Interference from Two-Photon Sources in Silica-on-Silicon Circuits at Telecom Wavelength

The integrated photonic chip is a promising way to realize future quantum technology. Here we demonstrate a two-photon interference in the standard telecommunication band on a silica-on-silicon integrated photonic chip. Two identical photons in the 1.55 μm band, which are indistinguishable in spatial, frequency and polarization, are generated by type-I collinear spontaneous parametric down-conversion via bismuth borate. The silica-on-silicon integrated chip, which has an insertion loss less than 1 dB, is a Mach–Zehnder interferometer with a thermo-optic phase shifter. A high visibility of 100% in the classical interference and 99.2% in the two-photon interference is achieved, indicating that the two-photon interference with high interference visibility on the chip is attained successfully.