Spin-lasers: spintronics beyond magnetoresistance

Abstract

Introducing spin-polarized carriers in semiconductor lasers reveals an alternative path to realize roomtemperature spintronic applications, beyond the usual magnetoresistive effects. Through carrier recombination, the angular momentum of the spin-polarized carriers is transferred to photons, thus leading to the circularly polarized emitted light. The intuition for the operation of such spin-lasers can be obtained from simple bucket and harmonic oscillator models, elucidating their steady-state and dynamic response, respectively. These lasers extend the functionalities of spintronic devices and exceed the performance of conventional (spin-unpolarized) lasers, including an order of magnitude faster modulation frequency. Surprisingly, this ultrafast operation relies on a short carrier spin relaxation time and a large anisotropy of the refractive index, both viewed as detrimental in spintronics and conventional lasers. Spin-lasers provide a platform to test novel concepts in spin devices and offer progress connected to the advances in more traditional areas of spintronics.

Spin‐Lasing in Bimodal Quantum Dot Micropillar Cavities

“…Deviations from the direct correspondence between the polarization‐oscillation frequency f PO and the mode splitting Δ f as depicted in Figure 4a can be fundamentally explained with the dependence of f PO on further laser properties such as photon density, photon lifetime, carrier recombination rate, spin‐flip rate, linewidth enhancement factor and saturation effects, especially in the low birefringence regime used here. [ 6 ] For one of the two samples with nominal 16% ellipticity the obtained dynamics remain ≈2–3 GHz below the expected value given by the mode splitting. Further experimental and theoretical studies are required to gain a thorough understanding of this variation and whether it is specific to high‐ β cQED lasers.…”

“…They can be observed in the S3 dynamics via angular momentum transfer between the carrier‐spin and the photon‐spin. [ 6 ] The oscillations can generally be understood as a beating between the two orthogonal linearly polarized fundamental modes in the micropillar cavity, frequency‐splitted due to the micropillar anisotropies. [ 5 ] Fitting the experimental data after background subtraction with a damped sinusoidal function (red trace in Figure 3c) yields a polarization‐ oscillation frequency f PO of (10.4 ± 0.1) GHz and a damping constant of (0.19 ± 0.01) ns.…”

Spin Laser Local Oscillators for Homodyne Detection in Coherent Optical Communications

“…The approach we propose in this study is the use of spin-controlled vertical-cavity surface-emitting lasers (spin-VCSELs) [16][17][18][19][20][21][22][23]. The up-spin and down-spin electron densities in an active region can be freely modulated when ferromagnetic electron spin injectors for each spin-polarized electron are fabricated [24,25].…”

Impacts of Crystal Quality on Carrier Recombination and Spin Dynamics in (110)-Oriented GaAs/AlGaAs Multiple Quantum Wells at Room Temperature

“…Semiconductor spintronics has attracted growing interest in the last three decades [ 1 ]. In nonmagnetic semiconductors, the retention time of electron spin polarization, i.e., the spin relaxation time ( τ s ), is one of the most important indexes because it significantly affects the performance of spintronic devices such as spin transistors [ 2 ] and spin-photonics devices [ 3 , 4 , 5 ]. For III-V compound semiconductors, τ s in bulk and (100)-oriented quantum wells (QWs) have been extensively investigated so far [ 6 , 7 ].…”