Strong and Omnidirectional Light Absorption from Ultraviolet to Near-Infrared Using GST Metasurface

For the perfect light absorber, it has been a huge challenge to simultaneously realize ultra-broadband and strong absorption of unpolarized light over a large angular range, though various materials and designs have been tried. The emergence of optical metasurface with powerful light field regulation ability provides a promising new strategy for achieving perfect absorbers. Here, a Ge2Sb2Te5 (GST)-based metasurface with an average 92.5%/94.7% (experiment/simulation) absorptivity of unpolarized light, covering an ultra-broadband from ultraviolet to near-infrared region is designed and demonstrated. This GST-based metasurface consists of double-layer GST interspaced by SiO2 layer, and both field localizations in the top patterned GST layer and intrinsic loss of the bottom patternless GST layer together contribute to this broadband absorption over wide incident angles up to 70 degrees. Strong absorbing ability, large angular responses, and feasibly scalable fabrication for such a perfect GST-based metasurface absorber offer more promising application opportunities in integrated optoelectronic devices.