Bright Silicon Carbide Single-Photon Emitting Diodes at Low Temperatures: Toward Quantum Photonics Applications

Color centers in silicon carbide have recently emerged as one of the most promising emitters for bright single-photon emitting diodes (SPEDs). It has been shown that, at room temperature, they can emit more than 109 photons per second under electrical excitation. However, the spectral emission properties of color centers in SiC at room temperature are far from ideal. The spectral properties could be significantly improved by decreasing the operating temperature. However, the densities of free charge carriers in SiC rapidly decrease as temperature decreases, which reduces the efficiency of electrical excitation of color centers by many orders of magnitude. Here, we study for the first time the temperature characteristics of SPEDs based on color centers in 4H-SiC. Using a rigorous numerical approach, we demonstrate that although the single-photon electroluminescence rate does rapidly decrease as temperature decreases, it is possible to increase the SPED brightness to 107 photons/s at 100 K using the recently predicted effect of hole superinjection in homojunction p-i-n diodes. This gives the possibility to achieve high brightness and good spectral properties at the same time, which paves the way toward novel quantum photonics applications of electrically driven color centers in silicon carbide.

Heterogeneously Integrated Photonic Chip on Lithium Niobate Thin-Film Waveguide

Lithium niobate thin film represents as an ideal material substrate for quantum photonics due to its strong electro-optic effect and high-speed modulation capability. Here, we propose a novel platform which heterogeneously integrates single self-assembled InAs/GaAs quantum dots for a single-photon source on a lithium niobate photonic chip. The InAs/GaAs quantum dots can be transferred to the lithium niobate waveguide via a substrate transfer procedure with nanometer precision and be integrated through van der Waals force. A down-tapered structure is designed and optimized to deliver the photon flux generated from the InAs quantum dots embedded in a GaAs waveguide to the lithium niobate waveguide with an overall efficiency of 42%. In addition, the electro-optical effect is used to tune, and therefore to tune the beam splitting ratio of the integrated lithium niobate directional coupler, which can simultaneously route multiple photons to different spatial modes, and subsequently fan out through grating couplers to achieve single-photon sub-multiplexing. The proposed device opens up novel opportunities for achieving multifunctional hybrid integrated photonic chips.

Envisioning Quantum Electrodynamic Frameworks Based on Bio-Photonic Cavities

A bio-photonic cavity quantum electrodynamic (C-QED) framework could be imagined as a system in which both the “cavity” and the “atom” participating in the light-matter interaction scenario are bio-inspired. Can a cavity be made of a bio-polymer? If so, how should such a cavity appear and what are the best polymers to fabricate it? Can a bioluminescent material stand the comparison with new-fashion semiconductors? In this review we answer these fundamental questions to pave the way toward an eco-friendly paradigm, in which the ever-increasing demand for more performing quantum photonics technologies meets the ever-increasing yet silent demand of our planet to reduce our environmental footprint.

Femtosecond laser micromachining for integrated quantum photonics

Integrated quantum photonics, i.e. the generation, manipulation, and detection of quantum states of light in integrated photonic chips, is revolutionizing the field of quantum information in all applications, from communications to computing. Although many different platforms are being currently developed, from silicon photonics to lithium niobate photonic circuits, none of them has shown the versatility of femtosecond laser micromachining (FLM) in producing all the components of a complete quantum system, encompassing quantum sources, reconfigurable state manipulation, quantum memories, and detection. It is in fact evident that FLM has been a key enabling tool in the first-time demonstration of many quantum devices and functionalities. Although FLM cannot achieve the same level of miniaturization of other platforms, it still has many unique advantages for integrated quantum photonics. In particular, in the last five years, FLM has greatly expanded its range of quantum applications with several scientific breakthroughs achieved. For these reasons, we believe that a review article on this topic is very timely and could further promote the development of this field by convincing end-users of the great potentials of this technological platform and by stimulating more research groups in FLM to direct their efforts to the exciting field of quantum technologies.