Light Phase Modulation with Transparent Paraffin-Based Phase Change Materials

Phase change materials (PCMs) have greatly impacted optics with applications from rewritable memories to smart windows, due to their thermal-induced optical property changes. However, they often lose optical transparency during phase transitions, limiting transmission-based functionalities. This issue is addressed here by creating PCM-based composites that remain transparent in the visible spectrum during phase transitions. The key is using 30 nm paraffin nanoparticles as PCMs, minimizing scattering within the host polymer matrix. We show that thin composite layers can modulate the phase of incident visible light with temperature, achieving uniform phase profiles and shifts up to π radians. When compared to reference materials like polydimethylsiloxane, our approach exhibits up to threefold larger phase changes for the same input power. Thus, paraffin-based composites hold promise for thermo-optical applications, such as wavefront shaping and aberration correction, potentially impacting various optical technologies.