There is an increasing demand for superconducting nanowire single photon detectors (SNSPDs) which combine high efficiency, low dark counts and fast response time. They play a crucial role in developing strategic application areas such as photon-based quantum computing and quantum key distribution. We demonstrate the fabrication of high crystalline quality NbN-based waveguide-integrated SNSPDs using a completely CMOS-compatible process on 200 mm SOI wafers. We achieve a detection efficiency over 80 % at 100 Hz dark count rate, a short decay time below 4 ns and a maximum count rate of 200 MHz.
Quantum information processing brings new protocols to the field of communications, by ensuring absolute security of information transfer thanks to the laws of quantum physics. Furthermore, in the field of computing, quantum processing offers the perspective of performing massively parallel calculations, orders of magnitude faster than with a classical computer. For these two applications, excellent detectors are required with ultimate performances. Superconducting nanowire single photon detectors (SNSPDs) are the best candidate, as they can reach near-unity detection efficiency. We are developing on-chip waveguide integrated SNSPDs on 200 mm SOI wafers, addressing both the material, architecture design and fabrication process challenges.
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.
Superconducting nanowire single photon detectors stand today as the best technology, due to their near-unity detection efficiency, low dark count rates, and low timing jitter. In this work, we demonstrate the improvement of the superconducting properties of NbN thin films on 8” silicon-on-insulator wafers by using an ultra-thin (10-15 nm) sputtered AlN buffer layer. The higher crystalline quality of NbN, leads to an increase of the superconducting critical temperature up to 10 K for 9-nm-thick NbN films. The material was validated for single photon detection using a fiber-coupled vertical SNSPD with half-cavity architecture. This results opens the way for the development of CMOS compatible waveguide-integrated detectors. The implementation of such guided devices is a keystone for the development of a fully integrated quantum photonics platform able to generate, manipulate and detect a large number of photonic qubits for secure communications and quantum computing applications.
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