Melamine is an insalubrious chemical, and has been frequently added into milk products illegally, to
make the products more protein-rich. However, it can cause some various diseases, such as kidney
stones and bladder cancer. In this paper, a novel optical fiber sensor with high sensitivity based on
absorption of the evanescent field for melamine detection is successfully proposed and developed.
Different concentrations of melamine changing from 0 to 10mg/mL have been detected using the
micro/nano-sensing fiber decorated with silver nanoparticles cluster layer. As the concentration
increases, the sensing fiber’s output intensity gradually deceases and the absorption of the analyte
becomes large. The concentration changing of 1mg/ml can cause the absorbance varying 0.664 and the
limit of the melamine detectable concentration is 1ug/mL. Besides, the coupling properties between
silver nanoparticles have also been analyzed by the FDTD method. Overall, this evanescent field
enhanced optical fiber sensor has potential to be used in oligo-analyte detection and will promote the
development of biomolecular and chemical sensing applications.
A 19 element segmented MEMS deformable mirror(DM) based on electrostatic repulsive-force actuator is proposed and
fabricated using a commercial surface micromachining process PolyMUMPs. Impacts of different sizes of actuator on
DM’s characterizations such as stroke, work bandwidth, driving voltage and fill factor are analyzed and optimized. An
analytical analysis combined numerical simulation has been performed on the deformation of repulsive flexural beam
actuator regarding actuator size and boundary condition. These analytic insights could provide guidelines for future
MEMS DMs optimum design. A maximum stroke of the fabricated DM is 2.6μm, is larger than 2μm for the sacrificial
layer thickness of PolyMUMPs. The preliminary aberration correction of the whole DM array is also analyzed.
Compared to conventional MEMS DMs, this design demonstrates the advantage of large stroke over a standard surface
micromachining fabrication process with a thin deposited layer, and it would expand the application of MEMS DMs in
We report on transmission enhancement and suppression in rectangular aperture arrays at terahertz range. Experiments
and simulations reveal that transmission maxima and minima of metal film perforated with rectangular apertures arrays
are caused by the shape resonance and the interference between surface waves respectively. To further investigate the
relative contributions of shape resonance and interference between SPPs, we have examined the density of electrons
whose distribution property is identified to the normal component of E-filed which clearly shows that transmission
resonance stems from excitation of shape resonance at the edge of the hole. This resonance dominated by cutoff function
is responsible for resonance peak at transmitted spectrum. The interference of SPPs originated at surface further
enhances the resonances and gives a set of minima in the transmittance spectrum. This study contributes a better
understanding of fundamental physics behind the extraordinary transmission of aperture arrays at THz range and
provides a simple method for the design of THz devices.
A new pyramid wavefront sensor (PWFS), which utilizes a reflective pyramid mirror instead of a refractive pyramid prism at the focus of a telescope, is presented. As a key optical component in this PWFS, the pyramid mirror requires accurate microfabrication for excellent quality of the tip, the turned edges, and the surfaces. The moving mask lithography process is proposed for its economic, simple, and precise control to make the cross-sectional shape of the structure. The completed pyramid mirror has a square base of 1-mm length and four side facets inclined to the base at 3.7 deg. The sizes of the pyramid tip and turned edges are both about 6 µm, which show excellent aspects of sharpening-tip and knife-edges. The root mean square of four facets is approximately 70 nm, and the maximum profile deviation is 0.2 µm.
We design a dual axis rotary mirror based on microelectromechanical system technology used for the endoscopic optical
coherence tomography (OCT) application. With the inherent advantages of the micromachined device such as small size,
low consumption and high reliability, it allows the miniaturization of conventional bulky OCT probe. The dimension of
the micro-mirror is 140um×270um. Through use of finite element method, the simulation results show that the scanning
mirror is capable of high frequency out-of-plane rotation in two mutually independent axes. The natural frequencies of
the first two modes, corresponding to tip and tilt modes, are 65.74 KHz and 65.75 KHz respectively. The MEMS
scanning mirror is electrostatically actuated with the supply voltage ranging from 30v to 40v. Via 2-axis scanning, a
three-dimensional image of biological tissue can be acquired when the MEMS mirror is integrated with the OCT probe
system. The entire MEMS scanner can be fabricated using the proposed surface-micromachining process, capable of
is paper demonstrates a 2D (two-dimensional) electrostatic MEMS scanning mirror. This scanner rotates on both axis
X and Y, giving a two degrees of freedom. Finite element analysis has shown that optical scanning angle on axis X is
5.0° at 120V and axis Y is 4.4°at 160V. The structure has been optimized to achieve good dynamic performance.
