Conditions for entangled photon emission from (111)B site-controlled pyramidal quantum dots

Abstract

A study of highly symmetric site-controlled Pyramidal In 0.25 Ga 0.75 As quantum dots (QDs) is presented. It is discussed that polarization-entangled photons can be also obtained from Pyramidal QDs of different designs from the one already reported in Juska et al. (Nat. Phot. 7, 527, 2013).Moreover, some of the limitations for a higher density of entangled photon emitters are addressed. Among these issues are (1) a remaining small fine-structure splitting and (2) an effective QD charging under non-resonant excitation conditions, which strongly reduce the number of useful biexcitonexciton recombination events. A possible solution of the charging problem is investigated exploiting a dual-wavelength excitation technique, which allows a gradual QD charge tuning from strongly negative to positive and, eventually, efficient detection of entangled photons from QDs, which would be otherwise ineffective under a single-wavelength (non-resonant) excitation.

Vanishing biexciton binding energy from stacked, MOVPE grown, site-controlled pyramidal quantum dots for twin photon generation

“…We consider here as representative/significant example the spectrum of a QD presented in Fig.3a: in this case it was possible to spectrally separate photons from each transition with our spectrometer while still having a significant overlap between the exciton and biexciton (which were identified using power dependence and cross-correlation, following criterions described in [24]). Fig.3b shows the cross- Fig.3 -a) A representative spectrum for a typical PQD with 2 QDs at 1nm inter-dot barrier; exciton and biexciton are labeled with X and XX respectively (while the brighter peak at longer wavelengths is relative to a negatively charged exciton [25]) Auto-correlation for the photons in the spectral overlap between the two excitonic transitions (schematically highlighted with the green color in a)) showing a significant bunching and a symmetric shape, as found in similar cases in literature for twin photons [14]. c) Cross-correlation between biexciton (start channel of the correlator) and exciton (stop channel), highlighted with the same color in a), showing strong bunching, confirming the cascade between the two transitions.…”

“…PQDs are fabricated starting from a patterned (111)B-oriented GaAs substrate (in which tetragonal recesses are obtained), on which MOVPE is performed depositing InGaAs dots with GaAs barriers, as for example discussed in ref [25] and [26]. The growth process is the interesting result of the competition between precursors decomposition rate anisotropies, and adatom diffusion and preferential attachment at concave recesses (also referred to in the literature as capillarity processes) [27] [28].…”

Лазерная генерация в микродисках с активной областью на основе решеточно-согласованных InP/AlInAs наноструктур

“…Эксперименты по определению порога лазерной генерации и эксперимен-ты с временным разрешением проводились с помощью стандартной системы микрофотолюминесценции, опи-санной в [10] PL , 10 a. u. области наноструктур (∼ 940 nm, 1.32 eV). Из литера-турных данных известно, что технология осаждения InP на AlInAs (и наоборот) существенно влияет на положе-ние полос ФЛ -положение полосы от гетероперехода варьирует в диапазоне 1.1−1.3 eV [3,11,12].…”

Lasing of InP/AlInAs quantum dots in AlInAs microdisk cavity

“…Photoluminescence (PL) experiments were conducted under CW (532 nm) and pulsed (635 nm, frequency 10 -80 MHz) excitation in a standard microphotoluminescence set-up with photon correlation capability, as described elsewhere [11]. The system enabled exciting and probing regions as small as a few μm 2 using an objective with 50 times magnification and numerical aperture of 0.5.…”