  Single-photon detection via absorption in current-biased nanoscale
superconducting structures has become a preferred technology in quantum optics
and related fields. Single-mode fiber packaged devices have seen new records
set in detection efficiency, timing jitter, recovery times, and largest
sustainable count rates. The popular approaches to decreasing polarization
sensitivity have thus far been limited to introduction of geometrically
symmetric nanowire meanders, such as spirals and fractals, in the active area.
The constraints on bending radii, and by extension, fill factors, in such
designs limits their maximum efficiency. The discovery of single-photon
sensitivity in micrometer-scale superconducting wires enables novel meander
patterns with no effective upper limit on fill factor. This work demonstrates
simultaneous low-polarization sensitivity ($1.02\pm 0.008$) and high detection
efficiency ($> 91.8\%$ with $67\%$ confidence at $2\times10^5$ counts per
second) across a $40$ nm bandwidth centered at 1550 nm in 0.51 $\mu\text{m}$
wide microwire devices made of silicon-rich tungsten silicide, with a $0.91$
fill factor in the active area. These devices boasted efficiencies of
$96.5-96.9\% \pm 0.5\%$ at $1\times10^5$ counts per second for 1550 nm light.
