Based on the Pancharatnam-Berry phase principle, metalens permits precise phase manipulation through spatial-variant micro/nano-structures. In this study, a bifocal metalens incorporating spatial-variant subwavelength silicon(Si) gratings is introduced for an incident wavelength of 1550 nm with orthogonally circular polarization. The metalens is segmented into two interleaved sub-apertures for right-handed circularly polarized(RCP) and left-handed circularly polarized(LCP) lights, respectively. For incident RCP light, the proposed bifocal metalens attains a focal length of 100 μm, which can be adjusted to 200 μm through polarization state switching to LCP. Furthermore, with inverse designed diaphragms and holographic optical element, a Fourier transform optical interference lithography system is utilized to generate multiple interference light beams simultaneously and fabricate targeted spatial-variant micro/nano-gratings in the photoresist film, which is promising for the production of the Pancharatnam-Berry phase metalens based on spatial-variant nanogratings.
To get multi-band antenna with reduced system load, we propose tri-band antennas utilizing shared aperture array which works in S-band, X-band and Ku-band, where three kinds of series-corporate microstrip antennas are interlaced on the flexible substrate. With the orthogonal polarization, layout of antenna arrays is optimized to ensure high channel isolation of antenna arrays’ different ports. The simulated results show the designed antennas having gain of 10.8 dBi, 11.8 dBi and 17.6 dBi respectively for S-band, X-band and Ku-band incidence. The side-lobe level (SLL) for S-band is -23.5 dB with return loss bandwidth of 50 MHz, while Ku-band antenna is -18 dB with bandwidth of 600 MHz respectively. And the bandwidth of circular polarization axial ratio (AR) less than 3 dB is around 1.1% for X-band. The isolation is better than - 40 dB among different ports of all arrays. Furthermore, the designed antennas can be flexibly covered on curved cylinder surface, maximum radiation gain is 2.4dBi, which is better than that of flat when the bending radius is 600mm for S-band. The proposed flexible microstrip antenna can be applied for conformal antennas, which shows great potential for flexible electronic device.
The extended depth of focus (DOF) of optical systems can improve the longitudinal range of imaging. Although it is possible to achieve a stable extension of the focal depth by using the traditional Inverse Quartic Axicon (IQAX) with the Seidel spherical aberration, its large volume and bulky structure prevent its application in small integrated optical systems. In contrast, a metasurface, with a small volume, thin thickness, and flexible control of light waves, provides a wider range of applications as extended DOF lenses. We have here developed a bifocal metalens with a polarization-dependent extended DOF. By combining the Pancharatnam – Berry phase with the spatial multiplexing method, the incident left circularly polarized light and right circularly polarized light were then focused on different transverse positions. The here-designed bifocal metasurface lens, with its extended DOF, can be applied in areas like multi-channel information encryption, optical imaging and detection.
KEYWORDS: Optoelectronics, Light emitting diodes, LED displays, Sensors, Automatic tracking, Infrared radiation, Lamps, Infrared detectors, Signal processing, Control systems
Driven by the idea of students-centered, aptitude-oriented cultivation, that is to educate each student according to his natural ability, the course content of the optoelectronic technology is optimized and integrated, and the extension project is added according to the ability of different students, which involves the scientific frontier and the practical training. To ensure the final implementation of the course reform, the assessment modes are designed and students are allowed to select their assessment test according to their interest and ability, just like a set menu. No matter what kind of assessment modes the students choose, all classmates are required to give an oral presentation about their extension project. The realization of multifaceted assessment enhances students’ participation and devotion to the course.
By imparting local, space-variant phase changes on an incident electromagnetic wave, metasurfaces are capable of manipulating lights. These surfaces have been constructed from nanometallic optical antennas as well as high-index dielectric antennas. We introduce a unique scalable Fourier transform 4-f system that is applied to lithography. We demonstrate the experimental realization of a flexible Fresnel element, where pixelated one dimensional gratings with space-variant frequencies and orientations are assembled in low-index material as the UV resin on polyethyleneterephthalate (PET) substrate, achieving good concentration performance in the visible spectrum.
