Cavity Soliton Laser Research Articles

Parametric interaction of laser cavity-solitons with an external CW pump

We study the interaction of a laser cavity-soliton microcomb with an externally coupled, co-propagating tunable CW pump, observing parametric Kerr interactions which lead to the formation of both a cross-phase modulation and a four-wave mixing replica of the laser cavity-soliton. We compare and explain the dependence of the microcomb spectra from both the cavity-soliton and pump parameters, demonstrating the ability to adjust the microcomb externally without breaking or interfering with the soliton state. The parametric nature of the process agrees with numerical simulations. The parametric extended state maintains the typical robustness of laser-cavity solitons.

Nonlocal bonding of a soliton and a blue-detuned state in a microcomb laser

Laser cavity-solitons can appear in a microresonator-filtered laser when judiciously balancing the slow nonlinearities of the system. Under certain conditions, such optical states can be made to self-emerge and recover spontaneously, and the understanding of their robustness is critical for practical applications. Here, we study the formation of a bonded state comprising a soliton and a blue-detuned continuous wave, whose coexistence is mediated by dispersion in the nonlinear refractive index. Our real-time dispersive Fourier transform measurements, supported by comprehensive theoretical analysis, reveal the presence of an elastic bonding between the two states, resulting in an enhancement of the soliton’s robustness.

Stability of laser cavity-solitons for metrological applications

Laser cavity-solitons can appear in systems comprised of a nonlinear microcavity nested within an amplifying fiber loop. These states are robust and self-emergent and constitute an attractive class of solitons that are highly suitable for microcomb generation. Here, we present a detailed study of the free-running stability properties of the carrier frequency and repetition rate of single solitons, which are the most suitable states for developing robust ultrafast and high repetition rate comb sources. We achieve free-running fractional stability on both optical carrier and repetition rate (i.e., 48.9 GHz) frequencies on the order of 10−9 for a 1 s gate time. The repetition rate results compare well with the performance of state-of-the-art (externally driven) microcomb sources, and the carrier frequency stability is in the range of performance typical of modern free-running fiber lasers. Finally, we show that these quantities can be controlled by modulating the laser pump current and the cavity length, providing a path for active locking and long-term stabilization.

Temporal cavity solitons in a laser-based microcomb: a path to a self-starting pulsed laser without saturable absorption.

We theoretically present a design of self-starting operation of microcombs based on laser-cavity solitons in a system composed of a micro-resonator nested in and coupled to an amplifying laser cavity. We demonstrate that it is possible to engineer the modulational-instability gain of the system's zero state to allow the start-up with a well-defined number of robust solitons. The approach can be implemented by using the system parameters, such as the cavity length mismatch and the gain shape, to control the number and repetition rate of the generated solitons. Because the setting does not require saturation of the gain, the results offer an alternative to standard techniques that provide laser mode-locking.

Observation of gain-pinned dissipative solitons in a microcavity laser

We demonstrate an experimental approach to create dissipative solitons in a microcavity laser. In particular, we shape the spatial gain profile of a quasi-one-dimensional microcavity laser with a nonresonant, pulsed optical pump to create spatially localised structures, called gain-pinned dissipative solitons that exist due to the balance of gain and nonlinear losses and are confined to a diffraction-limited volume. The ultrafast formation dynamics and decay of the gain-pinned solitons are probed directly, showing that they are created on a picosecond timescale, orders of magnitude faster than laser cavity solitons. All of the experimentally observed features and dynamics are reconstructed by using a standard complex Ginzburg-Landau model.

Mode-locked thulium-doped fiber laser with microfiber based polarization beam splitter

We report on a passively mode-locked thulium-doped all-fiber laser utilizing our fabricated microfiber-based polarization beam splitters (PBSs). The all-fiber PBSs composed of two parallel and coupled microfibers are fabricated to separate light in two orthogonal polarizations, when the coupling region length and microfiber diameter are appropriately chosen to meet the polarization splitting condition. By incorporating the PBSs into the thulium-doped fiber laser cavity, both traditional and dispersion-management solitons at anomalous and near-zero dispersion regimes have been attained. The experimental results have validated the potential of the microfiber-based PBS as an ideal artificial saturable absorber in mode-locked fiber laser, as well as other fiber systems.

