Parametric Scattering of Cavity Polaritons

Abstract

We report frequency-domain degenerate four-wave mixing results on excitons in a semiconductor microcavity in the strong coupling regime. The excitation is kept to the x ͑3͒ limit. The spectral response shows strong polarization dependence. We analyze the data with a new model where the degenerate four-wave mixing process is described as an elastic scattering of two cavity polaritons mediated by the state filling effect and the two-body attractive and repulsive interaction between excitons. From the polarization and detuning dependence, the ratio of the coupling constants of these three terms is uniquely determined. We find that the attractive interaction term and the state filling are the dominant contributions to the nonlinearity. [S0031-9007(97)03813-1] PACS numbers: 71.36. + c, 71.35.Lk The exciton-photon coupled system in a semiconductor microcavity structure is attracting a lot of current interest in both fundamental and applied research [1]. In the strong coupling regime very large normal mode splitting exists which is several orders of magnitude larger than that of the atomic system [2]. Various experimental and theoretical studies have been performed to elucidate the features characteristic to the excitonic system [2-7]. As long as linear optical responses are concerned the semiclassical picture with anomalous dispersion associated with excitons can well explain these features as it was pointed out for the atomic system [8]. In the nonlinear regime, the atom-cavity coupled system shows characteristic features originating from the granular nature of the radiation field [9]. Because of the similarities with the atomic system and ease of integration with the existing semiconductor technology, the exciton-cavity coupled system is expected to be suitable for the fabrication of quantum logic devices. However, the atomic two-level system can be saturated with as little as one photon and shows a large nonlinearity, whereas the excitonic system behaves mostly harmonic in the low density regime. Any deviation from this harmonic behavior is due to the nonideal bosonic nature of excitons. This deviation is essential to photon manipulation. Therefore, elucidation of the nonlinear optical responses of the exciton-cavity coupled system is crucial to the realization of the idea of quantum logic devices.In the conventional scheme of nonlinear optics the nonlinear polarization is evaluated as a higher-order perturbation of the exciton-photon dipole interaction. This framework is not applicable to the strong coupling regime, because the exciton-photon dipole interaction is fully taken into account nonperturbatively in order to form cavity polaritons. Nonlinear responses are described as higher-order scattering of cavity polaritons by the anharmonicities which originate from the fermionic nature and Coulomb interaction of the constituents of the excitons. Nonlinear optical processes of bulk polaritons should also be treated in the same framework. For the bulk case, however, the propagation effects of polaritons bring furt...

Impact of biexcitons on the relaxation mechanisms of polaritons in III-nitride based multiple quantum well microcavities

“…20 The latter have indeed been shown to be instrumental in analyzing four-wave mixing experiments performed on GaAs MCs. [21][22][23] The SCR between the biexciton transition and the cavity photon might even be observed in MCs submitted to intense circularly polarized excitation. 24 Compared to III-As or II-VI MQW MCs, disorder and biexcitons should play an even more important role in nitride-based systems.…”

Suppressed Polariton Scattering in Semiconductor Microcavities

“…Similarly when the upper line is pumped, it transiently redshifts by 0.3 meV, leaving the lower line almost unmoved. A complete description of this effect requires account of the bipolariton interactions [20]; however, it strongly resembles an ac Stark effect [12]. In a simplified explanation the intracavity field at v 1 both repels and broadens the higher energy bare exciton line, leading to an increase in v ex but a decrease in v R .…”

Collapses and revivals of exciton emission in a semiconductor microcavity: Detuning and phase-space filling effects

“…For small inplane wave vectors of the excitons and the photons, the nonlinear interaction constants 2A = 6Ry ex a 2 ex /S and B = g/ (n sat S), where Ry ex is the binding energy of the excitons, S the quantization area and n sat = 7/ 16πa 2 ex is the exciton saturation density [13,21]. The ratio of the exciton-exciton interaction constant A and the phasespace filling factor B may be determined by a degenerate four-wave mixing experiment [22,23]. In this paper, we assume that these two parameters are real and positive.…”