[Show abstract][Hide abstract] ABSTRACT: Polarization switching (PS) in 1550nm-VCSELs under single and double pulsed polarized optical injection is investigated experimentally and in theory. ‘Normal’ and ‘reverse’ PS were achieved, respectively, when the device was subject to single and double optical injection. Speed operation enhancement is observed for ‘reverse’ PS under double polarized optical injection. Also, the minimum injection power requirements for both ‘normal’ and ‘reverse’ PS have been analyzed showing significant differences for the two investigated cases. Furthermore, we have also investigated numerically the influence of important system parameters, such as the normalized bias current, the injection field strength and the linewidth enhancement factor in the optimal operation conditions for both types of PS. Overall good agreement between theory and experiments is found.
IEEE Journal of Selected Topics in Quantum Electronics 11/2015; 21(6). DOI:10.1109/JSTQE.2015.2413955 · 3.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The dynamics in a system of integrated self-and mutually-coupled lasers are analysed. For the first time, we present an overall comparison of the experimental and modelled dynamics of this system as functions of the frequency detuning and coupling magnitude parameters. Firstly, the non-trivial parameters affecting the dynamics, namely the group index and group index dispersion, the relaxation oscillation frequencies of the two lasers, and the coupling magnitude, are calibrated. A transition in dynamics depending on detuning is then demonstrated, for a range of coupling magnitudes, in both the experimental measurements and by using a travelling-wave model of the system. The dynamics are analysed rigorously using the correlation dimension of the time series to identify regions of linear and nonlinear interaction, and distinct dynamic boundaries separating these regions are then calculated. In addition we show, using results from the travelling wave model, the profound effect of the coupling phase on the dynamics
IEEE Journal of Selected Topics in Quantum Electronics 11/2015; 21(6):1-1. DOI:10.1109/JSTQE.2015.2422292 · 3.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We report the first room temperature quantum dot (QD) vertical-external-cavity surface-emitting laser operating at 1305 nm. The gain structure was composed of $5 times 3$ QD layers; each threefold group was positioned at an antinode of the standing wave of the optical field. Continuous wave optical output power >0.5 mW with threshold pump power of 21 mW was demonstrated using a very simple and compact laser configuration by employing a high reflection-coated fiber as the top mirror. Using a piezoelectric translation stage, the emission wavelength could be tuned over a 14-nm spectral range.
[Show abstract][Hide abstract] ABSTRACT: Simultaneous generation of microwave and millimeter-wave (mm-wave) signals is demonstrated experimentally using a 1310-nm Quantum Dot (QD) Distributed-Feedback (DFB) Laser. The reported technique is based on the period-1 dynamics and dual-mode lasing induced in the laser device under external optical injection. Tunability of the generated microwave and mm-wave signals is obtained. Furthermore, abrupt switching between different frequency regimes in the microwave and mm-wave bands is also observed. These novel frequency switching mechanisms added to the tuning capability of the system offers exciting prospects for novel uses of QD lasers in ultra-high frequency applications. Our approach also benefits from a simple experimental configuration using basic optical fibre components making our technique totally compatible with optical telecommunication networks.
IEEE Journal of Selected Topics in Quantum Electronics 06/2015; 21(6). DOI:10.1109/JSTQE.2015.2438435 · 3.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
Journal of the Optical Society of America B 04/2015; 32(4). DOI:10.1364/JOSAB.32.000683 · 1.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We report the experimental observation of circular polarization switching (PS) and polarization bistability (PB) in a 1300 nm dilute nitride spin-vertical cavity
surface emitting laser
(VCSEL). We demonstrate that the circularly polarized optical signal at 1300 nm can gradually or abruptly switch the polarization ellipticity of the spin-VCSEL from right-to-left circular polarization and vice versa. Moreover, different forms of PS and PB between right- and left-circular polarizations are observed by controlling the injection strength and the initial wavelength detuning. These results obtained at the telecom wavelength of 1300 nm open the door for novel uses of spin-VCSELs in polarization sensitive applications in future optical systems.
[Show abstract][Hide abstract] ABSTRACT: We experimentally demonstrate the control of the light polarization emitted by a 1310 nm dilute nitride spin-Vertical Cavity Surface Emitting Laser (VCSEL) at room temperature. This is achieved by means of a combination of polarized optical pumping and polarized optical injection. Without external injection, the polarization of the optical pump controls that of the spin-VCSEL. However, the addition of the externally injected signal polarized with either left- (LCP) or right-circular polarization (RCP) is able to control the polarization of the spin-VCSEL switching it at will to left- or right-circular polarization. A numerical model has been developed showing a very high degree of agreement with the experimental findings.
[Show abstract][Hide abstract] ABSTRACT: We report the first experimental observation of different forms of polarization switching and bistability in an optically injected 1300nm dilute nitride spin-VCSEL and for both (right- and left-) circularly polarized modes of the device.
[Show abstract][Hide abstract] ABSTRACT: We report the first quantum dot semiconductor disk laser operating at 1300 nm under
continuous optical pumping at room temperature. A threshold power of 21 mW and output power
above 0.5 mW have been achieved.
2014 IEEE International Semiconductor Laser Conference; 10/2014
[Show abstract][Hide abstract] ABSTRACT: We report the first optical injection experiment on a dilute nitride 1300 mm spin-VCSEL at room temperature. Effective control of the polarization of the light emitted by the spin-VCSEL is theoretically predicted and experimentally demonstrated.
