Quantum Optoelectronics

Abstract:

This work examines the reflectivity and transmissivity of a transverse‐electric (TE) polarized wave incident on a microcavity containing strongly coupled excitons with in‐plane uniaxially oriented transition dipole moments, and a different interpretation to a previous report is presented. The propagation of the electric field inside the cavity is discussed, and a distinction is made between two different physical cases: the first, previously observed, and the second, which enables the interpretation of measurements carried out on a microcavity containing an oriented layer of liquid‐crystalline poly(9,9‐dioctylfluorene). In all cases, the reflected and transmitted electric fields derive from photons leaking parallel and perpendicular to the transition dipole moment orientation.

Abstract:

We find that the emission from laterally coupled quantum dots is strongly polarized along the coupled direction [1 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 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 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.

Abstract:

We find that the emission from laterally coupled quantum dots is strongly polarized along the coupled direction [1[Formula: see text]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[Formula: see text]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[Formula: see text]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.

Abstract:

We have developed an inductively coupled plasma etching technique using a Faraday cage to create suspended gallium-nitride devices in a single step. The angle of the Faraday cage, gas mix, and chamber condition define the angle of the etch and the cross-sectional profile, which can feature undercut angles of up to 45°. We fabricate singly- and doubly-clamped cantilevers of a triangular cross section and show that they can support single optical modes in the telecom C-band.