We present an overview of the key aspects for the design of scalable silicon photonic switch matrices. We first discuss different possible configurations, and then we present the proposed architecture for a multiport transponder aggregator within the European project IRIS. We also analyze all the necessary photonic building blocks for this application; we will show design considerations as well as experimental demonstrations of many of them, discussing all the possible issues that must be considered for the system to work within specifications.
In this paper we present the first integration of a 2D Optical Phased Array (OPA) for 905nm LIDAR applications on our 300mm SWIR photonic platform DAPHNE, based on Si & SiN components.
Silicon photonics is one of the most prominent technology platforms for integrated photonics and can support a wide variety of applications. As we move towards a mature industrial core technology, we present the integration of silicon nitride (SiN) material to extend the capabilities of our silicon photonics platform. Depending on the application being targeted, we have developed several integration strategies for the incorporation of SiN. We present these processes, as well as key components for dedicated applications. In particular, we present the use of SiN for athermal multiplexing in optical transceivers for datacom applications, the nonlinear generation of frequency combs in SiN micro-resonators for ultra-high data rate transmission, spectroscopy or metrology applications and the use of SiN to realize optical phased arrays in the 800–1000 nm wavelength range for Light Detection And Ranging (LIDAR) applications. These functionalities are demonstrated using a 200 mm complementary metal-oxide-semiconductor (CMOS)-compatible pilot line, showing the versatility and scalability of the Si-SiN platform.
We investigate inelastic light scattering by longitudinal optic phonon-plasmon coupled modes (LOPCMs) in a series of heavily Se-doped, n-type GaAs1−xNx epilayers with x<0.4%. We perform a line shape analysis of the LOPCM spectra to estimate the optical effective mass, mopt∗, and the scattering time of the conduction electrons in GaAsN. We use these results to evaluate an effective carrier mobility for our samples. The values thus obtained, which we compare with measured electron Hall mobilities, indicate that the x-dependence of the mobility in GaAs1−xNx is dominated by the scattering time, rather than by the variation of the electron effective mass. The Raman analysis yields mopt∗ values that are lower than those obtained from the band anticrossing model.
An Optical Phased Array (OPA) is similar to a one dimensional (1D) dynamic diffraction array. The phase law of the emitters is numerically programmable and enables to form a beam, that point towards a targeted direction. OPAs have a high potential for a new generation of LiDAR (Light Detection and Ranging) systems, since they avoid mechanical beam scanning. For the development of such LiDAR, many characterizations are essential to optimize the OPA and to get a full control of their performance. To carry out these tests, CEA-Leti has developed a modular optical bench designed to characterize large scale 1D-OPAs in free space. This bench allows beam-forming calibration at various angles thanks to an optical setup based on far-field imaging in the Fourier plane. This set up directly analyses a field of view of 22° (-11°/+11°) and can rotate in the azimuthal plane of the OPA to cover angles ranging from -50° to +50°. The OPA board is mounted on an additional rotation stage to match the OPA beam output with the beam forming set-up optical axis. For practical use, the optical axis is parallel to the floor (i.e. to the optical table). Moreover, after calibration, additional options allow to switch the setup for practical operations, as the OPA use in real space, e.g. for aiming at a target. A Peltier and a regulation loop allow testing the OPA at various temperatures. Fast photodiodes have been implemented to measure the switching time between distinct angular positions. In this paper, we report data acquired with this setup on a 256 channels OPA operating at @1550 nm, that is based on grating antennas with 1.5 μm pitch and thermo-optic phase shifters.
We show that a phonon wave propagating through a semiconductor superlattice can induce a charge current even when no static electric field is applied. When the energy amplitude of the phonon wave is less than the width of the lowest superlattice miniband, we find strong resonant enhancement of electron transport, accompanied by very high frequency oscillations of the electron orbits. In this regime, the phonon wave drags the electrons through the superlattice, causing them to undergo quasi-periodic trajectories with a single dominant temporal frequency several orders of magnitude higher than that of the phonon deformation wave itself. This transformation of GHz frequency wave motion into highly coherent THz frequency electron dynamics provides a mechanism for frequency up-conversion, with a multiplication factor of ~20 in our present samples. For phonon wave amplitudes higher than the miniband width, the electrons perform Bloch-like oscillations, which dramatically suppresses transport.
