Desynchronization of temporal solitons in Kerr cavities with pulsed injection.

A numerical and analytical study was conducted to investigate the bifurcation mechanisms that cause desynchronization between the soliton repetition frequency and the frequency of external pulsed injection in a Kerr cavity described by the Lugiato-Lefever equation (LLE). The results suggest that desynchronization typically occurs through an Andronov-Hopf (AH) bifurcation. Additionally, a simple and intuitive criterion for this bifurcation to occur is proposed.

Decoherence and Turbulence Sources in a Long Laser.

We investigate the turn-on process in a laser cavity where the round-trip time is several orders of magnitude greater than the active medium timescales. In this long delay limit, we show that the universal evolution of the photon statistics from thermal to Poissonian distribution involves the emergence of power dropouts. While the largest number of these dropouts vanish after a few round-trips, some of them persist and seed coherent structures similar to dark solitons or Nozaki-Bekki holes described by the complex Ginzburg-Landau equation.

Turbulent coherent structures in a long cavity semiconductor laser near the lasing threshold: publisher's note.

This publisher's note contains corrections to Opt. Lett.45, 4903 (2020)OPLEDP0146-959210.

Turbulent coherent structures in a long cavity semiconductor laser near the lasing threshold.

We report on the formation of novel turbulent coherent structures in a long cavity semiconductor laser near the lasing threshold. Experimentally, the laser emits a series of power dropouts within a roundtrip, and the number of dropouts per series depends on a set of parameters including the bias current. At fixed parameters, the drops remain dynamically stable, repeating over many roundtrips.

Bifurcation structure of a swept-source laser.

We numerically analyze a delay differential equation model of a short-cavity semiconductor laser with an intracavity frequency-swept filter and reveal a complex bifurcation structure responsible for the asymmetry of the output characteristics of this laser. We show that depending on the direction of the frequency sweep of a narrow-band filter, there exist two bursting cycles determined by different parts of a continuous-wave solutions branch.

Coherence transfer in an akinetic swept source OCT laser with optical feedback.

We theoretically investigate the influence of optical feedback onto the dynamics of a semiconductor swept source laser. In particular, we show that optical feedback can be used to lock the phase of the successive lasing modes of a multi-section semiconductor laser commonly used for optical coherence tomography (OCT) applications. We also identify two different regimes called sliding frequency self-mixing and sliding frequency mode locking.

Dynamics of a class-A nonlinear mirror mode-locked laser.

Using a delay differential equation model we study theoretically the dynamics of a unidirectional class-A ring laser with a nonlinear amplifying loop mirror. We perform linear stability analysis of the continuous-wave regimes in the large delay limit and demonstrate that these regimes can be destabilized via modulational and Turing-type instabilities, as well as by an instability leading to the appearance of square-waves. We investigate the formation of square waves and mode-locked pulses in the system.

Third Order Dispersion in Time-Delayed Systems.

Time-delayed dynamical systems materialize in situations where distant, pointwise, nonlinear nodes exchange information that propagates at a finite speed. However, they are considered devoid of dispersive effects, which are known to play a leading role in pattern formation and wave dynamics. We show how dispersion may appear naturally in delayed systems and we exemplify our result by studying theoretically and experimentally the influence of third order dispersion in a system composed of coupled optical microcavities.

Convective Nozaki-Bekki holes in a long cavity OCT laser.

We show, both experimentally and theoretically, that the loss of coherence of a long cavity optical coherence tomography (OCT) laser can be described as a transition from laminar to turbulent flows. We demonstrate that in this strongly dissipative system, the transition happens either via an absolute or a convective instability depending on the laser parameters. In the latter case, the transition occurs via formation of localised structures in the laminar regime, which trigger the formation of growing and drifting puffs of turbulence.

Experimental electric field visualisation of multi-mode dynamics in a short cavity swept laser designed for OCT applications.

An experimental study into the modal dynamics of a short cavity, fast frequency-swept laser is presented. This commercially available external cavity swept source is designed for use in optical coherence tomography (OCT) applications and displays a number of dynamic lasing regimes during the course of the wavelength sweep. Interferometric full electric field reconstruction is employed, allowing for measurement of the laser operation in a time-resolved, single-shot manner.

Temporal localized structures in mode-locked vertical external-cavity surface-emitting lasers.

Temporal localized states (TLSs) are individually addressable structures traveling in optical resonators. They can be used to obtain bits of information and generate frequency combs with tunable spectral density. We show that a pair of specially designed nonlinear mirrors, a 1/2 vertical-cavity surface-emitting laser and a semiconductor saturable absorber, coupled in self-imaging conditions, can lead to the generation of such TLSs.

Delay induced high order locking effects in semiconductor lasers.

Multiple time scales appear in many nonlinear dynamical systems. Semiconductor lasers, in particular, provide a fertile testing ground for multiple time scale dynamics. For solitary semiconductor lasers, the two fundamental time scales are the cavity repetition rate and the relaxation oscillation frequency which is a characteristic of the field-matter interaction in the cavity.

Direct experimental measurement of single-mode and mode-hopping dynamics in frequency swept lasers.

