High-frequency dynamics of spin-polarized carriers and photons in a laser

Abstract

The high-frequency dynamics of spin-polarized carriers and photons in a spin laser have been studied. The transient response of the device obtained from the rate equations is characterized by two sets of relaxation oscillations in the carrier and photon distributions corresponding to the two polarization modes. Consequently two distinct resonant peaks are observed in the small-signal modulation response. The calculated transient characteristics indicate that the best results are obtained from a spin laser when only the favored polarization mode, with lower threshold, is operational. Under this condition the small-signal modulation bandwidth is higher than that in a conventional laser, the threshold current is lower and the output polarization can be 100% with appropriate bias conditions, independent of the spin polarization of carriers in the active region. Measurements were made at 230 K on a InAs/GaAs quantum dot spin vertical cavity surface emitting laser. A time-averaged output polarization of 55% is measured with an active region spin polarization of 5 -6 %. The experimental results are in good agreement with calculated data.

Stability and bifurcation analysis of spin-polarized vertical-cavity surface-emitting lasers

“…We obtain six eigenvalues (λ 1 ,λ 2 ,...,λ 6 ) in total, and one (λ 6 ) of them is always zero, which is associated with the arbitrariness of the phase of the electric field. These eigenvalues can be ordered as (8) where there are two complex conjugate pairs (λ 1 , λ 2 ) and (λ 3 , λ 4 ). Laser stability is determined by the least damped solution under small perturbations.…”

“…As a specific example of spintronic devices, spin-polarized vertical-cavity surface-emitting lasers (VCSELs) have attracted considerable attention [5][6][7][8][9]. In such lasers, the output polarization is controlled by injecting spin-polarized electrons into the laser active region.…”

Graphene spintronics: Spin injection and proximity effects from first principles

“…Through the angular momentum transfer, the injection of spin-polarized carriers leads to a stimulated emission of circularly polarized light [28][29][30][31]. Spin lasers offer an improved performance, such as a threshold reduction for lasing, an enhanced bandwidth, and reduced parasitic frequency modulation, as compared to their conventional (spin-unpolarized) counterparts [32][33][34][35][36][37][38][39][40].…”

Toward high-frequency operation of spin lasers

“…The gain active (gain) region, usually consists of III-V quantum wells (QWs) or quantum dots (QDs). [7][8][9]26,[37][38][39] The key effect of the active region is producing a stimulated emission and coherent light that makes the laser such a unique light source. The corresponding optical gain that describes stimulated emission, under sufficiently strong pumping/injection of carriers, can be illustrated pictorially in Figs.…”