Polarization control of electroluminescence from vertically stacked InAs/GaAs quantum dots

Abstract

We have developed a technique to control the polarization dependence of quantum dot (QD)-semiconductor optical amplifiers (SOAs) using vertically stacked self-assembled InAs QDs with moderately thick intermediate layers. By increasing the number of stacking layers, the transverse magnetic polarization component of electroluminescence (EL) from the cleaved edge surface of the SOA has been enhanced dramatically. Broadband and almost isotropic EL with a polarization difference of less than 1.2 dB has been demonstrated in a 1.3 μm optical communication band for nine-layer stacked QDs in the active region of the SOA.

In-plane polarization anisotropy of ground state optical intensity in InAs/GaAs quantum dots

“…5,23 Among these techniques, the exploitation of strain interactions between the quantum dot layers in multi-layer QD stacks have shown great potential to generate polarization-insensitive optical transitions at telecommunication wavelengths. 2,4,22,24,53 B. Aspect ratio of QDs increases above 0.3…”

“…Thus, a directional degree of polarization (DOP) should be measured (or calculated) to fully characterize the polarization response of quantum dot stacks. Previous theoretical and experimental studies have considered only a single value of DOP: either [110] The electronic structure of single and stacked InAs quantum dots (QDs) has been extensively studied in the last couple of decades for the design of optical devices [1][2][3][4][5][6][7][8] and devices suited to quantum information processing. [9][10][11][12] Recent efforts are focused to achieve isotropic polarization response of ground state optical intensity (GSOI) at telecommunication wavelengths (1300-1500 nm).…”

“…Several methods have been explored to reduce the value of DOP. These methods include (1) strain engineering by over-growing the InAs QDs with InGaAs quantum wells, also known as the strain reducing capping layers, 3 (2) inclusion of dilute impurities such as nitrogen "N," 19 antimony "Sb," 20 and phosphorous "P," 21 etc., (3) exploiting the strain interaction between the QDs in multi-layer QD stacks, 2,4,22 and (4) growing large stacks of QDs in the form of columnar QDs. 5,23 Among these techniques, the exploitation of strain interactions between the quantum dot layers in multi-layer QD stacks have shown great potential to generate polarization-insensitive optical transitions at telecommunication wavelengths.…”

“…[9][10][11][12] Recent efforts are focused to achieve isotropic polarization response of ground state optical intensity (GSOI) at telecommunication wavelengths (1300-1500 nm). 2,[4][5][6][7] The polarization response of QD samples is characterized in terms of degree of polarization:…”

Tuning of polarization sensitivity in closely stacked trilayer InAs/GaAs quantum dots induced by overgrowth dynamics

“…The flexibility in controlling their geometry by means of growth conditions and, in certain cases substrate patterning [2], has stimulated several studies on more complex structures able to add further potentialities to lensshaped or pyramidal nanostructures commonly obtained by the Stranski-Krastanov process. In this context, one relevant physical example are closely stacked quantum dots, either consisting of QD layers separated by a thin GaAs spacer [3][4][5], or without using any GaAs spacer (also known as columnar QDs [6] or quantum posts [7]). In these kinds of nanostructures, the strong compressive biaxial strain component at the center of the typical flat shape dot can be reduced to zero or towards tensile values by increasing the stack height (adding QD layers), thus providing the optical polarization insensitivity desirable for relevant technological applications such as semiconductor optical amplifiers for high speed communication networks [8][9][10].…”