The temporal–spectral mode of photons is a promising platform for quantum information processing due to its potential for implementing high dimensional networks in fiber and chip based photonic devices. To realize such a platform, the temporal-mode characterization of ultrashort pulses with subpicosecond time resolution is required. To address such a temporal resolution, in this talk, I present an interferometric technique for measuring the temporal energy envelope of ultrashort optical pulses based on tunable electro-optic spectral shearing interferometry.