  In this work, we study the black hole light echoes in terms of the two-photon
autocorrelation and explore their connection with the quasinormal modes. It is
shown that the above time-domain phenomenon can be analyzed by utilizing the
well-known frequency-domain relations between the quasinormal modes and
characteristic parameters of null geodesics. We found that the time-domain
correlator, obtained by the inverse Fourier transform, naturally acquires the
echo feature, which can be attributed to a collective effect of the asymptotic
poles through a weighted summation of the squared modulus of the relevant
Green's functions. Specifically, the contour integral leads to a summation
taking over both the overtone index and angular momentum. Moreover, the
dominant contributions to the light echoes are from those in the eikonal limit,
consistent with the existing findings using the geometric-optics arguments. For
the Schwarzschild black holes, we demonstrate the results numerically by
considering a transient spherical light source. Also, for the Kerr spacetimes,
we point out a potential difference between the resulting light echoes using
the geometric-optics approach and those obtained by the black hole perturbation
theory. Possible astrophysical implications of the present study are addressed.
