共查询到20条相似文献,搜索用时 15 毫秒
1.
A two-step white-light spectral interferometric technique to measure the relative phase change on reflection from a thin-film structure is presented. The technique is based on recording of the channeled spectra at the output of a Michelson interferometer and their processing by using a windowed Fourier transform to retrieve the phase functions. In the first step, the phase difference between the beams of the interferometer with a thin-film structure is retrieved. In the second step, the structure is replaced by a reference sample of known phase change on reflection and the corresponding phase difference is retrieved. From the two phase differences, the relative phase change on reflection from the thin-film structure is obtained. The feasibility of the simple method is confirmed in processing the experimental data for a SiO2 thin film on a Si wafer of known optical constants. Four samples of the thin film are used and their thicknesses are determined. The thicknesses obtained are compared with those resulting from reflectometric measurements, and good agreement is confirmed. 相似文献
2.
We present a spectral interferometric method to measure the thickness of an optical plate or a film with a single layer. The system is based on the Michelson interferometer configuration, and the spectral interference signal of a broadband light source is recorded by a spectrometer. The optical path difference (OPD) between two interfering beams can be obtained by Fourier transform from the spectral interferogram. Gaussian fitting is used to find the exact peak of fringe to enhance the precision of the measurements. When the sample is inserted into the sample beam, the film’s thickness can be calculated by comparing the change of OPD, provided that the sample group refractive index is known. Only a single measurement is needed to determine a film’s thickness after the initial OPD of the system is calibrated. As no moving parts are required, the system has good stability. In particular, a large range of thicknesses, from micrometers up to several millimeters, can be measured. Such a large range is valuable for optical measurements. For demonstration, we measured the thicknesses of preservative film, cover glass and carrier glass, which were 9.6 ± 0.55, 156.1 ± 0.75, 1008.44 ± 0.96 μm, respectively. 相似文献
3.
<正>The dispersion of Yb-doped fiber is measured by a spectral interferometric technique.The experimental verification is achieved by comparing the measured data with published data of the Nufern 1060xp fiber and the measurement relative error is 1.36%.The parameters of the experimental system,such as minimum required source bandwidth and minimum fiber length,are introduced and analyzed in the measurement. The minimum required source bandwidth predicted through theoretical calculation at the center wavelength of 1070 nm is 19.3 nm,which perfectly agrees with the experimental value. 相似文献
4.
V. G. Voevodin M. A. Krivov B. A. Kuritsyn A. N. Morozov 《Russian Physics Journal》1985,28(2):136-139
The processes occurring in the up-conversion of a spatially modulated signal in a nonlinear thin-film waveguide are subjected to Fourier analysis. The conditions of parametric image transformation with increase in frequency using a multimode waveguide are determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 55–58, 1985. 相似文献
5.
We present a new white-light interferometric technique to measure the group index of holey fibres over a wide wavelength range. The technique utilizes an unbalanced Mach–Zehnder interferometer with a fibre under test of known length placed in one of the interferometer arms and the other arm with adjustable path length. In a first step, the differential group index of the fibre is measured over a wide wavelength range. In a second step, the fibre is replaced by the reference sample of known thickness and group dispersion to determine precisely the group index of the fibre at one specific wavelength. The group index as a function of wavelength is measured for two different holey fibres, one made of pure silica glass and the other made of SK222 glass. For both fibres, the wavelength dependence of the group index of the outer cladding and modes supported by the fibre is measured. 相似文献
6.
A recently published method for the determination of phase derivatives maps by direct manipulation of three or more phase-shifted interferograms is tested for accuracy. The method is evaluated on computer-simulated holographic and electronic speckle pattern interferometry fringes and the results are assesed through the calculation of two comparative parameters: the relative image difference and the linear correlation coefficient. It is shown that errors in the phase derivative strongly depend on the filtering method used for smoothing the fringe patterns. An experimentally recorded ESPI fringe pattern is used to confirm the predictions of the numerical simulations. 相似文献
7.
S. Yu. Gavrilkin O. M. Ivanenko K. V. Mitsen A. Yu. Tsvetkov 《Bulletin of the Lebedev Physics Institute》2014,41(2):47-52
An advanced technique for contactless study of critical parameters of superconductor materials, based on measurements of the sample nonlinear response to local excitation by an ac magnetic field, is proposed. The results of numerical simulation of the nonlinear response signal spectrum are presented and compared with measurement results. The possibility of reconstructing the superconductor current-voltage characteristic by the response signal shape is considered. 相似文献
8.
