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

TL;DR

This paper investigates the conditions for generating polarization-entangled photons from (111)B site-controlled pyramidal InGaAs quantum dots, addressing limitations like fine-structure splitting and charging effects, and proposes dual-wavelength excitation as a solution.

Contribution

It demonstrates that entangled photon emission is possible from various pyramidal quantum dot designs and introduces a dual-wavelength excitation method to improve entangled photon yield.

Findings

Entangled photons can be obtained from different pyramidal QD designs.

Dual-wavelength excitation effectively tunes QD charge states.

Addressing charging issues enhances entangled photon detection.

Abstract

A study of highly symmetric site-controlled Pyramidal In0.25Ga0.75As 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 biexciton-exciton 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.