  The current work proposes a method for pulsed-light polarization of
nitrogen-vacancy (NV) center electron spin. To evaluate the influence of pulsed
spin polarization, we establish a polarization evaluation index based on
polarizability and polarization time. Master equation model are utilized to
theoretically calculate the spin polarization dynamics under light excitation
and the optimal polarization conditions for the conventional methods are
obtained. A novel pulsed-light polarization method is proposed by changing the
optical pumping rate in the master equation from a fixed value to a time
variable and an optimal waveform for proposed method is demonstrated through
the variational method, which can simultaneously achieve high polarizability
and requires a short polarization time. Hence, the polarization evaluation
index is improved by ~10%. Moreover, the proposed method is verified by a
pulsed-laser experimental system based on an arbitrary waveform generator. The
current report shall expand the application horizon of NV center based quantum
sensing.
