  Franson interference can be used to test the nonlocal features of energy-time
entanglement and has become a standard in quantum physics. However, most of the
previous Franson interference experiments were demonstrated in the time domain,
and the spectral properties of Franson interference have not been fully
explored. Here, we theoretically and experimentally demonstrate spectrally
resolved Franson interference using biphotons with different correlations,
including positive correlation, negative correlation, and non-correlation. It
is found that the joint spectral intensities of the biphotons can be modulated
along both the signal and idler directions, which has potential applications in
generating high-dimensional frequency entanglement and time-frequency grid
states. This work may provide a new perspective for understanding the
spectral-temporal properties of the Franson interferometer.
