Citation:

# Optical shaping of the polarization anisotropy in a laterally coupled quantum dot dimer

• Light: Science & Applications  9, Article number: 19 (2020)
• We find that the emission from laterally coupled quantum dots is strongly polarized along the coupled direction [1$\bar 1$0], and its polarization anisotropy can be shaped by changing the orientation of the polarized excitation. When the nonresonant excitation is linearly polarized perpendicular to the coupled direction [110], excitons (X1 and X2) and local biexcitons (X1X1 and X2X2) from the two separate quantum dots (QD1 and QD2) show emission anisotropy with a small degree of polarization (10%). On the other hand, when the excitation polarization is parallel to the coupled direction [1$\bar 1$0], the polarization anisotropy of excitons, local biexcitons, and coupled biexcitons (X1X2) is enhanced with a degree of polarization of 74%. We also observed a consistent anisotropy in the time-resolved photoluminescence. The decay rate of the polarized photoluminescence intensity along the coupled direction is relatively high, but the anisotropic decay rate can be modified by changing the orientation of the polarized excitation. An energy difference is also observed between the polarized emission spectra parallel and perpendicular to the coupled direction, and it increases by up to three times by changing the excitation polarization orientation from [110] to [1$\bar 1$0]. These results suggest that the dipole–dipole interaction across the two separate quantum dots is mediated and that the anisotropic wavefunctions of the excitons and biexcitons are shaped by the excitation polarization.
•  [1] Bayer, M. et al. Coupling and entangling of quantum states in quantum dot molecules. Science 291, 451–453 (2001). [2] Petta, J. R. et al. Coherent manipulation of coupled electron spins in semiconductor quantum dots. Science 309, 2180–2184 (2005). [3] Bester, G., Shumway, J. & Zunger, A. Theory of excitonic spectra and entanglement engineering in dot molecules. Phys. Rev. Lett. 93, 047401 (2004). [4] Robledo, L. et al. Conditional dynamics of interacting quantum dots. Science 320, 772–775 (2008). [5] Sheng, W. D. & Leburton, J. P. Anomalous quantum-confined stark effects in stacked InAs/GaAs self-assembled quantum dots. Phys. Rev. Lett. 88, 167401 (2002). [6] Emary, C. & Sham, L. J. Optically controlled logic gates for two spin qubits in vertically coupled quantum dots. Phys. Rev. B 75, 125317 (2007). [7] Weiss, K. M. et al. Coherent two-electron spin qubits in an optically active pair of coupled InGaAs quantum dots. Phys. Rev. Lett. 109, 107401 (2012). [8] Villas-Bôas, J. M., Govorov, A. O. & Ulloa, S. E. Coherent control of tunneling in a quantum dot molecule. Phys. Rev. B 69, 125342 (2004). [9] Xu, X. L., Williams, D. A. & Cleaver, J. A. R. Splitting of excitons and biexcitons in coupled InAs quantum dot molecules. Appl. Phys. Lett. 86, 012103 (2005). [10] Vora, P. M. et al. Spin-cavity interactions between a quantum dot molecule and a photonic crystal cavity. Nat. Commun. 6, 7665 (2015). [11] Kerfoot, M. L. et al. Optophononics with coupled quantum dots. Nat. Commun. 5, 3299 (2014). [12] Thierschmann, H. et al. Three-terminal energy harvester with coupled quantum dots. Nat. Nanotechnol. 10, 854–858 (2015). [13] Rontani, M. et al. Molecular phases in coupled quantum dots. Phys. Rev. B 69, 085327 (2004). [14] Zhou, X. R. et al. Coulomb interaction signatures in self-assembled lateral quantum dot molecules. Phys. Rev. B 87, 125309 (2013). [15] Zhou, X. R. & Doty, M. Design of 4-electrode optical device for application of vector electric fields to self-assembled quantum dot complexes. J. Appl. Phys. 116, 163101 (2014). [16] Doty, M. F. et al. Antibonding ground states in InAs quantum-dot molecules. Phys. Rev. Lett. 102, 047401 (2009). [17] Ma, X. Y. et al. Hole spins in an InAs/GaAs quantum dot molecule subject to lateral electric fields. Phys. Rev. B 93, 245402 (2016). [18] De La Giroday, A. B. et al. Excitonic couplings and Stark effect in individual quantum dot molecules. J. Appl. Phys. 110, 083511 (2011). [19] Ortner, G. et al. Control of vertically coupled InGaAs/GaAs quantum dots with electric fields. Phys. Rev. Lett. 94, 157401 (2005). [20] Kagan, C. R. & Murray, C. B. Charge transport in strongly coupled quantum dot solids. Nat. Nanotechnol. 10, 1013–1026 (2015). [21] Wijesundara, K. C. et al. Tunable exciton relaxation in vertically coupled semiconductor InAs quantum dots. Phys. Rev. B 84, 081404(R) (2011). [22] Stinaff, E. A. et al. Optical signatures of coupled quantum dots. Science 311, 636–639 (2006). [23] Krenner, H. J. et al. Optically probing spin and charge interactions in a tunable artificial molecule. Phys. Rev. Lett. 97, 076403 (2006). [24] Wang, L. J. et al. Self-assembled quantum dot molecules. Adv. Mater. 21, 2601–2618 (2009). [25] Liang, B. L. et al. Energy transfer within ultralow density twin InAs quantum dots grown by droplet epitaxy. ACS Nano 2, 2219–2224 (2008). [26] Unold, T. et al. Optical control of excitons in a pair of quantum dots coupled by the dipole–dipole interaction. Phys. Rev. Lett. 94, 137404 (2005). [27] Kim, H. et al. Exciton dipole–dipole interaction in a single coupled-quantum-dot structure via polarized excitation. Nano Lett. 16, 7755–7760 (2016). [28] Beyer, J. et al. Spin injection in lateral InAs quantum dot structures by optical orientation spectroscopy. Nanotechnology 20, 375401 (2009). [29] Cundiff, S. T. et al. Optical coherence in semiconductors: strong emission mediated by nondegenerate interactions. Phys. Rev. Lett. 77, 1107–1110 (1996). [30] Guenther, T. et al. Coherent nonlinear optical response of single quantum dots studied by ultrafast near-field spectroscopy. Phys. Rev. Lett. 89, 057401 (2002). [31] Kim, H. et al. Light controlled optical Aharonov–Bohm oscillations in a single quantum ring. Nano Lett. 18, 6188–6194 (2018). [32] Santori, C. et al. Submicrosecond correlations in photoluminescence from InAs quantum dots. Phys. Rev. B 69, 205324 (2004). [33] Sallen, G. et al. Subnanosecond spectral diffusion measurement using photon correlation. Nat. Photonics 4, 696–699 (2010). [34] Wang, Z. M. et al. Unusual role of the substrate in droplet-induced GaAs/AlGaAs quantum-dot pairs. Phys. Status Solidi Rapid Res. Lett. 2, 281–283 (2008). [35] Keizer, J. G. et al. Atomic scale analysis of self assembled GaAs/AlGaAs quantum dots grown by droplet epitaxy. Appl. Phys. Lett. 96, 062101 (2010). [36] Takagahara, T. et al. Theory of exciton doublet structures and polarization relaxation in single quantum dots. Phys. Rev. B 62, 16840 (2000). [37] Hafenbrak, R. et al. Triggered polarization-entangled photon pairs from a single quantum dot up to 30 K. N. J. Phys. 9, 315 (2007). [38] Kim, H. D. et al. Asymmetry of localised states in a single quantum ring: polarization dependence of excitons and biexcitons. Appl. Phys. Lett. 102, 033112 (2013). [39] Kodriano, Y. et al. Radiative cascade from quantum dot metastable spin-blockaded biexciton. Phys. Rev. B 82, 155329 (2010). [40] Hours, J. et al. Exciton radiative lifetime controlled by the lateral confinement energy in a single quantum dot. Phys. Rev. B 71, 161306(R) (2005). [41] Adachi, S. et al. Exciton-exciton interaction and heterobiexcitons in GaN. Phys. Rev. B 67, 205212 (2003).
###### 通讯作者: 陈斌, bchen63@163.com
• 1.