Laser cavity-soliton microcombs

The field of micro-cavity based frequency combs, or 'micro-combs'[1,2], has recently witnessed many fundamental breakthroughs[3-19] enabled by the discovery of temporal cavity-solitons, self-localised waves sustained by a background of radiation usually containing 95% of the total power[20]. Simple methods for their efficient generation and control are currently researched to finally establish micro-combs as out-of-the-lab widespread tools[21]. Here we demonstrate micro-comb laser cavity-solitons, an intrinsically highly-efficient, background free class of solitary waves. Laser cavity-solitons have underpinned key breakthroughs in semiconductor lasers[22,23] and photonic memories[24-26]. By merging their properties with the physics of both micro-resonators[1,2] and multi-mode systems[27], we provide a new paradigm for the generation and control of self-localised pulses in micro-cavities. We demonstrate 50 nm wide soliton combs induced with average powers one order of magnitude lower than those typically required by state-of-the-art approaches[26]. Furthermore, we can tune the repetition-rate to well over a megahertz with no-active feedback.

Localized optical micromotors based on twin laser cavity solitons

It has recently been shown that vertical-cavity surface-emitting lasers with an intracavity saturable absorber are capable of forming binary localized structures called twin laser cavity solitons (LCSs). Apart from their asymmetric intensity distribution, they can spontaneously rotate about their center of mass with a frequency that is controllable via a bifurcation parameter representing the ratio of carrier lifetimes in the amplifier and in the absorber. Moreover, circles of maximum phase are found to form around the center of the binary structure which start rotation once the twin LCSs begin to do so. In this paper, we propose to use the fact that these phase circles continually shrink on the center of mass to trap microparticles at the center and subsequently rotate them through the dipole force provided by the asymmetric intensity distribution. This finding can be regarded as a first step in the realization of a localized microdimensional optical motor potentially useful in the manipulation of microparticles and nanofluids.

All optical AND and OR gate with excitable cavity soliton

Cavity solitons (CSs) have an important role as information bits in all optical information processing. In this paper, we switched on a new type of CS as excitable cavity soliton in the cavity soliton laser (CSL). Also, we compared the behavior of excitable CS with self-pulsing and stable CSs by using of suitable values for system parameters and then we designed logical gates (AND, OR) with excitable CSs in the CSL. The capabilities of excitable CSs has been studied to improve possibilities for designing of all optical gates.

Ultra low-energy switch based on a cavity soliton laser with pump modulation

We study the effects of pump modulation in a cavity soliton laser consisting of a vertical cavity surface emitting laser with an intra-cavity saturable absorber. We show that a drifting soliton experiences enhanced mobility features by modulating the pump at the resonance frequency, and the effects are even larger below resonance. In particular, pump modulation reduces the rest time of the soliton in the initial stage of the motion and it increases its drift velocity in this regime. Moreover, pump modulation allows a decrease in the switching energy of the soliton to an amount equal to 36 photons. These results indicate that pump modulation is a promising way for the use of a cavity soliton laser as a fast optical buffer and an ultra low-energy optical switch.

Freezing of the moving cavity soliton in an array of cavity solitons

Cavity solitons (CS) are the most promising systems in all-optical information processing for future applications. In this paper, we show that moving cavity solitons can be controlled in the cavity soliton laser (CSL) with a finite square cross section and force interaction between CSs. We simulated an array of five moving CSs that the central moving CS stopped spontaneous motions. We guess this result would be a good step towards a CS as an information bit.

Modulational instability and zigzagging of dissipative solitons induced by delayed feedback

We report a destabilization mechanism of localized solutions in spatially extended systems which is induced by delayed feedback. Considering a model of a wide-aperture laser with a saturable absorber and delayed optical feedback, we demonstrate the appearance of multiple coexistent laser cavity solitons. We show that at large delays apart from the drift and phase instabilities the soliton can exhibit a delay-induced modulational instability associated with the translational neutral mode. The combination of drift and modulational instabilities produces a zigzagging motion of the solitons, which are either periodic, with the period close to the delay time, or chaotic, with low-frequency fluctuations in the direction of the soliton motion. The same type of modulational instability is demonstrated for localized solutions of the cubic-quintic complex Ginzburg-Landau equation.

Vector cavity solitons in broad area Vertical-Cavity Surface-Emitting Lasers.

We report the experimental observation of two-dimensional vector cavity solitons in a Vertical-Cavity Surface-Emitting Laser (VCSEL) under linearly polarized optical injection when varying optical injection linear polarization direction. The polarization of the cavity soliton is not the one of the optical injection as it acquires a distinct ellipticity. These experimental results are qualitatively reproduced by the spin-flip VCSEL model. Our findings open the road to polarization multiplexing when using cavity solitons in broad-area lasers as pixels in information technology.

