Abstract
AbstractSpin‐controlled lasers are highly interesting photonic devices and have been shown to provide ultrafast polarization dynamics in excess of 200 GHz. In contrast to conventional semiconductor lasers their temporal properties are not limited by the intensity dynamics, but are governed primarily by the interaction of the spin dynamics with the birefringent mode splitting that determines the polarization oscillation frequency. Another class of modern semiconductor lasers are high‐β emitters, which benefit from enhanced light–matter interaction due to strong mode confinement in low‐mode‐volume microcavities. In such structures, the emission properties can be tailored by the resonator geometry to realize for instance bimodal emission behavior in slightly elliptical micropillar cavities. This attractive feature is utilized to demonstrate and explore spin‐lasing effects in bimodal high‐β quantum dot micropillar lasers. The studied microlasers with a β‐factor of 4% show spin‐laser effects with experimental polarization oscillation frequencies up to 15 GHz and predicted frequencies up to about 100 GHz, which are controlled by the ellipticity of the resonator. These results reveal appealing prospects for very compact, ultrafast, and energy‐efficient spin‐lasers and can pave the way for future purely electrically injected spin‐lasers enabled by short injection path lengths.
Highlights
A high transmission bandwidth and stable transmission for optical communication systems are decisive for the Internet structure and the key to global digitization [1]
Such lasers are highly interesting for the realization of the spin-lasing effect because of their compactness, low-power operation and the strong lateral mode confinement
The mode splitting of the fundamental mode is controlled by the ellipticity and reaches values up to 160 μeV (~40 GHz)
Summary
A high transmission bandwidth and stable transmission for optical communication systems are decisive for the Internet structure and the key to global digitization [1]. With Internet traffic and computing power increasingly concentrated in high-scale data centers due to the growing importance of cloud computing services, short-range optical communication systems play an important role [1] These systems are mainly based on direct current modulated semiconductor lasers such as vertical-cavity surface-emitting lasers (VCSELs). Quantum dot (QD) micropillars are a very interesting type of high- microlasers which often show an increased bimodal behavior due to a (usually unintentional) asymmetry of the pillar’s cross section [13] This leads to pronounced temporal mode switching and intriguing nonlinear dynamics effects [14], such as complex injection locking [15] and zero-lag synchronization [16], under external feedback or mutual coupling of micropillar cavities. We etched about 1/3 of the lower distributed Bragg reflector (DBR) which is sufficient to achieve the desired lateral mode confinement and to maintain high quality (Q) factors in the range of 10.000 [18]
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