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ABSTRACT: The chiral structures have displayed some inevitable and fascinating properties in many research fields, such as chemistry, biology, mathematics and physics. In this paper, we report the use of step-wise glancing angle deposition technology to produce the 3D chiral nano-structures. Through the optimization of deposition parameters (such as the orientation angle of poly-styrene spheres (PSs) array, the deposition angle, thickness and number), a great number of chiral structures has been achieved, and their size is depended on the diameter of PS spheres. These chiral structures all can be simulated and predesigned through the use of a 3D geometrical model, which greatly improves the efficiency of this method. In addition, the circular dichroism spectrum shows that these chiral structures own obvious Cotton effect, indicating their potential application as 3D chiral metamaterials.
Langmuir 12/2012; · 4.19 Impact Factor
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ABSTRACT: We propose a new direct writing nanolithography approach using a plasmonic focusing device and a nano silver mirror with dual-wavelength illumination for high exposure depth. Arrays of pyramid aperture are used to focus the incident light beams into 80 nm light spots. The pyramid combined with a thin silver film coated on the substrate constructs a surface plasmon polaritons (SPP) coupling cavity, which amplifies the intensity of the light field in it by SPP effect and resonance. The transmission depth of the standing wave formed by forward and reflected light could reach hundreds of nanometers. Two lasers with different wavelengths are used as illumination sources to homogenize the light field through complementation between the two standing waves. Simulation results show by using 355 nm and 441 nm wavelengths, a space of 44 nm at the bottom of the photoresist could be obtained after exposure and development. The feature size of resist patterns could be further scaled down, depending on the optimization of parameters of photoresist exposure and development, illumination wavelengths, etc.
Optics Letters 01/2012; 37(2):247-9. · 3.40 Impact Factor
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ABSTRACT: A general conformal transformation method (CTM) is proposed to construct the conformal mapping between two irregular geometries. In order to find the material parameters corresponding to the conformal transformation between two irregular geometries, two polygons are utilized to approximate the two irregular geometries, and an intermediate geometry is used to connect the mapping relations between the two polygons. Based on these manipulations, the approximate material parameters for TE and TM waves are finally obtained by calculating the Schwarz-Christoffel (SC) mappings. To demonstrate the validity of the method, a phase modulator and a plane focal surface Luneburg lens are designed and simulated by the finite element method. The results show that the conformal transformation can be expanded to the cases that the transformed objects are with irregular geometries.
Optics Express 08/2011; 19(16):15119-26. · 3.59 Impact Factor
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ABSTRACT: We have recently shown that patterns with 30 nm line width and micrometer scale periodicity could be steadily fabricated by employing localized surface plasmons lithography based on a soft mold [Opt. Lett. 35, 13 (2009)]. In this paper, the dependence of the resolution (pattern periodicity), critical dimension, and electric field intensity on the geometrical parameters of the soft mold, such as ridge width, mold periodicity, ridge depth, and slope, have been systematically studied and analyzed. The relevant simulation results by finite-difference time-domain demonstrate that the critical dimension exhibits a perfect stabilization and the value of electric field intensity would be especially large, when the ridge depth is in the range from 100 to 270 nm and the slope angle is below 35°. Importantly, the optimal resolution and critical dimension can reach 100 and 17 nm, respectively, by reasonably designing the corresponding mold periodicity and ridge width, which indicates that the method is particularly suitable for obtaining patterns with high density and is extremely promising for bio-sensing and photonic crystals application.
Applied Optics 05/2011; 50(13):1963-7. · 1.41 Impact Factor
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ABSTRACT: For the experiments of surface plasmon polaritons (SPPs) interference lithography based on attenuated total reflection-coupling mode to be done conveniently, we introduce a backside-exposure technique in this paper. The physical mechanisms of SPPs interference with the backside -exposure method are studied and the interference fringes with feature size below 65 nm are experimentally obtained. The technique can be used to fabricate nanostructures conveniently with large area, and avoids the difficulties for seeking high refractive prism and matching fluid.
