Guillaume Croes

Three-dimensional sensing is critical for autonomous systems, robotics and industrial monitoring, motivating compact frequency-modulated continuous-wave (FMCW) LiDARs, which optically measure distance and velocity. However, current integrated designs using optical phased arrays (OPAs) for beam steering or focal-plane arrays (FPAs) for parallel reception face trade-offs in optical power, aperture and acquisition speed. Here we show a biaxial FMCW LiDAR that monolithically integrates an OPA transmitter and coherent FPA receiver with over 4500 functional components on separate optical paths, eliminating the need for circulators. A line-shaped beam enables agile steering, while a lens-assisted FPA provides a large receiving aperture and parallel single-wavelength readout. The system images at 20 m using 3.7 mW of emitted power, with 5 cm depth resolution and 1.4 mm/s velocity resolution. It produces point clouds at 10 frames per second (fps) and supports acquisition rates up to 41 fps, offering a compact and practical route towards integrated FMCW LiDAR.

The increasing demand for three-dimensional dynamic environmental perception is driving interest in solid-state frequency-modulated continuous-wave (FMCW) LiDAR technologies. However, integrated FMCW LiDAR based on either optical phased arrays (OPAs) or focal-plane arrays (FPAs) face intrinsic trade-offs that have not yet been addressed simultaneously. Here, we present a biaxial FMCW LiDAR architecture that monolithically integrates an OPA transmitter with a coherent FPA receiver, comprising over 4500 functional components and implemented on separate optical paths in a circulator-free configuration. The architecture combines the complementary strengths of OPAs and FPAs. The OPA easily supports high optical power handling and provides agile line-by-line steering enabled by an engineered line-shaped beam. The FPA can form a large receiving aperture assisted by an imaging lens and enables parallel coherent signal readout at a single wavelength. The system achieves single-wavelength three-dimensional imaging with a ranging distance of 20 m using 3.7 mW of emitted optical power. A depth resolution of 5 cm and a velocity resolution of 1 mm/s are obtained. Parallel point-cloud at 10 frames per second (fps) is demonstrated, while acquisition rates of up to 62 fps are supported by the architecture. These results position the biaxial OPA-FPA architecture as a compact and practical system-level approach for integrated FMCW LiDAR.

The next generation of tunable photonics requires highly conductive and light inert interconnects that enable fast switching of phase, amplitude, and polarization modulators without reducing their efficiency. As such, metallic electrodes should be avoided, as they introduce significant parasitic losses. Transparent conductive oxides, on the other hand, offer reduced absorption due to their high bandgap and good conductivity due to their relatively high carrier concentration. Here, we present a metamaterial that enables electrodes to be in contact with the light active part of optoelectronic devices without the accompanying metallic losses and scattering. To this end, we use transparent conductive oxides and refractive index matched dielectrics as the metamaterial constituents. We present the metamaterial construction together with various characterization techniques that confirm the desired optical and electrical properties.

We provide insight into the driving mechanisms and requirements to create an electro-optic spatial light modulator based on a Barium Titanate waveguide and an optically transparent electrode cladding layer. We have developed a generic framework of electric field simulations and non-linear optics to create any desired modulation in an area of interest, applicable for liquid crystals, Pockels and Kerr cells. Targeting our device structure, we have evaluated several design parameters of the arbitrarily reprogrammable SLM, capable of optical beamforming and high-quality holograms.

Perovskite light emitting diodes (PeLEDs) have reached external quantum efficiencies (EQEs) over 21%. Their EQE, however, drops at increasing current densities (J) and their lifetime is still limited to just a few hours. The mechanisms leading to EQE roll‐off and device instability require thorough investigation. Here, improvement in EQE, EQE roll‐off, and lifetime of PeLEDs is demonstrated by tuning the balance of electron/hole transport into a mixed 2D/3D perovskite emissive layer. The mixed 2D/3D perovskite layer induces exciton confinement and beneficially influences the electron/hole distribution inside the perovskite layer. By tuning the electron injection to match the hole injection in such active layer, a nearly flat EQE for J = 0.1–200 mA cm⁻², a reduced EQE roll‐off until J = 250 mA cm⁻², and a half‐lifetime of ≈47 h at J = 10 mA cm⁻² is reached. A model is also proposed to explain these improvements that account for the spatial electron/hole distributions.

Mixed 2D/3D perovskite films with self‐assembled quantum wells have significantly improved the performance of perovskite light emitting diodes (PeLEDs). In this work, such films are fabricated through a two‐step interdiffusion method that is widely employed in processing of perovskite solar cells, however, remains rarely explored for PeLEDs. The effects of incorporating large‐cation ligand, i.e., butylammonium bromide (BABr) into formamidinium lead bromide (FAPbBr₃) based perovskites, in terms of film composition, morphology, optoelectronic properties as well as device performance are thoroughly investigated in this method. By modulating BABr:PbBr₂ ratio in the precursor solution, the optimal device shows a maximum external quantum efficiency (EQE) of 7.36% at 147.7 mA cm⁻² and a brightness of 37 720 Cd m⁻² at 5 V. The performance is remarkably higher than a reference device without BABr that shows a maximum EQE of 2.53% and a brightness of 6190 Cd m⁻² at 5 V. The versatility of this method is further extended to another large‐cation ligand, 4‐fluoro‐benzylammonium bromide (F‐BZABr), which leads to maximum EQE of 8.55%. This work indicates two‐step processed mixed 2D/3D perovskites are promising for bright green PeLEDs.