MEMS deformable mirror (DM) has yet to be incorporated into a facility AO instrument especially for atmospheric
compensation. Apart from these drawbacks such as limited stroke, reliability, its optical efficiency should
also be concerted. The wavefront corrector in AO system should existing high optical efficiency especially atmospheric
compensation under faint stars. However the MEMS DM fabricated by surface process must have etch
holes in the surface of mirror. The diffraction results from etch holes decrease its optical efficiency. An MEMS
deformable mirror is fabricated by commercial PolyMUMPs. There is array of etch holes to ensure that the
sacrifice layer is released fully. The far field intensity distribution was simulated. The result has been analyzed
and used to constructed a simple modal of the studied MEMS DM.
A homogeneous aligned nematic liquid crystal (LC) cell can be used to phase modulate light. It has a series of
attractive characteristics of compactness, high density integration, low cost and possibility of batch production
in adaptive optics. However a problem has long existed for such devices is that they may be used only to control
the phase of light polarized along the LC extraordinary axis since only the extraordinary light index can be
varied by the application of the electric field. For a liquid crystal adaptive optics system using for astronomical
imaging, low level un-polarized light is collected by the telescope. So the high optical efficiency is important
and key factor for an adaptive optics system using for compensate atmosphere turbulence. If a polarizer placed
before LC, 50% of incident un-polarized light is wasted. In this paper, a simple method is detailed described
for phase modulating un-polarized light. Un-polarized light can be thought of as the superposition of any two
orthogonal polarization states that are mutually incoherent.
Iceland-spar OE crystal split incident un-polarized
light into two polarized light, two same LCs modulated these two polarized light separately. After that, both
these two polarized light beam are combined using another
Iceland-spar OE crystal. These double LC adaptive
optics system can phase modulate all incident un-polarized light, no light intensity is wasted.
For many astronomical systems, Adaptive Optics (AO) plays an important role. Here, we report some preliminary studies
on MEMS (Micro-Electro-Mechanical-System) Project for micro actuators in AO applications at the Institute of Optics
and Electronics, Chinese Academy of Science. This paper presents a few MEMS actuators based on repulsive
electrostatic driven mechanism, which can achieve large out-of-plane strokes through eliminating the electrostatic pull-in
effect. Design principles, including the layout and the physical dimension of electrodes, and FEA models are illustrated;
it provides helpful guidance for designing electrostatic repulsive actuators for being implemented in Deformable Mirrors
(DMs). Some repulsive electrostatic driven micro actuators are given, the analysis focus on the displacement versus
applied voltage and resonant frequency. Repulsive electrostatic driven actuators can achieve large strokes and high
resonant frequencies, they meet the important requirements for DMs.
This paper focuses on the study of sensitivities of microcantilever chemical sensors based on SOI POLYMUMPS
process. Through changing the geometry of beams and analyzing resonance frequency shift in a dynamic mode by using
FEA (finite element analysis) method, the most sensitive structure, which is a triangle, is selected out from various kinds
of beam designs. The relation between the sensitivity and the parameters such as length L, width W and thickness t is
obtained by dynamic analyzing with the commercial software Intellisuite. This research provides the primary instruction
for developing high sensitive multi-array biochips aiming at analyzing multiple parameters in parallel.
The Smart X-ray Optics project is a UK based consortium consisting of several institutions to investigate the application
of active/adaptive optics upon both small and large scale grazing incidence x-ray optics. The work done at University
College London (UCL) focuses on the application of piezoelectric materials to large scale optics in order to actively
deform the mirror's surface. These optics are geared towards the next generation of x-ray telescopes and it is hoped that
the project will be able to achieve a resolution greater than that currently available by Chandra (0.5"). One of the aims of
the consortium is to produce a working prototype. The initial design is based on a thin nickel ellipsoid segment with an
x-ray reflective coating, on the back of which will be bonded a series of piezoelectric actuators.
Investigation into the specification of the design of an active x-ray optic prototype and suitable support test structure has
been undertaken. The dimensions and constraints upon the prototype, and the manufacturing process to produce a nickel
shell are discussed. Finite element analysis (FEA) of the physical characteristics of piezoelectric materials has shown the
ability to deform the nickel surface to correct for errors of several microns. FEA has also been utilised in the
specification of the prototype's support structure to ensure that gravitational sag upon the optic is kept to a minimum.
