We develop a photorefractive time-domain differential detection (PR-TDDD) method in holographic data storage
systems with considering the temporal response of photorefractive two-wave mixing (PR-TWM). Optimizing the
parameters of PR-TDDD method provides high-precision distinction of phase-modulated signals, i.e. distinction of small
phase difference. In PR-TDDD method, the phase information can be sequentially-distinguished by monitoring the
output intensity of PR-TWM. This is because the output intensity of PR-TWM is changed when the signal phase is
changed. In addition, the changing rate of the output intensity corresponds to that of the signal phase. The advantages of
our method are high energy efficiency, alignment-free optics and the distinction of multi-valued phase-modulated signals.
Especially, we focus attention on applying to phase-based holographic data storage systems, which can achieve
homogeneous intensity distribution on recording plane, i.e. Fourier transform plane, in general, and high energy
efficiency because of 100% white rate. More noteworthy is that multi-valued phase-based holographic data storage can
be realized by using PR-TDDD method. In this work, we consider the important parameters in PR-TDDD method;
signal-to-pump beam intensity ratio, photorefractive coupling strength, and photorefractive time constant. The balance
between these parameters is important for realizing the high-precision distinction of phase-modulated signal.