  The near-unity system detection efficiency (SDE) and excellent timing
resolution of superconducting nanowire single-photon detectors (SNSPDs),
combined with their other merits, have enabled many classical and quantum
photonic applications. However, the prevalent design based on meandering
nanowires makes SDE dependent on the polarization states of the incident
photons; for unpolarized light, the major merit of high SDE would get
compromised, which could be detrimental for photon-starved applications. Here,
we create SNSPDs with an arced fractal geometry that almost completely
eliminates this polarization dependence of the SDE, and we experimentally
demonstrate 84$\pm$3$\%$ SDE, 1.02$^{+0.06}_{-0.02}$ polarization sensitivity
at the wavelength of 1575 nm, and 20.8 ps timing jitter in a 0.1-W closed-cycle
Gifford-McMahon cryocooler, at the base temperature of 2.0 K. This
demonstration provides a novel, practical device structure of SNSPDs, allowing
for operation in the visible, near-, and mid-infrared spectral ranges, and
paves the way for polarization-insensitive single-photon detection with high
SDE and high timing resolution