Temperature dependence of spontaneous switch-on and switch-off of laser cavity solitons in vertical-cavity surface-emitting lasers with frequency-selective feedback

A systematic experimental and numerical investigation of the conditions for the spontaneous formation of laser cavity solitons in broad-area vertical-cavity surface-emitting lasers with frequency-selective feedback by a volume Bragg grating is reported. It is shown that the switching thresholds are controlled by a combination of frequency shifts induced by ambient temperature and Joule heating. The gain level has only a minor influence on the threshold but controls mainly the power of the solitons. At large initial detuning and high threshold gain, the first observed structure can be a high order soliton. In real devices spatial disorder in the cavity length causes a pinning of solitons and a dispersion of thresholds. The experimental observations are in good agreement with numerical simulations taking into account disorder and the coupling of gain and cavity resonance due to Joule heating. In particular, we demonstrate that the existence of the traps explain the spontaneous switch on of the solitons, but do not modify the soliton shape significantly, i.e. the observed solitons are a good approximation of the ones expected in a homogeneous system.

Drifting of the Self-Pulsing Cavity Soliton in the Semiconductor Laser

We drift a self-pulsing cavity soliton (CS) in a CS laser by using of incoherent or semicoherent injections. These injections would be near of the self-pulsing CS. Our simulations show the attractive or repulsive interaction between self-pulsing CS and the injected beam. The type of interaction depends on the type of injection. We can drift the self-pulsing CS to a favorite final position by suitable selection of injection beam parameters. Therefore, we realized an optical switch between two states associated with different positions of the self-pulsing CS. This optical switch by using of self-pulsing CSs would be a compact device which it needs very low energy for applications.

Twin laser cavity solitons in a VCSEL with saturable absorber

We show numerically the existence and stability of double-peak (twin) laser cavity solitons in a model of a semiconductor laser containing a saturable absorber. The onset of twin laser cavity solitons is observed in a narrow range of switching pulse energies above the maximum energy required to switch a normal single laser cavity soliton. Also, the FWHM value of the population dip at the end of injection is found to be wider which later breaks into two closely spaced dips. Three regimes of oscillating, oscillating-rotating and oscillating-rotating-travelling twin laser cavity solitons are reported depending on the value of a bifurcation parameter given by the ratio of the lifetimes of carriers in amplifier and absorber materials. The associated dynamical behaviors in these three regimes are also discussed.

Enhanced Resonance Frequency and Modulation Bandwidth in a Cavity Soliton Laser

Cavity solitons in a driven vertical-cavity surface-emitting laser (VCSEL) above threshold can amplify the modulation of the injected field over a bandwidth larger than 100 GHz by exploiting the combined low frequency amplification of a bistable optical system with the enhanced relaxation oscillation frequency of an injection-locked laser.

BIFURCATION DIAGRAM AND CONTROL OF LOCALIZED LASER STRUCTURES

We describe experimentally the bifurcation diagram of localized lasing states in a cavity soliton laser (CSL). The CSL is based on two coupled semiconductor microcavities, one providing gain and the other providing saturable absorption. We show how single-peak lasing structures bifurcate from homogeneous background, how localized lasing complexes form and how their coexistence can be controlled. The relation between the local bifurcation diagram obtained and distant localized states is discussed.

Low-energy switch based on a cavity soliton laser

We show that the position of a soliton in a cavity soliton laser can be controlled by injecting incoherent or coherent beams close to the soliton. The interaction between the CS and the injected beam can be attractive or repulsive depending on the type of injection. The energy necessary to drift the soliton can be very small if the injected beam is frequency matched with the soliton and the laser operates near the drift instability threshold of the soliton. In this way an optical switch at very low energy in a miniaturized device can be realized.

Self–propelled soliton collisions in a semiconductor cavity soliton laser

Spontaneous soliton motion has been demonstrated in different systems supporting cavity solitons. Here we consider the case of a semiconductor laser with an intracavity saturable absorber, and study the interactions between self-propelled solitons when two of them collide or when they hit a localised defect in the material gain. According to the soliton velocity and impact parameter, destructive or repulsive collisions may take place between travelling solitons. On the other hand, a very rich variety of dynamical behaviors can be observed when a travelling soliton hits a material defect of comparable size. We observe soliton destruction, repulsive or attractive interaction and two trapped cases. The behavior is mainly determined by the gain contrast between the defect and the background.