MTL Annual Research Report 2012

Single-photon Detection up to 5-micron-wavelength with Superconducting Nanowire Single-photon Detectors

Figure 1: Detection efficiency (η) of a 30 nm width SNSPD as a function of normalized bias current (IB/Isw) measured at wavelength λ = 1.4 µm (blue curve), λ = 3.7 µm (red curve), and λ = 5 µm (black curve).

We report on the detection of single-photons in the middle-infrared (mid‑IR) range using superconducting nanowire single-photon detectors (SNSPDs). In 2011 our group managed to detect single-photons at a wavelength λ = 1.55 µm using SNSPDs based on ultra-narrow nanowires (30‑nm‑width) with a saturated detection efficiency of η = 20 % at a lower bias current than is possible for wider NbN nanowires[1] (I_B = 0.7 I_sw, where I_sw is the bias current after which the detectors switch to the normal state). These results suggest that ultra-narrow SNSPDs are suitable for detection of photons at longer wavelengths. Figure 1 shows the detection efficiency η measured as a function of the normalized bias current (I_B/I_sw) for λ = 1.4 µm (blue curve), λ = 3.6 µm (red curve), and λ = 5 µm (black curve). The detection efficiency measured at λ = 1.4 µm does not reach η = 20 % because the polarization of the photons could not be optimized to enhance the absorption in the nanowires as in reference ^[1] . The detection efficiency reaches a value of η = 4 % at λ = 3.7 µm, which is two orders of magnitude higher than what has been reported in the literature so far for this type of detector at this wavelength. The figure also shows that the detection efficiency reaches an appreciable value of η = 2 % at λ = 5 µm.

The authors thank E. Dauler and R. J. Molnar from Lincoln Laboratory for technical support and scientific discussions.

1. F. Marsili, F. Najafi, E. Dauler, F. Bellei, X. Hu, M. Csete, R.J. Molnar, and K.K. Berggren, “Single-photon detectors based on ultra-narrow superconducting nanowires,” Nano Letters, vol. 11, pp. 2048-53, May 2011. [↩]