We consider the inhomogeneous higher-order nonlinear Schrödinger equation and explicitly present exact combined solitary wave solutions that can describe the simultaneous propagation of bright and dark solitary waves in a combined form in inhomogeneous fiber media or in optical communication links with distributed parameters. Furthermore, we analyze the features of the solutions, and numerically discuss the stabilities of these solitary waves under slight violations of the parameter conditions and finite initial perturbations. The results show that there exist combined solitary wave solutions in an inhomogeneous fiber system, and the combined solitary wave solutions are stable under slight violations of the parameter conditions and finite initial perturbations. Finally, the interaction between two neighboring combined solitary waves is numerically discussed.

With the development of metasurfaces and the improvement of manufacturing technology, it is important and imperative to design novel metasurfaces that can flexibly manipulate terahertz (THz) waves. In this paper, a multifunctional metasurface (MFMS) based on graphene and photosensitive silicon (Si) is proposed, which integrates three functions: broadband absorption, broadband linear and circular polarization conversions in THz band. For absorption mode, the MFMS can absorb above 90% energy in the frequency band of 1.74-3.52 THz with the relative bandwidth of 67.6%. For both linear-linear and circular-circular polarization conversion modes, the relative bandwidth with over 90% polarization conversion rates (PCRs) reaches 49.3% in the frequency band of 1.54-2.55 THz. The working mechanism of the MFMS is analyzed by the surface current distributions, and its properties of the absorption and polarization conversion under oblique incident angles are investigated, respectively. The proposed metasurface has promising prospects in terahertz devices such as modulators, smart switches and other terahertz devices.

A reconfigurable multifunctional metasurface is proposed to realize the switching between broadband polarization conversion and perfect absorption by integrating the PIN diodes into the structure. An appropriate feed plate is designed to provide the bias voltage that controls the state of the diodes. When the diodes are in off-state, the metasurface will work in polarization conversion mode, which can convert the co-polarization wave into its cross-polarization state with polarization conversion ratio (PCR) of over 90% in the range from 2.97 to 6.03 GHz; While the diodes are in on-state, the metasurface exhibits perfect absorption with absorptivity of over 90% from 2.56 to 7.62 GHz, and the relative absorption bandwidth (RAB) reaches 99.4%. In addition, the metasurface is fabricated and measured to confirm the multifunctional performance. The proposed metasurface is expected to be applied in electromagnetic detection, stealth technology and communication system.

A dual-band and wide angle absorber with polarization insensitivity is built on basis of three proposed simple petal structure. It is found by simulations and experiments that the absorber exhibits good angular insensitivity for both TE and TM polarized waves. The absorber can achieve a dual-band absorptivity about 80% for TE polarization, and more than 95% for TM polarization when the incident angle is increased to 70 degrees. The absorption mechanism of the proposed absorbers is demonstrated by the surface current distributions at each absorption peak. The absorber is expected to be applied to electromagnetic pollution, radar technology, electromagnetic invisibility, etc.