Roughness investigation of the polished quartz and sital substrates, used as substrates for multilayer interference mirrors in circle laser gyroscopes, were carried out. Atomic force microscopy, x-ray scattering and angle-resolved scattering instruments were used. The power spectral density function and effective rms roughness were calculated. Good correlation of power spectral density functions and effective rms roughness was shown for all instruments. Essentially difference of the polishing quality was shown for sital substrates manufactured by two different producers.
Application of laser Michelson interferometers as the strainmeters for sensing of earthquake precursors is described. Earthquake precursors can appear as anomalous deformations (local irregular crustal movements and tilts, global slow periodical lithosphere oscillations) or anomalous changes of the Earth free oscillations in amplitude and frequency. The most perfect instrument with highest sensitivity to the crustal movements is the laser interferometer-strainmeter. The precursoral relative crustal movements have the order 10-6- 10-7 for irregular local strains and 2-3 orders less for slow global seismic oscillations. Laser interferometer sensitivity to the crustal movements is approved to reach about 10-12 and it is obviously enough for detection of any type of precursoral strains. Some results of two seismic stations equipped by the long-base laser interferometer-strainmeters and built in Russia, at the North Caucasus (Baksan canyon) and in the Ukraine, near the Black Sea (the Crimea peninsula) are analyzed. These stations make continuous monitoring to registrate the changes of crustal strains, investigate the total spectrum of the Earth free oscillations and dynamics of lithosphere slow deformations. The sensitivity of the instruments is so high that they registrate the earthquakes all over the world, and recent results are presented in this paper. There are some good approvals that the deformation precursors sensing is the most perspective way for the earthquake prediction, and the long-base laser interferometers-strainmeters demonstrate high possibilities in this application. Perspectives of development of the new laser interferometer-strainmeters based on Russia high optical technologies and unique design are discussed.
Light angle-resolved and total integral scattering (ARS and TIS) have been used for several decades to probe surface roughness and heterogeneities in optical multilayers and substrates. We present a summary of results reached in laser metrology techniques in our Institute. Elaboration of the optical surface finish technology requires non-destructive sensitive measurement methods subsequent development. Need optical surfaces for precision quantum electronics devices are usually composed of irregularities smaller than 1 nm "high" with "slope" of low gradient of perhaps 0,001 rad relative to the mean surface and destructive layer thickness about tens of nanometres. There are described application of ARS method and automatically device, based on this method for testing optically transparent surfaces by scattering indicatrix analysing. We discuss the problem: how it can measure surfaces roughness of inside scattering materials substrates and separate of surface roughness and substrates material heterogeneity effects. We touched up the questions: how surface rms-roughness of substrates correlates with scattering of mirrors and how smooth surfaces of substrates correlate with back specula scattering of ion-sputtering on these substrates mirrors. In some cases of our researches we compared the light scattering measurement results with the results of atomic force microscope (AFM) and X-rays scattering (XRS) measurement methods.
The opportunity to use the compact high-stable interferometer for testing of optical materials homogeneity, in particular, laser and nonlinear crystals, Q-switchers and others is analyzed. The interferometer is based on modified Michelson scheme with using corner cubes and works with laser sources of different visible and infrared wave lengths.
The analyzes and processes of interferometric picture visibility functions for using laser sources with different mode radiation are discussed. As it shown the laser source for interferometer may be not only one mode laser but a laser with some modes which has a periodical visibility function. In the presented interferometer the measurements of wave fronts distortions are realized with using of one mode He-Ne laser with wavelength radiation 0,63 μm and some modes YAG:Nd3+ on 1,06 μm. The comparison of measurements results showed good repeatability and repetitions.
It's shown that sensitive of this interferometer to transmitted wave front quality is about λ/10 on parameter peak to valley (PV) error representing the highest and lowest points, more good then 0.02-0.03 λ on parameter root mean square (RMS) deviations from plane front of radiation and some angular seconds to value of optical wedge.
Ion beam optical coatings based on titanium, tantalum and silicon oxides find wide application in visible and near IR lasers since they allow production of mirrors with a high coefficient of reflection as well as provide high laser damage thresholds. This paper reports on development of the coatings with low absorption and scattering and high coefficient of reflection (99.98%) at 632 nm for circular polarization and an angle of bean incidence of 45 degree(s) as well as on the protective antireflection coatings on BBO crystals and silicate glass at 1064 nm with high laser damage thresholds (15 . . .20 J/cm2). Absorption, scattering and loss in the mirrors as well as laser damage thresholds of the protective antireflection coatings have been measured.
Zeeman laser gyros have found wide application. Contrary to ordinary laser gyros operating at linear polarization of emission, Zeeman gyros require the use of mirrors having low losses in both polarizations at oblique incidence of laser emission and minimum phase anisotropy. High-reflection TiO2 and SiO2 mirrors at 632 nm for such gyros have been produced by ion-beam sputtering for the angle of beam incidence of 45 +/- 1 degree. The characteristics of the optical coatings have been measured by laser modulated photothermal radiometry, photothermal deflection technique, total integrated scattering measurements, the resonance method using the ring cavity, and the ellipsometrical method. The obtained results have allowed optimization of the coating deposition processes. For the 23...25-layer mirrors the following results have been obtained: (i)absorption - 30...70 ppm; (ii) total integrated scattering - 50...70 ppm; (iii) total loss - 250...300 ppm in circular polarization; (iv) phase anisotropy of p and s components of emission - 0.03...0.05 rad. The produced mirrors have allowed realization of compact Zeeman laser gyros with a lock-in about 100...200 Hz and an accuracy of angular velocity measurement at a level of 0.1 degree/h. The ways to reduce the ion-beam mirror losses are discussed.
