Abstract
The polarisation properties of a quantum well spin – vertical cavity surface emitting laser (spin – VCSEL), both without injection and with variable polarisation optical injection, are investigated experimentally and compared with the spin flip model (SFM). Without injection, we demonstrate two distinct types of VCSEL-pump response depending on the signs of the linewidth enhancement factor, birefringence and dichroism: firstly where the pump and VCSEL have the same sign of the ellipticity, and secondly where the VCSEL ellipticity, accompanied by the linear polarisation, switches sign. We show that by controlling the injected power, ellipticity or linear angle, near circular polarisation can be obtained. These responses both give insight into the electro-optical injected spin-VCSEL system, and have practical implications for the use of spin VCSELs in unique applications exploiting the ellipticity degree of freedom.
Highlights
S PIN VCSELs – devices which utilise conservation of spin angular momentum in the electron-photon lasing processes – have been shown to possess a variety of unique characteristics
We have examined experimentally and theoretically the principal types of pump-VCSEL ellipticity response in the solitary quantum well (QW) spin-VCSEL, and how these depend on the relative signs of α, γa and γp
The parameters used in the spin flip model (SFM) show that some of these responses can be tailored by changes in simple operational conditions e.g. relative injection strength, but others are reliant on selection of materials e.g. birefringence and spin relaxation rates
Summary
S PIN VCSELs – devices which utilise conservation of spin angular momentum in the electron-photon lasing processes – have been shown to possess a variety of unique characteristics Properties such as threshold reduction [1], [2], spin amplification [3]–[5] polarisation control [5]–[8], and high frequency polarisation oscillations [9]–[12] have been demonstrated. Our investigations reveal unusual input-output ellipticity responses, and these are explained in terms of the spin VCSEL parameters via the SFM model We demonstrate how these ellipticity responses can be altered and optimised, and we propose applications based on the ellipticity, to extend the current use of conventional VCSELs where the output is linearly polarised.
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