Semiconductor lasers are examined in the presence of quantum noise emanated from the gain medium. A pendulum-type, third order differential law for the phase of electric field is employed and the optical power spectrum of the system is rigorously derived as a sum of Lorentzians. The influence of injection level, linewidth enhancement factor, input detuning and noise strength on the photonic oscillator response is identified. The followed methodology paves the way towards the analytical treatment of quantum noise effect in multiple photonic integrated circuits hosting tunable limit cycles, powerful resonances and associated hysteresis phenomena.

Diode-pumped alkali metal vapor lasers (DPAL) offer significant promise for high average power. The DPAL system has high gain and will high output coupling and an unstable resonator to achieve excellent beam quality. We analyze the Rb-He system using average equations for the pump, laser and populations, including amplified spontaneous emission. We extend the formulation to include flow and temperature release and study its effects on the laser efficiency and beam quality. The design and analysis of the DPAL resonator and the influence of spatial variations in gain medium on far field beam quality are developed. A systematic study of the influence of gain medium aberrations, flow geometry, and resonator design on far field beam quality is reported. The relative advantages of longitudinal and transverse flow geometries to beam quality are evaluated. Finally, coupling of the pump and laser radiation fields is dramatic in the DPAL system. The standard approaches to merging CFD analysis of the gain medium with wave optics resonator simulations will require new techniques.

The performance of a 100 kW Rb-He diode pumped alkali laser system is predicted, including power scaling, optical efficiency, and beam quality. A transverse flow geometry with longitudinal diode pumping produces a nonlinear temperature profile in the flow direction, with temperature increasing by 124 K for a 0.5 m/s flow rate and a 30 kW/cm(2) pump intensity. The optical-to-optical efficiency is 70%, and the tilt-corrected Strehl is 0.545 for this slow flow, 45 ms residence time design. By increasing the flow speed to 15 m/s (1.5 ms residence time), the efficiency is improved to 82%, and the laminar flow beam quality is near the diffraction limit, Strehl > 0.99. Beam quality is adversely affected at higher helium pressure for the slow flow conditions.

The high gain Diode Pumped Alkali Laser (DPAL) system will require an unstable resonator with high Fresnel number and high output coupling to achieve excellent beam quality. Coupling of the diode pump and laser radiation fields is dramatic in the DPAL system. Merging flow field analysis of the gain medium with wave optics resonator simulations requires new techniques. We develop a wave-optics simulation of confocal, positive branch unstable resonators for the DPAL gain media to assess the limitations on far field beam quality. The design and analysis of the DPAL resonator and the influence of spatial variations in gain medium on far field beam quality are developed. The relative advantages of longitudinal and transverse flow geometries to beam quality are evaluated. A systematic study of the influence of gain medium aberrations, flow geometry, magnification, and resonator design on far field beam quality is reported.

This paper reports a detailed numerical study of the synchronization properties of two mutually delay-coupled semiconductor lasers in the framework of the Lang-Kobayashi model. By computing high-definition stability diagrams, we predict the complex distribution of periodic and chaotic laser oscillations on the coupling versus detuning control parameter plane. Such diagrams provide details concerning the behavior of the laser intensities, quantify objectively the synchronization between their electric fields, and display in-phase and out-of-phase laser behavior. In addition, we also describe the presence of a conspicuous abrupt change in the optimal shift for the greatest value of the cross-correlation function when varying the detuning between the optical angular frequencies of the lasers. (C) 2016 Optical Society of America

The classical problem of a semiconductor laser subject to polarized injection is revisited. From the laser rate equations for the transverse electric (TE) and transverse magnetic (TM) modes, we first determine the steady states. We then investigate their linear stability properties and derive analytical expressions for the steady, saddle-node, and Hopf bifurcation points. We highlight conditions for bistability between pure- and mixed-mode steady states for the laser subject to either TE or TM injection. To our knowledge, the first case has not been documented yet. An important parameter is the ratio of the polarization gain coefficients and we explore its effect on the stability and bifurcation diagrams.

The stability properties of an injected quantum cascade laser are investigated analytically on the basis of current estimates of the laser parameters. We show that in addition to stable locking, Hopf bifurcations leading to pulsating intensities are possible. We discuss the stability diagrams in terms of the detuning and the injection rate for different values of the linewidth enhancement factor. The analysis indicates domains of coexistence between two stable steady states (bistability) or between a stable steady state and stable periodic oscillations. All predictions are verified numerically by determining bifurcation diagrams from the laser rate equations.

