Ultrafast circular polarization oscillations in spin-polarized vertical-cavity surface-emitting laser devices

Abstract

Spin-polarized lasers offer new encouraging possibilities for future devices. We investigate the polarization dynamics of electrically pumped vertical-cavity surface-emitting lasers after additional spin injection at room temperature. We find that the circular polarization degree exhibits faster dynamics than the emitted light. Moreover the experimental results demonstrate a strongly damped ultrafast circular polarization oscillation due to spin injection with an oscillation frequency of approximately 11GHz depending on the birefringence in the VCSEL device. We compare our experimental results with theoretical calculations based on rate-equations. This allows us to predict undamped long persisting ultrafast polarization oscillations, which reveal the potential of spin-VCSELs for ultrafast modulation applications

Simulated dynamics of optically pumped dilute nitride 1300 nm spin vertical‐cavity surface‐emitting lasers

“…These results show a very good agreement with the experimental results presented in [6], where polarisation oscillations have been observed in the range of 8.6–11 GHz. Transient oscillations around 10 GHz have been reported at shorter wavelengths at room temperature for the spin‐VCSEL in [10–12].…”

“…Controlling the output polarisation by that of the input is experimentally demonstrated in [7–9]. Also, transient oscillations of the output ellipticity in response to pulsed optically spin‐polarised pumping were predicted and observed in [10–12] and were reported for conventional electrical pumping in [13, 14]. Simulations using the spin‐flip model (SFM) yielded good agreement with these experimental results, confirming that the oscillation frequency is dominated by the birefringence of the microcavity in combination with the dichroism and the spin relaxation rate, as originally predicted by Gahl et al .…”

Theory of quantum dot spin-lasers

“…1 Apart from the successful early demonstration of a spin-laser based on a bulk-like layer of GaAs, 7 most experiments in this field concentrated on structures with quantum well (QW) active regions, using optical pump, 2,8-10 electrical injection 3 or a combination of both. 4,11 Recently, however, an (In,Ga)As/GaAs quantum dot (QD) spin-laser with electrical injection has been demonstrated, lasing at temperatures 100 K higher than its QW counterparts. 12 QDs close a succession of reduced-dimensionality structures: quantum wells and wires, which have replaced bulk-like active regions of semiconductor lasers.…”