Superconducting Nanowire Single Photon Detector with Optical Cavity

Increasing the detection efficiency （DE） is a hot issue in the development of the superconducting nanowire single photon detector （SNSPD）. In this work, a cavity-integrated structure coupled to the SNSPD is used to enhance the light absorption of nanowire. Ultra-thin Nb films are successfully prepared by magnetron sputtering, which are used to fabricate Nb/Al SNSPD with the curve of lOOnm and the square area of 4 × 4μm2 by sputtering and the lift-off method. To characterize the optical and electrical performance of the cavity-integrated SNSPD, a reliable cryogenic research system is built up based on a He3 system. To satisfy the need of light coupling, a packaging structure with collimator is conducted. Both DE and the dark count rates increase with lb. It is also found that the DE of SNSPD with cavities can be up to 0.17% at the temperature of 0.7K under the infrared light of 1550nm, which is obviously higher than that of the SNSPD directly fabricated upon silicon without any cavity structure.

A High-Efficiency Broadband Superconducting Nanowire Single-Photon Detector with a Composite Optical Structure

Superconducting nanowire single-photon detectors （SNSPDs） with a composite optical structure composed of phase-grating and optical cavity structures are designed to enhance both the system detection efficiency and the response bandwidth. Numerical simulation by the finite-difference time-domain method shows that the photon absorption capacity of SNSPDs with a composite optical structure can be enhanced significantly by adjusting the parameters of the phase-grating and optical cavity structures at multiple frequency bands. The absorption capacity of the superconducting nanowires reaches 70%, 72%, 60.73%, 61.7%, 41.2%, and 46.5% at wavelengths of 684, 850, 732, 924, 1256, and 1426nm, respectively. The use of a composite optical structure reduces the total filling factor of superconducting nanowires to only 0.25, decreases the kinetic inductance of SNSPDs, and improves the count rates.

Key Enabling Techniques and Deployment of 120Gb/s Long-Haul Optical Transmission in Backbone Networks

The explosive increase in data traffic requires networks to provide higher capacity and long-haul transmission capabilities.This paper introduces new results on high-order modulation and efficient Digital Signal Processing algorithms to reduce various transmission limitations in coherent receiving systems.Polarization Division Multiplexed Quadrature Phase Shift Keying(PDM-QPSK)is deployed to reach high bit rates,provides modified digital clock recovery,and allows BER-Aided Constant Modulus Algorithm(BA-CMA)equalising.A Soft Decision-Forward Error Correction(SD-FEC)algorithm and a joint scheme with timing recovery and adaptive equaliser are used to achieve better performance.A compact coherent transceiver is also developed.These techniques have been applied in the largest 100 G Optical Transport Network(OTN)deployment in the world,the backbone expansion project for Phase 3 of the China Education and Research Network(CERNET),with a total transmission length of 10 000 km.

Superconducting nanowire single-photon detectors:recent progress

Research of superconducting nanowire singlephoton detectors(SNSPDs) has been progressing rapidly in recent years. The combined properties of high efficiency,low noise, and fast speed of SNSPDs permit its applications ranging from long-distance quantum teleportation to moonto-earth optical communications. Here we briefly discussed recent progress of SNSPDs, in particular(1) tungstensilicide SNSPDs,(2) waveguide-integrated SNSPDs, and(3) a few applied demonstrations.

Development and application of a modular test system for the HV-CMOS pixel sensor R&D of the ATLAS HL-LHC upgrade

Background High-voltage CMOS is a promising technology for the pixel sensor of tracking detectors in the collider experiments.Extensive studies are being carried out by theATLASCollaboration to investigate the possibility of using theHV-CMOS technology in the HL-LHC upgrade of the ATLAS inner tracker detector.Purpose The CaRIBOu(Control and Readout Itk BOards)is a modular test system developed to test the HV-CMOS pixel sensor prototypes and demonstrators.Methods This test system consists of pixel sensor specific front-end chip boards,a control and readout board(CaR board),a central interface board and the back-end DAQ system.Currently,two DAQ solutions are available for the CaRIBOu system,one is based on the FELIX(front-end link eXchange)readout system and the other is based on the Gigabit Ethernet link.Results Various testbeam experiments have been carried out with the CaRIBOu system since 2015 for the pixel sensors fabricated by the AMS HV-CMOS 180 nm and 350 nm technologies.Conclusion The test results show that this test system is very flexible and could be adapted to the test of different pixel sensors with minimum effort,and the performance meets the testbeam requirements.