Abstract
This thesis project aims to develop a laser system capable of intra-cavity generation of 3D structured light states, thanks to a self-imaging optical cavity and an active medium based on micro-lasers with an external cavity and surface emission (VECSEL). The self-imaging cavity offers the possibility of a large transverse aspect ratio, the laser spot size being small in front of the transverse plane of possible existence. Moreover, for the generation of temporally localized structures, this cavity can support a large temporal aspect ratio; indeed, the cavity can be very long without degradation over the spatial extent.The existence of individually addressable temporally localized structure (TLS) thanks to the addition of a fast saturable absorber has already been demonstrated in a system based on the same technology. Additionally spatially localized structures (SLS) in monolithic VCSEL microcavities or in a dye-based self-imaging system have been demonstrated. We propose in this manuscript to demonstrate the capabilities of a self-imaging system combined with a VECSEL device, to support both types of localization. Spatiotemporally localized structure (light bullet) controllable and addressable in the manner of bits, are interesting in the field of all-optical information processing. This work is in collaboration between the IES and INPHYNI laboratories within the framework of the ANR BLASON.The first element of the system is the non-linear active medium (gain and absorbent) based on III-V semiconductor nanostructures developed at C2N RENATECH. The generation of localized structures is possible thanks to an optical bistability and requires a large modulation of the saturable losses. A large optical gain is essential and constitutes a challenge. For the existence of TLS, a large spectral bandwidth is required. During the design, a compromise was made to limit the spatial and spectral filtering effect of the micro-cavity and to favor the coupling of the electromagnetic field with the external cavity. A saturable absorber (SESAM) was also simulated and manufactured to match the gain parameters. To first focus on the spatial structuring of the field temporal dynamics was avoided (long response time of matter) and a continuous regime was aimed for. Nonlinear reflectivity and carrier diffusion lengths measurements in the SESAM allowed us to identify a limitation on SLS.In a second step, a study of a high numerical aperture external optical cavity was carried out. To meet the need for a transversely and longitudinally extended system, the choice of a self-imaging cavity is obvious. We have highlighted the importance of effects perceived as perturbative, such as thermal lensing or optical aberrations. In 4-f configurations the thermal lens becomes the main force for the stability on the optical axis while the optical aberrations lift the degeneracy between the so-called spherical (on the axis) and conical (Bessel-Gauss) component.Despite these limitations, the current system is able to emit on different types of transverse photon states. Using an absorbing metasurface integrated on the semiconductor, the generation of arbitrary, near-field structured wave functions has been demonstrated. The multiplexing of several emitters or laser modes in a single optical cavity has also been shown. Finally, by combining the metasurfaces and the SESAM, a spatial localization was demonstrated, controlled by the inhomogeneities and a non-resonant injection. Using the non-linear and bi-Laplacian Schrödinger equation, an analysis of the spatial dynamics has made it possible to explain these localized states of light, their spatial dynamics, and ultimately the difficulty of observing SLS.