Spin-Polarized Dynamics in Surface-Emitting Lasers

Spin-polarized surface-emitting lasers harness the electron spin degree of freedom to control the polarisation and temporal response of the emitted light. In these devices, typically realised as vertical-cavity surface-emitting lasers (VCSELs) or vertical external-cavity surface-emitting lasers (VECSELs), spin-selective injection—either optical or electrical—creates an imbalance between spin-up and spin-down carrier populations. The ensuing interaction between spin-polarised carriers and cavity birefringence gives rise to rapid polarisation oscillations, ultrafast modulation speeds well beyond those of conventional intensity dynamics and novel nonlinear regimes. Key dynamical phenomena include polarisation switching, self-sustained oscillations, bifurcations to chaotic behaviour and polarization mode competition. The underlying physics is often captured by extensions of the spin-flip model, which integrates carrier recombination, spin relaxation and anisotropies in gain and refractive index. Advances in microcavity design, quantum-dot active regions and external feedback schemes have further enriched the dynamic landscape, offering new routes to energy-efficient, compact spin-lasers. These developments hold promise for ultrahigh-speed optical interconnects, polarisation-encoded data channels, secure communications and spintronic integration, underscoring the global significance of this field.

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Research from all publishers

Recent work has demonstrated bimodal quantum-dot micropillar cavities that support spin-lasing with polarisation oscillation frequencies reaching tens of gigahertz. By tailoring the ellipticity of the resonator, researchers achieved compact, high-β devices capable of ultrafast polarisation dynamics, paving the way for purely electrically injected spin-lasers. Numerical investigations of spin-VCSELs subject to optical feedback have revealed a rich tapestry of nonlinear regimes, including extended regions of periodic oscillations and transitions to chaos. Detailed bifurcation maps elucidate how feedback strength, delay time and spin relaxation rates govern the emergence of complex dynamics, offering guidelines for stabilised operation or deliberate chaos generation. Studies of laterally coupled pairs of spin-VCSELs have uncovered new normal-mode behaviours and bistability arising from evanescent coupling and high birefringence. These findings demonstrate that polarisation states in one laser can be switched via control of the neighbour, suggesting architectures for reconfigurable photonic circuits and logic elements based on spin-controlled coupling.

Spin-Polarized Dynamics in Surface-Emitting Lasers publication trend

The graph below shows the total number of articles in spin-polarized dynamics in surface-emitting lasers across all publications each year (not limited to Nature Index journals).

Technical terms

Vertical-Cavity Surface-Emitting Laser (VCSEL): A semiconductor laser with emission perpendicular to the wafer surface, featuring a short cavity and low threshold.

Spin Selective Injection: The process of preferentially exciting carriers with a particular spin orientation, either optically by circularly polarised light or electrically via spin-polarised contacts.

Birefringence: Anisotropy in refractive index that splits cavity modes into orthogonal polarisation states, influencing polarisation oscillation frequency.

Spin Relaxation: The process by which spin-polarised carriers lose their orientation, characterised by a spin-flip rate that competes with recombination.

Polarisation Oscillation: Rapid periodic switching of the emitted light’s polarisation state, driven by interplay between spin dynamics and mode splitting.

Spin-Flip Model (SFM): A rate-equation framework incorporating carrier populations, photon densities and spin-up/down dynamics to predict laser behaviour under spin-polarised pumping.

References

1. Spin‐Lasing in Bimodal Quantum Dot Micropillar Cavities. Laser & Photonics Review (2022).
2. Mapping bifurcation structure and parameter dependence in quantum dot spin-VCSELs.. Optics Express (2018).
3. Numerical Analysis of Nonlinear Dynamics Based on Spin-VCSELs with Optical Feedback. Photonics (2021).
4. Dynamics of Laterally-Coupled Pairs of Spin-VCSELs. IEEE Journal of Quantum Electronics (2020).