Laboratory experiments have tested a series of materials, different actuators and bonding methods, which could then be
applied to the prototype.
The continuing size reduction of integrated circuits to nano dimensions requires the development of advanced
lithographic techniques. In order to obtain the desired feature sizes, it has become increasingly complex and high-cost to
use the established methods of optical projection lithography at short optical wavelengths. Surface-plasmon polariton
interference lithography (SPPIL) can provide a feasible way to achieve or approach the ultimate resolution for a certain
wavelength without requiring complicated and expensive large numerical aperture optics. But it demands the fabrication
of gratings with very fine period as a mask to realize contact printing, and the imaging quality is seriously dependent on
the structure and materials of the mask, the illuminating light, photoresist, etc. So the optimization of the technological
parameters is important to improve the imaging quality of nanolithography based on surface-plasmon polariton(SPP). In
this paper, the simulation of near-field distribution of SPPIL is performed using Finite Difference Time Domain FDTD
method, and the impacts of some technological conditions to the exposure field are analyzed including the polarization
state and wavelength of the illuminating light, the periodicity, thickness and slit width of the mask, and so on. The
simulation results show that, it is possible to fabricate good quality pattern with about 60nm features, with SPPIL using a
436nm-wavelength incident light.
Proc. SPIE. 5636, Holography, Diffractive Optics, and Applications II
KEYWORDS: Diffractive optical elements, Modulation, High power lasers, Error analysis, Near field, Near field diffraction, Optical damage, Laser systems engineering, Diffraction gratings, Amplitude modulation
Color Separating Grating (CSG) is one of the important Diffractive Optical Elements (DOE) used in the final optical system of high power laser system. Its periodic step-phase structure can separate the third harmonic frequency from base- and second-harmonic waves in the far field. But the structure abbreviations of CSG, caused by the fabrication process, generate great modulations to the laser beam, which may lead to severe optical damages to CSG itself and the system. In this paper, a comprehensive error model is built, in which each structural parameter of CSG is expressed as a variable, and the structural parameter error induced by fabrication process is expressed as minute disturb of relative variable. With this error model, the near field diffraction pattern of CSG is calculated based on Fresnel diffractive theory. Through simulation and analysis, we obtain the amplitude modulation of different harmonic waves in near field, and also the relationship between the amplitude modulation and the fabrication error. The results show that beam modulations are mainly caused by the stair depth error and the slope error. This study provides a convenient way to estimate the possibility of optical damages induced by CSG.
An optimized coding gray-tone mask method with multi-parameters is presented in this paper. Precise calculations, which are performed on the dead area in the backward reflection of the pyramid prism, demonstrate that the fringe error caused by the coding gray-tone mask has little affect on the performance of the pyramid prisms. This not only greatly reduce the resolution requirement of the coding gray-tone mask, but also reduce the errors produced by the exposure
process. A satisfying simulation result is obtained with the designed coding gray-tone mask.
Ultrasound has been demonstrated to be a perfect tool for NDT. There are several detectors that can be applied in NDT, for example fibre Bragg grating, interferometry, etc. Here we concentrate in polarimetric optical fibre detection.
In this paper we develop a simple but realistic analysis of the ultrasonic wavefront integration technique along an optical fibre for acoustic detection. Our model considers the perturbation caused by the acoustic wave as an isotropic change in the effective refractive index of the sensing fibre used as the detection system and neglects the polarization modulation. Also we assume the stress homoegeneous through the section of the fibre.
The theoretical analysis has been simulated in MATLAB. In this program we have analyzed the relation between the length of the sensing fibre, its distance to the ultrasound source and its sensitivity to ultrasound detection, for different orientations of the source with respect to the sensing fibre. The results indicate that optimum ultrasonic detection may be achieved through careful positioning and orientation of the optical fibre. These results may be applied, for example in NDT, where scattered ultrasound from defects introduces new effective sources that may be characterized by arrays of these integrating sensors.
Aiming at correcting chromatic aberrations in a far-infrared band, the fabrication of a hybrid microlens array with one-step lithography is proposed, by using a coding grey-level mask. The designed hybrid microlens consists of a refractive microlens and a diffractive microlens in physics. Its structure parameters, in order to achieve the best correction of chromatic aberrations, are evaluated and optimized with the software OSLO to design the layout the grey-level mask. Based on the theory of partial coherent light, the photoresist exposure model and development model, the profile of hybrid microlens in the photoresist have been simulated, the nonlinear errors in the lithography process can be pre-compensated by correcting the mask design. A hybrid microlens array is fabricated through use of the designed mask.
