Song Hu

Microwave metamaterial absorber based on multiple square ring structures

In this paper, we report the design, analysis, and simulation of quintuple-band metamaterial absorber (MMA) in the microwave region. The absorber is constructed of a delicate periodic patterned structures and a metallic background plane, separated by a dielectric substrate. By manipulating the periodic patterned structures, high absorption can be obtained at five specific resonance frequencies. Moreover, the significantly high absorptions of quintuple-peaks are persistent with polarization independence, and the influence of angle of incidence for both TE and TM modes was also elucidated. For explaining the absorption mechanism of proposed structures, the electric and magnetic field distributions and resistance matching principal were given. Importantly, the design idea has the ability to be extended to other frequencies, like terahertz, infrared and optical frequencies.

Low-frequency metamaterial absorber with small-size unit cell based on corrugated surface

In this paper, we report the design, analysis, and simulation of the low-frequency perfect metamaterial absorber (MMA) based on corrugated surface, which has very small unit-cell size. The proposed MMA consist of a regular square-array and a metallic background plane, separated by a corrugated surface with periodic square-pillar-array. Through the optimized design, the ratios between lattice constant and resonance wavelength for nearly-perfect and high absorption MMA are close to 1/15 and 1/21, respectively. To explain the absorption mechanism of suggested structures, the surface current and electromagnetic field distributions are given. Moreover, the absorption peaks remain high with large angles of incidence for both transverse electric and transverse magnetic polarizations, which provide more efficient absorptions for oblique incident electromagnetic wave.

Moire interferometry with high alignment resolution in proximity lithographic process

Moiré interferometry is widely used as the precise metrology in many science and engineering fields. The schemes of moirés-based interferometry adopting diffraction gratings are presented in this paper for applications in a proximity lithographic system such as wafer-mask alignment, the in-plane twist angle adjustment, and tilts remediation. For the sake of adjustment of lateral offset as well as the tilt and in-plane twist angle, schemes of the (m,-m) and (m,0) moiré interferometry are explored, respectively. Fundamental derivation of the moiré interferometry and schemes for related applications are provided. Three pairs of gratings with close periods are fabricated to form the composite grating. And experiments are performed to confirm the moiré interferometry for related applications in our proximity lithographic system. Experimental results indicate that unaligned lateral offset is detectable with resolution at the nanometer level, and the tilt and in-plane twist angle between wafer and mask could be manually decreased down to the scope of 10(-3) and 10(-4)u2009u2009rad, respectively.

Spectrum-Integral Talbot Effect for UV Photolithography With Extended DOF

A route of spectrum-integral Talbot lithography (SITL) with extended depth-of-focus (DOF) for microfabrication of periodic structures was explored under broadband incoherent illumination in this letter. The transmitted diffraction fields by different spectral components integrate together to generate the successive periodicity since certain distance along the direction of propagation. The mechanism of DOF extension was derived and numerically elucidated using the spectrum of a practical ultraviolet source. Experiments of proximity lithography in term of the numeric results were performed to record the intensity distributions within the DOF area. Finally, the results reveal the validity of SITL and its potentials in high-fidelity lithography of periodic micropatterns with almost unlimited DOF and thus enhanced resolution.

Focusing Properties of Single-Focus Photon Sieve

In this letter, we present a single-focus photon sieve (SFPS), which can produce single focus with suppressed sidelobes, featuring a higher signal-to-noise ratio and improved image contrast. This is achieved through combining single-focus zone plates (SZPs) and photon sieves (PSs). Simulations and experiments were conducted to verify the single focusing property of SFPSs. The results illustrated the advantages of SFPSs over conventional PSs, as well as improved resolution compared with SZPs in terms of the same specific minimum feature size. SFPSs are extremely promising to replace PSs and Fresnel zone plates in the fields such as X-ray focusing, imaging, and nanometer lithography.

