Reconfigurable Flat Optics with Programmable Reflection Am- plitude Using Lithography-Free Phase-Change Materials Ultra Thin Films

Sébastien Cueff (1) , Arnaud X Taute (1) , Antoine Bourgade (2) , Julien Lumeau (2) , Stephane Monfray (3) , Qinghua Song (4) , Patrice Genevet (4) , Xavier Letartre (1) , L Berguiga (1)

1 INL - Institut des Nanotechnologies de Lyon
2 RCMO - RCMO
3 STMicroelectronics
4 CRHEA - Centre de recherche sur l'hétéroepitaxie et ses applications

We experimentally demonstrate a very large dynamic optical reflection modulation from a simple unpatterned layered stack of phase-change materials ultrathin films. Specifically, we theoretically and experimentally demonstrate that properly designed deeply sub-wavelength GeSbTe (GST) films on a metallic mirror produce a dynamic modulation of light in the near-infrared from very strong reflection (R > 80%) to perfect absorption (A > 99, 97%) by simply switching the crystalline state of the phase-change material. While the amplitude of modulation can lead to an optical contrast up to 10 6 , we can also actively "write" intermediate levels of reflection in between extreme values, corresponding to partial crystallization of the GST layer. We further explore several layered system designs and provide guidelines to tailor the wavelength efficiency range, the angle of operation and the degree of crystallization leading to perfect absorption.

Mots clés: Phase-change material; light modulation; perfect absorber; Thin films

Domaines: Optique / photonique

Sébastien Cueff, Arnaud X Taute, Antoine Bourgade, Julien Lumeau, Stephane Monfray, et al.. Reconfigurable Flat Optics with Programmable Reflection Am- plitude Using Lithography-Free Phase-Change Materials Ultra Thin Films. Advanced Optical Materials, 2020, ⟨10.1002/adom.202001291⟩. ⟨hal-02996004⟩