Photon pairs and heralded single photons are a useful resource in quantum communication, computation, and measurement. Room-temperature microchip-scale integrated devices could enable scalability, robustness and low-cost deployment in practical applications. Silicon is an attractive integration platform, since pair generation by spontaneous four-wave mixing at 1.2 - 1.6 micron wavelengths requires optical power levels that can be delivered by compact electrically-driven laser diodes. However, silicon photonics lacks a native laser device, and the propagation losses are not especially low, although they are somewhat lower than III-V integrated optics, which does have an integrated laser. Nevertheless, silicon photonics can be expected to become a widely-adopted platform for photonics – both classical and quantum – because of the ability to leverage the mature fabrication processes using large-area silicon wafers inherited from the development of microelectronics. Moreover, scalable quantum optics requires electronics for control, drivers and readout circuits, which silicon microelectronic technology can supply. Our research is improving the performance of silicon photonics components for quantum optical communications, and is increasing the level of integration in the quantum silicon photonics toolkit, using microelectronic components and electrically-driven hybrid silicon lasers.
Photon pairs and heralded single photons are a useful resource in quantum communication, computation, and measurement. Room-temperature microchip-scale integrated devices could enable scalability, robustness and low-cost deployment in practical applications. Silicon is an attractive integration platform, since pair generation by spontaneous four-wave mixing at 1.2 - 1.6 micron wavelengths requires optical power levels that can be delivered by compact electrically-driven laser diodes. However, silicon photonics lacks a native laser device, and the propagation losses are not especially low, although they are somewhat lower than III-V integrated optics, which does have an integrated laser. Nevertheless, silicon photonics can be expected to become a widely-adopted platform for photonics – both classical and quantum – because of the ability to leverage the mature fabrication processes using large-area silicon wafers inherited from the development of microelectronics. Moreover, scalable quantum optics requires electronics for control, drivers and readout circuits, which silicon microelectronic technology can supply. Our research is improving the performance of silicon photonics components for quantum optical communications, and is increasing the level of integration in the quantum silicon photonics toolkit, using microelectronic components and electrically-driven hybrid silicon lasers.
Silicon-on-insulator (SOI) wafers have been developed for electronic integrated circuits, but are also one of the most promising platforms in photonic integrated circuits due to its low loss, high refractive index, ability to fast phase modulation, and well-developed fabrication technologies. With advantages to handle light with a small volume and high modulation speed, silicon photonics has been intensively investigated as the next generation platform of signal processing, interconnection, and communication devices. Recently, silicon photonics has been attracted great interests in quantum optics communities as optical quantum systems for linear optical quantum computing are achievable using silicon photonic components including beam splitters, phase modulators, and filters and the small footprint of a silicon photonic quantum system has unprecedented performances of high stability and scalability. Here we show our recent results on the fabrication of silicon photonic elements for quantum applications. We fabricated low-loss optical waveguides, efficient fiber-to-waveguide grating couplers, resonator-based optical filters, and tunable beam splitters and tested their performances. A micro-sized heater is attached on a Mach-Zehnder interferometer, showing stable operation as a slow phase modulator. In addition, phase modulators using plasma dispersion effects are under investigation. Finally, the quantum characteristics of photon pairs generated by spontaneous four-wave mixing in silicon waveguides are investigated. These results will be an essential cornerstone for the realization of quantum optical computing and quantum communication devices.
Chip-scale integrated photonic circuits provide an attractive platform for the implementation of many quantum photonic technologies ranging from precise metrology to secure communication and quantum computation. In particular, silicon photonic platforms support micron-scale nonlinear optical sources of non-classical light which can be mass manufactured using the robust fabrication processes pioneered by the CMOS microelectronics industry. Integration of these quantum photonic sources with high-performance classical photonic devices on the same chip is required for truly scalable quantum information technologies. Integrated nonlinear resonators are investigated as sources of quantum mechanically correlated photon pair sources. An all-order dispersion engineering method is presented as a robust design synthesis for micoring sources. In addition, a novel concept of coupled mode dispersion compensation is proposed and demonstrated, providing significantly improved performance characteristics of resonant four-wave mixing sources. Next a photon pair source is demonstrated in a commercial CMOS microelectronics process opening the door to future integration of quantum photonics with electronic logic and control circuits. Classical nonlinear optical measurements of stimulated four-wave mixing are used for the first time to accurately predict the quantum correlations from the same device operating in the photon pair regime. Next the first demonstration of fully on-chip pump rejection is demonstrated with over 95 dB pump extinction improving the figures of merit from previous demonstrations by multiple orders of magnitude, including losses, detected pair rates and size. Finally, proposals for introducing novel degrees of freedom provided by an integrated platform are presented for further improving the performance of both photon pair and classical nonlinear optical sources.
