Utilizing weak pump depletion to stabilize squeezed vacuum states

TL;DR

This paper introduces a novel pump-phase locking method using weak pump depletion in an optical parametric oscillator, enabling stable squeezed vacuum states without degrading their quality.

Contribution

It demonstrates the first experimental realization of a pump-phase lock utilizing weak pump depletion, a previously neglected effect, for stabilizing squeezed states.

Findings

Successful implementation of pump-phase lock using WPD

No degradation of squeezed states during locking

Enhanced stability of squeezed vacuum states

Abstract

We propose and demonstrate a pump-phase locking technique that makes use of weak pump depletion (WPD) - an unavoidable effect that is usually neglected - in a sub-threshold optical parametric oscillator (OPO). We show that the phase difference between seed and pump beam is imprinted on both light fields by the non-linear interaction in the crystal and can be read out without disturbing the squeezed output. Our new locking technique allows for the first experimental realization of a pump-phase lock by reading out the pre-existing phase information in the pump field. There is no degradation of the detected squeezed states required to implement this scheme.