Optical anisotropy in self-assembled InP quantum dots

Sugisaki, Mitsuru; Ren, Hongwen; Nair, Selvakumar V.; Nishi, Kenichi; Sugou, S.; Okuno, Tsuyoshi; Masumoto, Yasuaki

doi:10.1103/physrevb.59.r5300

Cited by 84 publications

(82 citation statements)

References 16 publications

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“…A polarization rate of 30% is observed which is explained as due to size and shape anisotropies. Theoretically, it has been shown that circularly symmetric QDs can have a preferred optical polarization direction 7,9 due to composition gradients 7,10 and strain distribution 2,9,11 within the QDs.…”

Section: Introductionmentioning

confidence: 99%

Dichroic reflection of InAs∕GaAs quantum dots

Bogaart

Haverkort

Eijkemans

et al. 2005

Journal of Applied Physics

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Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Polarization-resolved reflection measurements are performed on nearly circular InAs/ GaAs quantum dots ͑QDs͒ by means of time-resolved differential reflection spectroscopy. We observe linear polarization anisotropy of the differential absorption, revealing the dichroic character of the QD reflection. The observed magnitude of the dichroism is ⌰ ͓110͔ / ⌰ ͓110͔ = 1.07. The polarization has a preferential direction orientated along the ͓110͔ crystal axis, which is confirmed by polarization-resolved photoluminescence. We observe that the polarization anisotropy of the reflectivity is strongly dependent on the pump excitation density, decreasing from = 0.14 at low excitation to = 0.06 at high excitation. The pump power dependence is described by a binomial model taking into account the statistics of carrier capture into a limited number of QDs.

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Section: Introductionmentioning

confidence: 99%

Dichroic reflection of InAs∕GaAs quantum dots

Bogaart

Haverkort

Eijkemans

et al. 2005

Journal of Applied Physics

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“…In theory, the polarization properties of photon pairs emitted through these two decay paths result entirely from properties of the optically-active 1X doublet [10,11,12]. For a symmetric quantum dot, the two 1X states are degenerate, and the two decay paths become "indistinguishable," ideally producing polarization-entangled photons [9].…”

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confidence: 99%

Polarization-correlated photon pairs from a single quantum dot

et al. 2002

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Polarization correlation in a linear basis, but not entanglement, is observed between the biexciton and single-exciton photons emitted by a single InAs quantum dot in a two-photon cascade. The results are well described quantitatively by a probabilistic model that includes two decay paths for a biexciton through a non-degenerate pair of one-exciton states, with the polarization of the emitted photons depending on the decay path. The results show that spin non-degeneracy due to quantumdot asymmetry is a significant obstacle to the realization of an entangled-photon generation device. [4,5,6], but they can also generate sequences of photons in a radiative cascade [7,8]. In such a cascade, each photon has a unique wavelength, and the photons may also have correlated, or even entangled [9] polarizations.In the two-photon cascade, a biexciton singlet state (two electrons and two holes, 2X) decays to one of two optically active single-exciton states (one electron and one hole, 1X) by emitting one photon, and then to the empty-dot state by emitting a second photon. In theory, the polarization properties of photon pairs emitted through these two decay paths result entirely from properties of the optically-active 1X doublet [10,11,12]. For a symmetric quantum dot, the two 1X states are degenerate, and the two decay paths become "indistinguishable," ideally producing polarization-entangled photons [9]. For an asymmetric quantum dot, the 1X doublet is split through the electron-hole exchange interaction into states that couple to photons having orthogonal linear polarizations [13,14,15]. If this splitting is much larger than the radiative linewidth, then the two paths become "distinguishable," with one decay path producing two horizontally-polarized photons and the other producing two vertically polarized photons, for example. In this case, polarization correlation is expected only in a single, preferred basis. Some additional factors are also important, such as spin flip [16] and decoherence processes [17,18,19] that randomize the intermediate 1X state, and valence-band mixing [20].In this article, we present an experimental study of the polarization correlation properties of photon pairs emitted through biexciton decay in a single InAs quantum dot. While temporal correlations between 1X and 2X photons have previously been seen [21], polarization correlation has not yet been reported, to our knowledge, although a lack of such correlation has been mentioned elsewhere [22]. For our sample, we observe a strong polarization correlation in a linear polarization basis, verifying the theoretical picture described above. However, we do not observe entanglement, suggesting that quantum-dot asymmetry is an obstacle to realizing an entangled photon source.A sample was fabricated containing self-assembled InAs quantum dots [3] grown by molecular-beam epitaxy on a (001) GaAs substrate, capped by 75 nm of GaAs. A high growth temperature increased intermixing between the InAs and surrounding GaAs, shortening the quantum-dot emission wa...

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“…The strong optical anisotropy is due to the formation of the natural superlattice. 9,27 The PL spectrum Wavelength (nm)…”

Section: A Photoluminescence and Pump-probe Measurementsmentioning

confidence: 99%

“…An interesting aspect of InP QDs is that the optical anisotropy is due to a combined effect of the shape as well as structural anisotropy. 9,10,[27][28][29][30] In this paper we demonstrate the use of time-resolved differential reflectivity for studying excitonic structure in InP QDs. The advantage of this technique is that it is relatively simple to implement and its time resolution is solely limited by the laser pulse width.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic optical response of InP self-assembled quantum dots studied by pump-probe spectroscopy

et al. 2007

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Transient anisotropic reflectivity change spectra of InP quantum dots have been observed by means of two-color pump-probe spectroscopy. The results show a fast decay component with a lifetime of 100-200 ps which depends on the probe energy, followed by the slow decay component of ϳ1 ns. The reflectivity change spectra have a dispersive shape having a maximum on the higher energy side of the photoluminescence ͑PL͒ band by 80 meV, and a dip located at the maximum of the PL band. Interestingly, the reflectivity change signals observed for the ͓110͔ and ͓110͔ polarizations have the opposite sign when the probe energy is set between the first and second exciton states. The temporal change of spectra is simulated by means of a Monte Carlo method, and the model is found to well reproduce the experimental result. Further, the model enables us to evaluate the microscopic exciton parameters of single quantum dots by macroscopic observations. The oscillator strengths along the ͓110͔ and ͓110͔ directions at the PL peak energy are evaluated to be f x = 0.37 and f y = 0.71, respectively. The oscillator strength is about five times smaller than simple theoretical estimates. This suggests a small overlap of the envelope functions which is consistent with the existence of a permanent dipole moment observed in these QDs.

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Optical anisotropy in self-assembled InP quantum dots

Cited by 84 publications

References 16 publications

Dichroic reflection of InAs∕GaAs quantum dots

Dichroic reflection of InAs∕GaAs quantum dots

Polarization-correlated photon pairs from a single quantum dot

Anisotropic optical response of InP self-assembled quantum dots studied by pump-probe spectroscopy

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