Search

Aiming at the problem of the resolution reduction in a miniaturized grating spectrometer, we presented a method to improve its spectral resolution by inserting a tunable Fabry-Perot filter into its optical path before the grating. The Fabry-Perot filter was designed to filter out a partial spectrogram and separate the original undistinguishable spectral lines so as to make their actual wavelengths can be detected. The different cavity length of the Fabry-Perot filter is corresponding to the different separated partial spectrogram. Combining all the separated partial spectrograms, an entire spectrogram with improved resolution can be achieved. Experimentally, the spectral resolution of a grating dispersive system was improved from 2 nm to 1.2nm in a broad spectral range by insetting a homemade tunable Fabry-Perot filter, which demonstrated the feasibility of this scheme. The tunable Fabry-Perot filter is fit for miniaturization by using MEMS technology and is able to work as an independent module. The method proposed provides a potential way to improve the spectral resolution without reducing the spectral range of the existing miniaturized grating spectrometers.

In recent years, with the development of technology of micro-display, advanced optics and the software and hardware, near-to-eye display ( NED) optical system will have a wide range of potential applications in the fields of amusement and virtual reality. However, research on the evaluating image quality of this kind optical system is comparatively lagging behind. Although now there are some methods and equipment for evaluation, they can’t be applied in commercial production because of their complex operation and inaccuracy. In this paper, an academic method is proposed and a Rapid Evaluation System (RES) is designed to evaluate the image of optical system rapidly and exactly. Firstly, a set of parameters that eyes are sensitive to and also express the quality of system should be extracted and quantized to be criterion, so the evaluation standards can be established. Then, some parameters can be detected by RES consisted of micro-display, CCD camera and computer and so on. By process of scaling, the measuring results of the RES are exact and creditable, relationship between object measurement, subjective evaluation and the RES will be established. After that, image quality of optical system can be evaluated just by detecting parameters of that. The RES is simple and the results of evaluation are exact and keeping with human vision. So the method can be used not only for optimizing design of optical system, but also for evaluation in commercial production.

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 adaptive optics.

The structure combining the microlens and DOE is not sensitive to the incident beam and can control the overall shape profile flexibly. So that the structure called DOE array is designed in this paper in order to shape the unstable laser beam to the four polar uniformity distribution. The paper gives the principle of the DOE array and the design process. The array element determines the profile of the output beam. It is designed using the G-S algorithm and the Adaptive Addition algorithm (A-A). The number of the DOEs is optimized and analyzed. The simulative diffraction efficiencies are 89% and non-uniformities are less than 3% when the incident beams are Gaussian, supper-Gaussian, paraboloid and random distributions. In experiment, diffraction efficiency of 77% and maximum non-uniformity of 5.6% are got on the condition of the different input laser beam. So the effect on the instability of the incident beam could be decreased.

The near-zero-index metamaterials (NZIMs) have been extensively studied in recent years. In this letter, we show that a NZIM can be achieved in metallic nanostructures in Mid-IR region. The structure is composed of parallel metal stripes arrays, so it can be easily fabricated. By scaling the dimensions of the structure, the effect can be tuned over a large bandwidth. Analysis is carried out to study the influence of the NZIM on infrared transmission in 28.3THz (10.6μm). The multilayer homogeneous medium model is employed based on the effective medium theory. Additionally, the theoretical analysis also provides a new method of determining the effective thickness of metamaterials, which is usually complicated. The results suggest that the ratio of the amplitude after the light beam propagates through the NZIM to that before it is about 80%, and there is a negative variation in the phase of the light transmitted through the NZIM, which is in agreement with numerical simulation. Simulation also indicates that there is a strong enhancement of the electric field between the metal stripes arrays, which plays an important role in the phase delay. This metamaterial has the potential to be used in some devices such as in waveguides.

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.

Brillouin distributed optical fiber sensing system based on spontaneous Brillouin scattering frequency shift measurement may measure temperature in the optical fiber, due to the dependence of spontaneous Brillouin scattering frequency shift on temperature. In this paper, nonlinear theoretical models of the Brillouin spectrum in the BOTDR temperature sensing system are analyzed. The model parameters are optimized with Levenberg-Marquardt algorithm. By numerical calculation, it is indicated that pseudo-Voigt function can approach approximated the Voigt profile well and quickly.

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.

