  We show that avoiding bends in a current-carrying superconducting nanowire
enhances the probability for low energy photons to be detected and that this
enhancement is entirely due to the increase in the experimentally achievable
critical current. We studied nanowires shaped as either meander or spiral. The
spirals had different layouts, a double-spiral layout with an S-turn in the
middle and a single-spiral layout without such turn. Nanowires were prepared
from films of niobium nitride with a thickness of 5 nm. For specimens with each
layout we measured the spectra of the single-photon response in the wavelength
range from 400 nm to 1600 nm and defined the cut-off wavelength ${\lambda}c$
beyond which the response rolls off. The largest and the smallest ${\lambda}c$
were found for the single-spiral layout and for the meander, respectively. For
all three layouts the relationship between ${\lambda}c$ and the relative bias
current falls onto a universal curve which has been predicted earlier in the
framework of the modified hot-spot model. For the single-spiral layout, the
efficiency of photon detection at wavelengths smaller than ${\lambda}c$ reaches
the expected absorbance of the spiral structure and the timing jitter per unit
length of the nanowire has the smallest value.
