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1、Optical Properties of Condensed Matters引言:光学过程的分类，光学系数，复折射率与复介电常数，光学材料(绝缘晶体，半导体 ，玻璃，金属，高分子材料等)，凝聚态物质光学性质的特征(对称性，电子能带，晶 格振动，态密度，局域态和集体激发等)，微观模型。光在凝聚态物质中传播的经典理论:光在稠密光学介质中的传播，偶极振子模型，色散理 论，光学各向异性:双折射。带间吸收:带间跃迁,直接跃迁的跃迁几率，直接带隙半导体的带边吸收，间接带隙半导体 的带边吸收，带边以上的带间吸收，吸收谱的测量，光探测材料与器件。激子:激子的概念，自由激子，外场中的自由激子，高密度的自由激子
2、，弗仑克尔激子发光:固体中光的发射，带间发光，光致发光，电致发光。量子阱与量子点:量子限制结构，半导体量子阱的结构与制备，电子能级，光的吸收与激 发，量子限制斯塔克效应，光发射，量子阱子的带间跃迁，Bloch振子，量子点。自由电子:Plasma反射率,自由载流子电导，金属，掺杂半导体，Plasmon。高分子材料:高分子材料简介，共轭分子的电子态，高分子光谱，芳烃共轭聚合物，有机 光电子学。发光中心:电子声子相互作用，色心，离子晶体中的顺磁杂质，固体激光器与放大器， 发光材料。声子:红外活性声子，极性晶体红外反射与吸收，极化激元，极化子，非弹性光散射，声 子寿命。非线性光学:非线性极化率张量，光
3、学非线性的物理起源，二阶非线性效应，三阶非线性 效应。光子晶体和光学微腔:光子能带，光子晶体的构成，光学微腔，腔量子电动力学简介。Chapter 1 Introduction1.1 Classification of optical processes Reflection Propagation TransmissionOptical mediumOptical mediumrefractive indexn() = c / v () Snells lawabsorption resonanceluminescence spontaneousemissionelastic and Inela
4、stic scatteringnonlinear-opticsPropagation1.2 Optical coefficientsCoefficient of reflection or reflectivity (R): R = reflected power / incident power Transmission or transmissivity (T): T = transmitted power / incident powerR + T = 1 Refractive index (n): Absorption coefficient () = - (d I / d z) /
5、I (z);Beers law: is strong function of frequencyLuminescence The atom jumps to an excited state by absorption of a photon, then relaxes to an intermediate state, before re- emitting a photon by spontaneous emission as it falls to the ground state. The photon emitted has a smaller energy than the abs
6、orbed photon. The reduction in the Photon energy is called the Stokes shift. Scattering Variation of n of the medium on a length scalesmaller than the of the lightN: the number of scattering centres / V;S: scattering cross-section; = N SRayleigh scattering : 1.3 The complex refractive index and diel
7、ectric constantComplex refractive index: extinction coefficientWhereComplex dielectric constantThe relationship between the real and imaginary parts of two coefficients: For weakly absorbing medium, is very small,The reflectivity (normal incidence) :In the transparent region of material : a is very
8、small, and 2 are negligible, one may consider only the real parts of n and ; In the absorption region, one need to know both the real and imaginary parts of n and .1.4 Optical materials1.41 Crystalline insulators and semiconductorsTransparency range, the index may be taken to be real with no imagina
9、ry component (approximately constant n=1.77) R = 0.077, hence T =(1-R)2=0.85Phonon absorption or lattice absorptionDue to absorption by bound electrons Fundamental absorption edge, is determined by the band gap.The optical properties of semiconductors are similar to those of insulators, expect that
10、the electronic and phonic transitions occur at longer wavelengths. Its transparency range lies outside the visible spectrum, so it has a dark Metallic appearance. 1.4 Optical materials1.41 Crystalline insulators and semiconductorsMaterials can take on new properties by controlled doping with optical
11、ly active substance.Transmission spectrum of ruby (ruby Al2O3 With 0.05% Cr3+) compared to sapphire(pure Al2O3). The thicknesses of the two crystals were 6.1 mm and 3.0 mm, respectivelyThe principle of doping optically active atoms into colourless hosts is employed extensively in the crystals used f
12、or solid state lasers. A typical example is the ruby crystal. Rubies consist of Cr+3 ions doped into Al2O3. In the natural crystals, the Cr+3 ions are present as impurities, but in synthetic crystals, the dopants are deliberately introduced in controlled quantities during the crystal growth process.
13、 1.4 Optical materials1.4.2 GlassMost types of glasses are made of silica (SiO2) with other chemicals. Insulator, all the characteristic features crystalline insulators, the trans range from around 200 nm to beyond 2000 nm; Small absorption and scattering losses; n changes byless than 1% over the wh
14、ole visible spectral region; Chemicals are commonly added to silica during the fusionprocess to alter the refractive index and transmission range; Stained glass and colour glass filter are made by adding semiconductors with gaps in visible spectral region.The molecular materials are held together by
15、 the weak van de Waals bonds, whereas the molecules are held together by strong covalent bonds. The optical properties of materials are similar to those of the individual molecules; Saturated compounds: compounds which do not contain any free valence (all the electrons are tightly held in their bond
16、s), and are transparent in the visible, absorb in the infrared and ultraviolet (insulator crystals); Conjugated molecules (bezene C6H6): The electrons form large delocalized orbitals called orbitals which spread out across the whole molecule, therefore are less tightly bound than the electrons in saturated molecules. The molecules with visible absorption also tend to emit strongly at
