Abrupt turn-on and hysteresis in a VCSEL with frequency-selective optical feedback

The emission characteristics of a vertical-cavity surface-emitting laser (VCSEL) operated in a single-transverse mode and coupled to an external cavity with a diffraction grating as a frequency-selective element are analyzed experimentally, numerically and analytically. The experiments yield a rather abrupt turn-on of the VCSEL to a high-amplitude emission state and hysteresis phenomena. The experimental results are explained by numerical simulations and analytical calculations demonstrating the possibility of bistability between lasing and non-lasing states close to threshold. Hence, the scheme might be useful in all-optical photonic switching applications. A detailed bifurcation analysis near threshold is given by superimposing the numerical results with analytical steady-state curves. The mode selection and switching behavior obtained in the simulations can be interpreted from the point of view of the preference of states with the minimal total losses

Polarization output power stabilization of a vertical-cavity surface-emitting laser

This paper provides an experimental investigation of the polarization stabilization at the output power of an 850 nm vertical-cavity surface-emitting laser (VCSEL) with optical feedback (OF) and a range of polarization angles, OF strength, and the bias current. The VCSEL’s polarization stabilization is evaluated using the extinction ratio measurements of the optical output power of the polarization modes of the VCSEL. The results clearly show that rotation of the polarization angle and the OF level can radically change the polarization stabilization of the VCSEL. Both the polarization angle and OF introduce polarization switching (PS) and instability in the optical output power of the VCSEL. Consequently, these lead to performance degradation of the VCSEL in terms of the operating point and the modulation bandwidth. At a fixed OF level of −7  dB, polarization destabilization is first observed at 45° with the increasing level of polarization angle, whereas for the fixed polarization angles of 40° and 90°, polarization destabilization is observed at −14.5  dB and −14  dB, respectively, with the increasing level of orthogonal OF. We show that, with parallel OF, no PS is observed over the entire OF level. The results also indicate that the VCSEL with no polarization angle requires higher levels of OF in order to ensure PS compared with the case with the polarization angle

Optical and electrical characteristics of vertical-cavity surface-emitting lasers for free space optical communications

Among the number of optical sources, vertical-cavity surface-emitting lasers (VCSELs) are relatively recent type of semiconductor laser devices, which are attractive for a number of applications particularly for free space optical (FSO) communication systems. In such systems reliable optical devices with lower power consumption and low cost are among the key requirements. VCSELs typically operate with unstable output polarization modes, and there is a need to improve their output power regarding to the polarization instability, particularly when introducing the optical feedback (OF). This thesis investigates a number of key properties of VCSEL including the polarization instability, hysteresis loop (HL), relative intensity noise (RIN) and how to control the polarization switching (PS). The investigations are based on the analytical studies and extensive experimental work. PS properties of VCSEL are investigated by introducing variable polarization optical feedback (VPOF) with the modulation frequency and modulation depth. The dependency conditions for the HL, RIN and PS are determined with VPOF. Under OF, the threshold current (Ith) of VCSEL is reduced by 11.5% and the PS, which is demonstrated theoretically and experimentally, is completely suppressed. The PS positions are depending on the polarization angle of OF, OF levels and the bias current. The PS disappeared with the modulation depth of 78.66%, whereas it is entirely vanished with the modulation frequency of 200 MHz. The hysteresis width of the VCSEL polarization modes is reduced by increasing the feedback level. The minimum RIN value of -156 dB/Hz is achieved at a zero degree of the polarization angle for the dominant polarization mode of VCSEL under VPOF. For the first time, a novel technique based on employing orthogonal polarization OF is proposed to supress the nonlinearity associated with the modulated VCSEL, where the second, third, and fourth harmonics are completely suppressed to the noise floor. Finally, optimal operating conditions for a high-quality polarization-resolved chaos synchronization of the polarization modes of VCSEL with VPOF are experimentally and theoretically studied. A perfect value of 99% of the correlation dynamics for the chaotic synchronization of the polarization modes of VCSEL is found with a zero time delay over a wide range of polarization angle. Finally, Simulink and Origin software version 6.1 are used in this work to simulate and plot the results. The simulation results are agreed with the experimental results, which show that the chaotic synchronization dynamic of the polarization modes can be achieved by VPOF

Fundamentals and applications of spatial dissipative solitons in photonic devices : [Chapter 6]

We review the properties of optical spatial dissipative solitons (SDS). These are stable, self‐localized optical excitations sitting on a uniform, or quasi‐uniform, background in a dissipative environment like a nonlinear optical cavity. Indeed, in optics they are often termed “cavity solitons.” We discuss their dynamics and interactions in both ideal and imperfect systems, making comparison with experiments. SDS in lasers offer important advantages for applications. We review candidate schemes and the tremendous recent progress in semiconductor‐based cavity soliton lasers. We examine SDS in periodic structures, and we show how SDS can be quantitatively related to the locking of fronts. We conclude with an assessment of potential applications of SDS in photonics, arguing that best use of their particular features is made by exploiting their mobility, for example in all‐optical delay lines

