Search

We experimentally demonstrate that dielectric metasurface can generate multi-channel vortex beams possessing different orbital angular momentums with arbitrarily engineered spin-orbit interactions. We propose a design principle of the proposed meta-atom that can modulate and switch spatial complex-amplitude information. Experimental results show that the proposed metasurface can generate multi-channel vortex beam arrays without interval noises, and it can make each vortex beam channel possess different spin-orbit conversion when the incident polarization is changed. These results provide a new opportunity to implement a novel vortex beam modulator, which can be applied for future development of quantum optics and optical communications.

Here, we present the metasurface design to split the incident light into transmission and reflection spaces according to its polarization states, and at the same time, the distinct phase profiles are imparted to each space. For implementation of this scheme, the linearly birefringent meta-atom is utilized for distinct phases at different polarization states. Interleaving methods is also utilized for switching the transmission-type into reflection-type. Three samples are fabricated for experimental demonstration of proposed scheme, each of them is operating in linear, circular, and elliptical polarization pair. We expect the miniaturization of conventional system might be achieved using this scheme.

Nanophotonic all-optical devices have been enthusiastically studied to overcome the speed bottleneck of electrical devices. Recently, chalcogenide phase change material Ge2Sb2Te5 (GST) based active metasurfaces have emerged as a novel platform as complement of all-optical device. GST has two phase, so called amorphous and crystalline phases that can be changed within nanosecond scale by applying external thermal stimuli. Hence, various ultrafast 2-level switchable GST based meta-devices have been proposed and demonstrated. However, since only two switching levels are provided, there are limitations in applying to various photonic fields. In this paper, we expand its switching functionality to three-level through designing two different sizes of GST nanorod that exhibits different heat generation density in case of top-hat shape light illumination. Thanks to this thermo-optical phenomenon, we can obtain partial phase changed state, so called intermediate state once the appropriate intensity of control light is illuminated. Harnessing intermediate state, we propose novel cryptography platform that can provide high security level encryption while providing ultrafast communication speed.

We proposed a refractive index sensor using a phase-compensated cavity whose resonant wavelength can be tuned by the alignment between layers. The structures are composed of double-layered nanoslit array, which has total thickness of 100 nm while the cavity length is 30 nm thick. Using nanoslit array as a reflector has made it possible to design the phase shift carefully so that the subwavelength Fabry-Perot cavity can be obtained. When the cavity is filled with sensing medium, where the field enhancement is achieved by Fabry-Perot (FP) resonance, the proposed structure is found to achieve sensitivity ranging from 337 nm/RIU to 1250 nm/RIU at each different alignment. The resonant wavelength ranges from 1100 nm to 2500 nm, which contains biological windows and telecommunication wavelength range, so the structure is expected to be used in various purposes.