沈阳化工大学材料科学与工程学院 沈阳 110142

Figures(5)

## Article Metrics

Article views(70) PDF downloads(1) Citation(0) Citation counts are provided from Web of Science. The counts may vary by service, and are reliant on the availability of their data.

## Optical shaping of the polarization anisotropy in a laterally coupled quantum dot dimer

• 1. School of Physics, Northeast Normal University, 130024 Changchun, China
• 2. Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
• 3. Department of Opto-mechatronics, Pusan Nat'l University, Busan 609-735, Republic of Korea
• 4. Department of Physics, Yeungnam University, Gyeongsan 712-749, Republic of Korea
• 5. Nano-Photonics Research Center, KIST, Seoul 136-791, Republic of Korea
• 6. Department of Physics, Pusan Nat'l University, Busan 609-735, Republic of Korea
###### Robert A. Taylor, robert.taylor@physics.ox.ac.uk;

Abstract: We find that the emission from laterally coupled quantum dots is strongly polarized along the coupled direction [1$\bar 1$0], and its polarization anisotropy can be shaped by changing the orientation of the polarized excitation. When the nonresonant excitation is linearly polarized perpendicular to the coupled direction [110], excitons (X1 and X2) and local biexcitons (X1X1 and X2X2) from the two separate quantum dots (QD1 and QD2) show emission anisotropy with a small degree of polarization (10%). On the other hand, when the excitation polarization is parallel to the coupled direction [1$\bar 1$0], the polarization anisotropy of excitons, local biexcitons, and coupled biexcitons (X1X2) is enhanced with a degree of polarization of 74%. We also observed a consistent anisotropy in the time-resolved photoluminescence. The decay rate of the polarized photoluminescence intensity along the coupled direction is relatively high, but the anisotropic decay rate can be modified by changing the orientation of the polarized excitation. An energy difference is also observed between the polarized emission spectra parallel and perpendicular to the coupled direction, and it increases by up to three times by changing the excitation polarization orientation from [110] to [1$\bar 1$0]. These results suggest that the dipole–dipole interaction across the two separate quantum dots is mediated and that the anisotropic wavefunctions of the excitons and biexcitons are shaped by the excitation polarization.

• Reference (41)

/