Nonlinear Dynamics of solitary and optically-injected spin vertical-cavity lasers

This work investigates the nonlinear dynamics and polarisation properties of Spin-Vertical-(External)-Cavity Surface-Emitting Lasers (V(E)CSELs). The focus is on gaining a broad understanding of the various polarised resolved nonlinear dynamical effects in solitary and injected 1300 nm spin-V(E)CSELs. We report a comprehensive study including theory, based on the Spin Flip Model, and experiments of the stability characteristics of solitary 1300 nm dilute nitride Quantum-Well (QW) spin-VCSELs. Various forms of oscillatory behaviour causing self-sustained oscillations in the polarisation of the spin-VCSEL subject to Continuous-Wave (CW) pumping are found. Additionally, this work is extended to study experimentally and theoretically the evolution of the output polarisation ellipticity, and experimentally the nonlinear dynamics of the light polarisation emitted by the QW spin VCSELs under polarised optical injection. Rich nonlinear dynamics of the optically injected QW spin-VCSEL are reported ranging from polarisation control, polarisation switching and bistability to periodic oscillations and chaos. Good agreement is found between measurements and calculations where theoretical results are available. We also report the first 1300 nm Quantum-Dot (QD) Semiconductor Disk Laser (SDL) using a very simple and compact laser configuration involving a high reflection (HR)-coated fibre as the top mirror. Moreover, by applying spin injection to the 1300 nm SDL via CW polarised optical pumping we also demonstrate the first 1300 nm QD spin Vertical-External-Cavity Surface-Emitting Laser (Spin-VECSEL). This is also accompanied by an investigation of the dynamics of the solitary 1300 nm QD spin-VECSEL. Finally, we present the first experimental study of the evolution of the output polarisation ellipticity and nonlinear dynamics of the 1300 nm QD spin-VECSEL under polarised optical injection. Our findings show nonlinear effects similar to the ones seen in optically injected QW spin-VCSELs

Exploiting nonlinearity and noise in optical tweezers and semiconductor lasers : from resonant damping to stochastic logic gates and extreme pulses

This thesis is focused on the study of stochastic and nonlinear dynamics in optical systems. First, we study experimentally the dynamics of a Brownian nanometer particle in an optical trap subjected to an external forcing. Specifically, we consider the effects of parametric noise added to a monostable or bistable optical trap and discovered a new effect which we named stochastic resonant damping (SRD). SRD concerns the minimization of the output variance position of a particle held in a harmonic trap, when an external parametric noise was added to the position trap. We compared the classical stochastic resonance (SR) with SRD and found that they are two phenomena which coexist in the same system but in different regimes. The experimentally studied monostable system showed a maximum in the signal to noise ratio, a clear signature of a resonance. We also developed a new technique to increase 10-fold the detection range of the quadrant photodiode that we used in this study, which exploits the channel crosstalk. Second, we study the stochastic dynamics of a type of semiconductor laser (SCL), known as vertical-cavity surface-emitting laser (VCSEL), that exhibits polarization bistability and hysteresis, either when the injection current or when the optically injected power are varied. We have shown how these properties can be exploited for logic operations due to the effect of the spontaneous emission noise. Two logical input signals have been encoded in three levels of optically injected power from a master laser, and the logical output response was decoded from the emitted polarization of the injected VCSEL. Correct and robust operation was obtained when the three levels of injected power were adjusted to favor one polarization at two levels and to favor the orthogonal polarization at the third level. We numerically demonstrated that the VCSEL-based logic operator allows to reproduce the truth table for the OR and NOR logic operators, while the extension to AND and NAND is straightforward. With this all-optical configuration we have been able to reduce the minimum bit time required for correct operation from 30 ns, obtained in a previous work with an optoelectronic configuration, to 5 ns. The third focus of this thesis is the study of the chaotic nonlinear dynamics of a SCL optically injected, in the regime where it can display sporadic huge intensities pulses, referred to as Rogue Waves (RWs). We found that, when adding optical noise, the region where RWs appear becomes wider. This behavior is observed for high enough noise; however, on the contrary, for very weak noise we found that noise diminishes the number of RW events in certain regions. In order to suppress or induce extreme pulses, we investigated the effects of an external periodic modulation of the laser current. We found that the modulation at specific frequencies modifies the dynamics from chaotic to periodic. Depending on the parameter region, current modulation can contribute to an increased threshold for RWs. Therefore, we concluded that the modulation can be effective for suppressing the RWs dynamics

Polarization and Transverse Mode Selection in Quantum Well Vertical-Cavity Surface-Emitting Lasers: Index-and Gain-guided Devices