Nanobowl Array Fabrication via Conglutination Process Based on Thiol–Ene Polymer

The technique to fabricate nanostructures with high resolution is of crucial importance to nanosciences and nanotechnology. This paper presented a nonconventional method to fabricate metallic nanobowl arrays via the conglutination process, which relied on the high adhesive material to “stick” nanostructures. The ultraviolet (UV)-curable thiol-ene had low viscosity and was cured under UV light to form a cross-linked polymer with high Youngs modulus and high surface energy via “click chemistry,” which was used as the adhesive material to firmly stick nanostructures from the mold. By using the method, a self-assembly polystyrene (PS) sphere template with a metallic layer was stuck by the cross-linked thiol-ene polymer from the substrate. After removing the PS spheres, the metallic nanobowl structure with the thiol-ene substrate was achieved. In this paper, we fabricated gold nanobowl arrays composed of nanoheaves with the average diameter of ca. 60 nm between nanobowls, which verified the feasibility of the fabrication method.

Scalar-Based Analysis of Phase Gratings Etched in the Micro/nanofabrication Process

The diffraction characteristics of several types of phase gratings often etched on the substrate by the micro/nanofabrication techniques are analytically explored using scalar-based analysis in this paper. The process of an incident wave being reflected or transmitted by the diffraction grating is regarded as a process of modulation, and the reflectance or transmittance can be unified as the modulation index. The mechanisms of phase modulation, amplitude modulation, and the amplitude-phase hybrid modulation in different situations are discussed. Analytical results indicate that the diffraction efficiency is directly determined by the phase difference of adjacent features, i.e., the cyclically distributed ridges and grooves that induce different phase and amplitude variations. The absolute phase grating with phase difference equivalent to π has the maximum diffraction efficiency among all types of gratings. The conclusions could, in general, provide guidance for the design and micro/nanofabrication of phase gratings for many diffraction-based applications of optical metrology or imaging.

Fabrication of nano-pillar with sub-100nm resolution based on thiol-ene

This paper demonstrates an approach to fabricate nano-pillar based on thiol-ene via soft-lithography. The template is anodic aluminum oxygen (AAO) with ordered nano-holes with the diameter of 90nm.The nano-pillar consists of rigid thiol-ene features on an elastic poly(dimethylsiloxane) (PDMS) support. It is capable of patterning both flat and curved substrate. The thiol-ene is a new green UV-curable polymer material, including a number of advantages such as rapid UV-curing in the natural environment, low-cost, high resolution, and regulative performance characteristic. Here, we fabricated a two-layer structure, which included rigid thiol-ene nano-pillar with sub-100nm resolution and soft PDMS substrate. The experiment results show that this approach can be used to fabricate high-resolution features and the thiol-ene is an excellent imprint material. The fabrication technique in this paper is simple, low-cost, high-resolution and easy to high throughput, which has broad application prospects in the preparation of nanostructures.

Fabrication of resonant subwavelength grating based on thiol-ene

This paper presents an approach used to fabricate resonant subwavelength grating based on thiol-ene material. First of all, polydimethylsiloxane soft imprint stamp with opposite structure of the subwavelength grating master mold is made by casting. Then, the desired subwavelength grating with UV-curable thiol-ene material grating structure is fabricated using the polydimethylsioxane soft stamp by UV-curable soft-lithography. Here, we fabricate a subwavelength grating with period of 300nm using the approach, which could reflect blue light with wavelength ranging from 448nm to 482nm at a specific angle and presents the excellent resonant characteristic. The experimental results are consistent with the simulation results, demonstrating that the approach proposed in this paper could effectively fabricate the thiol-ene material resonant subwavelength grating structure. The thiol-ene material is a new green UV-curable polymer material, including a number of advantages such as rapid UV-curing in the natural environment, low-cost, high resolution, and regulative performance characteristic. The fabrication technique in this paper is simple, low-cost, and easy to high throughput, which has broad application prospects in the preparation of micro and nano structures.

Designing continuous-phase super-resolving filters by differential evolution and conjugate gradient method

Abstract. A method for designing a class of phase-only super-resolving filters with continuous-phase that can be described by a sum of Zernike polynomials with weight coefficients is presented. With the use of the global search algorithm, differential evolution method, and the local search algorithm, the conjugate gradient method, three filters were designed as examples. The main-lobe size of the point spread function of the three filters can be reduced, keeping allowable central intensity and sidelobe intensity for some typical applications. This type of filter has the advantage of lower scatter compared with other phase-only filters composed of discontinuous phase. In particular, such filters can be implemented dynamically by a phase-controlling device.