We developed a novel concept of retinal projection for augmented reality (AR) glasses combining optical integrated optics and holography. Our thin and lens-free concept overcomes limitations of current AR devices such as bulky optics and limited field-of-view. The integrated circuit is transparent and guide visible wavelengths by using Si3N4 as the core material of the waveguides. This work presents a detailed description of the optical principles behind the concept, including the self-focusing effect. Furthermore, we present the design of the first building blocks used for the optical integrated circuit at a visible wavelength (λ = 532 nm): single-mode waveguides, bent waveguides, cross-talk, grating couplers and MMI splitters (MultiMode Interference). Numerical simulation results of each component are presented. A prototype combining these optical building blocks in a 1024 waveguide array is designed to provide future experimental proof of concept of our retinal projection concept. In addition to this prototype, test structures are inserted on a photolithography mask to experimentally validate the simulations of each optical building block in future work. Next steps of development will include densifying the integrated optical architecture using serial coupling effects and multiple waveguide layers.

We recently presented a novel retinal projection concept based on the combination of integrated optics and holography. Our lens-free optical system uses disruptive technologies to overcome the limitations of current devices such as a limited field-of-view and bulky optical assemblies. An integrated optical network of Si3N4 waveguides has been designed in the visible range in order to control the intensity of an optical field originating from an emissive point distribution (EPD) at a glass surface. In addition, the phase and orientation of the optical field are controlled by incorporating a pixelated holographic layer. The Si3N4 waveguides are transparent, allowing ambient light to pass through the device for augmented reality applications. This study focuses on the design of the components used for the optical circuit at lambda = 532 nm (hologram laser recording wavelength): single-mode waveguides, bent waveguides, cross-talk, diffraction grating couplers, MMI splitters (MultiMode Interference) and directional couplers. The parameters of the components are optimized with various numerical methods. Furthermore, an optical circuit used as the first test structure is presented. An optical set-up based on a goniometric configuration has been built to characterize the efficiency of our components with a particular focus on the angular properties. Future work will focus on the hologram recording process that will involve interferences between the EPD output beams and free-space planar light waves.

This paper, “Technologies pour les microlasers et la micro-optique, was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

Stimulated emission and optical gain in CdTe/CdMnTe graded index separate confinement quantum wells have been investigated as a function of optical excitation powers and temperatures. Maximum gain of about 100 cm-1 is obtained at 95K for a single quantum well under 2-3 kW/cm2 excitation. This value allows to design laser cavities compatible with the microgun pumped laser device concept. The temperature dependence of the gain still remains a problem (T0 = 110K).

Nous avons etudie le dopage extrinseque de type P du CdHgTe realise par epitaxie par jets moleculaires et avons montre que l'impurete arsenic etait le meilleur candidat pour ce dopage. L'incorporation du dopant P lors de la croissance cristalline du materiau a ete obtenue grâce a trois sources differentes: une cellule a effusion, une cellule cracker et une cellule plasma. Apres un recuit d'activation, les mesures electriques de ces echantillons ont montre un dopage P de quelques 1016 a quelques 1018 porteurs par centimetre cube. En comparant ces mesures et les taux d'arsenic incorpores lors de la croissance il est apparu qu'une grande partie des atomes arsenic n'etaient pas electriquement actifs apres recuit. Afin de mieux comprendre les phenomenes mis en jeu lors de la croissance cristalline et lors du recuit d'activation, une campagne de mesures EXAFS a ete conduite a l'European Synchrotron Radiation Facility. Nous avons alors montre qu'apres croissance l'environnement cristallin des atomes d'arsenic etait cristallin alors qu'apres recuit cet environnement devenait amorphe. Nous avons enfin realise des dispositifs electriques et mis en evidence les premieres diodes dopees par ajout d'arsenic.

Dans un Laser a Semiconducteur a Micropointes (LSM), le milieu amplificateur est pompe par un faisceau d'electrons issus de micropointes a effet de champ. Ce type de laser est particulierement adapte aux semi-conducteurs a grands gaps tels que les nitrures GaN et AIN emettant dans l'UltraViolet, pour lesquels le dopage et la prise de contact ohmique deviennent problematiques. Ce papier presente ce dispositif et l'etat d'avancement des travaux.

Self-assembled InGaN islands were grown by molecular-beam epitaxy on GaN, following a Stranski–Krastanow growth mode. Atomic force microscopy revealed that their dimensions were small enough to expect zero-dimensional quantum effects: the islands were typically 27 nm wide and 2.9 nm high. Strong blue-violet photoluminescence of the dots is observed, persisting up to room temperature. The temperature dependence of the photoluminescence is analyzed and compared to that of InGaN quantum well and bulk samples.

The principle of pump noise suppression is applied to a Nd:YVO4 microchip laser, optically pumped by laser diodes. The noise of the microchip laser at low frequency (below the relaxation oscillation frequency) is compared for noisy and amplitude squeezed laser diodes. The minimum intensity noise of the microchip laser is 7 dB above SNL at a frequency of 40 kHz. Very good agreement between experimental results and theoretical predictions of a model based on quantum Langevin equations is found.