10 – Degenerate Four-Wave Mixing in Semiconductors*

There is a confusion present in much of the recent literature on semiconductor nonlinear refraction. This confusion originates from the development of several apparently independent theories. Here we consider five theoretical approaches to the calculation of the nonlinear susceptibility ( X (3) ) and show that each is associated with the effect of interband transitions, even though some are conventionally referred to as free-carrier theories. By comparing groups of terms in X (3) the physical equivalence of the theories is established. New near-resonance calculations are presented, and the circumstances in which each of the various theories can be applied is discussed.

A comparison of theories of resonant nonlinear refraction in semiconductors

Four-wave mixing from composite artificial Kerr media consisting of ellipsoidal microparticles suspended in a host liquid is discussed. Calculations of nonlinear grating formation and decay times are given in a dynamic model that includes the effect of random collisions on the particulates. Phase-conjugate efficiencies for a model configuration are given as well as operating limits imposed by particulate scattering from the composite.

Degenerate four-wave mixing from anisotropic artificial Kerr media

A novel self-pulsation regime is observed in multisection laser diodes which consist of a loss-coupled distributed-feedback (DFB) section, a phase control section, and gain sections, where 10-GHz self-pulsation due to compound cavity mode beating has been reported with the DFB section operated as a single-mode laser. When the DFB section is below threshold current, the devices give the self-pulsation in a very wide operating range. We attribute the pulsation to passive mode-locking and also confirm that this structure is applicable to 40-GHz operation

Self-pulsation in multisection laser diodes with a DFB reflector

A coherent radiation-exciton interaction model is employed to study analytically the phenomenon of nonlinear absorption in important III—V semiconductors (viz., GaAs, GaSb, InSb, InAs), the crystals being irradiated by suitable lasers with energies (hω) nearly equal to the band gap energies (hωg). The nonoptical processesare accounted for phenomenologically by introducing a damping parameter into the equation of motion of the probability amplitude of the excited electron—hole pair state. The Wannier-Mott type of exciton wave function is found to be responsible for the giant nonlinearity of the crystal absorption coefficient in the near resonant optical interband transition regime with h | ω - ωg | of the order of the crystal exciton binding energy. The effect of renormalization of the crystal band gap in the presence of Coulomb interaction and Starkbroadening is also discussed.



Es wird ein Wechselwirkungsmodell, koharente-Strahlung—Exziton, benutzt, um nichtlineare Absorption in wichtigen III—V-Halbleitern (z. B. GaAs, GaSb, InSb, InAs) zu untersuchen, wobei die Kristalle mittels geeigneter Laser bei Energien (hω), die fastden Bandluckenerergien (hωg) entsprechen, bestrahlt werden. Nichtoptische Prozesse werden phanomenologisch durch Einfuhrung eines Dampfungsparameters in die Bewegungsgleichung der Wahrscheinlichkeitsamplitude des angeregten Elektron—Loch-Paarzustands berucksichtigt. Es wird gefunden, das die Wannier-Mott-Wellenfunktion des Exzitons fur die grose Nichtlinearitat des Absorptionskoeffizienten des Kristalls im Bereich der resonanten optischen Interbandubergange (mit h(ω - ωg) von der Grosenordnung der Exzitonenbindungsenergie des Kristalls) verantwortlich ist. Der Einflus der Renormierung der Bandlucke des Kristalls fur Coulombwechselwirkung und Starkverbreiterung wird ebenfalls diskutiert.

Nonlinear Absorption in III—V Semiconductors

We discuss degenerate four-wave mixing and phase conjugation near the band edge of direct-gap semiconductors and show that the reflectivity for conjugate waves is enhanced in the vicinity of the band edge. We also compare the quantum-mechanical results with the classical Drude model.

A. Elçi

Papers

Four-wave mixing and phase conjugation near the band edge