(INVITED) Optimized optical fiber poling configurations

• Published in: Optical materials. X Vol. 1; p. 100016
• Main Authors: De Lucia, Francesco, Anthony Sazio, Pier John
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2019; Elsevier
• ISSN: 2590-1478; 2590-1478
• DOI: 10.1016/j.omx.2019.100016

The creation of an effective second order nonlinearity via the process of thermal poling in materials such as glasses, which naturally lack any second order susceptibility, has been known since the early 1990s. In this review, we present a historical overview via an introduction presenting early evidence of second order nonlinear effects in glass to explain the working principles of the thermal poling technique. An overview is then given to the transfer of the technique from bulk materials to optical fibers. Different configurations of poling are presented and compared, namely the conventional anode-cathode set-up, the development of the cathode-less process and most recently, the induction poling technique, which allows for poling fibers without any physical contact between the embedded electrodes and the high voltage supply. 2D-numerical models of the induction poling technique are later presented. An overview is also given of the different solutions for embedding electrodes inside the cladding holes of the fiber. Apart from solid electrodes, the more recent results have been presented about the adoption of liquid electrodes, both metallic and aqueous. For the first time silica optical fibers have been thermally poled using tap water as electrode. Both these two main results, namely induction poling and the liquid electrodes can allow to overcome some of the apparently intrinsic limits shown by the thermal poling technique so far, such as for example the length of the nonlinear devices and the complexity of the geometrical structure of microstructured optical fibres, both solid and PCF. Finally, we review the most recent outcomes and published applications of periodically poled silica fibers from our group, including high harmonic generation and phase sensitive amplification. All these promising results demonstrate that the way towards a full exploitation of the thermal poling technique for all-fiber nonlinear photonics is opening up many new vistas. •In this review, we present a historical overview of the optical fiber poling technique.•We detail how numerical modelling has allowed for a much deeper understanding of the poling mechanism itself.•We describe the latest developments and conclude with some of our recent poled silica fiber publications and applications.