A time-resolved study is presented of the single-mode and mode-switching dynamics observed in swept source vertical cavity surfing emitting lasers and swept wavelength short external cavity lasers. A self-delayed interferometric technique is used to experimentally measure the phase and intensity of these frequency swept lasers, allowing direct examination of the modal dynamics. Visualisation of the instantaneous optical spectrum reveals mode-hop free single mode lasing in the case of the vertical cavity laser, with a tuning rate of 6.

Dispersive Time-Delay Dynamical Systems.

We present a theoretical approach to investigate the effect of dispersion in dynamical systems commonly described by time-delay models. The introduction of a polarization equation provides a means to introduce dispersion as a distributed delay term. The expansion of this term in power series, as usually performed to study the propagation of waves in spatially extended systems, can lead to the appearance of spurious instabilities.

Realization of high-contrast gratings operating at 10 μm.

We present a new material pairing that can be used to realize high-contrast gratings at wavelengths of 10 μm and greater. Using only optical lithography, the material pair solves the absorption issue limiting the popular Si/SiO pairing from operation above 6 μm. We describe the obstacles that exist with the currently used grating materials for this wavelength range and outline why our chosen materials overcome this obstacle.

Injection-induced, tunable all-optical gating in a two-state quantum dot laser.

We demonstrate a tunable all-optical gating phenomenon in a single-section quantum dot laser. The free-running operation of the device is emission from the excited state. Optical injection into the ground state of the material can induce a switch to emission from the ground state with complete suppression of the excited state.

Optically induced hysteresis in a two-state quantum dot laser.

Quantum dot lasers can lase from the ground state only, simultaneously from both the ground and first excited states and from the excited state only. We examine the influence of optical injection at frequencies close to the ground state when the free-running operation of the device is excited state lasing only. We demonstrate the existence of an injection-induced bistability between ground state dominated emission and excited state dominated emission and the consequent hysteresis loop in the lasing output.

Emergence of resonant mode-locking via delayed feedback in quantum dot semiconductor lasers.

With conventional semiconductor lasers undergoing external optical feedback, a chaotic output is typically observed even for moderate levels of the feedback strength. In this paper we examine single mode quantum dot lasers under strong optical feedback conditions and show that an entirely new dynamical regime is found consisting of spontaneous mode-locking via a resonance between the relaxation oscillation frequency and the external cavity repetition rate. Experimental observations are supported by detailed numerical simulations of rate equations appropriate for this laser type.

Optical ultrafast random number generation at 1 Tb/s using a turbulent semiconductor ring cavity laser.

A simple method of high-speed random bit generation is presented that utilizes the turbulent output of a fiber ring cavity semiconductor laser. Random bits are generated by multi-bit sampling of the chaotic optical waveform passed through a simple post-processing procedure, leading to generation rates up to and potentially exceeding 1 Tb/s. The resulting random bit streams are tested statistically using a software package designed to test random number generators, the NIST statistical test suite.

Single shot, time-resolved measurement of the coherence properties of OCT swept source lasers.

A novel, time-resolved interferometric technique is presented that allows the reconstruction of the complex electric field output of a swept source laser in a single-shot measurement. The power of the technique is demonstrated by examining a short cavity swept source designed for optical coherence tomography (OCT) applications with a spectral width of over 100 nm. The novel analysis allows a time-resolved real-time characterization of the roll-off, optical spectrum, linewidth, and coherence properties of a dynamic, rapidly swept laser source.

Effect of dynamical instability on timing jitter in passively mode-locked quantum-dot lasers.

We study the effect of noise on the dynamics of passively mode-locked semiconductor lasers both experimentally and theoretically. A method combining analytical and numerical approaches for estimation of pulse timing jitter is proposed. We investigate how the presence of dynamical features such as wavelength bistability in a quantum-dot laser affects timing jitter.

Bistability and hysteresis in an optically injected two-section semiconductor laser.

The effect of coherent single frequency injection on two-section semiconductor lasers is studied numerically using a model based on a set of delay differential equations. The existence of bistability between different continuous-wave and nonstationary regimes of operation is demonstrated in the case of sufficiently large linewidth enhancement factors.

Dynamics of a short cavity swept source OCT laser.

We investigate the behaviour of a short cavity swept source laser with an intra cavity swept filter both experimentally and theoretically. We characterise the behaviour of the device with real-time intensity measurements using a fast digital oscilloscope, showing several distinct regimes, most notably regions of mode-hopping, frequency sliding mode-locking and chaos. A delay differential equation model is proposed that shows close agreement with the experimental results.

All-optical switching with a dual-state, single-section quantum dot laser via optical injection.

An all-optical switching mechanism via optical injection of an InAs/GaAs quantum dot laser is presented. Relative state suppression in excess of 40 dB is achieved, and experimental switching times of the order of a few hundred picoseconds are demonstrated.

Coherence and incoherence in an optical comb.

We demonstrate a coexistence of coherent and incoherent modes in the optical comb generated by a passively mode-locked quantum dot laser. This is experimentally achieved by means of optical linewidth, radio frequency spectrum, and optical spectrum measurements and confirmed numerically by a delay-differential equation model showing excellent agreement with the experiment. We interpret the state as a chimera state.