A reflective color filter based on the standing-wave resonance is proposed, incorporating an asymmetric cross-shaped aluminum grating on top, a sandwiched silicon nitride layer and an aluminum mirror at bottom. By varying the length of grating arms or the polarization of incident lights, reflective colors as cyan, magenta and yellow can be obtained conveniently. Specially, reflections show good angular tolerance up to 60° for transverse electric polarization, while they demonstrate high sensitivity to incident angles of transverse magnetic polarization. Furthermore, the black color can be realized in reflection by encoding four gratings into one pixel at the optical diffraction limit. The color filter proposed here has great potential in applications as reflective LCD, full color printing and anti-counterfeiting.
A reflective color filter showing polarization dependent is proposed, where on a SiO2 substrate, a Si-grating is embedded inside a dielectric Si3N4 overlay. By varying the period of the grating, cyan, magenta and yellow (CMY) colors are gained for the transverse electric (TE) polarized incidence. With the polarization of incident light changed from TE polarization to transverse magnetic (TM) polarization, the structure’s reflective color varies accordingly. Therefore, the proposed structure has application prospects in the field of anti-counterfeiting and color display.
A reflective color filter based on the micro-cavity incorporating a nanostructure is proposed, which consists of a nano-metallic grating, a dielectric layer and an aluminum (Al) film. By varying the duty cycle of the metallic grating, red, green and blue (RGB) colors can be obtained for the transverse electric (TE) polarized incidence, having a good angular tolerance up to 30°. While these structures show different colors for transverse magnetic (TM) polarized light, and the color difference caused by polarization changes with the duty cycle chosen in different range. Therefore, the proposed structure demonstrates distinct reflections with different duty cycles, which can be utilized for reflective color displays as well as anti-counterfeiting devices.
In view of some problems about the traditional photoelectric specialty experimental teaching process, such as separation of theoretical teaching and practical teaching, immobilization of experimental teaching contents, low quality of experiments and no obvious effect, we explored and practiced a new experimental teaching model of "theoretical teaching, virtual simulation and physical experiment", which combined the characteristics of photoelectric information science and engineering major and the essential requirements of engineering innovation talents cultivation. The virtual simulation experiment platform has many advantages, such as high performance-to-price ratio, easy operation and open experimental process, which makes virtual simulation combine physical experiment, complete each other with virtual for practical. After the users log into the virtual simulation experimental platform, they will first study the contents of the experiment, clarify the purpose and requirements of the experiment, master the method of using the instrument and the relevant notes, and then use the experimental instruments provided by the platform to build the corresponding experimental system. Once the experimenter's optical path is set incorrectly or the instrument parameters are set incorrectly, the error or warning message will be automatically triggered, and the reference information will be given instructing the student to complete the correct experimental operation. The results of our practice in recent years show that the teaching reform of the photoelectric specialty experiments has not only brought great convenience to the experimental teaching management, broadened the students' thinking and vision, enhanced the students' experimental skills and comprehensive qualities, but also made the students participate in the experiment with their enthusiasm. During the construction of experiment programs, the students' engineering practical ability and independent innovation awareness has been improved greatly. In the next time, based on the development trend of optoelectronic discipline and our own major characteristics, we will further perfect and enrich the construction of virtual simulation experimental platform and continuously improve the quality of experimental teaching.
