Defect-induced ultimately fast volume phonon-polaritons in the wurtzite Zn0.74Mg0.26Se mixed crystal

H Dicko,A En Naciri,L Broch,J.-P Itié,F Firszt,A Maillard,K Strzałkowski,W Paszkowicz,O Pagès,A Polian,M B Shoker,Y Battie,A V Postnikov

doi:10.1038/s41598-019-44273-5

Abstract

Volume-phonon-polaritons (VPP’s) propagating at a light-in-vacuum-like speed are identified in the wurtzite-type Zn0.74Mg0.26Se mixed crystal by near-forward Raman scattering. Their detection is selective to both the laser energy and the laser polarization, depending on whether the ordinary (n0) or extraordinary (ne) refractive index is addressed. Yet, no significant linear birefringence (n0 {boldsymbol{simeq }} ne) is observed by ellipsometry. The current access to ultrafast VPP’s is attributed to the quasi-resonant Raman probing of an anomalous dispersion of n0 due to impurity levels created deep in the optical band gap by oriented structural defects. The resonance conditions are evidenced by a dramatic enhancement of the Raman signals due to the polar modes. Hence, this work reveals a capacity for the lattice defects’ engineering to “accelerate” the VPP’s of a mixed crystal up to light-in-vacuum-like speeds. This is attractive for ultrafast signal processing in the terahertz range. On the fundamental side we provide an insight into the VPP’s created by alloying ultimately close to the center of the Brillouin zone.

Highlights

Replacement of electrons by photons as the carrier of information, leading to the development of photonics besides electronics, is highly promising in view to accelerate the signal processing in matter
The confinement of light at the surface offers a possibility to achieve light localization into volumes down to a few nanometers, i.e. at a length scale much below the diffraction limit[1,15]. This is promising in view of optical signal processing in miniaturized devices at a level of integration comparable to that achieved in modern electronics
No significant linear birefringence could be detected by ellipsometry in the visible where operates the Raman scattering

Summary

Introduction

Replacement of electrons by photons as the carrier of information, leading to the development of photonics besides electronics, is highly promising in view to accelerate the signal processing in matter. The lacking insight into the PPint mode near Γ is searched for by trying near-forward Raman scattering on a wurtzite-type ZnSe-based mixed crystal, using Zn0.74Mg0.26Se as a case study.

Results

Conclusion