The alignment of single mode optical fibres using thermally actuated cantilever platforms is investinated. These devices depend on their operation on differential thermal expansion of materials. An analysis and modeling of these thermal microactuators for fibre alignment purposes is discussed. The simulation results of microactuator deflection and the coupling losses of single mode fibres by using designed ?-Shape microactuator are presented. By setting the length of the beam to 3mm and the length of the deflecting cantilever section to 2mm, the fibre-to-fibre coupling loss is only 0.315 dB.
The beam sampling grating is one of the important diffractive optical elements used in the field of laser sampling. It can be considered as an off-axis, binary phase, Fresnel zone plate. Base don the theory of interference, the principle of the variable period grating formation process is analyzed perfectly and the transmissive function of the BSG is obtained. This paper repots to fabricate the BSG with electron-beam direct writing. Compared with the holographic method, the new method is simpler, cheaper, and more efficient to manufacture elements on a large scale.
FRTH is a new kind of hologram, which is different form common Fresnel holograms and Fourier transform holograms. It can be applied for fractional Fourier transform filtering and anti-counterfeiting, etc. Due to the flexibility of holographic lens, we present a method that uses the -1 diffraction wave of holographic lens as the object wave and the 0 diffraction wave as the reference wave to record FRTH. It provides a new simple way to record FRTH. In this paper, the theory of achieving FRT and recording FRTH with holographic lens has been discussed, and the experimental results are also presented.
In this paper, we present a new method to improve the image quality and resolution of photolithography by filtering in fractional Fourier domain. Introducing a filter into fractional Fourier domain can not only increase the flexibility of the filtering operation, but also enhance the image quality and the depth of focus in photolithography. The corresponding simulation results are illustrated.
A new method has been developed to fabricate refractive microlens by etching ammonium dichromate gelatin (ADG) with enzyme solution. Unlike previous methods which are used to fabricate refractive microlens with photoresist, the process of fabricating microlens by etching ADG with enzyme solution doesn't require the use of expensive equipment, and it isn't sophisticated and time consuming. The light exposes ADG through a high contrast binary mask, then the exposed parts of ADS generate cross- linking reaction. Usually, the relief achieved by water developing is very shallow (<1um) when nonpre-harden gelatin is used, so we compound a certain concentration enzyme solution, and because of surface tension, ADG turns to spherical structure after developing. The optimum technique parameters of this process are presented. Results are presented for experiments and evaluated by profile meter and interference microscope.
Generally, a laser direct writing lithography system can only produce feature sizes larger than its beam spot size. When the feature size is comparable to its spot size, corner rounding and line shortening appears. This is caused by optical proximity effect. The effect is mainly due to light intensity spread in a laser beam which causes the spread of photon energy in resist layer. A new pre-compensation method has been developed to correct the optical proximity effect. The method has been implemented in the ISI-2802 laser direct write system. Feature size down to 0.6 micrometers has been produced with the system which normally can only produce 1 micrometers lithography without proximity correction.
The fabrication of refractive microlens by introducing the melting process with coding gray-tone mask is reported. The applied mask is obtained by the coding method, nonlinear effects in intensity distribution through the gray-tone mask have been taken into account to correct the mask design. A continuous relief is formed in photoresist after exposing, and then the excellent surface shape microlens can be gained by melting. The technical parameters of this process are also presented. Results are presented for experiments and evaluated by profile meter and scanning electronic microscope. The fabrication technology of refractive microlens by this process is simple and it indicates the enormous potential to extend the fabrication range ofrefractive microlens.
A new method is proposed to design gray-tone masks for fabrication of surface relief microstructures. 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. Using the new method a gray-tone mask has been designed to produce a hemispherical shape relief structure. 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 taken into account to correct the mask design. The accuracy of the gray-tone mask design has been confirmed by simulation of 3D resist profiles.
This paper aims at the request of dividing harmonic waves in the high power laser system used to perform Inertial Confinement Fusion. Dividing harmonic waves is realized by introducing binary optical element. Based on scalar diffraction theory, the distribution of its diffraction field was calculated and the fabrication parameters were also optimized. The element is fabricated with RIE. We also measured the relief structure and diffraction efficiency of each harmonic wave and analyze the errors.