We study on the joint training mode of optical engineering (OE) master in the ways of teaching, scientific research and practice cooperation. Our goal is to enhance the abilities and research level of OE graduate students by establishing the joint training cooperation with the domestic or foreign high level universities, the top research institutes and the famous enterprises, and to let more and more graduate students enter the high level universities and companies. In addition, we want to create the training quality evaluation index and evaluation system of the OE master students to evaluate this joint training mode.
Guided-mode resonance filter (GMRF) with variable bandwidth using coupling gratings near the Brewster angle is presented. For the contact coupling gratings, the bandwidth of the GMRF can be significantly altered with the resonance location kept almost the same as the transverse shift is varied. The resonance location blue-shifts with the increase of the air gap thickness in both cases of S=0 and S=0.5. The filter bandwidth is increased exponentially with the increase of the air gap thickness at the aligned condition due to the decreased mode confinement. In the case of the maximum misaligned condition, the filter bandwidth is reduced exponentially with the increase of the air gap thickness due to the decreased mode coupling between the two misaligned gratings. The spectral response of the coupling gratings coincides with each other for both the aligned condition and the maximum misaligned condition when the thickness of the air gap is large enough. The resonance location almost does not move as it approaches the cutoff wavelength of the substrate. The sideband level is kept low as the transverse and horizontal shifts are varied due to the Brewster antireflection (AR) effect.
We propose an ultra-compact graphene-based plasmonic modulation that is compatible with complementary metaloxide- semiconductor processing. The proposed structure uses a monolayer graphene as a mid-infrared surface waveguide, whose optical response is spatially modulated using electric fields to form a Fabry-Perot cavity. By varying the voltage acting on the cavity, the transmitted wavelength of the device could be controled at room temperature. The finite element method (FEM) has been employed to verify our designs. This design has potential applications in the graphene-based silicon optoelectronic devices as it offers new possibilities for developing new ultra-compact spectrometers and low-cost hyperspectral imaging sensors in mid-infrared region.
The phenomenon of plasmon-induced transparency (PIT) is realized in surface plasmon polariton waveguide at the visible and near-infrared ranges. By adding one and two resonant cavities, the PIT peak(s) was (were) achieved due to destructive interference between the side-coupled rectangle cavity and the bus waveguide. The proposed structures were demonstrated by the finite element method. The simulation results showed that for three rectangle resonators system, not only can we manipulate each single PIT window, but also the double PIT windows simultaneously by adjusting one of the geometrical parameters of the system; for four rectangle resonators system, by changing the widths, the lengths and the refractive index of three cavities simultaneously, we would realize treble PIT peaks and induce an off-to-on PIT optical response. Our novel plasmonic structures and the findings pave the way for new design and engineering of highly integrated optical circuit such as nanoscale optical switching, nanosensor and wavelength-selecting nanostructure.
In this paper, we investigate a monolayer graphene placed on a doped-silicon grating numerically and studied the
dependence of its transmission spectra on the geometrical parameters of the grating. A stop-band with great tunability in
the mid-infrared region of the transmission spectra are obtained in a much more compact structure size compared to a
traditional fiber Bragg grating (FBG). In addition, by inserting a defect into the center of the structure, we introduce a
phase shift of π phase shift into the field, leading to an open window in the stop-band transmission spectra. With the
good tunability and compact size, our proposed structure can be utilized as graphene-based ultra-compact and highly
sensitive plasmonic senors for potential applications.
A novel hybrid plasmonic waveguide of the graphene-coated V-groove and waveguide structure is proposed. The
subwavelength confinements and the propagation of the graphene surface plasmon polaritons modes of the hybrid
graphene-coated waveguide are reached. The mode field energies can be well confined in the V-groove or the waveguide
and be adjusted by varying the chemical potential of graphene. The mode confinement becomes weaker and the
propagation length gets longer as the chemical potential of grapheme increasing. In addition, adjusting the radius of the
waveguide and the frequencies could change the mode propagation and the higher mode is achieved. The finite element
method (FEM) has been employed to study the mode distributions and electromagnetic responses of our designs at midinfrared
Electromagnetically induced transparency (EIT) has been proposed numerically in the plasmonic waveguides composed of unsymmetrical slots shaped metal–insulator-metal (MIM) structures. By the transmission line theory and Fabry-Perot model, the formation and evolution mechanisms of Plasmon induced transparency are exactly analyzed. The analysis shows that the peak of EIT-like transmission can be changed easily according to certain rules by adjusting the geometrical parameters of the slot structures, including the coupling distances and slot depths. We can find a new method to design nanoscale optical switch, devices in optical storage and optical computing. It is found that the slow light effects are emerged in the unsymmetrical slot structures. A small group velocity(c/80) can be achieved.
We have proposed a couple of plasmonic devices based on graphene sheets and ring resonators. The highly frequency-tunable multi-mode plasmonically induced transparency (PIT) device based on monolayer graphene and rings for the mid-IR region is presented in theory firstly. The multi-mode transparency windows in the spectral responses and slow light effects can be achieved in plasmonic configuration composed of two graphene resonators coupled with single-layer graphene waveguide. By varying the Fermi energy of the graphene, the multi-mode PIT resonance can be dynamic controlled without reoptimizing the geometric parameters of the structures. Based on the coupled mode theory (CMT) and Fabry-Perot (FP), we numerically investigated direct coupling and indirect coupling in the graphene-integrated PIT systems. In addition, the theoretical plasmonic devices based on graphene sheets and ring resonators are also proposed to perform as 1×2 optical spatial switch or ultra -compact Mach-Zehnder interferometer. The finite element method (FEM) is carried on to verify our designs. Those designs may pave the ways for the further development of the compact high-performance plasmonic communication devices.
The image quality in off-axis digital holography (DH) is often degraded by inaccuracies in the reference wave used for reconstruction and the spatial filtering adopted to avoid twin images and zeroth order diffraction. To enhance the image quality in such cases, coherent diffraction imaging is combined with a DH technique to iteratively reconstruct the hologram. By using a small aperture on the sample plane as a spatial constraint and the recorded diffraction pattern as an intensity constraint, a higher spatial resolution than usual is obtained with the proposed method.
Automatic Linguistic Annotation is a promising solution to bridge the semantic gap in content-based image retrieval.
However, two crucial issues are not well addressed in state-of-art annotation algorithms: 1. The Small Sample Size (3S)
problem in keyword classifier/model learning; 2. Most of annotation algorithms can not extend to real-time online usage
due to their low computational efficiencies. This paper presents a novel Manifold-based Biased Fisher Discriminant
Analysis (MBFDA) algorithm to address these two issues by transductive semantic learning and keyword filtering. To
address the 3S problem, Co-Training based Manifold learning is adopted for keyword model construction. To achieve
real-time annotation, a Bias Fisher Discriminant Analysis (BFDA) based semantic feature reduction algorithm is
presented for keyword confidence discrimination and semantic feature reduction. Different from all existing annotation
methods, MBFDA views image annotation from a novel Eigen semantic feature (which corresponds to keywords)
selection aspect. As demonstrated in experiments, our manifold-based biased Fisher discriminant analysis annotation
algorithm outperforms classical and state-of-art annotation methods (1.K-NN Expansion; 2.One-to-All SVM; 3.PWC-SVM) in both computational time and annotation accuracy with a large margin.