We present the lithography scheme that use high-numerical-aperture photon sieves array as focusing elements in a scanning X-ray maskless nanolithography system. The system operating at wavelength of 0.5~2nm synchrotron light sources radiated, each of a large array of photon sieves focuses incident X-ray into a diffraction-limited on-axis nanoscale spot on the substrate coated photoresist. The X-ray intensity of each spot is modulated by means of a spatial light modulator. Patterns of arbitrary geometry are exposed and written in a dot matrix fashion while the substrate on a stepping stage is precisely driven in two dimensions according to the computer program. The characteristics of synchrotron radiation light, resolution limits and depth of focus of the lithographic system are discussed. The design and fabrication of photon sieve are illustrated with a low-numerical-aperture amplitude-photon sieve fabricated on a chrome-coated quarts plate by means of laser-beam lithographic process, which minimum size of pinhole was 5.6um. The focusing performance of the photon sieve operating at wavelength of 632.8nm was simulated and tested.

A wave aberration compensation method for optical system and human eyes has been studied. The wave distortion of the human eye can be measured using a Shack-Hartmann sensor and described in an eight-order Zernike polynomial. By picking up the higher order’s terms of the wave aberration from the measured polynomial, characteristics of the higher order wave aberration were analyzed and concluded. The conjugate phase plates were designed based on the distribution of the single and the overall wave aberration of the eye. The thermal-filtered halftone mask technique is developed to manufacture such an abnormity micro-optical structure. The compensators for the single or the overall wave aberration were fabricated respectively. The relief profiles were evaluated using both three-dimensional profiler and interferometer. A primary experiment for compensating the higher-order wave aberration of an artificial eye was demonstrated.

It is reported in this paper a method to fabricate three dimensional continuous micro-optical structures using half tone masks and proximity printing. The frequency modulation coded half tone masks are employed to obtain the predetermined exposure distribution. Several components like Cylinder microlens arrays, phase correctors are realized in photoresists.

A maskless lithography imaging simulation using digital micromirror device (DMD) was investigated. The DMD acts as a reflective spatial light modulator. The micro-mirrors on DMD can be instructed by the computer to tilt them ±12° off their normal position which produces a mask pattern, and then the mask pattern can be carried onto the surface of wafer by the imaging system. Because the imaging of the maskless lithography is a complex process, it is necessary to simulate and analyze its practical process. In this paper, we present a partial coherent imaging model of maskless lithography considering the practical projection characterization of DMD. With the model, it is convenient to simulate the lithography of arbitrarily shaped microstructure using DMD. Through calculation, the spatial image in maskless lithography process based on gray scale photolithography with DMD real-time masks was obtained.

In order to form the proper aspherical microlens array profile with larger NA on photosensitive materials, a method is developed based on the characteristics of resist and processing parameters during development, for designing the exposure distribution, an experience formula has been proposed in the paper. Using the moving mask method, the exposure energy distribution function related to the photolithographic mask function can be determined by the experience formula. The profile control procedure is formed especially for the deeper relief profiles, after the binary mask data are slightly modified, the micro-structure with aspherical lens profile can be fabricated on the selected thicker resist, the micro relief profile error can be controlled in a certain range. The micro-profile is farther transferred to fused silica by ICP etching system. By our method, the fast microlens array elements with good fidelity and reasonable roughness have been fabricated and applied to the laser diode collimating system.

A new method for microlens profile design was developed based on the analysis to the main parameters of microlens array, including micro profile formation, the numerical aperture ( NA ), the maximum sag depth for the refractive lens and the minimum zones width for the diffractive lens. With the relationships among the parameters, the microlens array in different profile can be determined effectively. The moving mask method[1] is used to realize the required profiles, an unique photolithography system have been built for implementing the mask moving exposure in both X and Y directions for the creation of microlens array. By modifying the binary moving mask, optimizing the photosensitive materials and the processing technique, the microlens profile error can be controlled in the range of 0.4µm~3µm depending on effective reliefdepth of the microlens. In our method, both diffractive and refractive microlens array with larger NA and higher fill factor can be fabricated for satisfying a plenty of purposes.

Performances of diffractive and refractive microlens array have been studied and compared. Besides the diffractive microlens array which can be fabricated by means of the microfabrication technologies, method for manufacturing continuous profile refractive microlens array with larger sag depth has been developed for solving the unique problems like diode laser alignment. Both diffractive and refractive microlens array with different numerical aperture and other parameters are fabricated according to the application requirements, experimental results are given.

A new type of diffractive microlens array concentrator has been designed and fabricated for improving the performance of infrared detector array. An experiment was made by coupling the concentrator into a focal plane detector array, the detectivity of the coupled device was increased to nearly 2.8 fold.

In this paper, a method for improving the performance of unit infrared detector has been proposed. An experiment was carried out by putting micro-concentrator in front of the tested detector, micro-concentrators are diffractive microlens with different numerical aperture (N.A.) which were obtained by special design and fabrication. The performance has been evaluated for the coupled detector and compared with the simulation.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.