The comparison of different methods of measuring surface roughness parameters, i.e. angle-resolved scattering (ARS) technique and atomic force microscope (AFM) profilometry, was performed for quartz precise optical surfaces, obtained by different polishing processes. The functions of power spectral density, calculated form ARS, using vector scattering theory, and form AFM data are in good agreement in the range of polar scatter angles 30..75 degrees. In this range the angular scattering is well predicted using the exponential autocorrelation function with parameters, calculated from surface profile. The autocorrelation length, calculated from ARS data in above range using exponential statistics, remains practically constant for different surfaces, obtained by the same polishing process. The latter allows to consider it as the characteristic parameter of certain polishing process.
The comparison of different methods of measuring surface roughness parameters, i.e. angle-resolved scattering (ARS) technique and atomic force microscope (AFM) profilometry, was performed for quartz precise optical surface, obtained by different polishing processes. The functions of power spectral density, calculated from ARS, using vector scattering theory, and from AFM data are in good agreement in the range of polar scatter angles 30..75 degrees. In this range the angular scattering is well predicted using the exponential autocorrelation function, with parameters, calculated from surface profile. The autocorrelation length, calculated from ARS data is above range using exponential statistics, remains practically constant for different surfaces, obtained by the same polishing process. The latter allows to consider it as the characteristic parameter of certain polishing process.
This paper presents complex method and the description of the setup based on it that allows to control different parameters of ring laser cavities for gyro sensors during the technological process of manufacturing. First of all this is accuracy of mono-block cavity manufacturing, accuracy of mirror alignment, the level of cavity selection, the control of sphericity of cavity, measurement of diffraction cavity losses, back scattering and the active substance gain in the cavity. Complex method combines the analysis of cavity transmission spectrum, measurement of the resonance transmission peak and measurement of radiation decay time in the cavity. The analysis of the influence of cavity characteristics on the accuracy of laser gyros is carried on.
It is described the method and the laser system for measure of high quality optical cavity characteristics based on the multibeam Interferometric effects. The discussion of the opportunity to make coefficients of total and diffraction cavity loss measurements, reflectivity measurements of low-loss highly reflecting mirror coatings and gain measurements of the active substance is given. The possibility to control of the resonance cavity spectrum, a level of selection, a quality of the mirrors alignment and an accuracy of the cavity monoblock making is discussed. It is shown that measurement method and system are suitable for measure R before 0.9999 and has own primary range of application.
Necessity of supersmooth optical radiation transparent surfaces and laser mirrors with minimum losses through scattering creation required the subsequent development of refiectometric nondestructive surface roughness measurement methods. There are the scalar theory of reflectivity from rough es' and the vector theory 2 have been worked out in the present time. The last of them takes in account interaction of the electromagnetic radiation with surface electrons and influence of the reflectivity material constants. There is the comparative analysis of the scattering light spatial distribution measurement methods given in this paper. The reflectivity radiation diffusion component is examined as a function of the statistical parameters root mean square (rms) surface roughness a, autocovariance length of the surface a and root mean square microfacet pitch tg y = a/a. There is the optical radiation transparent measurement method3 discussed in this work. The results of this measuring method for supersmooth surfaces were compared with theory and ones obtained with other methods and it was received good agreement. The connection of the scattering indicatrix with the parameters of the high quality laser mirrors has been described in this work. The methods which allow to measure back scattering and scattering "in mode" and influence this differential scattering to the interferometrical measurement devices parameters are discussed.
Analyzed are different measurement methods of high quality optical cavity characteristics based on the many-beams interferometry effects. The discussion of the opportunity to make coefficients of total and diffraction cavity loss measurements, reflectivity measurements of low-loss highly reflecting mirror coatings and gain measurements of the active substance is given. The possibility to control of the resonance cavity spectrum, a level of selection, a quality of the mirrors alignment and an accuracy of the cavity monoblock making is discussed. Compared is the method based on the analysis of the cavity transmission spectrum and an alternative method based on the exponential decay time measurement. It is shown that examined methods are suitable for high quality cavity loss measurements although each of them has own peculiarity and own primary sphere of application. Each of them may be more or less of use for others enumerated laser parameters measurements.
The automatic measuring device for the control of technology and for polishing surface roughness
measurements has been described in this work. This device has very high sensibility and allows to measure
rms ( root mean squared ) roughness U equal some angstroms. There is noncontactive and nondestructive
photometric measurement. It is based on the differential scattering measurement. We develop the theoretical
framework for the device to definite absolute quantity rms roughness a and correlation length a. It has been
demonstrated that this device together with method allows to measure surface roughness of samples from
different materials including transparent ones for laser light. It was foreseen that the scattering from the
untest surface of sample would be led out. It allowed to measure the transparent samples without sputtering
reflective films. Sensibility of defination of rms roughness is about 1 A, with precision about 30%.
The results of this measuring method were compared with ones obtained with other methods and it was
received good agreement. The results of the investigation of the surface samples roughness with different
technology has been described. This method of measurement has an industrial application for control
different surfaces roughness.
Described are procedure and technique capable of analyzing cavity spectra,making coefficients of total
and diffracted cavity loss measurements,reflectivity measurements of low-loss highly reflecting mirror
coatings and gain measurements of active substance. Measurer also makes it possible to control a level of
selection, a quality of mirrors alignment and an accuracy of cavity monoblock making. The apparatus
analyzes transmission or reflectivity spectra of controled cavity, directly measure output pulse width
proportional to cavity linewidth (FWHM intensity) and time proportional to frequency distances apart the
transmission or reflectivity lines. We develope the theoretical framework for the device and discuss in what
conditions and to what extent the output pulse width and the time proportional to frequency distances apart
the lines measuremcits represents a true measure of cavity parameters. Current apparatus provides a cavity
loss and gain resolution 0.0001 and spectral resolution 10 kHz.
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