Cavité Laser a Auto-Collimation – CLAC

Following the pioneering studies of H. Kosaka, many studies focused these last years on the engineering of ultra-refraction effects. Ultra-refraction effects are classically divided into two main categories: superprism effect and self-collimation effects. The superprism effect allows one to strongly modify a beam direction with only a small variation of either the wavelength or the incidence direction. The self-collimation effect allows controlling the lateral extension of a beam by nulling its divergence. These dispersive effects are widely studied in passive crystals, and were successfully applied to design and conceive passive, highly integrated and functional passive optical components functions such as filtering, routing' It was recently theoretically pointed out that so-called 'self-collimating' photonic crystals could be used to design semiconductor laser cavities. The goal of this project is to demonstrate the validity of this postulate and to explore some of its most interesting promises. Among these we shall quote and investigate an integrated laser source, made of the same material which was demonstrated to be very efficient to guide, bend, or tailor beam properties. It is also worthwhile to note the very promising opportunities offered by the use of a material which is intrinsically spectrally dispersive and spatially selective as different modes will behave differently. Understanding up to which extent will be a major goal of this project, to help designing large area single spatial and spectral mode laser sources. These two goals, a laser source monolithically integrable, together with a large area single mode single line cavity, correspond to two of the main challenges left in the semiconductor laser source design. In this prospective direction, the main objectives of this project are divided into 3 main tasks, corresponding to the three main identified challenges, namely: Task 1: Demonstration of lasing in self-collimating photonic crystals. This first task will be devoted to the demonstration of lasing in a cavity entirely defined by photonic crystals in the self-collimation regime on a semiconductor membrane. We will particularly study the impact of the lateral extension of the mode on the lasing performances and cavity stability. A compromise between spectral selectivity and lateral mode width is expected. Task 2: Towards the largest single-mode laser ever. During this second task, we will study how we can enforce spectral single-mode operation for large lateral extensions of the mode. Using either localized or distributed selective reflectors we will try to push the compromise found during task 1 towards larger modes. Task 3: Playing with self-collimation - Study of a cross laser. In this last task, we will study one specificity of self-collimation laser, namely the ability to lase simultaneously into two orthogonal directions that can support different spectral modes. The success of this project will rest on the synergy between three domains of expertise, namely laser science, fundamental optics and near-field imaging. The LAAS-CNRS group has developed particularly innovative concepts of AlGaAs/GaAs quantum well lasers. In this project, this group will process and characterize a planar self-collimation laser source, based on a GaAs membrane, incorporating a GaInAs quantum well for an emission wavelength around 1 µm. The GES expertise field concerns theoretical and numerical researches on photonic crystal and metamaterial devices. Its pioneer research on graded photonic crystals which increase the control of self-collimated beam will be in particular benefit for the success of this project. The expertise in ab initio modeling of complex photonic structures and metamaterials in addition to the computational facilities available for the GES will be crucial for the success of this project. Since the light modes we will use are located below the light line and are not coupled to the free space above the sample, near field imaging will be a crucial tool in the exploration of the lasers modal properties. ICD-LNIO will bring this expertise to the consortium, realizing near field imaging experiments of active samples under optical pumping.