Opt Express. 2015 Jun 29;23(13):16517-28. doi: 10.1364/OE.23.016517.

Utilizing weak pump depletion to stabilize squeezed vacuum states.

Optics express

T Denker, D Schütte, M H Wimmer, T A Wheatley, E H Huntington, M Heurs

PMID: 26191663 DOI: 10.1364/OE.23.016517

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. In our experimental setup we observe squeezing levels of 1.96 ± 0.01 dB, with an anti-squeezing level of 3.78 ± 0.02 dB (for a 0.55 mW seed beam at 1064 nm and 67.8 mW of pump light at 532 nm). 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.

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• Journal Article