Papers by Keyword: Diffraction Grating

Abstract: This paper presents a design study of an optical three-axis angle sensor for measurement of angular error motions of long-stroke precision linear stages. The three-axis angle sensor, which is based on a laser autocollimation method, can detect angular motions about the XYZ-axes simultaneously by using zeroth-and first-order diffraction beams from a diffraction grating mounted on a measuring target as a reflector. In this paper, an optical sensor head is designed in such a way that the three-axis angle sensor shares a diffraction grating with an optical sensor head of a linear encoder, which is already installed in a stage system. The optical sensor head of the three-axis angle sensor is designed in a size of smaller than 50 mm × 30 mm × 30 mm so that the sensor head can be compatible with the linear encoder. Details of the optical configuration designed for the sensor head, and some results of experiments are reported.

Abstract: Inertial Confinement Fusion (ICF) is an effective method to alleviate the energy crisis . As the key segment in the construction process of laser fusion device, mechanical tiling technology has played an important role in the field of laser pulse compression and final optics assembly. For this reason, grating tiling and off-axis parabolic mirror tiling are discussed primarily in this paper. The primary principle of tiled-grating assembly design is elucidated briefly, the movement adjustment process of 1¡Á3 type tiled-grating and the driving process of 5PTSP-PPS serial-parallel tiling mechanism are reviewed. By analyzing the adjustment method of primary mirror in E-ELT, ideas to realize tiling off-axis parabolic mirror are proposed. Finally, some suggestions for further study on mechanical tiling technology are commented.

Abstract: We present the study based on extended Maxwell-Garnett effective medium theory for the effective dielectric function of the diamond like carbon film with embedded silver nanoparticles (DLC-Ag) and rigorous coupled-wave analysis to evaluate resonance characteristics in a visible range of periodic 1-D grating structure on their base. The relief sub-wavelength grating structures on base DLC-Ag nanocomposite have been investigated for sensing applications.

Abstract: A method of mixed gas quantitative analysis with near infrared spectroscopy （NIR）is described. A single plane diffraction grating is used in the monochromatic spectrum system. A quantitative analysis system is designed and constructed according to the parameters of the monochromator. The narrowband beam testing and spectral scanning experiments with methane and ethane are carried out. A 10nm narrowband beam is successfully obtained by the monochromatic system when the entrance slit width is 2mm. And a step-scanning resolution of the outgoing beam’s centre wavelength with 0.1nm can be realized within the spectra of 1.0-1.8μm. The results show that methane and ethane have a maxim characteristic absorption spectrum respectively with the centre wavelength of 1653nm and 1690nm existing between the spectra of 1.6-1.8μm, which is consistent with the HITRAN database. Presented approach has a successful application in online mixed gas monitoring with the characteristics of simple structure and low cost.

Abstract: We have fabricated X-ray diffraction gratings for X-ray phase imaging using X-ray Talbot interferometer. In this paper, we propose the new low cost fabrication process using Si mold of Si dry etching and nano-imprint techniques. Si dry etching makes it possible to fabricate high aspect ratio rectangular microstructures. Therefore, this technique is expected to fabricate high precision grating pattern. In this paper, we propose the new low cost fabrication processes using Si mold of ICP-RIE and nano-imprint techniques. And, in order to form transparence imprint mold, we used thermal oxidation of Si mold. These demonstrations of thermal oxidation are promising method for high precision transparence imprint mold with low cost, and realized low cost optical device such as diffraction gratings.

Abstract: This paper proposes an idea for manufacturing internal patterns using a femtosecond laser. The femtosecond laser can easily be focused within transparent materials because of the advantages of multi-photon absorption and high energy density. The parameters of a femtosecond laser can be adjusted to modify the local area inside the glass and to design internal structures. The internal structures can produce optical effects. Through this process, optical plates can be manufactured in glass without wasting excess space.

Abstract: Back–side diffraction gratings enhance a solar cell’s near–band–gap response by diffracting light into higher orders and thereby reducing front–side escape losses. The resulting increased photon absorption and carrier generation improves short–circuit current densities and solar cell efficiencies. Combining rigorous coupled–wave analysis and ray tracing yields a three–dimensional, polarization sensitive optical model to calculate Si absorbance, front–side and back–side losses. For industrially used, pyramidally textured, 180 μm Si solar cells with 85 nm SiN_x anti–reflection coating, the application of an optimized back–side grating enhances the short–circuit current density by ≈ +1 mA/cm², a relative increase of ≈ +2.7 %.

Abstract: Nano-structures on the wing of Morpho butterflies generate bright blue color, and this color is sensitive to ambient gas, or more specifically, the refractive index of ambient gas. It was found that even slight change of the refractive index can lead to obvious change of the color. Such phenomenon has caught much attention and was employed as a sensing principle for detecting gas. In the present study, a typical nano-structure on the wing of Morpho butterflies is mimicked and simplified for constructing a refractive index based gas sensor. Moreover, partial derivative of the optical reflection efficiency with respect to the refractive index of ambient gas, i.e., sensitivity of the sensor, is utilized based on the rigorous coupled-wave analysis (RCWA) method. Finally, the effects of the nano-structure’s shape on the partial derivative are analyzed. The results can be applied to the design of the bioinspired refractive index based gas sensor.

Abstract: We report on micro-structuring of iron-doped lithium niobate using femtosecond direct laser writing (DLW) technique. Formation of extended, stable index modulation micro-structures, such as diffraction gratings and linear waveguides is achieved by translation of a focused femtosecond laser beam inside lithium niobate crystals. From diffraction efficiency of the recorded gratings refractive index modulation amplitude of n ~ 10-3 is estimated. It is demonstrated that the recorded structures can be optically erased and re-written.

Abstract: This paper considers the possibility of creation of a micromechanical optical scanner (MOEMS-scanner) for terahertz spectrum diapason of radiation frequencies.