Photoluminescence of InAs/GaAs quantum dots under direct two-photon excitation

Abstract

Self-assembled quantum dots grown by molecular beam epitaxy have been a hotbed for various fundamental research and device applications over the past decades. Among them, InAs/GaAs quantum dots have shown great potential for applications in quantum information, quantum computing, infrared photodetection, etc. Though intensively studied, some of the optical nonlinear properties of InAs/GaAs quantum dots, specifically the associated two-photon absorption of the wetting and barrier layers, have not been investigated yet. Here we report a study of the photoluminescence of these dots by using direct two-photon excitation. The quadratic power law dependence of the photoluminescence intensity, together with the ground-state resonant peak of quantum dots appearing in the photoluminescence excitation spectrum, unambiguously confirms the occurrence of the direct two-photon absorption in the dots. A three-level rate equation model is proposed to describe the photogenerated carrier dynamics in the quantum dot-wetting layer-GaAs system. Moreover, higher-order power law dependence of photoluminescence intensity is observed on both the GaAs substrate and the wetting layer by two-photon excitation, which is accounted for by a model involving the third-harmonic generation at the sample interface. Our results open a door for understanding the optical nonlinear effects associated with this fundamentally and technologically important platform.

Multi-Pass Free Electron Laser Assisted Spectral and Imaging Applications in the Terahertz/Far-IR Range Using the Future Superconducting Electron Source BriXSinO

“…One can use the mapping of the double resonance FIR modulated photoluminescence spectroscopy for distinguishing the mechanisms from dot to dot in correlation with the size and composition distributions [93,94]. The non-linear optics of intra-band transitions including the third-harmonic generation [95,96] is associated with resonant intra-valence band transitions, second harmonic generation [97,98] and two-photon absorption [99,100]. Polaron dynamics [101,102] has been studied with the absorption saturation technique [103] and pump-probe spectroscopy [104][105][106][107].…”

Quality Research Follows the Power Law

“…Such a behavior is akin to the Pareto distribution originated from the heterogeneity in the system. 22,[28][29][30] We have therefore proposed that high quality publication is a result of the heterogeneous relaxation pathways from the loaded state after a scientist has obtained research resources. Such a power law dependency between H-index and publications/citations allows us to propose indices (Qs) with the intensive property to evaluate the quality research (using H-index as a virtual state indicator) of individual scientists with respect to that predicted from the reference group (e.g., top 2% scientists) with the same citation or publication records.…”

Chip-Scale Quantum Emitters

“…High-fidelity optical electron-spin initialization and long electron-spin lifetimes for these quantum dots were observed [39]. Hu et al [40] explained the direct two-photon excitation effect on the photoluminescence of self-assembled InAs/GaAs quantum dots grown by molecular beam epitaxy. The direct two-photon absorption in the dots was unambiguously confirmed by the quadratic power law dependence of the photoluminescence intensity.…”

“…The direct two-photon absorption in the dots was unambiguously confirmed by the quadratic power law dependence of the photoluminescence intensity. Another reason for the direct two-photon absorption was distinguished by the ground-state resonant peak of quantum dots appearing in the photoluminescence excitation spectrum [40]. The photogenerated carrier dynamics in the quantum dot-wetting layer-GaAs system was described using a three-level rate equation model.…”

“…The photogenerated carrier dynamics in the quantum dot-wetting layer-GaAs system was described using a three-level rate equation model. In this approach, the use of two-photon excitation leads to higher-order power law dependence of photoluminescence intensity on both the GaAs substrate and the wetting layer [40]. Holewa and co-workers [41] used a ripening step in molecular beam epitaxial growth of InAs quantum dots (QDs) embedded in an (In,Al,Ga)As barrier lattice matched to InP(001) that led to the growth of in-plane symmetric QDs.…”