Dual frequency-combs have been relevant for applications such as spectroscopy [1], Many methods are used to generate dual-combs like polarization multiplexing [2] or wavelength/space multiplexing [3], [4]. We demonstrated two passively mode-locked dual-comb configurations in a single Vertical External-Cavity Surface-Emitting Laser (VECSEL) using a InGaAs/GaAs based optically-pumped gain mirror (1/2-VCSEL) and a fast Semiconductor Saturable Absorber Mirror (SESAM) for an emission at $1.06\mu \mathrm{m}$ with a pulse width of 5ps at 1GHz repetition rate. Fig. 1 a) shows the cavity design where two lenses are used to control the beam ratio on the gain mirror and the SESAM for a stable mode-locking state, $f_{1,2}$ and $d_{1,2,3}$ are chosen in order to get a stable Laguerre-Gauss (LG) transverse modes oscillations with one optical axis and two transverse states as shown in Fig. 1 b) (up), or a modeless self-imaging cavity with two optical axes as shown in Fig. 1 b) (down). Fig. 1 c) shows the temporal evolution of the dual-comb where the $\text{LG}_{00}$ comb's repetition rate is $f_{rep}=1/T$ and the LG03 comb's one is $f_{rep}+\Delta f$ where $T$ is the roundtrip time of 1 ns and $\Delta f\approx 100\text{kHz}$.

We demonstrate the existence of a multiplicity of co-existing frequency combs in a harmonically mode-locked laser that we link to the splay phases of the Kuramoto model with short range interactions. These splay states are multistable and the laser may wander between them under the influence of stochastic forces. Consequently, the many pulses circulating in the cavity are not necessarily coherent with each other. We show that this partially disordered state for the phase of the optical field features regular train of pulses in the field intensity, a state that we term an incoherent crystal of optical pulses. We provide evidence that the notion of coherence should be interpreted by comparing the duration of the measurement time with the Kramers' escape time of each splay state. Our results are confirmed experimentally by studying a passively mode-locked vertical external-cavity surface-emitting laser.

THz photonics-based sources are attractive as they offer room-temperature solutions that rely on mature photonics technology and provide broadband tunability and large modulation bandwidth to address specific THz applications such as high-data-rate communications or spectroscopy. We will present an overview of our recent results on coherent and structured light emitted from III-V semiconductor lasers and we will focus on THz generation based on these original near-infrared lasers operating at 1064 nm. Vertical external-cavity surface-emitting lasers that exploit parity symmetry breaking together with integrated meta-surfaces can generate unconventional light states such as vortex light, spatially modeless laser, transverse multiplexing, non-linear structured light... Coherent THz emission has been obtained from a dual-mode laser, that operates simultaneously on two Laguerre-Gauss transverse modes, using either uni-traveling-carrier photodiodes and plasmonic photo-conductive antennas. We will discuss the ongoing work towards multiplex structured coherent photonic sources that offer high potential for powerful THz emission.

We show that a III-V semiconductor Vertical External-Cavity Surface-Emitting Lasers (VECSELs) can be engineered to generate light with a customizable spatio-temporal structure. The temporal control is achieved through the emission of Temporal Localized Structures (TLSs), a particular mode-locking regime that allows the individual addressing of the pulses traveling back and forth in the cavity. The spatial profile control relies on a degenerate external cavity and it is implemented thanks to an absorptive mask deposited onto the gain mirror that limits the positive net gain within two circular spots in the transverse section of the VECSEL. We show that each spot emits spatially uncorrelated TLS. Hence, the spatio-temporal structure of the light emitted can be shaped by individually addressing the pulses emitted by each spot. Because the maximum number of pulses circulating in the cavity and the number of positive net-gain spots in the VECSEL can be increased straightforwardly, this result is a proof of concept of a laser platform capable of handling light states of scalable complexity. We discuss applications to three dimensional all-optical buffer and to multiplexing of frequency combs that share the same laser cavity.

