A collaborative research team has successfully visualized in real space the ultrafast optical modulation of hyperbolic phonon polaritons (HPhPs) in a van der Waals heterostructure composed of hBN and WS2. The research is published in the journal Nano Letters, and was led by Kazuki Kamada of the Institute for Molecular Science (IMS) and Osaka Metropolitan University, along with Dr. Jun Nishida, assistant professor at IMS, and Takashi Kumagai, associate professor at IMS.