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Download as PDFCoupling Gold Nanoantennas to SNSPDs to Increase Mid-IR Detection
The system detection efficiency of systems integrated with superconducting nanowire single photon detectors (SNSPDs) has been limited to 24% due to losses along the optical path [1] and the small active area of the detector (typically less than 100 µm2). SNSPDs are typically fabricated with a meandering structure to cover a large area; but the kinetic inductance, which limits device performance, increases with the nanowire length, limiting the ultimate area that can be covered. Integrating SNSPDs with antennas can lead to better detection of low photon flux IR sources, such as is required for VLSI circuit evaluation and long-wavelength astronomical observations, by increasing the area over which light is collected and concentrating it on the active area of the detector active.
Preliminary finite element simulations were performed to determine the coupling between a single NbN nanowire and a log-periodic gold antenna in the near IR range based on a previously reported design [2] , shown in Figure 1, using the RF module of COMSOL Multiphysics. The log-periodic design is broadband, but the resonance properties of the antenna are influenced by the electrical properties of the metal and the presence of the metallic superconducting nanowire, as shown in Figure 2. The preliminary design showed an increase in the absorption of light in the nanowire by a factor of 2.4 compared to the absorption in the nanowire without the antenna. Further simulations will be performed to optimize the structure of the nanoantenna for coupling to a boustrophedonic SNSPD structure in the mid-IR range.
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- Figure 1: The simulated structure: the variables for optimization include the radii of the arcs and the ratio, τ, between them.
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- Figure 2: The electric field intensity for the case with an antenna (left) and without an antenna (right). The incident light is a plane wave travelling in the –z-direction.
- X. Hu, T. Zhong, J.E. White, E.A. Dauler, F. Najafi, C.H. Herder, F.N.C. Wong, K.K. Berggren, “Fiber-coupled nanowire photon counter at 1550 nm with 24% system detection efficiency,” Optics Letters, vol. 34, pp. 3607-3609, Nov. 2009. [↩]
- F. J. Gonzales and G.D. Boreman, “Comparison of dipole, bowtie, spiral and log-periodic IR antennas,” Infrared Science and Technology, vol. 46, pp. 418-428, June 2005. [↩]