  Squeezed light has evolved into a powerful tool for quantum technology,
ranging from quantum enhanced sensing and quantum state engineering based on
partial post-selection techniques. The pulsed generation of squeezed light is
of particular interest, as it can provide accurate time stamp and physically
defined temporal mode, which are highly preferred in complex communication
networks and large-scale information processing. However, the multimode feature
of pulsed squeezing in conventional single-pass configuration limits the purity
of the output state, negatively impacting its application in quantum
technology. In this Letter, we propose a new approach to generate pulsed
squeezing with high temporal purity. Pulsed squeezing based on parametric
down-conversion in photonic cavities is analyzed. We show that the effective
mode number of the output squeezed light approaches unity. Such a high-purity
squeezed light can be realized with broad parameters and low pump power,
providing a robust approach to generate large-scale quantum resource.
