Optical modes in semiconductor microdisk lasers

We present a method for calculation of the optical modes in microdisk resonant cavities. The optical field distribution, the eigenvalue equation for resonant wavelengths, and the formula for the Q values of microdisks are established. Numerical results for emitting modes of long-wavelength semiconductor microdisk lasers are presented in detail and compared with experimental data     

Spectrum and electron-phonon interaction in a medium with a cylindrical quantum wire

The effect of multiphonon processes on the electronic (hole) spectrum in a β-HgS/CdS nanoheterostructure (cylindrical quantum wire in a bulk medium) is studied in the dielectriccontinuum model. The electron-phonon interaction Hamiltonian is obtained for a potential well of finite depth. The shift of the electron (hole) energy level as a result of the interaction with optical longitudinal (confined) and interface phonons is determined. The dependence of the band gap of the nanosystem β-HgS/CdS on the radius of the quantum wire is found. It is established that interface phonons play the dominant role in the renormalization of the electronic (hole) spectrum in a quantum wire with small transverse dimensions. Fiz. Tekh. Poluprovodn. 33, 598–602 (May 1999)     

Collective modes in coupled semiconductor disk lasers in the case of whispering-gallery modes

Samples of coupled semiconductor disk laser based on quantum-dimensional GaInAsSb/AlGaAsSb nanoheterostructures (emission wavelength of λ ≈ 2.28 μm) operating in the whispering-gallery modes are fabricated and studied. The emission spectra and directivity patterns are studied for laser systems of two types, i.e., coupled disk lasers with a bridge between resonators and those without it. It is found that both types of these lasers generate collective modes with an intermodal difference twice as small as that for a single disk laser. It is suggested that this effect is caused by the propagation of radiation from one disk laser to the other.     

Normal modes of carrier waves in semiconductor plates

A dispersion relation for waves in an extrinsic semiconductor plate or film with an applied electric field is derived. It is shown that there exists an infinite number of modes. An arbitrary perturbation can be expressed as a superposition of modes. Expressions for the expansion coefficients are derived. Finally, it is shown that a perturbation which is initially a plane wave in a thick plate, remains an approximate plane wave in a time interval corresponding to the decay time, except near the boundaries. Thus, an apparent discrepancy between the theories of infinite- and finite-dimension semiconductors is resolved.     

Gain ripple minimisation and higher-order modes in semiconductor optical amplifiers

Theoretical results are presented about the gain ripple performance of various structures proposed to obtain true travelling-wave operation in optical semiconductor laser amplifiers. Higher-order transverse modes are shown to limit the efficiency of antireflection mechanisms, especially in the case of misaligned stripes.<>     

Elimination of the electron-phonon interaction in superlattices in a quantizing magnetic field

The energy and wave-vector conservation laws impose rigid constraints on the possible electron-phonon interaction processes in a superlattice immersed in a quantizing magnetic field directed along its growth axis. If the width of the Landau subband is smaller than the maximum energy of an acoustic phonon in the superlattice, single-phonon intraband scattering becomes impossible for all electron states in the subband considered. Therefore, the phonon contribution to the electron scattering processes can become negligible in superlattices with a large period in the presence of a quantizing magnetic field. Fiz. Tekh. Poluprovodn. 32, 730–732 (June 1998)     

Vibration modes of oxygen dimers in germanium

Absorption in the infrared region of the spectrum was studied for both the as-grown Ge crystals and the Ge crystals irradiated with fast electrons (with subsequent heat treatment); the crystals were preliminarily enriched with ¹⁶O or ¹⁸O isotopes. The vibrational absorption bands observed in Ge and peaked at 780, 818, and 857 cm^?1 are attributed to complexes composed of two atoms (dimers) of ¹⁶O, whereas the bands at 741, 776, and 811 cm^?1 are attributed to complexes of ¹⁸O atoms. It is established that electron irradiation of Ge crystals at temperatures near 295 K with subsequent heat treatment at 120–250°C brings about an increase in the intensities of bands peaked at 780 and 818 cm^?1. The band peaked at 857 cm^?1 does not change its intensity under irradiation and, by analogy with Si, is identified with another configuration of oxygen dimers in Ge. The bonding energy of dimers responsible for the bands peaked at 780 and 818 cm^?1 is estimated at 0.35–0.4 eV.     

电子-声子相互作用对非对称Morse势阱中光整流效应的影响

从理论上研究了电声相互作用对Morse势阱中光整流效应的影响，首先利用微扰论的方法求解在考虑电声相互作用时Morse量子阱的波函数和能级, 然后采用密度矩阵方法和迭代法得到光整流系数，最后以典型的GaAs/AlGaAs Morse 势阱为例进行数值计算。数值结果表明在考虑电声相互作用后，获得的光整流系数比仅考虑电子情况的大15%～30%左右。并且电声相互作用使光整流系数峰值向高能方向偏移。因此要得到比较精确的结果，有必要考虑电声相互作用的影响。     

含半导体超常媒质的矩形波导的导模研究

采用改进后的马可梯里方法推导出了半导体超常媒质矩形波导中体模和表面模的色散方程,讨论了最低阶TM模的截止频率并画出了布里渊图。结果显示不同的波导高度具有不同的导模频带,波导高度大的对应的导模频带较宽,并且彼此之间没有重叠。除此之外,不同模式还存在着简并的趋势。最后采用作图法验证了表面模的存在性。     

Electromigration failure modes in aluminum metallization for semiconductor devices

Two wear-out type failure modes involving aluminum metallization for semiconductor devices are described. Both modes involve mass transport by momentum exchange between conducting electrons and metal ions. The first failure mode is the formation of an electrically open circuit due to the condensation of vacancies in the aluminum to form voids. The second is the formation of etch pits into silicon by the dissolution of silicon into aluminum, and the transport of the solute ions down the aluminum conductor away from the silicon-aluminum interface by electron wind forces. The process continues until an etch pit grows into the silicon to a depth sufficient to short out an underlying junction.     

