The vibrational spectrum of calcite (CaCO3) is evaluated at an ab initio periodic quantum-mechanical level by using the CRYSTAL package. A localized basis set of Gaussian-type functions and the B3LYP hybrid Hamiltonian are adopted. The dynamical matrix is obtained by differentiating numerically the analytical first derivatives of the energy. The accuracy with respect to all computational parameters is documented. The calculated frequencies are compared with available IR and RAMAN data (16 and 5 peaks, respectively), the mean absolute error being less than 12 cm−1 (frequencies range from 100 to 1600 cm−1). Overall, the agreement with experiment is very satisfactory, and shows that simulation can produce at a relatively low cost the full spectra of crystalline compounds of mineralogical interest.

The vibrational spectrum of calcite (CaCO3): an ab initio quantum-mechanical calculation Note: Theoretically derived structure

Low-power integrated projection technology can play a key role in development of low-cost mobile devices with built-in high-resolution projectors. Low-cost 3D imaging and holography systems are also among applications of such a technology. In this paper, an integrated projection system based on a two-dimensional optical phased array with fast beam steering capability is reported. Forward biased p-i-n phase modulators with 200MHz bandwidth are used per each array element for rapid phase control. An optimization algorithm is implemented to compensate for the phase dependent attenuation of the p-i-n modulators. Using rapid vector scanning technique, images were formed and recorded within a single snapshot of the IR camera.

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Nanophotonic projection system.

Nanoparticles and core–shell nanocomposite based new generation water remediation materials and analytical techniques: A review

We present a light emitting diode (LED)-based ultramini digital micromirror device projector with a size of 75 mm x 67 mm x 42 mm and a weight of 338 g. The LED illuminator inside this projector makes it possible to achieve a volume of 18 cm(3) by using a dichroic filter and a collimating lens. The illumination system consists of high uniformity of 93% through a microlens array as a homogenizer. A total internal reflection prism is also used to reduce the size of both the illumination system and the telecentric projection lens. A projection lens system with an ultrasmall track of 42 mm, including a high modulation transfer function value of 0.4 at 46.2 line pairs/mm, an optical distortion of only 0.25 %, and a television distortion of 0.01%, is designed. Through the above superior specification, we can produce a 20 in. (51 cm) color display comparable in brightness to a laptop with a contrast of 3700:1. The device is compact and suitable for personal use.

High efficiency pocket-size projector with a compact projection lens and a light emitting diode-based light source system.

Nanotechnology is a fast-emerging field and has received applications in almost every field of life. Exploration of new synthetic technologies for size and shape control of nanomaterials is getting immense consideration owing to their exceptional properties and applications. Magnetic nanoparticles (MNPs) are among the most important group of nanoparticles thanks to their diverse applications in medical, electronic, environmental, and industrial sectors. There have been numerous synthetic routes of MNPs including thermal decomposition, co-precipitation, microemulsion, microwave assisted, chemical vapor deposition, combustion synthesis, and laser pyrolysis synthesis. The synthesized MNPs have been successfully applied in medical fields for therapy, bioimaging, drug delivery, and so on. Among environmental aspects, there has been great intimidation of organic pollutants in air and water. Utilization of various wastes as adsorbents has removed 80 to 99.9% of pollutants from contaminated water. MNPs as adsorbents compared to coarse-grained counterparts have seven times higher capacity in removing water pollutants and degrading organic contaminants. This study is focused to introduce and compile various routes of MNP synthesis together with their significant role in water purifications and degradation of organic compounds. The review has compiled recent investigation, and we hope it will find the interest of researchers dealing with nanoparticles and environmental research.

Current advancements of magnetic nanoparticles in adsorption and degradation of organic pollutants.

In order to solve the problem that the grating quality cannot be monitored directly in real time, we provided a method based on Rayleigh criterion with our designing optical measurement structure to measure yaw and displacement errors of a grating ruling machine feeding system. Gratings are ruled with or without errors correction by the real-time monitoring system . It shows that the resolution obtained without errors correction is reduced from 99.97% to 87.47% of theoretical value, while the resolution obtained with errors correction is stable, remaining at 99.99%–97.21%. The experimental result is that the grating quality can be guaranteed by monitoring grating resolution in real time.

Real-time monitoring of ruling grating resolution by digital wavefront

A measuring method was studied to further improve the manufacturing accuracy of the lead screw. Firstly, factors that can axially displace the screw shaft were analyzed and a relationship between factors and axial displacement was given. The axial displacement of the screw shaft was measured using a laser interferometer, and results show that the variation amplitude of the screw-shaft axial displacement was about 80 nm while the variation period was consistent with the rotation period of the screw shaft. Next, two methods of measuring the manufacturing accuracy of the lead screw were considered: a traditional method that measures the absolute position of the nut and an improved method that measures the displacement between the nut and screw shaft. A No. 4 screw shaft was manufactured under the guidance of results obtained using the improved measuring method. Experimental measurements were then made; results show that the pitch displacement errors obtained using the traditional and improved measuring methods were 0.6 and 0.4 μm, respectively, indicating that the improved measuring method is more exact. Finally, an echelle grating ruled by a grating ruling engine that used the No. 4 screw shaft as a macro-positioning element was introduced. Its excellent parameters indirectly show that the improved measuring method has better accuracy.

An improved accuracy-measuring method in manufacturing the lead screw of grating ruling engine

Establishment and correction of an Echelle cross-prism spectrogram reduction model

The invention relates to an optical path structure of a small echelle grating spectrometer. The structure includes a condenser lens, an incident pinhole, a collimating lens, an echelle grating, a cross dispersion prism, a focusing lens, a cylindrical lens and an area-array detector; the collimating lens and the focusing mirror are spherical mirrors; the condenser lens makes an incident light beam focused to the incident pinhole; a light beam emitted from the incident pinhole irradiates the collimating lens; a parallel light reflected by the collimating lens directly is directly incident to the surface of the echelle grating; a light beam diffracted by the echelle grating irradiates the focusing lens through the reflection of the cross dispersion prism; and a focused light reflected by the focusing lens is received by the area-array detector after the achromatic treatment of the cylindrical lens. The optical path structure can be used for effectively balancing the contradiction between the high resolution and the small size of a conventional grating spectrometer and realizing the high spectral resolution with the structure of the small size and has the advantages of compact structure, small size, light weight, no moving parts, simultaneous measurement of wide spectral bands and the like.

Optical path structure of small echelle grating spectrometer

This paper proposes a more accurate eccentricity and tilt
measurement method based on Young’s interference experiment. The
basic principle of the method is introduced first before the method is
simulated. Then the results are obtained when a to-be-adjusted focusing
lens with eccentricity and tilt is simulated. The optical sensitivity also
is obtained from these simulation results, and the expression for the
change in optical path length caused by eccentricity and tilt is analyzed.
Use of this method to detect eccentricity and tilt and assist in
adjustment of the system allows the instrument to achieve higher accuracy
and thus obtain improved imaging quality and spectral
resolution.

Jicheng Cui

Papers

Real-time monitoring of ruling grating resolution by digital wavefront

An improved accuracy-measuring method in manufacturing the lead screw of grating ruling engine

Establishment and correction of an Echelle cross-prism spectrogram reduction model

Optical path structure of small echelle grating spectrometer

Method for measurement of eccentricity and tilt of lenslet array integral field spectrometer.