As one of the "excellent engineer education program" of the Ministry of Education and one of the characteristic majors of Jiangsu Province, the major of optoelectronic information science and engineering in Soochow University has a long history and distinctive features. In recent years, aiming to the talents training objective of "broad foundation, practiceoriented, to be creative", education and teaching reforms have been carried out, which emphasize basis of theoretical teaching, carrier of practical training, promotion of projects and discussion, and development of second class. By optimizing the teaching contents and course system of the theoretical courses, the engineering innovative talents training mode based on the project-driven has been implemented with playing a practical training carrier role and overall managing the second class teaching for cultivating students’ innovative spirit and practical ability. Meanwhile, the evaluation mechanism of the students' comprehensive performance mainly based on "scores of theory test" is being gradually changed, and the activities such as scientific research, discipline competitions and social practices are playing an increasing important role in the students' comprehensive assessment. The produced achievements show that the proposed training model based on project-driven could stimulate the students' enthusiasm and initiative to participate in research activities and promote the training of students' ability of engineering practice and consciousness of innovation.
Color filters based on different Fabry-Perot structures are investigated extensively, and incident angle dependency is an important characteristic in practical applications. Here, we investigated a color filter incorporating a Fabry-Perot structure, discussing its reflective angular sensitivity related to refractive index of its dielectric material. By finite difference time domain(FDTD) theory, the refractive index of the dielectric material is found to influence the angular sensitivity greatly while the optical thickness keeps constant. The simulated results shows that the higher the dielectric layer’s refractive index is, the more angular insensitive of the reflection will be obtained and a good angular insensitive will achieved when the refractive index is larger than 2.1. Finally, samples with different dielectric layer are fabricated in experiment and the measured results verify influence of the refractive index of dielectric layer on the spectra angular sensitivity, which is helpful for the application of color filter in color display, image sensors and decoration.
A printable color filter based on the photonic micro-cavity incorporating a nanostructure is proposed, which consists of a nano-metallic grating, a dielectric layer and aluminum (Al) film. According to the resonance induced by different dielectric depths of the micro-cavity, two dielectric heights for the same resonant wavelength are chosen to form the grating heights relative to the Al film. With the contribution of the cavity resonance and the surface plasmon resonance, the proposed structure performs enhanced broadband filtering characteristics with good angular tolerance up to 48° compared to the one of the micro-cavity as well as the one of the metallic grating. Therefore, reflective filters for RGB colors are designed incorporating the proposed structure. Furthermore, for the proposed structure shows great polarization dependence even at normal incidence, it can also be utilized as an anticounterfeiting certificate.
An ultra-flexible and low-sheet resistance transparent conductive film is developed from nickel metal-mesh (Ni metal-mesh) embedded in a polyimide (PI) by exploiting selective deposition technique coupled with photolithography and subsequent inverted film-processing method. The fabricated conductive film achieved sheet resistance values as low as 0.15 Ω sq-1, with corresponding optical transmittance as 80% at 550 nm corresponding the figure of merit up to 1.1×104. The film shows excellent adhesion and also preserves its structural integrity and good contact with the substrate for severe bending showing less than 4% decrease of conductivity even after 104 cycles. Finally, employing the fabricated Ni metal-mesh/PI conductive film, a hybrid transparent thin-film heater is demonstrated, which exhibited higher heating temperatures (110°C) under the lower operating voltage (1 V), lower power consumption (79.1°C cm2 W-1), and shorter response time (T < 2 s) than other heaters, as well as stability after repeated test.
We numerically and analytically report an ultra-broadband near perfect absorber based on one-dimensional metal-dielectric-metal grating at visible light for TM polarization. A unit cell of this design is composed of metal-dielectric-metal grating, where the bottom metallic layer and the upper metallic coating are separated from each other by the intermediate dielectric grating. The absorber exhibits an average absorption of over 90% in the range 400-700nm. Moreover, they remain very high over a wide range of incident angle up to 45°.The electromagnetic field distributions are investigated, which reveals that this broadband absorption behavior is ascribed to the combination of surface plasmon resonance and cavity resonance. Furthermore, impedance calculations were carried out to explain the absorption behavior. The ultra-broadband near-perfect angle-robust absorber can be a good candidate for many fascinating applications, including solar-energy harvesting as well as producing artificial colors on a large scale substrate.
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