Nadir Ali Khan

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.

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.

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.

Temperature dependent dynamics in a 1550 nm VCSEL subject to polarised optical injection

We present novel experimental results on the dynamics of a 1550 nm vertical-cavity surface-emitting laser (VCSEL) under polarised optical injection for temperatures ranging from −20° C to 60° C. Only one theoretical study of the temperature sensitivity of optically-injected VCSELs has been reported [1], while previous experimental investigations have been confined to room temperature for devices at 850 nm [2] and 1550 nm [3].

Experimental stability maps of a 1550nm-VCSEL subject to polarized optical injection

We report an experimental study of the injection locking properties and nonlinear dynamics of a 1550nm-Vertical Cavity Surface Emitting Laser (VCSEL) subject to parallel and to orthogonal polarized optical injection into the two orthogonal polarizations of the fundamental transverse mode of the device. A rich variety of nonlinear dynamics have been observed for both parallel and orthogonal optical injection outside the stable locking range, including limit cycle, period doubling, chaos and polarization switching. Additionally, for the case of orthogonal optical injection, we report a first experimental observation of the change in the shape of the stability map as the applied bias current is increased well above threshold.

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.

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.

Polarization effects in Optically-Injected Long-Wavelength Vertical-Cavity Surface Emitting Lasers

We present our work studying the effects of polarized optical injection in Long-Wavelength Vertical-Cavity Surface Emitting Lasers (LW-VCSELs). The properties of the polarization switching (PS) and bistability (PB) arising in these devices under orthogonally-polarized optical injection are discussed. We also review our experimental and theoretical analyses on the injection locking and nonlinear dynamics that appear in LW-VCSELs under different polarized injection. Finally, we also report the instabilities induced in spin-polarized VCSELs. This rich variety of nonlinear effects observed at the important telecom wavelength of 1550 nm offers exciting prospects for the practical use of VCSELs in novel applications in optical networks.

Polarization effects in optically injected telecom lasers

Vertical-cavity surface-emitting lasers (VCSELs) operating at the important telecommunication wavelength of 1550nm are expected to play a key role in present and future optical networks. They offer significant inherent advantages over traditional in-plane semiconductor lasers. These include low fabrication costs, high coupling efficiency to optical fibres, and easy integration into 2D arrays. In addition, optical injection is a well-known technique for improving the performance of a semiconductor laser without modifying its design. Hence, in recent years considerable effort has gone into the study of optically injected 1550nm VCSELs. Despite this, not much attention has been paid to the effects of different polarized injection. We analyzed the behavior of 1550nm VCSELs under the external injection of light with different polarization states. We identified various phenomena, including polarization switching (PS), polarization bistability (PB), injection locking (IL), and nonlinear dynamics, which could enable novel uses of these devices. We first plotted a spectrum of a solitary 1550nm VCSEL: see Figure 1(a). The two modes, one lasing and one subsidiary, correspond to the two orthogonal polarizations of the fundamental transverse mode of the VCSEL. We refer to the lasing and subsidiary modes as parallel and orthogonal, respectively. We also plotted the spectrum after injection of an orthogonally polarized optical signal: see Figure 1(b). In this situation, the orthogonal mode locks to the externally injected signal, the parallel mode is suppressed, and PS occurs as the emitted polarization of the VCSEL switches from parallel to orthogonal.1 Hysteresis may also occur associated with PS, and for those cases we also obtained PB.1, 2 Furthermore, we were able to use optical injection to induce IL in 1550nm-VCSELs. We measured locking for these devices Figure 1. Spectra of a 1550nm vertical-cavity surface-emitting laser in solitary conditions (a) and under orthogonal polarized injection (b).

Polarized optical injection in long-wavelength vertical-cavity surface emitting lasers

We report a comprehensive study of the effects of polarized optical injection in long-wavelength Vertical-Cavity Surface Emitting Lasers (LW-VCSELs) emitting at the telecom wavelength of 1550nm. We analyze the properties of the polarization switching and bistability that can be induced in a 1550nm-VCSEL under orthogonal and arbitrary polarized optical injection. Additionally, we study the injection locking bandwidth of these devices when subject to different polarized optical injection. Furthermore, we also analyze the relationship existing between the injection locking bandwidth and the polarization switching range when the device is subject to orthogonally-polarized optical injection. Finally, we have identified regions of different nonlinear dynamics outside the injection locking bandwidth, including regions of periodic dynamics (such as limit cycle and period doubling) and chaos when these devices are subject to parallel and to orthogonal optical injection. This rich variety of nonlinear effects observed at 1550nm offers exciting prospects for novel practical uses of VCSELs in optical switching/routing applications in optical networks.