Holographic exposure mosaic technology is a feasible solution to fabricate large-area pulse compression gratings, where the mosaic grating method of developing region by region is one of the mosaic approaches. In this method, an exposed area of the substrate is firstly developed, and then the developed photoresist grating mask is put back into the previous exposure system. The next area grating mask is fabricated by aligning the interference fringes formed by the exposure beam and the developed real grating. However, since the unequal exposure and inconsistent development, the groove shapes of grating masks in two areas, including groove depth and duty cycle, will be different. When detecting the mosaic grating error, the differences of the groove shapes will cause the dislocation in the -1-order reflected diffraction wavefront at gap of the mosaic grating. It will be superimposed on the phase change caused by the lateral displacement error, so that the judgement of lateral displacement error will be seriously interfered. To solve this problem, the measurement method of the 0-order diffraction wavefront under multiple incident angles is proposed to precisely judge the lateral displacement error in the mosaic grating. In this paper, the grating diffraction analysis program based on the rigorous coupled-wave analysis is firstly written, and then the initial phase of 0-order reflected diffraction wavefront of mosaic grating mask is calculated. Subsequently, the sample is tested by atomic force microscopy and interferometer. By importing the measurement data into the searching program, the groove parameters of grating masks are obtained by the library matching method. Then, the lateral displacement error of the mosaic grating is further deduced. Finally, the feasibility of the proposed judgment method is confirmed by the experiment.
KEYWORDS: Holograms, Digital holography, Fresnel lenses, Computer generated holography, Spatial light modulators, Reconstruction algorithms, 3D modeling, 3D image processing, 3D displays, 3D image reconstruction
In this paper, a voxel-based algorithm for calculating phase-only three-dimensional (3D) computer generated holograms (CGHs) with occlusion effect is proposed. The 3D object can be firstly decomposed into a number of self-luminous voxels, which is the minimum imaging unit of the object. According to occlusion relationship, the 3D position and propagation direction of each voxel can be determined, where the axial position, lateral position and the propagation direction are precisely controlled by digital Fresnel lens, digital grating and hologram segmentation, respectively. Then, in order to reconstruct the 3D object composed of multiple voxels, the pre-calculated holograms for all of the voxels are synthesized with the interweaving arrangement method. Moreover, the look-up-table (LUT) method is used in the hologram generation process to improve the calculating speed. An experimental verification system for the proposed algorithm is constructed using a single SLM. The optical reconstruction results demonstrate that the CGHs generated by the proposed algorithm can successfully provide 3D sensation with occlusion effect.
In this paper the diffraction characteristics of the blazed grating is investigated by using rigorous coupled-wave analysis, which indicates that within the near infrared broadband, the first-order diffraction efficiency can be over 10% at 1.2μm and over 65% at 2.3μm through controlling the blaze angle of the blazed grating. The blazed grating with the period of 8.33μm, the blaze angle about 7.3 degree, and the antiblaze angle about 41.8 degree has been fabricated by holographic lithography - ion beam etching. Theoretical analysis has showed that the diffraction efficiency of these blazed grating can reach 15% at 1.2μm, 73% at 2.3μm and 75% at blazed wavelength.
The high diffraction efficiency of the convex blazed gratings cannot be realized in the broadband. Therefore, we have designed the convex dual-blazed grating to realize higher and uniform diffraction efficiency in the wavelength from 0.4 μm to 2.5 μm. The diffraction efficiency of the convex dual-blazed grating is investigated by using rigorous coupled wave analysis. The results show: when the two blaze angles of the convex dual-blazed grating, one within the range from 2.7 degree to 3.4 degree and the other one within the range from 8 degree to 9 degree respectively, the first-order diffraction efficiency is more than 25 percent at the visible-near infrared band. The convex dual-blazed grating with the period of 5μm in the center will be fabricated by holographic lithography-segmented ion beam etching in late 2017.
In this paper, we investigate the nonlinear optical properties of unsymmetrical trimethine cyanine dyes(ethyl-4-(3-(3-ethylbenzo[d]xazole-2(3H)-ylidene)prop-1-en-1-yl)quinolin-1-iumiodidebenzo[d]xa zole group) by conducting Z-scan technique at 532 nm and time-resolved pump probe with phase object (POPP). Pronounced reverse saturable absorption (RSA) and positive refraction are observed. Moreover, the relevant third-order NLO photo-physical parameters of unsymmetrical trimethine cyanine dyes determined unambiguously.
The third-order nonlinear optical response of molybdenum disulfide dissolved in ethanol was investigated using a modified time-resolved pumpeprobe measurement with phase object at 532 nm with pico-second laser pulse. The experimental results clearly indicate that the observed nonlinear response should be of excited-state origin. The compound exhibits strong saturable absorption and long excited-state lifetimes. The nonlinear absorptive and refractive parameters of the phenoxazinium salt were evaluated by combination of picosecond pumpeprobe measurements and picosecond Z-Scan experiments. The experiment results demonstrate this compound is a promising nonlinear optical material.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.