Abstract We study polarization switching and transverse mode competition in Vertical Cavity Surface Emitting Lasers in the absence of temperature e ects. We use a model that incorporates the vector nature of the laser eld, saturable dispersion, di erent carrier populations associated with di erent magnetic sublevels of the conduction and heavy hole valence bands in quantum well media, spin-ip relaxation processes and cavity birefringence and dichroism. We consider both index-guided and gain-guided VCSELs, and we nd that spin-ip dynamics and linewidth enhancement factor are crucial for the selection of the polarization state corresponding to a given injection current. For index-guided VCSELs the e ect of spatial hole burning on the polarization behavior within the fundamental mode regime is discussed. For gain-guided VCSELs, transverse mode and polarization selection is studied within a Maxwell-Bloch approximation which includes eld di raction and carrier di usion. Polarization switching is found in the fundamental mode regime. The rst order transverse mode starts lasing orthogonally 1 polarized to the fundamental mode. At larger currents polarization coexistence with several active transverse modes occurs

Nonlinear Dynamics of Semiconductor Lasers and Their Applications

Semiconductor lasers are key components in many optical systems due to their advantages, including their small size, low cost, high efficiency, and low power consumption. It is well-known that semiconductor lasers under external perturbations, such as optical injection, optical feedback, or delayed coupling can exhibit a large variety of complex dynamical behaviors. Nowadays, cutting-edge engineering applications based on the complex dynamics of diode lasers are being conducted in areas, such as optical communications, optical signal processing, encoded communications, neuro-inspired ultra-fast optical computing devices, microwave signal generation, RADAR and LIDAR applications, biomedical imaging, and broadband spectroscopy. The prospects for these applications are even more exciting with the advent of photonic integrated circuits. This Special Issue focuses on theoretical and experimental advances in the nonlinear dynamics of semiconductor lasers subject to different types of external perturbations

Properties of III-Nitride-Based Polariton and Spin Polariton Diode Lasers

The cavity electrodynamic regime of strong coupling of emitter-photon interactions in a semiconductor microcavity gives rise to new light-matter entangled quasiparticles, also known as exciton-polaritons. The non-linear nature of the energy-momentum dispersions of these composite bosons has been suitably engineered and efficiently utilized to demonstrate inversionless coherent emission, or polariton lasing in submicron-scale optical cavities. Previous theoretical as well as experimental work on Gallium Arsenide and Cadmium Telluride-based systems operated at cryogenic temperatures, have shown the central importance of the nature of the output polarization of the emitted light originating from the radiative decomposition of these polaritons. Room-temperature operation of these lasers necessitates the use of wide-band gap semiconductors such as Gallium Nitride, because of their large free excitonic binding energies and oscillator strengths, which consequently lead to stronger and more robust exciton-photon strong coupling. Thus, the steady state output polarization characteristics of Gallium Nitride-based microcavity polariton lasers operated with unpolarized electrical injection, have been examined at room temperature. The output is essentially unpolarized below the nonlinear threshold injection current and is linearly polarized above it with a maximum degree of polarization of ∼ 22%. Besides other advantages, a spin-polarized laser offers inherent control of the output circular polarization. Electrical spin injection in a bulk Gallium Nitride-based microcavity polariton diode laser enables the realization of an electrically modulated low-energy circularly-polarized coherent light source. Successful electrical spin injection in bulk Gallium Nitride, which is the active layer of the polariton diode laser, has been independently confirmed from room-temperature four-terminal Hanlè spin precession measurements made on Gallium Nitride-based spin valves, and observation of hysteretic circular polarization in III-nitride-based light-emitting diodes. The optical selection rules governing the operation of the latter have also been elucidated. Electrical injection of spin polarized electrons is accomplished in all the above-mentioned devices via a n-type Cobalt Iron alloy/Magnesium Oxide spin injector contact. The output polarization characteristics of this polariton diode laser have been examined at room temperature. A degree of output circular (linear) polarization of ~ 25 (33) % is recorded under remanent magnetization. The helicity as well as the degree of the steady-state circular polarization is deterministically governed by the magnetizing field used to magnetize the ferromagnetic contacts. The variation of output circular and linear polarization with spin-polarized injection current has been analyzed employing two distinct spin-dependent rate equation models, and there is good agreement between measured and calculated data in both cases. The present work also theoretically explores other optoelectronic properties of these spin polariton lasers. Optical effects arising from spin-induced gain anisotropy such as threshold reduction and emission intensity enhancement have been theoretically predicted for these diode lasers. An electrical excitation mechanism has also been formulated, which can potentially magnify the degree of a deterministic circular polarization of the output emission by an order of magnitude, compared to the injected electron spin polarization. The dissertation concludes with the discussion of the observation of a non-linear enhancement in the excitation-dependent photocurrent characteristics of the microcavity diodes with a threshold, which is consistent with the polariton lasing threshold. This is explained in the framework of an Auger-like process of excitonic dissociation into its constituent electron-hole pairs, which can be stimulated by the occupation of the polariton lasing states and the observed effect is therefore a unique manifestation of the bosonic final-state stimulation effect in polariton lasers.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/145800/1/anirudb_1.pd