High Q Resonant Graphene Absorber with Lossless Phase Change Material Sb2S3

Graphene absorbers have attracted lots of interest in recent years. They provide huge potential for applications such as photodetectors, modulators, and thermal emitters. In this letter, we design a high-quality (Q) factor resonant graphene absorber based on the phase change material Sb2S3. In the proposed structure, a refractive index grating is formed at the subwavelength scale due to the periodical distributions of amorphous and crystalline states, and the structure is intrinsically flat. The numerical simulation shows that nearly 100% absorption can be achieved at the wavelength of 1550 nm, and the Q factor is more than hundreds due to the loss-less value of Sb2S3 in the near-infrared region. The absorption spectra can be engineered by changing the crystallization fraction of the Sb2S3 as well as by varying the duty cycle of the grating, which can be employed not only to switch the resonant wavelength but also to achieve resonances with higher Q factors. This provides a promising method for realizing integrated graphene optoelectronic devices with the desired functionalities.

All-optical logical gates based on photoinduced molecules reorientation in amorphous polymer films

A type of all-optical logical gate based on two kinds of refractive index grating in azo-dye doped polymer film is studied in this paper. Using interference recording method with two 532[Formula: see text]nm laser beams, the transient refractive gratings can be formed in poly(methyl methacrylate) (PMMA) films containing azo-dye Disperse Red 13 (DR13). The characteristics of the transient gratings in films which are recorded by two 532[Formula: see text]nm laser beams with different polarization states are investigated by monitoring the first-order diffraction intensity of the readout He–Ne laser beam (632.8[Formula: see text]nm). It is found that the transient gratings in the polymeric films can be established and decayed in several seconds. Furthermore, we realize XOR and XNOR all-optical logical operation based on the relationship among the polarization states of the recording beams, the reading beam, and the diffraction beam.