Wideband 360° microwave photonic phase shifter based on slow light in semiconductor optical amplifiers

Weiqi Xue,José Capmany,Jesper Mørk,Salvador Sales

doi:10.1364/oe.18.006156

Abstract

In this work we demonstrate for the first time, to the best of our knowledge, a continuously tunable 360 degrees microwave phase shifter spanning a microwave bandwidth of several tens of GHz (up to 40 GHz). The proposed device exploits the phenomenon of coherent population oscillations, enhanced by optical filtering, in combination with a regeneration stage realized by four-wave mixing effects. This combination provides scalability: three hybrid stages are demonstrated but the technology allows an all-integrated device. The microwave operation frequency limitations of the suggested technique, dictated by the underlying physics, are also analyzed.

Highlights

The possibility of controlling the speed of light has stimulated significant research efforts [1,2,3,4,5,6,7,8,9] in the past several years due to intriguing physics as well as a number of promising applications [10,11]
In this work we demonstrate for the first time, to the best of our knowledge, a continuously tunable 360° microwave phase shifter spanning a microwave bandwidth of several tens of GHz by slow light effects
The proposed device exploits the phenomenon of coherent population oscillations, enhanced by optical filtering, in combination with a regeneration stage realized by four-wave mixing effects

Summary

Introduction

The possibility of controlling the speed of light has stimulated significant research efforts [1,2,3,4,5,6,7,8,9] in the past several years due to intriguing physics as well as a number of promising applications [10,11]. It can be shown that the contribution of the temporal index grating leads to an antisymmetric detuning dependence of the probe phase, and upon detection of both sidebands this effect cancels out and the phase change is governed solely by the gain dynamics [12] In this regime the slow/fast light effects can be described as the effect of absorption/gain saturation and will be limited in frequency and magnitude by the carrier recovery of the electro-absorbers/SOAs. Recently, we showed that the dynamics of the refractive index can be used to advantage by introducing optical filtering and obtained a 150° phase shift at the microwave frequency of 19 GHz [15]. Both the phase shift and the regeneration can be accomplished using the same technology of active semiconductor waveguides

Theoretical simulations

Experimental demonstrations

Summary and outlook