[Paper Review] A single-photon detector with high efficiency and sub-10ps time resolution

Iman Esmaeil Zadeh, Johannes W. N. Los+5 more|arXiv (Cornell University)|Jan 19, 2018

Advanced Optical Sensing Technologies18 citations

TL;DR

This paper presents a superconducting nanowire single-photon detector (SNSPD) with sub-10 ps timing jitter and >86% detection efficiency by optimizing nanowire geometry and film thickness in NbTiN-based devices. By employing a low-pass filter for multi-photon excitation, the authors achieve a record <3 ps intrinsic time resolution, setting a new benchmark for ultrafast optical detection in quantum optics and ultrafast science.

ABSTRACT

The observation of fast physical dynamics using optical techniques currently relies on indirect methods, such as pump-probe measurements. One reason for this is the lack of an efficient detector with high time resolution. Single-photon detectors with high efficiency and ultra-high time resolution serve as the best candidates for replacing such indirect methods. We engineer the nano-structure of Superconducting Nanowire Single-Photon Detectors (SNSPDs) to achieve a time resolution better than 10ps and at the same time a high efficiency (&gt;86%). Furthermore, at the limit of multiphoton excitation, using an improved readout technique, we reach an unprecedented time resolution of &lt;3ps. These findings set a new upper limit for the intrinsic time resolution of SNSPDs and open up new possibilities for direct observation of fast phenomena in different fields of science.

Motivation & Objective

• To develop a single-photon detector with both high detection efficiency and ultra-high time resolution to replace indirect methods like pump-probe measurements.
• To overcome the trade-off between high efficiency and low timing jitter in SNSPDs by engineering nanowire geometry and film thickness.
• To achieve sub-10 ps timing jitter at near-infrared wavelengths (787 nm and 1550 nm) using optimized NbTiN films and fabrication techniques.
• To explore the limits of intrinsic timing resolution under high excitation powers by minimizing contributions from photon absorption and geometric effects.
• To demonstrate a novel low-pass filter readout technique enabling operation under multi-photon excitation with minimal jitter.

Proposed method

• Fabricated SNSPDs using sputtered NbTiN films on a λ/4 SiO2 cavity with a gold mirror to enhance optical absorption.
• Optimized nanowire meander geometry for high uniformity and filling factors (0.5–0.6 for 787 nm, 0.4–0.45 for 1550 nm) to saturate internal efficiency.
• Used 9 nm thick NbTiN films for 787 nm operation and 8.5 nm films for 1550 nm to balance critical current and quasiparticle generation.
• Employed cryogenic and room-temperature amplifiers to measure timing jitter, with careful calibration of gain and bandwidth.
• Implemented a low-pass filter in parallel with the SNSPD to allow high-frequency signal coupling while providing DC path to ground, enabling multi-photon excitation up to 1–10 nW.
• Performed photon correlation measurements at varying count-rates to analyze jitter distribution and dead-time effects.

Experimental results

Research questions

• RQ1 Can SNSPDs achieve sub-10 ps timing jitter while maintaining >86% detection efficiency across different near-infrared wavelengths?
• RQ2 What is the intrinsic limit of timing jitter in SNSPDs when extrinsic contributions (e.g., absorption geometry, photon arrival time) are minimized?
• RQ3 How does multi-photon excitation affect timing jitter, and can it be used to extract the true intrinsic jitter of the detector?
• RQ4 To what extent does the ratio of detector count-rate to laser repetition rate influence the shape of the jitter distribution?
• RQ5 Can a low-pass filter readout scheme enable stable operation under high optical power without latching into the normal state?

Key findings

• The SNSPD achieved a timing jitter of <3 ps after decoupling contributions from the correlator and photodiode, representing the lowest reported intrinsic jitter in SNSPDs.
• At 787 nm, the detector reached >86% detection efficiency with sub-10 ps timing jitter using a 9 nm thick NbTiN film and optimized nanowire geometry.
• At 1550 nm, the detector achieved >72% efficiency and sub-10 ps jitter using an 8.5 nm thick film with a 45 nm wide nanowire and filling factor of ~0.4.
• Under multi-photon excitation (1–10 nW), the jitter was measured at 3.66 ps, with the intrinsic jitter estimated at <3 ps when external components were decoupled.
• The jitter distribution deviated from a single Gaussian at high count-rates (>0.1× laser rep-rate), indicating interference between detection events due to incomplete recovery of the bias current.
• The use of a low-pass filter enabled stable operation under high excitation powers without latching, allowing the system to operate at the laser repetition rate (50 MHz), thus averaging out geometric and absorption-related jitter sources.