Detecting Single Infrared Photons with 93% System Efficiency (1209.5774v1)

Abstract: Single-photon detectors (SPDs) at near infrared wavelengths with high system detection efficiency (> 90%), low dark count rate (< 1 counts per second, cps), low timing jitter (< 100 ps), and short reset time (< 100 ns) would enable landmark experiments in a variety of fields. Although some of the existing approaches to single-photon detection fulfill one or two of the above specifications, to date no detector has met all of the specifications simultaneously. Here we report on a fiber-coupled single-photon-detection system employing superconducting nanowire single photon detectors (SNSPDs) that closely approaches the ideal performance of SPDs. Our detector system has a system detection efficiency (SDE), including optical coupling losses, greater than 90% in the wavelength range \lambda = 1520-1610 nm; device dark count rate (measured with the device shielded from room-temperature blackbody radiation) of ~ 0.01 cps; timing jitter of ~ 150 ps FWHM; and reset time of 40 ns.

• The paper presents a WSi-based SNSPD achieving 93% detection efficiency at 1550 nm, surpassing previous NbN systems.
• It employs advanced optical coupling and precise nanowire fabrication to minimize dark counts and optimize timing performance.
• The study highlights robust operation at low temperatures and potential future improvements through parallel detector architectures.

Overview of High-Efficiency Single Infrared Photon Detection Using WSi SNSPDs

This paper presents the development and characterization of a superconducting nanowire single-photon detector (SNSPD) system utilizing amorphous tungsten silicide (WSi) nanowires. The system achieved a remarkable system detection efficiency (SDE) of approximately 93% for near-infrared wavelengths, particularly around λ = 1550 nm. This significant achievement overcomes previous limitations in SNSPDs based on NbN that only reached efficiency in the vicinity of 20%. This work marks a critical advancement in the field of single-photon detection, mainly due to the enhanced material properties of WSi and sophisticated optical coupling techniques.

Key Features and Results

The SNSPDs in this paper are constructed with WSi nanowires embedded in an optical stack specifically designed to maximize absorption of light at telecom wavelengths. Key results and features of the WSi-based photon detection system include:

• System Detection Efficiency (SDE): The SDE of ≈ 93% was achieved around 1550 nm, a substantial improvement compared to earlier NbN-based devices.
• Device Dark Count Rate (DDCR): Measured at less than 1 count per second (cps), indicating a device almost devoid of spurious photon count incidences when the system is properly shielded.
• Timing Jitter and Reset Time: The system demonstrated a timing jitter of 150 ps Full Width at Half Maximum (FWHM) and a reset time of 40 ns, which are satisfactory metrics for high-performance single-photon detection.
• Temperature Performance: The SNSPD maintained its performance characteristics, with a detection efficiency of 93% and a DDCR below 10 cps up to 2 K, showcasing robustness across operational temperatures.

Methodological Innovations

The paper emphasizes the robustness of WSi nanowires relative to their NbN counterparts. The structural homogeneity of WSi allows for easier customization and broader fabrication capabilities, including on different substrates. The optical coupling was optimized through a self-aligned fiber-coupling system facilitated by silicon micromachining, which minimizes alignment losses and thus enhances efficiency.

Theoretical and Practical Implications

Theoretically, this research opens avenues for further understanding of disordered superconducting films and their photon absorption characteristics. The practical implications are far-reaching in applications requiring high fidelity single-photon detection, such as quantum communication and sensitive optical measurements. This enhanced detector efficiency can facilitate more accurate and reliable data in these burgeoning fields.

Future Developments

The paper suggests potential future directions to further optimize these WSi SNSPDs. One interesting pathway is the integration of a parallel architecture, known as the superconducting nanowire avalanche photodetector (SNAP), which may reduce the reset time below 10 ns and amplify the signal-to-noise ratio, potentially improving jitter characteristics. Additionally, the higher fabrication yields and versatile substrate compatibility promise the future development of extensive SNSPD arrays covering a broader spectral range from visible to mid-infrared.

In conclusion, the demonstrated performance of WSi-based SNSPDs in this paper represents a promising evolution in single-photon detection technology, setting the stage for developments that can enhance a range of scientific and commercial photonic applications.