Photonic approaches emulating the powerful computational capabilities of the brain are receiving increasing research interest for radically new paradigms in ultrafast neuromorphic (brain-like) information processing and Artificial Intelligence (AI). This talk will report our research on light-enabled neuromorphic systems built with artificial photonic spiking neurons and photonic spiking neural networks (SNN). We will review the properties and performance of the photonic devices employed for the implementation of optical spiking neurons, including semiconductor lasers (e.g. Vertical Cavity Surface Emitting Lasers) and resonant tunnelling diodes. We will also discuss the strategies for their network-connectivity into photonic SNN architectures, and the techniques and algorithms realised for their use in complex functional information processing tasks (e.g. pattern recognition, image processing, data classification). We will also showcase the potentials of these spike-based photonic processing systems for ultrafast, low-energy and high-accuracy performance, with a hardware-friendly implementation that benefits from spike-based learning protocols with highly-reduced complexity.

Photonic-crystal waveguides have led to a new generation of integrated high-Q Kerr-nonlinear microresonators, in which linear and nonlinear dynamics can be strongly influenced and tailored. We discuss ultrashort pulse and frequency comb formation in such resonators, novel self- and sideband injection locking dynamics, as well as, methods for full phase-stabilization as needed for chip-based optical precision metrology.

We present the remarkable tunability of the output spectrum of an Optically Injected Semiconductor Laser under an input signal, in the form of a periodic pulse train, modulating the current. Conditions for discrete output spectra, in the form of frequency combs, are determined. The characteristics of the output frequency combs in terms of the number, the distance and the amplitude of the spectral lines, are shown to be controlled by the parameters of the input periodic pulse signal, namely the pulse amplitude, duration and period, suggesting a multi-functional device for a variety of applications.

Broad-area edge-emitting semiconductor lasers are well known for their spatio-temporal instabilities caused by the interaction of multiple transverse modes. We perform high-resolution spatio-spectral measurements using heterodyning of a 50 µm wide broad-area laser to obtain the mode profiles and linewidths of all transverse modes. First, we find that the profiles of certain transverse modes depend significantly on the pump current, which we attribute to carrier-induced index changes and thermal lensing effects. Second, we observe the formation of multiplets of 1st and 2nd order transverse modes which generate a narrow RF beat note. Since the linewidths of the involved modes are much larger than that of the beat note, we conclude that these transverse modes are phase locked. The analysis of the phase fluctuations of the heterodyning time traces confirms the observation of spontaneous phase-locking of transverse modes in a broad-area laser.

Exceptional points (EPs) are spectral singularities at which two or more eigenvalues of a non-Hermitian operator (often Hamiltonians), together with their corresponding eigenvectors, coalesce. Systems operating at or near EPs can give rise to many unique phenomena, such as self-termination of laser and unidirectional invisibility. However, in the aforementioned works, EPs are accessed below the lasing threshold, and therefore are of linear nature. In this work, we experimentally locate and track the EPs above the lasing threshold in coupled semiconductor photonic crystal nanocavities featuring gain/loss components. These EPs are inherently nonlinear, i.e. they are bifurcation points of a nonlinear dynamical system.

In anisotropic spin-lasers, the ultrafast dynamics of a coupled system between carrier and photon spins will be exploited to realize spin and polarization modulation at frequencies above 200 GHz, far beyond the current limits for conventional current-modulated laser devices. This makes spin-VCSELs excellent candidates not only for the next generation of ultrafast optical communication systems, but also for many other emerging applications such as polarization-based optical communication, neuromorphic computing, chaos-based random bit generation, or microwave and THz generation. Here we present our recent developments on ultrafast spin and polarization control in anisotropic spin-lasers and discuss the prospects and challenges of this new technology on its way to application.

This work presents photonic integrated multi-channel transmitters for free-space optical communication systems applications. The circuits were designed and fabricated using the generic indium phosphide technology, which offers integration of passive and active elements and light amplification within the classical telecom C and L bands. The transmitters comprise an array of DBR laser light sources connected to electro-absorption modulators and an arrayed waveguide grating used as a wavelength multiplexer. The validity of the applied solution was investigated and confirmed with high-speed transmission experiments, including BER and eye diagram measurements of one and two-channel operations. The performance of the transmitters has been verified in the back-to-back configuration, and the first tests of free-space optical transmission have also been performed. The obtained results confirm the applicability of integrated transmitters in novel FSOC systems.

