dependence of the coefficient of multiphoton absorption of polarized radiation with allowance for transitions between subbands of heavy and light holes is obtained.     

第一性原理研究B掺杂Mn_4Si_7的电子结构和光学性质

采用基于密度泛函理论的第一性原理计算方法,对未掺杂及B掺杂Mn_4Si_7的电子结构和光学性质进行理论计算.研究结果表明,未掺杂Mn_4Si_7是间接带隙半导体,其禁带宽度为0.786 eV,B掺杂后其禁带宽度下降为0.723 eV. B掺杂Mn_4Si_7是p型半导体材料.未掺杂Mn_4Si_7在近红外区的吸收系数达到10~5 cm~(-1),B掺杂引起Mn_4Si_7的折射率、吸收系数、反射系数及光电导率增加.     

Coupling strength,coupling-induced asymmetry and shifts in the absorption spectrum in semiconductor quantum dots

The coupling effects on the optical absorption spectrum of semiconductor quantum dots arestudied by using the standard model with valence and conduction band levels coupled todispersive quantum phonons of infinite modes. By deducing the analytical expression of theoptical absorption coefficient, the relationship between the measurable quantities and theintrinsic properties of the semiconductor quantum dot is established. By this expression,the peak position, the line shape, the linewidth, and the energy shift of the absorptionspectrum of semiconductor quantum dot can be calculated precisely for a wide range ofparameters. The role of coupling strength as a mechanism of absorption line asymmetry isinvestigated, and the calculation results clearly show the coupling-induced asymmetry inthe absorption line. This analytical approach is applied to GaAs quantum dot, and theresults are consistent with those of experiment observations.     

Intense laser field effects on the linear and nonlinear intersubband optical properties of a semi-parabolic quantum well

By using the compact-density matrix approach, the effect of a nonresonant intense laser field on the linear and nonlinear optical absorptions based on intersubband transitions and the refractive index changes in an asymmetric semiconductor quantum well have been presented. Our results show that the peak position of the absorption coefficient is sensitive to intense laser field, the absorption maximum shifts towards lower energies for increasing intense laser field value. Also we observe as the intense laser field strength increases, the total refractive index change has been increased in magnitude and also shifted towards lower energies. The results indicate that linear and nonlinear optical properties of the low dimensional semiconductor heterostructures can be adjusted in a desired energy range by using intense laser field.     

Photoacoustic spectroscopy analysis of thin semiconductor samples

This paper is an analysis of determination possibility of the optical absorption coefficient spectra of thin semiconductor layers from their normalized photoacoustic amplitude spectra. Influence of multiple reflections of light in thin layers on their photoacoustic and optical absorption coefficient spectra is presented and discussed in detail. Practical formulae for the optical absorption coefficient spectrum as a function of the normalized photoacoustic amplitude spectrum are derived and presented. Next, they were applied for computations of the optical absorption coefficient spectra of thin In₂S₃ thin layers deposited on a glass substrate. This method was experimentally verified with the optical transmission method.     

Absorption coefficient versus induced electric field dependence as a basis for optical bistability in a semiconductor

Using computer simulation, the feasibility of absorption optical bistability based on the dependence of the absorption coefficient on an electric field induced by a high-intensity laser pulse acting on a semiconductor and shifting the energy levels of atoms is demonstrated. Unlike the known mechanisms behind absorption optical bistability, here enhanced diffusion of charged particles does not change the rate of switching the system from the lower to upper state. Radiation-semiconductor interaction conditions are found when, after being switched to the upper state, the system remains in it until the laser pulse disappears.     

Interband optical absorption in a heteropolar semiconductor with microcrystalline structure

The nature of the intrinsic random field of a heteropolar semiconductor with microcrystalline structure is investigated and the frequency dependence is determined for the light absorption coefficient in the tail domain, which is due to this field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 78–82, November, 1984.The author is grateful to V. L. Bonch-Bruevich for useful discussion of the research.     

铝镓氮薄膜双光子吸收效应

基于飞秒激发Z扫描实验技术,研究了氮化镓薄膜和不同铝掺杂含量的掺铝氮化镓(以下简称铝镓氮)薄膜的超快非线性光学响应特性。在开孔Z-scan测试中,纯Ga N晶体薄膜表现出典型的双光子吸收特性,双光子吸收系数为3.5 cm/GW,且随着激发光强的增大而逐渐减小。随后测试了不同铝掺杂含量的Al_xGa_(1-x)N薄膜的非线性吸收系数。结果表明,随着铝掺杂摩尔分数的提高(0,19%,32%,42%),非线性吸收系数逐渐减小(18,10,6,5.6 cm/GW)。结合半导体非线性吸收理论分析,Al_xGa_(1-x)N薄膜材料的非线性过程主要是双光子吸收主导非线性响应物理过程。实验结果与半导体双光子吸收过程Sheik-Bahae理论符合得很好。