π-phase modulated monolayer supercritical lens

The emerging monolayer transition metal dichalcogenides have provided an unprecedented material platform for miniaturized opto-electronic devices with integrated functionalities. Although excitonic light-matter interactions associated with their direct bandgaps have received tremendous research efforts, wavefront engineering is less appreciated due to the suppressed phase accumulation effects resulting from the vanishingly small thicknesses. By introducing loss-assisted singular phase behaviour near the critical coupling point, we demonstrate that integration of monolayer MoS2 on a planar ZnO/Si substrate, approaching the physical thickness limit of the material, enables a phase jump. Moreover, highly dispersive extinctions of MoS2 further empowers broadband phase regulation and enables binary phase-modulated supercritical lenses manifesting constant sub-diffraction-limited focal spots of 0.7 Airy units (AU) from the blue to yellow wavelength range. Our demonstrations downscaling optical elements to atomic thicknesses open new routes for ultra-compact opto-electronic systems harnessing two-dimensional semiconductor platforms with integrated functionalities. Here the authors report binary phase supercritical lenses by patterning monolayer TMD materials. Through placement of atomic thin 2D TMD with sufficient absorption, a spot of critical coupling is created to facilitate a pi phase jump and subdiffraction focusing over bandwidth of 150 nm in visible range.

Automated summary

Researchers demonstrate binary phase-modulated supercritical lenses on monolayer transition metal dichalcogenides, enabling sub-diffraction-limit focal spots over a bandwidth of 150 nm in the visible range through loss-assisted singular phase behavior.