Recently , quantum cascade laser proved to be an extremely interesting platform for frequency combs both in Mid-IR and THz frequency ranges. We will discuss some peculiar aspects of these devices arising from the combination of ultrafast gain, circular cavities and strong RF modulation. Despite the ultrafast nature of the gain medium, by properly engineering dispersion we demonstrate dissipative Kerr solitons both in Mid-IR and THz , with pulse durations of 3.7 ps in the Mid-IR and 10 ps in the THz. Then, by RF modulating a circular cavity, we demonstrate a quantum walk comb in synthetic frequency space. The initially ballistic quantum walk does not dissipate into low supermode states of the synthetic lattice; instead, the state stabilizes in a broad frequency comb, unlocking the full potential of the synthetic frequency lattice. Combs as broad as 100 cm-1 in the Mid-IR with flat top profile are reported.

In this contribution we will report on the realization of a single frequency, high-power 2.0 μm VECSEL laser for a specific quantum frequency conversion process and the development of the locking scheme using an optical frequency comb for the wavelength stabilization. We were able to reach a single frequency output power of 2.3 W in CW-operation at 2062 nm with a long-time absolute wavelength stability in the MHz range.

The width of a laser line may be reduced by increasing the length of a laser cavity with the help of an extended cavity (optical feedback), or also by transferring the purity from another laser (master laser) through the process of frequency-locking brought by optical injection. In this presentation, using a Hz-linewidth master laser, we reduce the linewidth a DFB laser by around 70 dB of magnitude (depending on the operating pump rate). The result is obtained for a null detuning (or a null frequency difference between the master and the slave). We show that the optically-injected laser is indeed operating as a laser and not an optical amplifier by studying the frequency-locking threshold with respect to the injected optical power. This result is not in contradiction with the Schawlow-Townes limit, which is obtained for an internal source, the spontaneous emission, which is coupled to the stimulated emission, while in this case, the seeding photons for the laser process are coming from the external master source. However, these results clearly show that a laser can operate well below its Schawlow-Townes limit.

Photoinduced phase segregation and low coupling efficiency between QDs and cavities make is challenging to achieve stable blue cavity-enhanced superfluorescence in halide-doped perovskite QD system. Here, long-range-ordered CsPbBr2Cl QD superlattices are developed, in which the two core issues can be appropriately addressed. Based on the CsPbBr2Cl QD superlattices with regularly geometrical structures, stable and ultrafast blue cavity-enhanced superfluorescence was realized.

Group IV materials suffers from a lack of efficient light generation for the on-chip integration of active photonic component on silicon (Si). One of the solutions is to use new material like Germanium-tin alloys (GeSn) that can provide direct band gap alignment of the band structure. The use quantum well (QW) is known, in principle, to favor room temperature laser operation at reasonable thresholds over bulk material. While most of advances were performed with bulk materials, exploring adequate designs of GeSn/SiGeSn based QW including strain engineering should be helpful for futures developments of Si-based active photonic devices.

Here we demonstrate up to 290 K laser operation in GeSn/GeSn multi-QW microdisks cavities under optical pumping. The QW and barrier were performed by varying the Sn content. We used specific layer transfer technology and a Silicon Nitride (SiN) stressor layer was introduced to inject tensile strain in the active region such to enhance the directness of the transition. Interestingly this is the highest temperature of operation for GeSn quantum wells lasers. This progress opens the route towards room temperature electrically pumped laser operating.

Advancements in semiconductor materials, particularly within Group IV, are crucial to meet the demand for efficient and adaptable laser sources. Germanium-tin (GeSn) alloys have emerged as promising candidates, facilitating full monolithic integration into silicon photonics. Progress in optically pumped GeSn lasers is remarkable, but electrically injected ones face challenges due to low index contrast to effectively confine the optical mode. We propose an electrically pumped laser design based on GeSnOI (GeSn On Insulator) scheme. Modal analysis was performed at 2500 nm wavelength using finite element method, optimizing electromagnetic wave confinement, and mitigating direct electrical contact deposition on the active zone. Simulation results indicated that the most effective fabrication approach involves bonding with another silicon substrate using SiN dielectric layer as cladding, thus taking advantage of high optical index contrast. This advancement heralds the potential for room temperature operation of electrically pumped lasers.