Room-Temperature Spin Polariton Diode Laser

Abstract

2The output of a microcavity coherent light source is generally linearly polarized in the emitter-cavity photon strong coupling regime in the absence of pinning caused by photonic structural disorders [1][2][3]. However, it has been experimentally demonstrated that the orientation of this polarization is stochastic and hence the polarization cannot be experimentally recorded in the steady state [4,5]. Linear polarization can be observed in the steady state output only by pinning along a preferred crystallographic axis [6][7][8][9][10] and the degree of polarization decreases at high pumping levels due to the depinning effect caused by polariton-polariton repulsive interactions and self-induced Larmor precession of the Stokes vector of the condensate [11].These trends in the linear polarization have been observed in polariton lasers pumped optically[9] and electrically [10]. In the case of optical excitation, it is also possible to obtain a circularly polarized output above threshold and this behavior has been verified experimentally in the steady state at cryogenic temperatures [12][13][14][15]. The degree of circular polarization is determined by the interplay of polariton thermalization by scattering (polariton-phonon, polariton-electron and polariton-polariton) and polariton pseudospin precession in the effective magnetic field due to the TE-TM splitting [2,16]. Circular polarization has not been observed in the output of an electrically injected polariton laser since carriers are injected with no net polarization [17]. The output can be circularly polarized due to the interplay of spin-dependent polariton-polariton interactions and stimulated relaxation of exciton polaritons at high injection densities where the depinning of linear polarization is observed [9], but this circular polarization is small, random and largely uncontrolled. On the other hand, it is possible to obtain a controlled and variable circularly polarized output by electrically injecting spin polarized carriers with a suitable ferromagnetic contact [20,21] based on a pump and probe scheme in a semiconductor microcavity, wherein a localized trigger switches on a large pump area and thus controls the polarization of the full emission [31]. In all these previous reports, the devices have been optically excited and their operation was limited to cryogenic temperatures. We demonstrate here, for the first time, modulation of circular polarization of the output of a GaN-based polariton laser at room temperature by electrical injection of spin-polarized electrons using a FeCo/MgO tunnel spin injector contact.We have characterized several identical electrically pumped bulk GaN-based microcavity polariton lasers fabricated from a single epitaxially grown heterostructure sample schematically shown in Fig. 1(a). Device fabrication is described in the Supplemental Material [34]. Two significant changes are incorporated in our previously reported [10,[35][36][37] polariton laser diodes to accomplish successful electrical spin injection and transport. Fi...

Impact of the Energetic Landscape on Polariton Condensates' Propagation along a Coupler

“…Concurrently, diverse polariton devices have been proposed, such as polariton lasers, [ 11–13 ] optical gates, [ 14 ] transistors, [ 15–17 ] spin‐based elements, [ 18–21 ] and integrated circuits. [ 22–24 ] Yet, a close look at the dynamics of propagating polariton condensates along non‐straight circuits is lacking, a void we start filling with this work.…”

Evidence of a strong perpendicular magnetic anisotropy in Au/Co/MgO/GaN heterostructures

“…25) and $25% (ref. 26) have been demonstrated for GaN based spin LED and spin polariton diode lasers at room temperature (RT), respectively. This paves the way for the development of III-nitride based spin opto-electronics.…”

“…In the applications of spin-LED and spin lasers with surface emission geometries, such as 3D displays, the actually used spin injector (GaMnN, 21,22 GaCrN, 23 Fe 3 O 4 , 24,27 and CoFe 25,26 ) with inplane magnetization anisotropy is not possible for practical application. This is because, according to the optical selection rules, 28 the magnetization of the spin injector has to be maintained perpendicular to the quantum-well (QW) LED surface in order to emit circularly polarized light from the surface.…”

Co - Fe - B/MgO/Djeffal1, Cadiz2, Stoffel3 et al. 2018Phys. Rev. Applied5040View full textAdd to dashboardCite

“…It was found that the ferromagnetic spin injector plays a key role in determining the efficiency of the spin injection [8,9]. In most cases, the spin-LED was studied in III-V-based semiconductors such as GaAs [10][11][12][13][14] or GaN [15][16][17]. However, the reverse process: a spin photodiode [18], i.e., the electrical detection of a spin-polarized current when a ferromagnetic/insulator/semiconductor heterojunction is illuminated by a circularly polarized light has gained much less attention.…”