Biphoton Waveforms of Photon Pair from Velocity-Selective Atoms in a Doppler-Broadened Atomic Ensemble

Telecom band photonic quantum states generated from atomic systems are critical quantum resources for long-distance and scalable quantum communication networks. Here, the beat phenomenon in the autocorrelation function of the telecom-wavelength photon due to the velocity-selective classes of the atoms in a Doppler-broadened atomic ensemble of the cascade-type 5S_1/2–5P_3/2–4D_5/2 transition of ⁸⁷Rb is reported. Although the signal (1529 nm) and idler (780 nm) photons are emitted from a single-atomic ensemble, the autocorrelation functions of the signal and idler photons exhibit significantly different features, with temporal widths of 7 and 0.13 ns, respectively. Furthermore, the biphoton spectral waveform of the telecom band photon pair is measured using a stimulated emission method. The biphoton waveforms of the telecom-wavelength biphoton source demonstrate good agreement with the magnitude of the Fourier components of the measured biphoton temporal and spectral waveforms.