Silicon photonics based on CMOS technology is a very attractive platform to build compact, low-cost and scalable quantum photonics integrated circuits addressing the requirements of quantum key distribution protocols. We show record low propagation losses below 0.5 dB/cm and below 0.05 dB/cm for silicon and silicon nitride waveguides respectively. We will present our results on integrated components such as hybrid III-V on silicon lasers for weak coherent pulse generation, high-quality microresonators for entangled photon pair generation and we will show our recent developments on high crystalline quality NbN thin films with improved critical temperature for waveguide-integrated superconducting single photon detectors.
Silicon photonics is a dynamic research field of integrated optics. It allows to miniaturize numerous optical functionalities such as lasers, electro-optical modulators, routers, detectors, for telecom wavelengths, LIDAR, sensor, metrology or even spectroscopy, all while been able to propose large scale production high precision technologies. On another side, quantum optics suffers from difficulties to scale optical systems, requires extreme stability, perfect alignment, and many bulky optical elements, while solving these issues follows a natural path in integrated photonics. Development of integrated quantum photonics can thus open the door to cheap, powerful, and scalable systems for quantum cryptography, telecoms, and computation. In a significant way, quantum requirements are not the ones of classical circuits with respect to photonic components and circuits. The generation of quantum states indeed requires more than 100dB of pump laser rejection, while being able to manage ultra-low useful optical signals and get rid of on-chip optical noise. In this context, this thesis is dedicated to the study, dimension, realization, and characterization of silicon photonic components and circuits for quantum optics on a chip. The target goal is to generate entangled states in energy-time and manipulate them on chip. The qualification of the quantum properties is also explored to better understand the limitations of the silicon platform in the followed objectives. Another choice of this work is to stay in telecoms wavelength and aligned with the standard channels (ITU grid), to only use off-the-shelf components, all while been CMOS compatible and compliant with standard fabrication process, this to allow the possibility to produce on large scale.
We report photon pairs and heralded single photons generated at 1310 nm wavelengths using silicon photonics technology, demonstrating that comparable performance could be achieved when a silicon microring resonator was pumped either by a desktop laser instrument or by an electrically injected, room-temperature hybrid silicon laser. Measurements showed that 130 kilo-coincidence-counts per second pair rates could be generated, with coincidences-to-accidentals ratio approximately 100 at about 0.34 mW optical pump power and anti-bunching upon heralding with second-order intensity correlation g(2)(0) = 0.06 at about 0.9 mW optical pump power. These results suggest that hybrid silicon lasers, which are ultra-compact and wafer-scale manufacturable, could be used in place of packaged, stand-alone lasers for generating photon pairs at data communication wavelengths and enable large-scale, cost-effective manufacturing of integrated sources for quantum communications and computing.
Integrated photonics offers great potential for quantum communication devices in terms of complexity, robustness, and scalability. Silicon photonics in particular is a leading platform for quantum photonic technologies, with further benefits of miniaturization, cost-effective device manufacture, and compatibility with CMOS microelectronics. However, effective techniques for high-speed modulation of quantum states in standard silicon photonic platforms have been limited. Here we overcome this limitation and demonstrate high-speed low-error quantum key distribution modulation with silicon photonic devices combining slow thermo-optic DC biases and fast (10 GHz bandwidth) carrier-depletion modulation. The ability to scale up these integrated circuits and incorporate microelectronics opens the way to new and advanced integrated quantum communication technologies and larger adoption of quantumsecured communications.