Nonlinear SU(1,1) interferometers with an on-chip parametric amplifier

SU(1,1) interferometers use two active parametric amplifiers to replace passive beam splitters of traditional interferometers for wave splitting and superposition. These interferometers involve quantum entangled signal and idler fields and possess a number of advantages over traditional interferometers. Here, we investigate a variant of the SU(1,1) interferometer by using only one parametric amplifier but with either one or both of the signal and idler fields fed back to the same parametric amplifier. Such a geometry is used to accommodate an on-chip micro-ring optical parametric oscillator made of high-index silica glass. An interference fringe is observed, and quantum noise reduction of 4-dB due to destructive quantum interference is measured in the output off the chip. Such an integrated device has potential applications in on-chip precision phase sensing.