With the split-step-Fourier-transform method for solving the nonlinear paraxial wave equation, the intensity distribution of the light field when the pits diameter or depth change is obtained by using numerical simulation, include the intensity distribution inside optical element, the beam near-field, the different distances behind the element and the beam far-field. Results show that with the increase of pits diameter or depth, the light field peak intensity and the contrast inside of element corresponding enhancement. The contrast of the intensity distribution of the rear surface of the element will increase slightly. The peak intensity produced by a specific location element downstream of thermal effect will continue to increase, the damage probability in optics placed here is greatly increased. For the intensity distribution of the far-field, increase the pitting diameter or depth will cause the focal spot intensity distribution changes, and the energy of the spectrum center region increase constantly. This work provide a basis for quantitative design and inspection for pitting defects, which provides a reference for the design of optical path arrangement.
Z-scan technology is a popular experimental technique for determining the nonlinear refractive index of the material. However, it encounters a great difficulty in measuring the weak nonlinear material like fused silica which is about two orders of magnitude below the nonlinear refractive index of most of the materials studied with the nanosecond and picosecond Z-scan methods. In this case, the change of refractive index introduced by accumulation of thermal effects cannot be neglected. In order to have a reliable measurement of the nonlinear refractive index, a metrology bench based on the femtosecond Z-scan technology is developed. The intensity modulation component and the differential measurement system are applied to guarantee the accuracy of the measuring system. Based on the femtosecond Z-scan theory, the femtosecond laser Z-scan technique is performed on fused silica, and the nonlinear refractive index of Fused silica is determined to be 9.2039×10-14esu for 800nm, 37fs pulse duration at I0=50GW/cm2 with a good repeatability of 6.7%.
The focal length is one of the important parameters in the optical element, and the high precision measurement of the focal length has become a key problem in the processing and use of the optical element. The laser differential confocal length measurement system is introduced, and the uncertainty of the two sets of focal length measurement is evaluated. The relative error (K = 2) is better than 4.77×10-5, and the relative error is 0.00025%.
Z-scan technology is an experimental technique for determining the nonlinear refractive index based on the principle of transformation of phase distortion to amplitude distortion when a laser beam propagates through a nonlinear material. For most of the Z-scan system based on the nanosecond or picosecond laser, the accumulation of thermal effects becomes a big problem in nonlinear refractive index measurement especially for the nonlinear materials such as fused quartz and neodymium glass which have a weak nonlinear refractive effect. To overcome this problem, a system for determining the nonlinear refractive index of optical materials based on the femtosecond laser Z-scan technology is presented. Using this system, the nonlinear refractive index of the fused quartz is investigated.
In this paper, a method is introduced to test wavefront aberration of parallel optical plate wavefront, which based on
Fourier transform. When testing the wavefront aberration of parallel optical plate, there is multiple-surface interference
which phase-shifting interferometry cannot handle with. With the help of wavelength-modulation phase-shifting
interferometry and Fourier transform, this method can isolate the multiple-surface interference fringes in frequency
domain. This paper expound the principle of the method, and analyze the key parameter of the testing method: the
suitable cavity/thickness ratio and sampling frame number. A simulation experiment is set up to verify the accuracy of
this method, then the comparison test with traditional method shows that the relative deviation between the two methods
For multilayer films system, in order to obtain the thickness and surface profile in each layer of thin film, a method to measure the 3D morphology of a multilayer films system based on scanning white light interferometer has been proposed in this article. At first, the mathematical relationship between reflection phase and thickness of each film layer has been obtained by using the electromagnetic field boundary conditions. Then, a nonlinear least square algorithm has been used to fit the reflection phase which had been found through a scanning white light interferometer, in this way the linear and nonlinear terms of the reflection phase have been separated, which made it possible to measure top-layer surface profile and thickness of each thin film layer respectively and avoided the interference with each other, because the linear term is related to the top layer’s surface profile but the nonlinear term is correlated to the thickness of each film layer in multilayer thin films system. Thus, the three-dimensional morphology of multilayer thin films system could be reconstructed. Experimental results showed this method was effective in the three-dimensional morphology measurement for multilayer thin films. And the measurement could be completed just using the existing commercial scanning white light interferometer, as a consequence the measurement cost is low, and the operation will be quite simple.
In many long focal distance lens focal length detection method, laser confocal combined focal length measurement with
ultra high focusing accuracy, more and more attention and application. The accurate measurement of the distance
between the lens focus and the focus in the measurement process is the key to improve the accuracy of the whole
measurement. By repeating the measurement of focal distance under different environmental conditions, the results of
repeated measurements of influenced by the environmental conditions. The results show that air disturbance is the
measurement repeatability factors having the greatest impact, for better use of the equipment and in the equipment
development research foundation laid the foundation.
A simple method for focal length measurement based on image processing is demonstrated and discussed. The collimated beam, detector, motorized translation stage and computer make up of this test system. The two spots pass through the tested lens is accepted by detector, which is transferred twice by motorized translation stage. By acquired the difference of two spots by image processing, the focal length of the tested lens can be gained. The error sources in the measurement are analyzed. Then the results of experiment show that the relative error was 0.1%. This method can be used in workshop and labs for its convenience and low cost.
