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The objective of this paper is to review the characterisation methods and procedures used to laser switch phase change materials, and then assess their applicability for characterising phase change materials for active photonics devices. Specifically we characterise the performance of our pump-probe laser system and compare it with other ‘static’ and ‘dynamic’ testers. Our pump-probe system was developed to measure the phase transformation kinetics of chalcogenide films by simultaneously measuring the transmission and reflection of a probe laser with a temporal resolution of 1 ns. We also use the system to measure the second order nonlinear refractive index of chalcogenide thin films. Laser switching of chalcogenides are efficient methods to screen new materials but the switching time seems to have a strong dependence on the measurement method and procedure. Therefore in this article we recommend bespoke methods and procedures for assessing the performance of new chalcogenide compositions for specific photonic devices.

A metal/phase-change material/metal tri-layer planar chiral metamaterial in the shape of a gammadion is numerically modelled. The chiral metamaterial is integrated with Ge2Sb2Te5 phase-change material (PCM) to accomplish a wide tuning range of the circular dichroism (CD) in the mid-infrared wavelength regime. A photothermal model is used to study the temporal variation of the temperature of the Ge2Sb2Te5 layer and to show the potential for fast switching the phase of Ge2Sb2Te5 under a low incident light intensity of 0.016mW/μm2.

We present the design of a polarization-independent tunable absorbing metamaterial (MM) in the mid-infrared wavelength regime. Our structure is composed of an array of thin gold (Au) squares separated from a continuous Au film by a phase-change material (PCM) layer. It is shown that a 10% tuning of the absorbance peak can be obtained by switching the PCM between its amorphous and crystalline states. The strong absorbance shows a substantial overlap between TE and TM polarization states over a wide range of incident angles. The electric field, magnetic field, and current distributions in the absorber are investigated to further explain the physical origin of the absorption. The study provides a path toward the realization of tunable absorbers for applications, such as selective thermal emitters, sensors, and bolometers.

The tunable optical response of elliptical nanohole arrays penetrating through metal–phase change material–metal (Au−Ge2Sb1Te4−Au) films is numerically investigated using the finite difference time domain method in the mid-infrared spectral region. The influence of amorphous and crystalline structural states of Ge2Sb1Te4 on the effective optical parameters of the structure is analyzed. Switching between these states provides a large wavelength shift of the structure’s effective optical parameters.