Rihab Al-Seyab

Dynamics of Polarized Optical Injection in 1550-nm VCSELs: Theory and Experiments

We report novel theoretical results obtained from combining the method of largest Lyapunov exponent (LLE) with the spin-flip model (SFM), including noise, to model a vertical-cavity surface emitting laser (VCSEL) subject to polarized optical injection. The LLE is applied to the numerical solutions in order to automatically calculate stability maps that characterize the dynamics. The SFM has been extended and generalized to allow for optical injection of arbitrary polarization. Measurements on a 1550-nm VCSEL have been used to estimate the values of key parameters for use in the model and with these we demonstrate excellent agreement between theory and experiment.

Instabilities in Spin-Polarized Vertical-Cavity Surface-Emitting Lasers

We report a first comprehensive theoretical analysis of optically pumped spin-polarized vertical-cavity surface-emitting lasers, which combines the spin-flip model with the largest Lyapunov exponent technique to determine regions of stability and instability. The dependence of these regions on a wide range of fundamental device parameters is investigated, and results were presented in a new form of maps of the polarization versus the magnitude of the optical pump. We also reveal the importance of considering both the birefringence rate and the linewidth enhancement factor when engineering a device for high-frequency applications.

Dynamics of VCSELs Subject to Optical Injection of Arbitrary Polarization

New theoretical results are presented on polarized optical injection of vertical-cavity surface-emitting lasers (VCSELs) based on the spin-flip model extended to consider both the azimuth and ellipticity of the injected light. Experiments to investigate these effects are performed on two 1550-nm VCSELs with different frequency spacing between the resonances of the orthogonal polarizations of the fundamental transverse mode. Excellent agreement is found between experiment and theory for the stability and polarizations of the two VCSELs subject to polarized optical injection. The input polarization angle has a strong effect on both the dynamics and polarization of each VCSEL, whereas the ellipticity of the injected light affects only the polarization.

Instabilities in quantum-dot spin-VCSELs

A modified spin-flip model is used to investigate the stability of optically-pumped quantum-dot spin-vertical cavity surface-emitting lasers. in terms of pump intensity and polarization. The stability maps exhibit pronounced polarization switching in the stable regions. Periodic oscillations in unstable regions are attributed to competition between spin relaxation and birefringence.

Controlled Single- and Multiple-Pulse Excitability in VCSELs for Novel Spiking Photonic Neurons

Excitability in VCSELs under parallel- and orthogonally-polarized optical injection is investigated numerically. Controlled single- and multiple-pulse excitability is found for the two polarizations offering prospects for novel VCSEL-based ultrafast spiking photonic neurons.

Stability analysis of spin-polarized VCSELs

The ability to control the output polarization of spin-polarized VCSELs, by electrical injection and/or optical pumping of spin-polarized carriers, holds much potential for ultrafast all-optical elements. Research interest has been boosted by recent experimental demonstrations of electrically-pumped [1] and optically-pumped spin-VCSELs [2]. Such devices can exhibit rich dynamics due to the competition of spin-flip processes and birefringence. Stability maps for spin-VCSELs dynamics are reported here, for the first time to our knowledge, using the spin flip model (SFM) [3] and the largest Lyapunov exponent (LLE) method [4]. Our approach accounts for dichroism and birefringence with rates γa and γp, respectively, using the parameter set used in [5]. We choose fixed values of cavity decay rate κ = 125 ns−1, carrier recombination rate γ = 1 ns−1 and γa = 0. The stability maps are presented in terms of polarization ellipticity P and normalized amplitude η of the pumping (electrical or optical); only negative values of P are shown since the results are symmetric about P = 0.

Elliptical injection of a 1550nm-VCSEL: Theory and experiment

We show new theoretical results on polarized optical injection of VCSELs based on the spin flip model extended to consider both the azimuth and ellipticity of the injected light, and demonstrate excellent agreement with experiment.

Novel theory and experiments on dynamics of polarised optical injection in long-wavelength VCSELs

We show new theoretical results from combining the largest Lyapunov exponent with the spin flip model, including noise, to produce a description of VCSELs subject to polarised optical injection and demonstrate excellent agreement with experiment.

Dynamics and polarization of conventional and spin-VCSELs in the presence of an axial magnetic field

The spin flip model is used to investigate the effects of an axial magnetic field on the polarization and dynamics of conventional vertical cavity surface-emitting lasers (VCSELs) and spin-VCSELs where polarized optical pumping is used to inject a spin-polarized electron population. It is found that the ratio of the circular birefringence caused by the magnetic field to the intrinsic linear birefringence plays an important role in exciting oscillations in the intensities and polarization of the VCSELs studied. For a conventional VCSEL, higher values of the linear birefringence require larger axial magnetic fields to cause output power and polarization oscillations. In the case of spin-VCSELs, it is found that both magnitude and sign of the magnetic field can affect the stability and dynamics, as represented on maps in the plane of polarization ellipticity versus magnitude of the pump. A reversal in the sign of the field is equivalent to reversing the sign of the pump ellipticity. Potential applications of these effects in terms of optical oscillators and magnetic field sensors are identified.

Progress on the analysis of polarised optical injection in 1550nm-VCSELs

We review our recent work analysing the polarisation effects in optically injected VCSELs operating at the important telecom wavelength of 1550 nm. We summarise our studies on the polarisation, time and temperature dependence of the nonlinear dynamics induced in these devices when subject to different types of polarised optical injection. In addition, we also discuss the potentials of VCSELs for the optical emulation of different neuronal behaviours offering prospects for novel uses of these devices in future neuromorphic systems and novel computing paradigms.