In this work, two split U-shaped metamaterials with photoconductive silicon layer are presented and numerically investigated. The electromagnetically induced transparency can be manipulated by changing angles of the incident wave and the conductivity of silicon. At oblique incidence of 50°, the metamaterials exhibit an obvious photoswitching effect. The transmittance peaks of both two structures are as high as about 0.7, respectively. The fishscale metamaterials with integrated silicon layer show a very high modulation depth. Based on the modulation of the conductivity of the silicon, the scheme can be readily applied to realize THz metamaterial switch.
In this work, a metamaterial with 90°-twisted nanorods is presented and numerically investigated. Numerical simulated results demonstrate that our scheme can realize strong chiroptical response of the metamaterial to circularly polarized waves. We investigate circular dichroism in a bilayer chiral metamaterial in the optical range. The circular dichroism is very strong up to 75%. We also consider how the incident angle of the circular polarized wave affects the circular dichroism. We can achieve strong circular dichroism by changing the incident angle. The proposed metamaterial will be a good candidate for biosensing applications.
Here we will mainly investigate the coupling mechanism of bilayered optical metamaterials with a standing wave and the selective coherent perfect absorption in bilayered optical metamaterials by the two coherent beams. The metamaterials consist of bilayered asymmetrically split rings (ASR) with different twist angles 0° and 180°, spatially separated by a very thin dielectric substrate. Electric and magnetic dipolar excitations can be selectively enhanced or eliminated when the ASR is placed at the antinode and the node of the standing waves, meaning that the phase difference of the signal and control beams is 0° and 180‡°. The simulated results show that coherent perfect absorption can be realized at different frequencies and in particular each one can be switched on/off depending on the phase difference between the signal and control beams. In comparison with 35% absorption in the single-layer ASR metamaterial, the coherent perfect absorption occurs with larger than 95% absorption. In summary, we realize an ultra-thin subwavelength coherent absorber that holds much more flexibility operating at any frequency ranging from microwave to optical regimes. The response of metamaterials can be coherently tailored by easily changing their positions in the standing wave.
A novel anti-bending long period grating (LPG) in an embedded-core hollow optical fiber (ECOF) is proposed and experimentally demonstrated. A piece of ECOF was rotated by 180° around the geometrical center of the fiber, and then it and other ECOF were aligned along the fiber core and spliced. And a LPG, the center of which is the fusion splicing point, was fabricated in the ECOF by using a high-frequency CO<sub>2</sub> laser to form an anti-bending sensor. The dependence of the resonant peak on the bending was studied. Experimental results show that the maximum sensitivity of bending is only 0.47 nm/m<sup>-1</sup>.
This paper introduced the idea of teaching reformation of photoelectric information science and engineering specialty experiments. The teaching reformation of specialty experiments was analyzed from many aspects, such as construction of specialized laboratory, experimental methods, experiment content, experiment assessing mechanism, and so on. The teaching of specialty experiments was composed of four levels experiments: basic experiments, comprehensive and designing experiments, innovative research experiments and engineering experiments which are aiming at enterprise production. Scientific research achievements and advanced technology on photoelectric technology were brought into the teaching of specialty experiments, which will develop the students’ scientific research ability and make them to be the talent suitable for photoelectric industry.
This paper combines the characteristics of optoelectronic technology with that of bilingual teaching. The course pays attention to integrating theory with practice, and cultivating learners' ability. Reform and exploration have been done in the fields of teaching materials, teaching content, teaching methods, etc. The concrete content mainly includes five parts: selecting teaching materials, establishing teaching syllabus, choosing suitable teaching method, making multimedia courseware and improving the test system, which can arouse students’ interest in their study and their autonomous learning ability to provide beneficial references for improving the quality of talents of optoelectronic bilingual courses.
A novel Mach-Zehnder interferometer (MZI) based on a pair of long period fiber gratings (LPGs) in an embedded-core hollow optical fiber (ECOF) are proposed and demonstrated experimentally. Two similar LPGs with peak attenuation of approximately 3dB are fabricated in an ECOF by using high-frequency CO<sub>2</sub> laser to form an in-fiber MZI. The dependences of the resonant peak on the temperature and the axial strain were studied. Experimental results show that sensitivities of the temperature and the axial strain are 64.3 pm/°С and 0.4 pm/με, respectively.
In the present work, a compact all-fiber plasmonic focusing beam generator with single and multiple spots is proposed and demonstrated in a conventional multimode fiber. Here, the focusing beam generator is composed of air slit arrays perforated through the gold films deposited on the end facet of a multimode fiber. The array of nanoscale slits with varying widths is used to modulate phase distribution of the focused light. An all-fiber focusing beam generator provides many advantages, such as self-alignment, high flexibility, lower insert loss, and easy portability, which is of importance to realize optical trapping, micromanipulation, beam shaping, and fiber integrated devices.
We propose an ultrathin planar metamaterial with an abrupt phase change along its surface for beam manipulation. The metamaterial is composed of bilayered asymmetrical split ring apertures (ASRAs) on either side of a dielectric substrate. The proposed metamaterial relies on eight variable ASRAs in a super cell to modulate the phase of transmitted wave. Efficient beam direction manipulation for cross-polarization transmission has been achieved and co-polarization transmission has been completely suppressed. Numerical simulation results show that the linearly polarized incident wave can deflect in a designated direction passing through the ultrathin metamaterial. An intensity efficiency of 70% and a deflection angle of 24° at 6.2GHz have been verified.
We demonstrate selective coherent perfect absorption based on interaction between bilayered asymmetrically split rings (ASRs) metamaterials and a standing wave formed by two coherent counter propagating beams. The selective coherent perfect absorbers with high absorption have been achieved depending on the phase difference between two coherent beams. The selective coherent control absorbers can be well designed by changing the thickness of the dielectric layer and the asymmetry of the ASRs. The coherently controlled metamaterials provide an opportunity to realize selective multiband absorption and ultrafast information processing.