[Show abstract][Hide abstract] ABSTRACT: The authors report a theoretical analysis of optically pumped 1300 nm dilute nitride spin-polarised vertical-cavity surface-emitting lasers (VCSELs) using the spin-flip model to determine the regions of stability and instability. The dependence of the output polarisation ellipticity on that of the pump is investigated, and the results are presented in twodimensional contour maps of the pump polarisation against the magnitude of the optical pump. Rich dynamics and various forms of oscillatory behaviour causing self-sustained oscillations in the polarisation of the spin-VCSEL subject to continuouswave pumping have been found because of the competition of the spin-flip processes and birefringence. The authors also reveal the importance of considering both the birefringence rate and the linewidth enhancement factor when engineering a device for high-frequency applications. A very good agreement is found with the experimental results reported by the authors?? group.
IET Optoelectronics 04/2014; 8(2):117-121. DOI:10.1049/iet-opt.2013.0044 · 0.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: Tunable microwave (MW), millimeter-wave (MMW) and THz signal generation with frequencies ranging from below 1 GHz to 1 THz are demonstrated experimentally with a 1310-nm Quantum Dot (QD) Distributed-Feedback (DFB) laser. Continuously tunable MW signals from below 1 GHz to over 40 GHz are produced using the period-1 dynamics induced in the QD DFB laser when subject to optical injection into its lasing mode. In addition, we report a novel technique for MMW and THz signal generation which is based on the dual-mode laser operation and Four-Wave-Mixing induced in the QD DFB laser under single-beam optical injection into one of its residual Fabry-Perot modes. Coarse and fine frequency tunability of the generated MMW and THz signals from 117 GHz to 954 GHz is also demonstrated experimentally. The simplicity of the experimental configuration used in this work offers promise for novel uses of QD lasers as MW, MMW and THz signal sources for Radio-over-Fiber (RoF) applications and future mobile communication networks.
2013 IEEE International Topical Meeting on Microwave Photonics (MWP 2013); 10/2013
[Show abstract][Hide abstract] ABSTRACT: Generation of tunable millimeter-wave (MMW) and terahertz (THz) signals is experimentally demonstrated with an optically injected 1310-nm quantum dot distributed feedback (QD DFB) laser. A novel technique for MMW and THz signal generation is proposed, which is based on the dual-mode laser operation and the four-wave mixing induced in the QD DFB under single-beam optical injection into one of its residual Fabry-Perot modes. Coarse and fine tunability of the MMW and THz signals from 117 to 954 GHz is also demonstrated by injecting the external light into different residual modes of the QD laser and by controlling the injection strength and the initial frequency detuning.
[Show abstract][Hide abstract] ABSTRACT: 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.
IEEE Journal of Selected Topics in Quantum Electronics 07/2013; 19(4):1700512-1700512. DOI:10.1109/JSTQE.2013.2239614 · 3.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Tunable microwave signal generation with frequencies ranging from below 1 GHz to over 40 GHz is demonstrated experimentally using the period-1 dynamics induced in a 1310-nm Quantum Dot Distributed-Feedback laser under external optical injection.
[Show abstract][Hide abstract] ABSTRACT: Tunable dual-mode lasing is experimentally demonstrated in a 1310-nm quantum dot (QD) distributed-feedback (DFB) laser under single-beam optical injection. The wavelength spacing between the two lasing modes is controlled by injecting the external optical signal into different residual Fabry-Perot modes of the QD DFB laser. The influence of important parameters, i.e., injection strength and bias current, is also analyzed. The simple experimental configuration used to achieve tunable dual-mode lasing and the theoretically superior properties of the QD laser offer exciting prospects for the use of these devices in microwave signal generation and radio-over-fiber applications for future mobile communication networks.
[Show abstract][Hide abstract] ABSTRACT: Tunable microwave signal generation with frequencies ranging from below 1 GHz to values over 40 GHz is demonstrated experimentally with a 1310nm Quantum Dot (QD) Distributed-Feedback (DFB) laser. Microwave signal generation is achieved using the period 1 dynamics induced in the QD DFB under optical injection. Continuous tuning in the positive detuning frequency range of the quantum dot's unique stability map is demonstrated. The simplicity of the experimental configuration offers promise for novel uses of these nanostructure lasers in Radio-over-Fiber (RoF) applications and future mobile networks.
[Show abstract][Hide abstract] ABSTRACT: Recently the first demonstration of room temperature optical spin-injection in a dilute nitride 1300 nm VCSEL under continuous-wave optical pumping was reported by our group . The experimental results showed that the VCSEL polarisation could be controlled by the polarisation of the 980 nm pump. The six rate equations of the spin-flip model (SFM) [2-4] were used to simulate this behaviour and very good agreement was demonstrated with experiment . In the present contribution the SFM is used to predict the more general dependence of spin-VCSEL output power and polarisation on the pump power and polarisation for 1300 nm dilute nitride structures.
13' SIOE, Semiconductor and Integrated Optoelectronics Conference; 04/2013
[Show abstract][Hide abstract] ABSTRACT: We present the first elastic, space division multiplexing, and multi-granular network based on two 7-core MCF links and four programmable optical nodes able to switch traffic utilising the space, frequency and time dimensions with over 6000-fold bandwidth granularity. Results show good end-to-end performance on all channels with power penalties between 0.75 dB and 3.7 dB.