Multifunctional analysis and verification of lightning-type electromagnetic metasurfaces.

Aiming at the problems that most of the existing electromagnetic metasurfaces have single function and narrow application scope, a highly integrated lightning-type metasurface is proposed in this study. It can realize the functions of circular dichroism (CD), absorption of electromagnetic waves, broadband x-to-y cross polarization conversion (CPC) function, linear-to-circular polarization conversion (LTC-PC) function and asymmetric transmission (AT), and its functions are also analyzed and verified. The designed metasurface consists of the bottom grating structure, the lower SiO2, the middle lightning-type graphene, the upper SiO2, the top graphene and photosensitive silicon. Through numerical calculations, the CD of design can reach more than 85% at 4.22 THz. The function of bimodal absorption is achieved at 4.09 and 8.69 THz. At 7.41∼8.21 THz, the polarization conversion ratio (PCR) of the metasurface reaches more than 99%. Simultaneously, the function of LTC-PC can be formed when PCR is 50%. Finally, when the designed metasurface is in the transmissive state, the AT of design is close to 60% at 7.84 THz. This design provides a new design idea and method for biomedical detection, image processing, modulators, smart switches, optical diodes and other fields.

Ultrafast metamaterial all-optical switching based on coherent modulation.

We report a demonstration of an ultrafast all-optical switching with unique light control effects. The all-optical switching consists of a gold film with asymmetric split rings and a silica substrate. The device effectively controls the transmission and absorption of continuous pulses in the communication band (1200-1800 nm) and short pulses with a pulse duration of 80 fs by using the interaction of two coherent beams on nano-metamaterials with a thickness of only 50 nm. The metamaterial can achieve more than 90 % output control under continuous light irradiation. When the pulse duration is 80 fs, the switching contrast ratio is greater than 3 : 1 and the modulation bandwidth is greater than 12.5 THz. Switching time can be on the order of femtosecond. This paper provides a new structure for ultra-high speed optical data processing components in coherent networks.