  In the last decade phase change materials (PCM) research has switched from
practical application in optical data storage toward electrical phase change
random access memory technologies (PCRAM). As these devices are commercialised,
we expect the research direction to switch once again toward
electrical-photonic devices. The objective of this review is to introduce the
concepts in PCM-tuned photonics. We will start by highlighting the key works in
the field, before concentrating on PCM-tuned Metal-Dielectric-Metal (MDM)
structures. We will discuss how to design tuneable-MDM photonics devices, their
advantages, and their limitations. Finally we will discuss new materials for
phase change photonics.
