Zirconium oxide films were prepared with and without ion beam assisted deposition (IBAD) by an electron beam. The effects of Ar-ion bombardment on the optical inhomogeneity of ZrO2 films deposited at room temperature were investigated. The results show that all samples are amorphous, and the refractive index of sample A without IBAD randomly changed with the film thickness, while the relative inhomogeneity of samples B, C, D with IBAD nearly zero. It was found that the energy of depositing molecule or atom had an important effect on the optical inhomogeneity of films, and the optical inhomogeneity of amorphous ZrO2 films could be improved by IBAD.
The periodic dielectric phase retarders that produce a ±90° phase shift between the p- and s- polarization components at the incident angle of 54° and the wavelength of 1315nm while maintaining high reflectivity for both components are designed. An optimization technique has been used to determine the layer thickness for a coating design that produce a 270±1° phase shift between the p- and s- polarization components over 1285-1345nm while the average reflectivity is over 99.5%. Then the designed retarders were prepared by ion beam sputtering (IBS), and the phase shift was 262.4±1.8° and the reflectivity was over 99.6% at the design waveband.
The ion cleaning effect on the roughness of substrates and laser induced damage thresholds (LIDT) of films were investigated. It is found that ion cleaning has different effects on the roughness of substrates with the different ion cleaning time, and it improves the LIDT of single layer films greatly.
The influence of inhomogeneous transitional layers on the spectral characteristics of AR coatings is discussed in this paper, and some results have been got: Inhomogeneous layers between substrate and coatings results in decreasing of the anti-reflection performance along with extremum shift to short wavelength; and among several kinds of inhomogeneous layers between two coatings, sine transition increases the anti-reflection performance, linearity, hyperbolae and exponent decrease the anti-reflection performance. Then a good fitting was given to the experiment of AR coatings and it was discovered that the sine transition between substrate and coatings is similar to experiment very well.
A few reasons to cause the half-wave hole for the short-wave pass filter had been analyzed. According to these reasons, the application of a new admittance-matching method and a photoelectric maximum control with half-wavelength effectively eliminated the half-wave hole. The matching stack consisted of a symmetrically periodic structure and provided a complete matching at the desired wavelength; i.e., both conditions for the equivalent admittance and phase thickness were fulfilled. Furthermore, both the theoretical and the tested curves had been given, and a good agreement between them was obtained.
The LIDT and damage morphology of the AR coatings on quartz and sapphire are investigated. A very interesting phenomena is found in the measurement: In the case of single pulse laser, the LIDT of the AR coatings on quartz is higher than that of sapphire; on the contrary, for free pulse laser, the LIDT of the AR coatings on sapphire is higher than that of quartz.
Several kinds of high reflection thin films are prepared by electron beam gun with different designs and coating materials. The reflectivity, transmission, absorption and scattering of these thin films are measured and calculated, the loss of absorption and scattering of the thin films are mainly discussed. Furthermore, the absorption of films are also analyzed under different annealing temperature, it is found that the absorption loss can be dramatically reduced after annealing. At the same time, the compositions of thin films are tested by AES (Auger electron spectroscopy) to detect whether there is impurity or contamination.
KEYWORDS: Signal to noise ratio, Signal attenuation, Reflection, Signal detection, Data processing, Water, Backscatter, Airborne laser technology, Electronic filtering, Wavelets
A laser airborne depth mapping (LADM) for the topography of coastal water was developed in China. System was implemented in South China Sea between 2001 and 2002. Data processing subsystem is introduced in this paper. Three automated waveform processing algorithms have been developed around several sets of heuristic rules to extract reliably accurate depths with a low false alarm rate. The position, pulse width and ratio of signal to noise are obtained by the low-pass differentiator algorithm (LD). The floor reflecting is determined by the signal above some thresholds in LD method. According to the characteristics of water attenuation, the received signal is revised by the inverse of the water attenuation coefficient (here after, RA method). The bottom is easier to distinguished from the enhanced contrast between the floor reflecting and water scattering. The LD and RA algorithms show a consist results in the post-flight data processing. A more simple and fast algorithms of delayed signal subtracter (DS) is used on flight as a real time data processing, in which the signal is delayed some time abd subtracted by the original signal. The three methods are analyzed in details. The result of data processing isalso presented.