Spectral index method for polarized modes in semiconductor ribwaveguides

A fast way of modeling polarized modes in semiconductor rib waveguides is presented and shown to be in excellent agreement with a semivectorial finite-difference computer program. The method uses little storage and has been implemented on a personal computer     

Guided modes in a rectangular waveguide with semiconductor metamaterial

The dispersion equations of bulk modes and surface modes in a rectangular waveguide of semiconductor metamaterial are derived by a modified "Marcatili's method".The cutoff frequencies of the lowest TM bulk mode are discussed,and the Brillouin diagrams of different bulk modes are drawn.They demonstrate that different heights correspond to different guidance frequency ranges which have no superposition with each other and a waveguide with a larger height possesses a wider passband of light.In addition,tendencies of degeneracy for different modes are observed.Finally,the existence of surface modes is verified by a graphical method.     

Selection mechanisms of transverse modes in semiconductor injection lasers

A discussion of the transverse mode selection in the conventional double-heterostructure injection lasers is given. The mechanisms considered as responsible for mode selection are 1) the nonnormal incidence in the plane perpendicular to the junction of the EM waves at the end faces; and 2) an uneven gain distribution across the active region. By using a multilayer waveguide model, results are presented that show the regions of preference of each of the modes as determined by each mechanism both in isolation and simultaneously. Hence, the regions of dominance of each mechanism are determined.     

Small-signal modulation of multitransverse modes vertical-cavitysurface-emitting semiconductor lasers

The small-signal modulation response of multi-transverse modes, proton-implanted vertical-cavity semiconductor lasers was studied experimentally and theoretically. Multiresonance frequencies and notches in the modulation response were obtained and the detailed characteristics varied for different overlap levels between the lasing modes. The theoretical modeling matched the experimental results and revealed the coupled oscillators manifestation for highly overlapping transverse modes     

Phase correlation between longitudinal modes in semiconductor self-pulsating DBR lasers

Phase correlation leading to self-pulsation (SP) in semiconductor distributed Bragg reflector (DBR) lasers is investigated experimentally and theoretically. Under proper biasing conditions, the laser oscillates with three main modes and we observe that each two-modes beating provides SP with identical spectral linewidth. Under the same operating conditions, the measured spectral linewidths of the beating modes are much larger than the linewidth of the self-pulsating signal. These results demonstrate the natural occurrence of passive mode-locking (PML) and phase correlation in semiconductor DBR lasers. A model based on multimode coupled-wave rate equations, including four-wave mixing (FWM), is developed to describe PML and SP in the gain region of the laser cavity. This model demonstrates that the existence of phase correlation between longitudinal modes is due to FWM.     

Nonlinear interaction of waves in a semiconductor superlattice

The nonlinear wave interaction in a periodic structure formed by alternating semiconductor and insulator layers has been studied. The translation symmetry of the structure is shown to be the reason for a number of peculiarities of the nonlinear interaction. Conditions of the resonance interaction between the first and second harmonics are analyzed. The excitation of the second harmonic via the interaction of the first spatial harmonics propagating in the opposite directions is considered for the first time. An explanation is given for the significant enhancement of the wave interaction near the passband edge.     

Effect of the configuration of a quantum wire on the electron-phonon interaction

The dissipation of the electric current on acoustic phonons in a one-dimensional conductor is of an activational character. The activation energy of phonon scattering of an electron depends on the spatial configuration of the conductor. For this reason, electron scattering by phonons can be substantially weakened and the phonon contribution to the resistance thereby can be decreased by choosing an appropriate form of the conductor. Fiz. Tekh. Poluprovodn. 33, 1232–1234 (October 1999)     

An equation for the amplitudes of the modes in semiconductor lasers

A quite general equation for the time-dependent amplitudes of the modes of the electromagnetic field of a semiconductor laser is derived in the small-signal approximation. It is shown that the modes fulfil a general orthogonality relation that follows directly from Maxwell's equations. The dependence of the dielectric function on temporally varying carrier densities is taken into account. The local changes of the carrier densities lead to a coupling of different modes. The equations for the mode amplitudes are used to derive rate equations for the photon number and the phase of a mode     

Fast and accurate method for calculation of polarised modes in semiconductor rib waveguides

A new semivectorial 'spectral index' (SI) method for finding the guided modes of semiconductor rib waveguides is described. The results are shown by comparison to be of the same accuracy as well established finite difference calculations. A useful by-product is a contour map of the principal field component. The propagation constants are found using novel transcendental equations which are easy to set up and are given here explicitly. These discriminate clearly between the TE and TM modes and are variational in nature.<>