Phase-sensitive amplification of an optical field using microwaves.

Asha Karigowda,S Sudha,Pradosh K Nayak,Barry C Sanders,Andal Narayanan,Fabien Bretenaker,Adwaith K V

doi:10.1364/oe.27.032111

Abstract

We report phase-sensitive amplification (PSA) of a near-infrared electromagnetic field using room-temperature 85Rb atoms possessing ground-state coherence. Our novelty is in achieving significant optical PSA by manipulating the intensity and phase of a frequency-separated microwave field. PSA is obtained by inducing a three-wave mixing nonlinear process utilising a three-level cyclic scheme in the D1 manifold. We achieve a near-ideal PSA with a gain of 7 dB over a range of 500 kHz bandwidth with very low pump-field intensities and with low optical depths. Such a hybrid, ground-state-coherence-assisted PSA is the first such demonstration using atomic ensembles.

Highlights

Frequency conversion of electromagnetic waves through nonlinear parametric processes can be accompanied by amplification at a selected frequency [1,2,3,4]
Exploiting this three-wave mixing interaction in 85Rb atoms at room temperature, we demonstrate in this paper for the first time that significant amplification is achieved for an EM field
We show that our phase-sensitive amplification (PSA)’s performance achieves the near-ideal limit, which implies that the amplification process adds very little noise to the signal

Summary

Introduction

Frequency conversion of electromagnetic waves through nonlinear parametric processes can be accompanied by amplification at a selected frequency [1,2,3,4]. After the discovery of coherent population trapping (CPT) phenomena [5,6,7] and the associated electromagnetically induced transparency (EIT) effect [8,9], gaseous alkali atoms have been increasingly used to achieve nonlinear amplification of weak signals [10,11,12] This is because CPT shelves the atom in a dark state thereby eliminating its linear response to incident electromagnetic (EM) fields. The magnetic-dipole interaction breaks the symmetry requirement and enables a three-wave mixing response to emerge in the centro-symmetric atomic system Exploiting this three-wave mixing interaction in 85Rb atoms at room temperature, we demonstrate in this paper for the first time that significant amplification is achieved for an EM field. Low optical-field intensities and relatively low optical depths of our atomic ensemble makes our CPT-based PSA a very promising architecture to transfer and amplify quantum signals across different frequency domains

Methods

Demonstration of near-ideal amplification

Numerical modeling

Significance of our experimental results

Conclusion