With the requirement of safe navigation in South China Sea, airborne laser bathymetry technique becomes attractive in China recently. A prototype of laser airborne depth mapping (LADM-I) system was developed. System included a diode laser pumped solid-state laser with a repetition rate of 200 Hz and the peak power of 2 Mw, a 15°nadir quasi-elliptical scanner, a combination unit of DGPS and an electronics compass, and a post-flight data processor. System has been demonstrated in South China Sea during last two years. In order to improve sounding density, survey productivity, maximum penetrable depth and accuracy of depth, a new generation of LADM-II is under developed. System will be constituted of a 1 kHz diode pumped laser, INS and KGPS. The performance will also upgrade to meet the higher requirement. In this paper, the detail parameters and specifications of LADM-I, and the experimental result will be reported. The protocol of LADM-II system will be also present.
In this paper, the periodic all dielectric multilayers of high reflection phase retarders are designed. And the software of Tfcalc has been used to optimized for the design that produces a 900phase shift between the p- and s- polarization components at the incidence angle of 540 and at the wavelength of 1315 nm while maintaining high reflectivity (>99.90%) for both components. A tolerance analysis indicates that the coating layers must be deposited within ±14% to achieve a 90± iO° phase shift error.
Airglow measurement is an important method of studying the dynamic processes in the upper atmosphere. In this paper, we will provide a brief review for airglow measuring methods of atmospheric wind, temperature and short-period wave process in the thermosphere and mesopause region. First, we give the measuring principles, application and major measured result of Fabry-Perot optical interferometer used to the measurement of atmospheric wind and temperature. Then, airglow measurements in the mesopause region are discussed, and a brief description of the tilting-filter photometer developed by CSSAR is given. Finally we will give an introduction on the future plane of upper atmospheric optical measurements in China.
In this paper, we discuss the method of spectrum deconvolution and its application in the atmospheric remote sensing. This paper consists of three respects of content. First, we discuss the influence of the spectrum resolution of the instrument on the atmospheric remote sensing detectable height. In the second part of this paper, we discuss the deconvolution method of the atmospheric absorption spectra and its ability of spectrum resolution enhancement. Finally, we will discus the application of the atmospheric spectrum deconvolution method in the ground-based atmospheric remote sensing. Two methods of the atmospheric inversion that use the atmospheric spectrum deconvolution method to increase the resolution of observed spectrum will be presented. One is the effective instrument function method. Another is the circulation method of ground-based atmospheric remote sensing inversion. The study indicated that the spectrum deconvolution method can be used to increase the detectable altitude of the ground-based atmospheric remote sensing.
A 37 element adaptive optics system has been built in the Institute of Optics and Electronics for experimental research of atmospheric effect compensation. In this system a 37 subaperture Shack-Hartmann sensor with frame rate 380 Hz is used as wavefront sensor, a 37/55 element deformable mirror and a fast steering mirror as wavefront correctors, a digital signal processor with peak operation speed 100 Mops as wavefront processor and controller, and 39 channels of high voltage amplifier for controlling the wavefront correctors. This system has been integrated with a turbulence cell developed by the Anhui Institute of Optics and Fine Mechanics and experiments for compensating for wavefront errors induced by the turbulence of the cell with different strength have been conducted. Another Shack- Hartmann wavefront sensor is used for measuring the strength of turbulence. The integrated probability density functions of both the coherence length r0 and the Strehl ratio of S of the focused spot are used to describe the strength of turbulence and the sharpness of focused spots with and without correction. In this paper the adaptive optics system and the experimental results are briefly reported.
A numerical code for simulating light propagation in the atmosphere and adaptive optics compensation for wavefront degradation induced by turbulence is described. Adaptive optics is simulated on the basis of the tilt-direct wavefront reconstruction. The compensation results are given in the sense of Strehl ratio variation with turbulence coherence length. The variation of residual phase deviation with d/r0 is also discussed.
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