The monolayer graphene-based terahertz (THz) perfect absorber has made significant progress in switchable devices with diverse functionalities. However, existing methods for achieving switchability rely on either multilayered metasurface with complex configurations or complicated patterned metasurfaces. A switchable absorber that switches between n-band and m-band modes (n, m correspond to the number of resonance peaks) using tunable materials is also interesting but has not yet been mentioned. Here, a dynamically switchable multiband perfect absorber with a digital coding graphene metasurface is proposed and demonstrated. By integrating multiple metasurface units with different Fermi levels into a newly generated period, we realize a multiband perfect absorber with a rather simple and straightforward configuration composed of a patterned metasurface. Through introducing a digital coding metasurface into the perfect absorber, we use the digital signals via FPGA (field programmable gate array) to convert n-band into m-band absorption modes. Moreover, the results reveal that the THz perfect absorber, possessing great impedance matching with the free space, has excellent angle tolerance and robustness. Such a perfect absorber offers a flexible tool for selecting THz channels and may pave the way for ${\mathrm{sixth}}^{-}$generation communication.

In this study, we report on the fractional Talbot effect of nonparaxial self-accelerating beams in a multilevel electromagnetically induced transparency (EIT) atomic configuration, which, to the best of our knowledge, is the first study on this subject. The Talbot effect originates from superposed eigenmodes of the Helmholtz equation and forms in the EIT window in the presence of both linear and cubic susceptibilities. The Talbot effect can be realized by appropriately selecting the coefficients of the beam components. Our results indicate that the larger the radial difference between beam components, the stronger the interference between them, the smaller the Talbot angle is. The results of this study can be useful when studying optical imaging, optical measurements, and optical computing.

The theory of proof-of-principle triple-mode squeezing is proposed via spontaneous parametric six-wave mixing process in an atomic-cavity coupled system. Special attention is focused on the role of dressed state and nonlinear gain on triple-mode squeezing process. Using the dressed state theory, we find that optical squeezing and Autler-Towns splitting of cavity mode can be realized with nonlinear gain, while the efficiency and the location of maximum squeezing point can be effectively shaped by dressed state in atomic ensemble. Our proposal can find applications in multi-channel communication and multi-channel quantum imaging.

Submicron lenses and cylinders exhibiting excellent properties in photodetector and quantum applications have been fabricated on a diamond surface by an inductively-coupled plasma (ICP) etching technique. During ICP etching, a layer containing 500 nm diameter balls of SiO₂ was employed as mask. By changing the mixing ratio of O₂, Ar and CF₄ during ICP etching, several submicron structures were fabricated, such as cylinders and lenses. The simulation results demonstrated that such submicron structures on a diamond’s surface can greatly enhance the photon out-coupling efficiency of embedded nitrogen-vacancy center.

The emergence of monolayer material has opened new avenue for manipulating light beyond the capability of traditional optics. However, controlling the terahertz (THz) wave with magnetized monolayer graphene based on multi-beam interference method is interesting but yet reported. In this article, we report an optically induced lattice with tunability in THz by interfering four plane waves in the magnetized monolayer graphene. We show that the optical properties of the induced optical lattice can be efficiently tuned by varying the optical parameter of the interference beams (i.e., the photon detuning and the Rabi frequency), resulting in both amplitude- and phase-type lattice. Based on Fraunhofer diffraction theory, it is found that the far-field diffraction efficiency is adjustable via varying the probe detuning. Moreover, it is also found that the probe field is diffracted into the high-order direction when the photon detuning is within the triangle-like anti-centrosymmetric region. Such a tunable THz lattice may provide a versatile tool for all-optical switching at the few photons level and paves the way for next generation high-speed wireless communication.