We show that nearly-degenerate Vertical External-Cavity Surface-Emitting Lasers may emit a set of tilted beams of individually addressable mode-locked pulses. These time localized beams feature a Gaussian profile and they are emitted in pairs with opposite transverse k-vector. Because they are phase locked, their interference leads to a non homothetic pattern in the near-field emission of the laser. In the simplest situation, when a single pair is emitted, this is a stripe pattern. Our analysis discloses the role of third order (spherical) aberrations of the cavity in stabilizing this spatio-temporal mode-locked regime and in selecting the value of the transverse k-vector.

We demonstrate two highly coherent tunable high power laser concepts, based on a III-V semiconductor VECSEL technology, operating in the 1 mu m wavelength range. We report experimentally and theoretically the existence of deterministic dynamics of a coherent semiconductor laser field, with a route to robust single-frequency operation exhibiting broad nonlinear frequency pulling far above the thermally-assisted conventional tuning range. Thanks to a complementary design, we demonstrate an inhibited laser state exhibiting high power, high spatial and temporal coherence under ultralow light matter interaction, overcoming fundamental and technical limitations of common on the shelf laser technology, like quantum, electronic and thermal noise, as well as thermal lensing induced wave aberration.

Self-starting mode-locking is observed in a laser based on a compact III-V diode-pumped quantum-well surface-emitting semiconductor laser technology with a saturable-absorber-free but dispersive cavity. Continuous wave generation of picosecond pulses at a rate of 100 GHz is demonstrated by recording microwave intensity noises, beat frequency, time-resolved optical spectra, and intensity autocorrelation. Coherence of the pulse train is obtained through the frequency noise measurement of the demodulated beat note, demonstrating a timing jitter as low as 110 fs, near the quantum limit. Using a theoretical model based on a generalized Haus master equation, we demonstrate the existence of this mode locked state without the need for saturable absorption. The fundamental physical mechanism is the interplay between self-phase modulation and anomalous dispersion like in cavity soliton together with light–matter interaction-induced time symmetry breaking.

We consider the transverse nonlinear dynamics of an optical system with spherical aberrations. We assume the simplest possible system which consists in a cavity composed of a nonlinear mirror (a MIXSEL), a lens, and a curved mirror. Close to the self-imaging condition, small defects such as the spherical aberration become relevant and we derive analitically a model for the effective dynamics of the transverse profile, assuming that we have either a temporal localized state or CW emission along the propagation axis. In both cases, we find that the latter is a Rosanov Equation [1] perturbed by a bi-laplacian term.

Temporal localized structures (TLS) are individually addressable pulses circulating in an optical cavity [1]. Their existence is related to the presence of a generalized multistability between pulsating emission states having different number of pulses per roundtrip. They appear in passively mode-locked Vertical External-Cavity Surface-Emitting Lasers (VECSELs) when i) the cavity roundtrip $(\tau_{\mathrm{c}})$ is larger than the carrier recovery time (typically 1 ns) and ii) the saturable absorber mirror (SESAM) exhibits a modulation depth above a critical value (typically 8%) [2], [3]. When the external cavity is nearly degenerate, i.e. close to self-imaging condition, temporal-localized patterns are observed [4]. On the other hand, degenerate cavities enable arbitrary spatial shaping of the lasing emission profile [5].

Emission dynamics of a multimode broadband interband semiconductor laser have been investigated experimentally and theoretically. Non-linear dynamics of a III-V semiconductor quantum well surface-emitting laser reveal the existence of a modulational instability, observed in the anomalous dispersion regime. An additional unstable region arises in the normal dispersion regime, owing to carrier dynamics, and has no analogy in systems with fast gain recovery. The interplay between cavity dispersion and phase sensitive non-linearities is shown to affect the character of laser emission with phase turbulence, leading to regular self-excited oscillations of mode intensity, self-mode locking, and single-frequency emission stabilized by spectral symmetry breaking. Such physical behavior is a general phenomenon for any laser with a slow gain medium relative to the round trip time, in the absence of spatial inhomogeneities.

Continuous-wave tunable photonics-based THz sources present limited output power due to the restricted input optical power accepted by photomixers, along with reduced radiation resulting from low paraxial field amplitude. Here, we investigate multipolar antenna designs to increase the available continuous-wave THz output power by incorporating more photomixers. For this purpose, the spatial structures of the optical and THz E-fields are designed to enhance THz power and radiation in the far field. Simulations of 2 to 4 dipole antennas are conducted, demonstrating an improvement in antenna gain compared to standard dipole antennas. This is in addition to a potential increase in THz power and radiation for photomixing applications. Such work also paves the way for functionalizing the spatial structure of THz light for advanced applications.

