PR40_Designing Integrated Silicon Photonics Flexible High-Data Rate Transceivers (NNX16AD14G-Y1)

We study a transceiver architecture, which is based on an innovative design which generates a flexible number of communication streams from a single laser. This approach can achieve reductions in size, weight, and energy consumption, and improvements on link performance and bandwidth compared to both RF communications and existing optical technologies Summary of a Project Outcomes report of research funded by NASA.

Ultra-Compact and Ultra-Broadband Polarization-Insensitive Mach–Zehnder Interferometer in Silicon-on-Insulator Platform for Quantum Internet Application

Polarization dependence in integrated silicon photonics has a detrimental effect on the manipulation of quantum state with different polarizations in the quantum technology. Those limits have profound implications for further technological developments, especially in quantum photonic internet. Here, we propose a polarization-independent Mach–Zehnder interferometer (MZI) structure based on a 340 nm-thick silicon-on-insulator (SOI) platform. The MZI facilitates low loss, broad operating bandwidth, and large tolerance of the fabrication imperfection. We achieve an excess loss of <10% and an extinction radio of >18 in the 100 nm bandwidth (1500∼1600 nm) for both transverse electric (TE) and transverse magnetic (TM) modes. We numerically demonstrate an interference visibility of 99% and a polarization-independent loss (PDL) of 0.03 for both polarizations at 1550 nm. Furthermore, by using the principle of phase compensation and self-image, we shorten the length of the waveguide taper by almost an order of magnitude with the transmission of >95% for both TE and TM polarizations. Up to now, the proposed structure could significantly improve the integration and promote the development of monolithic integrated quantum internet.

Near-Infrared Photoresponse in Ge/Si Quantum Dots Enhanced by Photon-Trapping Hole Arrays

Group-IV photonic devices that contain Si and Ge are very attractive due to their compatibility with integrated silicon photonics platforms. Despite the recent progress in fabrication of Ge/Si quantum dot (QD) photodetectors, their low quantum efficiency still remains a major challenge and different approaches to improve the QD photoresponse are under investigation. In this paper, we report on the fabrication and optical characterization of Ge/Si QD pin photodiodes integrated with photon-trapping microstructures for near-infrared photodetection. The photon traps represent vertical holes having 2D periodicity with a feature size of about 1 μm on the diode surface, which significantly increase the normal incidence light absorption of Ge/Si QDs due to generation of lateral optical modes in the wide telecommunication wavelength range. For a hole array periodicity of 1700 nm and hole diameter of 1130 nm, the responsivity of the photon-trapping device is found to be enhanced by about 25 times at λ=1.2 μm and by 34 times at λ≈1.6 μm relative to a bare detector without holes. These results make the micro/nanohole Ge/Si QD photodiodes promising to cover the operation wavelength range from the telecom O-band (1260–1360 nm) up to the L-band (1565–1625 nm).

Full daylight quantum-key-distribution at 1550 nm enabled by integrated silicon photonics

The future envisaged global-scale quantum-communication network will comprise various nodes interconnected via optical fibers or free-space channels, depending on the link distance. The free-space segment of such a network should guarantee certain key requirements, such as daytime operation and the compatibility with the complementary telecom-based fiber infrastructure. In addition, space-to-ground links will require the capability of designing light and compact quantum devices to be placed in orbit. For these reasons, investigating available solutions matching all the above requirements is still necessary. Here we present a full prototype for daylight quantum key distribution at 1550 nm exploiting an integrated silicon-photonics chip as state encoder. We tested our prototype in the urban area of Padua (Italy) over a 145 m-long free-space link, obtaining a quantum bit error rate around 0.5% and an averaged secret key rate of 30 kbps during a whole sunny day (from 11:00 to 20:00). The developed chip represents a cost-effective solution for portable free-space transmitters and a promising resource to design quantum optical payloads for future satellite missions.

Embedded Silicon Nanoparticles as Enabler of a Novel CMOS-Compatible Fully Integrated Silicon Photonics Platform

The historical bottleneck for truly high scale integrated photonics is the light emitter. The lack of monolithically integrable light sources increases costs and reduces scalability. Quantum phenomena found in embedded Si particles in the nanometer scale is a way of overcoming the limitations for bulk Si to emit light. Integrable light sources based in Si nanoparticles can be obtained by different CMOS (Complementary Metal Oxide Semiconductor) -compatible materials and techniques. Such materials in combination with Si3N4 photonic elements allow for integrated Si photonics, in which photodetectors can also be included directly in standard Si wafers, taking advantage of the emission in the visible range by the embedded Si nanocrystals/nanoparticles. We present the advances and perspectives on seamless monolithic integration of CMOS-compatible visible light emitters, photonic elements, and photodetectors, which are shown to be viable and promising well within the technological limits imposed by standard fabrication methods.

Integrated Silicon Photonics for Enabling Next-Generation Space Systems

A review of silicon photonics for space applications is presented. The benefits and advantages of size, weight, power, and cost (SWaP-C) metrics inherent to silicon photonics are summarized. Motivation for their use in optical communications systems and microwave photonics is addressed. The current state of our understanding of radiation effects in silicon photonics is included in this discussion. Total-ionizing dose, displacement damage, and single-event transient effects are discussed in detail for germanium-integrated photodiodes, silicon waveguides, and Mach-Zehnder modulators. Areas needing further study are suggested.