We study experimentally the dynamics of vertical-cavity surface-emitting lasers (VCSELs) with polarization-rotated (PR) optical feedback, such that the natural lasing polarization of a VCSEL is rotated by 90 deg and then is reinjected into the laser. We observe noisy, square-wave-like polarization switchings with periodicity slightly longer than twice the delay time, which degrade to (or alternate with) bursts of irregular oscillations. We present results of simulations that are in good agreement with the observations. The simulations demonstrate that close to threshold the regular switching is very sensitive to noise, while well above threshold is less affected by the noise strength. The frequency splitting between the two polarizations plays a key role in the switching regularity, and we identify wide parameter regions where deterministic and robust switching can be observed.

We study the dynamics of two vertical-cavity surface-emitting lasers (VCSELs) mutually coupled such that the natural lasing polarization of each laser is rotated by 90 degrees and then is injected into the other laser. Simulations based on the spin-flip model show transient square-wave polarization switchings before a stationary state is reached. The influence of various model parameters on the duration of the stochastic transient time and on the lasers' dynamics in the stationary state is investigated.

Numerical and experimental results are presented for an edge-emitting diode laser with delayed optical feedback, where the polarization state of the feedback is rotated such that the natural laser mode is coupled into the orthogonal, unsupported mode. We examine the bifurcation structure and dynamics that give rise to a class of periodic, polarization-modulated solutions, the simplest of which is a square wave solution with a period related to but longer than twice the external cavity roundtrip time. Such solutions typically emerge when the feedback is strong and the differential losses in the normally unsupported polarization mode are small. We also observe more complex waveforms that maintain the same periodicity.

Two edge-emitting lasers mutually coupled through orthogonal optical injection exhibit square-wave oscillations in their polarization modes. The TE and TM modes within each individual laser are always in antiphase, but the TE mode of one laser leads the TM of the other by the one-way time of flight between lasers. The duty cycle of the square waves is tunable with pump current and coupling strength, while the total period remains close to the roundtrip time. Numerical simulations give similar results and reveal the role of noise in stabilizing the oscillations.

Two edge-emitting lasers coupled through polarization-rotated optical injection exhibit square-wave oscillations provided the roundtrip time from laser to laser and back is sufficiently large. If the mutual coupling between the lasers is relatively weak, the two plateaus of the square-waves exhibit different durations even though the total period remains close to the roundtrip time. This asymmetry progressively disappears as the feedback strength is increased. The experimental observations are confirmed by numerical simulations. The simulations also reveal that the square-wave regimes appear through a series of complex bifurcations and that a sufficiently large roundtrip time is needed.

Identity synchronization is observed experimentally and numerically in the chaotic dynamics of a system of two unidirectionally coupled semiconductor lasers. The transmitter and receiver lasers are subjected to polarization-rotated optical feedback and injection, respectively. Numerical and analytical results show that identity synchronization requires parameter matching through a relationship between the injection and feedback strengths, and linewidth enhancement factors of the lasers. Inverse synchronization is also observed experimentally.

The square-wave. response of edge-emitting diode lasers subject to a delayed polarization-rotated optical feedback is studied in detail. Specifically, the polarization state of the feedback is rotated such that the natural laser mode is coupled into the orthogonal, unsupported mode. Square-wave self-modulated polarization intensities oscillating in antiphase are observed experimentally. We find numerically that these oscillations naturally appear for a broad range of values of parameters, provided that the feedback is sufficiently strong and the differential losses in the normally unsupported polarization mode are small. We then investigate the laser equations analytically and find that the square-wave oscillations are the result of a bifurcation phenomenon. (c) 2006 Optical Society of America.

Experimental and theoretical investigations into a chaotic system of diode lasers with polarization-rotated optical feedback and injection demonstrate multiple synchronization solutions. The role of parameter mismatch is also considered.

We demonstrate experimental chaos synchronization between two chaotic semiconductor lasers subjected to polarization-rotated optical feedback and unidirectional injection. This system allows high-quality synchronization to be obtained between dissimilar lasers in a wide range of chaotic operating regimes. Another feature of this system is its operation at high characteristic frequencies, taking advantage of all-optical implementation. Time series and RF spectra showing synchronization are confirmed by high correlation coefficients in excess of 0.85.

We present the time dependence, steady state behavior and spectra of a dual fiber-laser compound cavity. This particular cavity is formed with two Er-doped fiber amplifiers, each terminated with a fiber Bragg grating, and coupled through a 50/50 coupler to a common feedback and output coupling element. The experiment and theory show that a low Q, high gain symmetric compound cavity extracts nearly all the incoherent power in a coherent mode when the two fiber polarizations are aligned. This extraction is maintained even when there is significant difference in the optical pathlengths of the two component elements.

We observe experimentally and numerically novel mixed-mode dynamic states of a diode laser subject to two delayed optical feedbacks. These states have been proposed and analyzed within the framework of the Lang-Kobayashi single-feedback model. Such states are combinations of two distinct external cavity modes and can be identified through a characteristic sequence of a Hopf bifurcation followed by a secondary quasi-periodic bifurcation. We present experimental and numerical results that demonstrate such sequences.