In recent years, degenerate laser cavities have gathered attention for their versatility in the transverse structuration of laser emission [1], [2]. In non-linear optics, they are also used to generate patterns of temporally localized structures [3]. Degenerated laser system with high Fresnel number and saturable absorption are also suited for spatial localized structure (SLS). They appear as individually addressable peaks of lights in the transverse plane of the laser system [4]. In this work, we design a spatially degenerated self-imaging laser cavity integrating a slow saturable absorber semiconductor mirror (SESAM) and a high gain ( $\sim$ 15%) semiconductor mirror for SLS generation. The optical cavity is composed of two high numerical aperture (0.2 NA) and low aberrations lenses in a 4-f configuration. It improves the degenerated system response while allowing for normal and anomalous diffraction tuning. A thin $(< \lambda)$ chromium layer was deposited on the gain surface to define an area with strong absorptive boundary condition for light particle observation.

Laser technology is finding applications in areas such as high-resolution spectroscopy, radar-lidar, velocimetry, or atomic clock where highly-coherent tunable high-power light sources are required. Offering such performances in the Near- and Middle-IR range, III-V semiconductor-based Vertical-external-Cavity Surface-Emitting Lasers (VeCSEL) technologies seem to be a well-suited path to meet the required specifications of demanding annlications [1].

Spatiotemporal mode-locking is a promising lasing regime for developing coherent sources for multimode nonlinear photonics. In this paper we show that large-aspect-ratio vertical external-cavity surface-emitting lasers (VECSELs) can be operated in this regime. The emitted pulses exhibit a spatial profile resulting from the phase locking between an axial plane wave and a set of tilted waves having a hexagonal arrangement in the Fourier space. Moreover, we show that these pulsating patterns are temporally localized, i.e., they can be individually addressed by pulsing the optical pump. The theoretical analysis discloses that the emergence of these pulsating patterns is a signature of a Turing instability whose critical wave vector depends on the spherical aberrations of the optical elements. Our result reveals that large-aspect-ratio VECSELs offer unique opportunities for studying fully developed spatiotemporal dynamics and for applications to multidimensional control of light.

Continuous-wave photonics- based THz sources present limited output power due to the restricted input optical power accepted by photomixers. Here, we investigate multipolar antenna design to increase the available THz output power by increasing the number of photomixers. Simulations of 4 to 8 dipole arms antennas are conducted, showing an improvement of antenna gain in comparison to standard dipole antennas, additionally to a potential increase of the THz power for photomixing applications.

We investigate spatially-extended self-imaging VECSELs in the regime localized mode-locking and we report on the observation of pulsating patterns which can be individually addressed. The patterns consist of a combination of an axial plane-wave with a set of tilted waves having a nearly hexagonal arrangement in the Fourier space.

Abstract We show that large aspect-ratio Vertical External-Cavity Surface-Emitting Lasers (VECSELs) with a saturable absorber can be operated in the regime of spatio-temporal mode locking. The emitted pulses exhibit a spatial profile resulting from the phase locking between an axial plane-wave with a set of tilted waves having a hexagonal arrangement in the Fourier space. We show that these pulsating patterns are temporally localized, i.e. they can be individually addressed by modulating the optical pump.The theoretical analysis shows that the emergence of these pulsating patterns is a signature of a Turing instability whose critical wave vector depends on spherical aberrations of the optical elements. Our result reveals that large aspect-ratio VECSELs offer unique opportunities for studying fully developed spatio-temporal dynamics.

We present a classification of the transverse light states observed in a 3D degenerated optical system using a specially design VECSEL based on III-V semiconductor nanotechnology with weak light confinement in matter. A broad transverse area system with low but tunable diffraction combine with saturable absorption is used for light confinement. These light states include CW paraxial spherical coherent beams linearly polarized, conical waves and spatially degenerate coherent light. A first result of a non-linear structuration is also shown