Optics Express 07/2010; 18(15):15975-80. · 3.59 Impact Factor
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ABSTRACT: Three-dimensional (3D) nanoscale focusing of radially polarized light in far field by a simple plasmonic lens composed of an annular slit and a single concentric groove is reported. The numerical calculations reveal that the incident light is coupled to surface plasmon polaritons (SPP) by the annular slit and a focal spot with a size less than a half of the illumination wavelength is formed in the far field due to the constructive interference of the scattered light by the groove. More importantly, the focal length can be modulated by changing the groove diameter. This structure provides an admirable choice for the nano-optical devices.
Optics Express 07/2010; 18(14):14664-70. · 3.59 Impact Factor
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ABSTRACT: We propose a photolithographic method to fabricate nanostructures by employing a localized surface plasmon (LSP) mask generated by a soft mold on a thin metal film. The soft mold can be formed by transparent materials, such as polydimethylsiloxane, contacting firmly to the metal film. The pattern edges of the mold, serving as the fine tapers, can be used to excite LSPs and accumulate a large amount of localized energy from the incident light field, providing a modulated optical field in the resist with nanometer feature size. Nanolithographic results with a minimum feature size of 30 nm are demonstrated.
Optics Letters 07/2010; 35(13):2143-5. · 3.40 Impact Factor
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ABSTRACT: In the surface plasmon polaritons (SPPs) interference lithography, the scattering effect caused by the rough surface of silver film deteriorates the quality of lithography patterns. Research shows that under this condition the light field in the photoresist is not the results of SPPs interference but comes from the SPPs assisted imaging in which the scattered light propagates from the upper surface of the silver film to the photoresist. The near-field optical transfer function (NOTF) is used to study this process and a method of evaluating the imaging quality is presented. The validity of NOTF is verified by both SPPs assisted interference imaging experiments and simulations by the FDTD. It is also shown that the NOTF method is not only a convenient approach to describe the nano-scale information transmission in the near-field but also a good method to optimize experimental parameters.
Optics Express 05/2010; 18(10):10685-93. · 3.59 Impact Factor
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ABSTRACT: An idea is proposed to convert optical information of the near field into propagation waves by an isosceles triangle phase-grating coated metal film for super-resolution imaging. We analyzed the reverse process of exciting surface plasmon polaritons (SPPs) by attenuated total reflection coupling mode, and found it was possible and effective to transfer the nanoscale information from near field to far field by the special phase grating. In this article, the excitation mechanisms of the SPPs and the details of the high-efficiency coupling output of the near-field light waves were explored. A special coupling microstructure was designed so that the near-field information could be collected in the far field. We also built an optical transfer function of the superlens imaging system, and reconstructed the simulation image of nanoscale object. Analysis and calculation shows that the isosceles triangle phase-grating coated metal film plays an important role in far-field imaging beyond the diffraction limit, namely, converting evanescent waves to propagating waves and changing the direction of the optical wave by the phase modulation. The methods provide a way to quickly get the near-field information without complicated requirements.
Journal of Applied Physics 09/2007; 102(7):074301-074301-6. · 2.17 Impact Factor
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ABSTRACT: Large-area surface-plasmon polariton (SPP) interference lithography is presented, which uses an attenuated total reflection-coupling mode to excite the interference of the SPPs. The interference of the SPPs causes a highly directional intensity range in a finite depth of the electric field, which is good for noncontact. Finite-difference time-domain simulations of the interference on a thin resist layer show that broad-beam illumination with a p-polarized light at a wavelength of 441 nm can produce features as small as 60 nm with high contrast, smaller than lambda/7. Our results illustrate the potential for patterning periodic structures over large areas at low cost.
Optics Letters 10/2006; 31(17):2613-5. · 3.40 Impact Factor
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ABSTRACT: A new method to fabricate hybrid micro-optical elements in one-step lithography is proposed in this paper. A gray-tone coding method has been developed to achieve one step photolithography of achromatic hybrid micro-optical elements. Design and simulation of hybrid lens with grey-tone mask are presented. The aberrations of optical elements are pre-corrected in the lithography process. The operating range of the hybrid optical element is in infrared band (8.0∼12.0 μm) with the central wavelength at 10.6 μm.
Microelectronic Engineering.
