Nano-optical photoresponse mapping of superconducting nanowires with enhanced near infrared absorption

Kleanthis Erotokritou,Archan Banerjee,Robert M Heath,Hirotaka Terai,Gregor G Taylor,Shigehito Miki,Alessandro Casaburi,Robert H Hadfield,Cheng Tian,Chandra M Natarajan

doi:10.1088/1361-6668/aae4bb

Abstract

Superconducting nanowire single-photon detectors (SNSPDs) play an important role in emerging optical quantum technologies. We report on advanced nanometric characterization of a high efficiency near infrared SNSPD design based on a low roughness tantalum pentoxide (Ta2O5)/silicon dioxide (SiO2) distributed Bragg reflector (DBR) cavity structure. We have performed high resolution transmission electron microscopy analysis to verify the smoothness of the DBR. Optical reflectance measurements show excellent correspondence with DBR simulations. We have carried out precision nano-optical photoresponse mapping studies at 940 nm wavelength at T = 3.5 K, indicating excellent large area device uniformity (peak efficiency 55% at 100 Hz dark count rate (DCR)) with a full width half maximum timing jitter of 60 ps. With manual fibre coupling with single mode fibre, we achieve a system detection efficiency (SDE) of 57.5% at 940 nm wavelength (100 Hz DCR) at T = 2.3 K and a low polarization dependence of 1.20 ± 0.03. For coupling with multimode fibre, we achieve SDE of 90% at 940 nm (200 Hz DCR) at T = 2.3 K. These SNSPD devices are promising candidates for use in quantum dot photoluminescence studies and optical quantum technology applications.

Highlights

We report on advanced nanometric characterization of a high efficiency near infrared superconducting nanowire single-photon detectors (SNSPDs) design based on a low roughness tantalum pentoxide (Ta2O5)/silicon dioxide (SiO2) distributed Bragg reflector (DBR) cavity structure
SNSPDs are typically based on an ultra-thin (
In this study we present comprehensive nanometric characterisation of a NbTiN SNSPD design atop a Ta2O5/SiO2 DBR tuned for maximum optical absorption at 940 nm

Summary

Introduction

Since the pioneering work of Gol’tsman et al demonstrating single-photon detection in niobium nitride (NbN). Optical QIP requires efficient generation and detection of single-photons [5]. The most promising candidates for near infrared (NIR) single-photon generation are InAs/ GaAs quantum dot (QD) single-photon sources These can achieve extremely high purity (>99.99%) [24] and a photon indistinguishability of up to 97% [25]. To characterise the performance of a QD single-photon source and exploit these sources in QIP applications, highly efficient SNSPDs operating at 940 nm are required. With a view to deploying this SNSPD design in QD single-photon emitter studies we manually couple a device with single mode optical fibre achieving an SDE of 57.5% at 940 nm wavelength at T = 2.3 K at 100 Hz DCR. Using multimode optical fibre we achieve SDE of 90.0% at 940 nm wavelength at T =2.3 K at 200 Hz DCR

Materials and methods

Results and discussion

Conclusion