  Spirals in multiphoton pair production are revisited by two counter-rotating
fields with time delay for different cycles in pulse. Novel findings include
that for subcycle fields, the remarkable spiral structure in the momentum
spectrum can be still caused by a large time delay compared to the previous
study for supercycle case where it is easier to be generated by a small time
delay. And also there exist a range of critical polarization values for the
spirals appearance corresponding to the different cycle number. The relative
phase difference between two fields causes not only severe symmetry breaking of
the momentum spectra pattern and spiral, but also a significant change for the
shape and the number of spiral arm. Upon the number density, it is found a more
sensitive to the cycle number, in particularly, it is enhanced by more than one
order of magnitude for small cycle pulse, while it is increased about few times
when the time delay is small. These results provide an abundant theoretical
testbed for the possible experimental observation on the multiphoton pair
production in future. Meanwhile, it is applicable to regard the particles
momentum signatures as a new probing to the laser field information with it
from the vacuum.