Reflection Z-scan technique allows the measurements of optical nonlinearities of highly absorbing media and surface of transparent media, when transmission Z-scan can not be used. However, Reflection Z-scan needs multiple measurements under strong laser pulse excitation in the scanning process. This can induce damage in the sample in some cases. In this paper, a Non-scanning Reflection Technique (NRT) for measurement of optical nonlinearities is presented to overcome this drawback. Both the nonlinear refraction index and nonlinear absorption coefficient can be determined by measuring the reflection in combination of variable attenuator and an aperture. Based on the Fresnel theory, a theoretical analysis of Non-scanning Reflection Technique (NRT) demonstrates the feasibility of this approach is given and a general expression for the normalized reflectance is derived. In order to illustrate our analytical results, we performed a numerical simulation of the normalized reflectance. Besides, retardance and size of the induced phase plate also make contributions to the normalized reflectance. Moreover, this technique shows a higher sensitivity property compared with traditional reflection Z-scan method.
Three-flat test can separate the reference surface error from the test part surface in the surface measurement by interferometry. The solution based on mirror symmetry of three-flat test is compact and highly accurate. In practice, the error will be introduced when the position of three flats are misalignment or the relative rotation angle are not accurate. The influence of rotation angle error are simulated and discussed. Then the experiment was carried out on three reference flats and the flat surface profiles were derived by mirror symmetry method. The experiment results show good agreement and the difference is in a nanometer level.
Multiple surfaces transform interferometery is a preferred technology for surface profile and index homogeneity measurement using a Fourier based analysis method combined with phase-shifting interferometer. As a four-surface cavity for example, the surface form and index inhomogeneity of the parallel plate are deduced by extracting the information from the corresponding interference frequency. The errors of surface form and index homogeneity are simultaneously simulated and analyzed with different sampling buckets. The results show the feasibility and high precision of this approach compared with traditional methods.
A Static Polarizing Atmospheric Michelson Interferometer (SPAMI) system for multiple emission lines is reviewed. It changes the Optical Path Difference (OPD) by Polarization Array (PA) at one time, instead of rotating the polarizer by four times in traditional polarizing Michelson interferometer. This allows the NPAMI system to make simultaneous measurements. PA is a key element cemented by four polarizers with different polarization orientations in the SPAMI system. In practice, assembly error is brought to the polarization array unexpected. It is proved that the temperature and wind velocity measurements are highly depended on the polarization orientations of polarizers in PA. In this paper, the effect of deflection of polarization orientation on temperature and wind velocity are analyzed and discussed. Moreover, a proper approach is proposed to improve the accuracy of alignment.
Several novel designs of wide-field-of-view polarization imaging spectrometers based on combined Savart polariscopes are presented. By numerical modeling and analysis, we show that the field of view can be extended when the polariscopes are made of the same uniaxial crystal or positive and negative uniaxial crystals are combined. The designs with increased fields of view enable the acquisition of undistorted interferogram and high étendue for the spectrometer systems.
In this paper, FeXAl1-X films have been deposited on silicon substrates using electron beam evaporation, which have been
not reported to prepare FeXAl1-X films before. Subsequently, the films were annealed in vacuum better than 3×10-4Pa for
1 hour at 100°C, 280°C, 330°C, 450°C and 500°C, respectively. Electrical resistivities of the samples were been
measured by four point probe, and microstructures of the samples were characterized by X-ray diffraction(XRD). The
results show that, the resistivity of films reduces gradually with increasing of the annealing temperature, and the
structure of films can be improved after annealing. In addition, the resistivity of film reduces gradually with increasing
thickness and comes closed to the that of bulk when the film thickness becomes thicker than 100nm.
FexAl1-x thin films had been prepared on Si (100) substrates by electron beam evaporation. The substrate temperature was
varied from room temperature to 450°C at an interval of 100°C. The crystalline orientation of deposited FexAl1-x thin
films had been characterized by X-ray diffraction (XRD) and the thickness was measured by Atomic profiler. The results
show that the crystalline orientation of FexAl1-x thin films depends on the substrate temperature. The thin films are crystal
at different substrate temperatures. The deposition rate becomes bigger from 30°C to 250°C and smaller from 250°C to
450°C. The surface morphology of deposited FexAl1-x thin films had been investigated by atomic force microscopy
(AFM). The results show that the surface roughness increases with increasing the substrates temperature to 450°C.
Perdeuterated polystyrene (DPS) was synthesized by free radical polymer. DPS films with thickness 50 ~ 400 μm were prepared by casting. The influence of heat curing on the properties of DPS films were investigated by different scanning calorimeter (DSC), dynamical thermal mechanical analysis (DMA) and tensile strength measurement. It was approved that the heat curing process of films influenced the glass transition temperature, dynamical thermal mechanical properties and tensile strengths of the films.