Kevin Schires

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.

Investigation of vertical cavity surface emitting laser dynamics for neuromorphic photonic systems

We report an approach based upon vertical cavity surface emitting lasers (VCSELs) to reproduce optically different behaviors exhibited by biological neurons but on a much faster timescale. The technique proposed is based on the polarization switching and nonlinear dynamics induced in a single VCSEL under polarized optical injection. The particular attributes of VCSELs and the simple experimental configuration used in this work offer prospects of fast, reconfigurable processing elements with excellent fan-out and scaling potentials for use in future computational paradigms and artificial neural networks.

Optically-pumped dilute nitride spin-VCSEL

We report the first room temperature optical spin-injection of a dilute nitride 1300 nm vertical-cavity surface-emitting laser (VCSEL) under continuous-wave optical pumping. We also present a novel experimental protocol for the investigation of optical spin-injection with a fiber setup. The experimental results indicate that the VCSEL polarization can be controlled by the pump polarization, and the measured behavior is in excellent agreement with theoretical predictions using the spin flip model. The ability to control the polarization of a long-wavelength VCSEL at room temperature emitting at the wavelength of 1.3 µm opens up a new exciting research avenue for novel uses in disparate fields of technology ranging from spintronics to optical telecommunication networks.

Polarization and Time-Resolved Dynamics of a 1550-nm VCSEL Subject to Orthogonally Polarized Optical Injection

We report a first experimental study of the simultaneous temporal and polarization-resolved dynamics of a 1550-nm vertical-cavity surface-emitting laser (VCSEL) subject to orthogonally polarized optical injection. A novel technique is used to reveal the behavior of both polarizations at the VCSELs output. In general, the same type of dynamics can be seen in both polarizations of the fundamental transverse mode but with unequal intensity/modulation depth. We show that both polarizations exhibit period one and chaotic dynamics and reveal antiphase dynamics. These results offer promise for the development of dual-channel, anticorrelated periodic and chaotic-signal generators with a single VCSEL for use as oscillators or chaotic sources in present and future optical networks.

Comprehensive experimental analysis of nonlinear dynamics in an optically-injected semiconductor laser

We present the first comprehensive experimental study, to our knowledge, of the routes between nonlinear dynamics induced in a semiconductor laser under external optical injection based on an analysis of time-averaged measurements of the optical and RF spectra and phasors of real-time series of the laser output. The different means of analysis are compared for several types of routes and the benefits of each are discussed in terms of the identification and mapping of the nonlinear dynamics. Finally, the results are presented in a novel audio/video format that describes the evolution of the dynamics with the injection parameters.

Dynamic Characteristics of an All-Optical Inverter Based on Polarization Switching in Long-Wavelength VCSELs

An all-optical inverter using polarization switching (PS) of a long-wavelength single-mode vertical-cavity surface-emitting laser (VCSEL) is experimentally demonstrated. PS appears when linearly polarized light is injected orthogonally to the linear polarization of the solitary VCSEL. The dynamic behavior of an all-optical inverter under different pulsed optical inputs is analyzed. Time traces, rise and fall times of the linearly polarized output signals are reported. The dependence of these quantities on the bias current and injected optical power is investigated. This analysis permits us to identify proper operation conditions for the all-optical inversion. The PS-based all-optical inverter is demonstrated with a 2.5-Gb/s non-return-to-zero input signal.

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.

Temperature Dependent Dynamics in a 1550-nm VCSEL Subject to Polarized Optical Injection

We report the first comprehensive experimental analysis on the dynamics of an optically injected 1550-nm vertical-cavity surface-emitting laser (VCSEL) over a wide temperature range going from -20°C to 60°C . We show the variations with temperature on the measured stability maps of the 1550-nm VCSEL when subject to parallel and orthogonal polarized optical injection and for different applied bias currents above threshold. The change in the shape of the stable locking region with temperature with the device subject to parallel polarized optical injection is attributed to the change of linewidth enhancement factor (α). In addition, we also show the changes of the polarization switching and locking regions with temperature for the case of orthogonal polarized optical injection.

Stability of the nonlinear dynamics of an optically injected VCSEL

Automated protocols have been developed to characterize time series data in terms of stability. These techniques are applied to the output power time series of an optically injected vertical cavity surface emitting laser (VCSEL) subject to varying injection strength and optical frequency detuning between master and slave lasers. Dynamic maps, generated from high resolution, computer controlled experiments, identify regions of dynamic instability in the parameter space.

Measurement of Temperature-Dependent Relaxation Oscillation Frequency and Linewidth Enhancement Factor of a 1550 nm VCSEL

In this paper, we present detailed measurements of the temperature-dependent relaxation oscillation frequency and polarization resolved linewidth enhancement factor (α) of a 1550-nm vertical cavity surface emitting laser (VCSEL). The thermal effects on these parameters are investigated for a temperature range of -20°C to 60°C. Comparison is made between the experimental observations and theoretical predictions for similar VCSELs and with those different in operating wavelength and/or materials.