Single is better than double: theoretical and experimental comparison between two thermal poling configurations of optical fibers.

Francesco De Lucia,Rex Bannerman,Pier John Anthony Sazio,James Gates,Jayanta Sahu,Martin Miguel Angel Nunez Velazquez,Nicolas Englebert,Simon-Pierre Gorza,Francois Leo

doi:10.1364/oe.27.027761

Abstract

Thermal poling, a technique to create permanently effective second-order susceptibility in silica optical fibers, has a suite of applications including frequency conversion and mixing for high harmonic generation and phase sensitive amplification, optical switching and modulation, and polarization-entangled photon pair generation. In this work, we compare both theoretically and experimentally two different electrode configurations for poling optical fibers, namely double-anode and single-anode, for two different geometries of the cladding holes. This analysis reveals that the single-anode configuration is optimal, both for the absolute value of effective χ (2) created in the fiber core, and for the simplification of the fiber fabrication process.

Highlights

The thermal poling technique, invented at the beginning of the 90’s by Myers et al [1], is a method for creating a quadratic nonlinear optical response in centrosymmetric materials, which, in the dipole approximation, do not normally possess any χ(2) [2]
Used for bulk glasses, the technique was later adopted to pole optical fibers, provided they were equipped with electrodes embedded inside cladding channels located adjacent to the fiber core [3]
In 2009 an important step further towards a better exploitation of the thermal poling technique was presented by the work of Margulis et al [6], who introduced a new configuration for poling optical fibers, called thermal “charging”

Summary

Introduction

The thermal poling technique, invented at the beginning of the 90’s by Myers et al [1], is a method for creating a quadratic nonlinear optical response in centrosymmetric materials, which, in the dipole approximation, do not normally possess any χ(2) [2]. The most relevant observation coming from our numerical study is that for long poling periods (≈ 120 minutes) the value of χe(2ff) calculated from the distribution of the electric field frozen inside the symmetric fiber poled in D-A configuration is zero at the center of the fiber This fact pushed us to investigate a different poling configuration, namely single-anode (S-A), where only one of the cladding holes of the fiber is equipped with an embedded electrode contacted to high positive voltages. This result is expected in the S-A configuration due to the lack of competitive action of two positive electric potentials that is typical of the D-A configuration This result allows for a significant simplification of fiber fabrication process and associated manufacturing tolerances as it only requires a single hole instead of two whilst simultaneously removing all the issues related to the precise location of the two cladding channels with respect to the core to optimize the value of χe(2ff).

Experimental determination of κ for the two poling configurations of PPSF

Fabrication of the PPSFs

Experimental measurement of κ in both poling configurations

Conclusions