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ABSTRACT: We propose to use two-dimensional metal hole-array (TMH) and spatial light modulator (SLM) technology to construct a parallel direct-writing system. SLM and movable platform are used to control the system for realizing multi-beam parallel scanning exposure to fabricate arbitrary patterns. In this system TMH is the key component which focuses the incident light beams into light spots in the photoresist by exciting local surface plasmon polariton (LSPP). Parameters of TMH are optimized to improve the focusing efficiency and transmission depth of the light spots. Theoretical analysis and numerical simulations show that the feature size and transmission depth can reach sub-80 nm and 90 nm, respectively, by an optimized TMH, which is feasible for parallel direct writing lithography.
Microelectronic Engineering 88(8):1931-1934. · 1.56 Impact Factor
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ABSTRACT: Large-area surface plasmon polariton interference lithography (LSPPIL) is a promising nano-fabrication technique for making periodic nano-patterns. In this paper, for reducing further the feature size of a lithography pattern, we propose to use 193 nm illumination wavelength in LSPPIL and replace the silver coating by tungsten. Theoretical analysis and preliminary numerical simulations indicate that 193 nm-LSPPIL can produce periodic patterns with a critical dimension as small as 30 nm with high contrast and enough long exposure depth. 193 nm interference nanolithography based on SPP has the potential to realize the 32 nm node periodic nano-structure manufacture.
Microelectronic Engineering 85:754-757. · 1.56 Impact Factor
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ABSTRACT: The aperture-coded or multilevel phase grating can obtain higher diffraction efficiency for laser beam shaping than general binary phase grating (BPG). In this paper, a multiple phase grating (MPG) for coherent addition of 5 × 5 laser beams is designed. The grating can be fabricated by the gray-tone photolithography technology, which employs the computer controlled spatial-light-modulator (SLM) as a mask. This fabrication method is simple, cheap and some aberrations in photolithography process can be reduced in one-step exposure. We have simulated the exposure dose of the gray-tone photolithography for fabricating the multilevel phase grating, and the effects of fabrication error were analysed. The simulation results showed that the coupling efficiency of MPG for laser beams was 78.74%.
Microelectronic Engineering 83:1368-1371. · 1.56 Impact Factor
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ABSTRACT: A new spatial filtering technique is proposed for improving image contrast and depth of focus in projection photolithography. The technique is based on fractional Fourier domain filtering. Unlike the current pupil filtering method, the fractional filter can be placed at any location along the projection optical path other than the pupil plane. The theory of partial coherent diffraction combined with fractional Fourier domain filtering is presented. Phase filters for contact hole and line-space patterns have been designed. Computer simulation of complete imaging process including fractional Fourier domain filtering have been carried out. The simulation has demonstrated that the new filtering technique can significantly improve image fidelity, reduce the optical proximity effect and increase the depth of focus. Because of the flexibility in filter location, it is predicted to be easier to implement in a practical optical lithography system.
Microelectronic Engineering · 1.56 Impact Factor
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ABSTRACT: Distortion effects in alternating phase shift masks on wafer level imaging have been investigated using a combined simulation of the photomask patterning process and projection optical lithography. Unlike the previous simulation of the optical proximity effect, which were based on ideal mask designs, the simulation presented in this paper is based on distorted mask features. The mask feature distortion comes from simulation of laser scanning lithography. Proximity effects in laser direct writing has been taken into account for the generation of mask features. The simulations have demonstrated that phase shift masks also suffer from the optical proximity effect. The effect is worsened if mask distortion is taken into account. Compared with no phase shifting masks, phase shifting in mask features can slightly offset the proximity effect.
Microelectronic Engineering · 1.56 Impact Factor
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ABSTRACT: A new method has been developed to design gray-tone masks for microlens fabrication. Unlike previous methods which modulate the light intensity by changing the cell size or cell pitch only, the method relays on adjusting both the shape and position of a cell which gives an extra freedom to control the design accuracy. Based on the theory of partial coherent light and the resist development model, the intensity distribution through the gray-tone mask and exposure of photoresist have been simulated. Nonlinear effects in aerial image and resist development have been take into account to correct the mask design. A grey tone mask for microlens array has been fabricated and printed by a g-line stepper. Hemispherical photoresist structures have been achieved.
Microelectronic Engineering.