《Optics Communications》2004,229(1-6):29-37
An speckle interferometric technique to monitor the thinning process of vertical soap film before the film rupture is presented. The interferometric arrangement consists in a double aperture pupil optical system which images an input diffuser. In a first step, a reference specklegram is stored in the computer buffer memory. Afterwards, the soap film is located in front of one pupil aperture, an uniform displacement of the diffuser is produced and a new speckle pattern is stored. The soap film status is characterized in terms of the changes that this dynamic phase object introduces in the correlation fringes obtained by applying a FFT algorithm to the resulting summed specklegram. This procedure is done in real time as far as the soap film evolves in the successive status. It is experimentally demonstrated that the soap film during drawing acts as a variable wedge. The correlation fringes behavior becomes an important tool to establish the wedge shaped soap film angle and the thickness variations. 相似文献
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10.
We measure the spectral densities of fluctuations of an underdamped nonlinear micromechanical oscillator. By applying a sufficiently large periodic excitation, two stable dynamical states are obtained within a particular range of driving frequency. White noise is injected into the excitation, allowing the system to overcome the activation barrier and switch between the two states. While the oscillator predominately resides in one of the two states for most frequencies, a narrow range of frequencies exist where the occupations of the two states are approximately equal. At these frequencies, the oscillator undergoes a kinetic phase transition that resembles the phase transition of thermal equilibrium systems. We observe a supernarrow peak in the spectral densities of fluctuations of the oscillator. This peak is centered at the excitation frequency and arises as a result of noise-induced transitions between the two dynamical states. 相似文献
11.
B. Bhushan 《Optics and Spectroscopy》2016,121(2):276-282
We have reported the measurement of third-order optical nonlinearity by antiresonant ring interferometric nonlinear spectroscopic (ARINS) technique and discussed its usefulness over other popular measuring techniques such as Z-scan, degenerate four wave mixing (DFWM) and third harmonic generation (THG). The measurement has been simulated theoretically by taking different numerical values as well as sign of δ, which is a key parameter of ARINS. The technique has been benchmarked using toluene and the theoretical simulation has been substantiated experimentally by measuring the nonlinear optical coefficients (n2 and β) of two different samples. The disadvantages of the technique have also been discussed. However, a number of advantages of ARINS override its disadvantages and therefore, ARINS may be preferred over other measuring techniques for the measurement of nonlinear optical parameters. 相似文献
12.
L. M. Blinov V. V. Lazarev S. P. Palto S. G. Yudin 《Journal of Experimental and Theoretical Physics》2014,118(6):990-994
A new method is proposed to study the macroscopic ac fields in the elements of thin-film ferroelectric-dielectric heterostructures during their electric switching. For this purpose, the local field surrounding dielectric molecules is measured. It is important that the dielectric has a characteristic very narrow molecular absorption band, which is used as an electric-field probe. The heterostructure under study consists of a glass substrate, a transparent electrode, a 170-nm-thick layer of polymer ferroelectric, a 40-nm-thick dielectric layer, and a semitransparent electrode. Both functional layers are grown by the Langmuir-Blodgett method. An ac electric field is applied to the electrodes, and the local field having appeared in the dielectric is measured by the electroabsorption method. With allowance for the Lorentz factor, the local field is easily converted into the macroscopic field in the dielectric layer and, then, in the ferroelectric layer. The classical Sawyer-Tower scheme is used as an additional tool to determine the surface charge to be switched at the dielectric-ferroelectric interface. 相似文献
13.
Radunsky AS Williams EM Walmsley IA Wasylczyk P Wasilewski W U'Ren AB Anderson ME 《Optics letters》2006,31(7):1008-1010
We propose and demonstrate a novel implementation of spectral-shearing interferometry (SSI) for reconstructing the electric field of ultrashort pulses by utilizing asymmetric group velocity matching in a long nonlinear crystal. The proposed configuration eliminates the requirement for a linearly chirped auxiliary pulse that is in common in all existing SSI methods, relying on nonlinear conversion to produce a spectral shear. 相似文献
14.
In this study a novel method for determining surface flatness based on spectral interferometry is reported. In the traditional method a laser is used to produce intensity interference fringes and by measuring the shift in the position of a fringe when a test plate is put on a reference plate, the surface flatness of the test plate is determined. In the present study we have used a broad-band source for determining the flatness of a test plate. By studying the changes in the spectrum of the source on interference that are produced when a test plate is put on a reference plate, the surface flatness is determined. It has been found that the surface flatness determined by spectral studies comes out to be of the same order as that with a quasi-monochromatic laser light. This method might provide an edge over the present method by reducing the time taken in the study and also provide a cost-effective solution. 相似文献
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16.
A. A. Kovalyov O. P. Pchelyakov V. V. Preobrazhenskii M. A. Putyato N. N. Rubtsova 《Laser Physics》2007,17(4):478-481
A reflection interferometer based on a thin metal film is proposed to measure the phase of the reflection spectrum of laser mirrors. The device is applied to the study of the phase characteristics of the all-semiconductor mirror which combines the functions of the saturable absorber and the dispersion compensator (all-in-one) in the Nd3+:KGd(WO4)2 laser operating in the ultrashort-pulse regime. The method provides improvement of spectral resolutions and an increase in the accuracy in the measurement of the phase characteristics. 相似文献
17.
We present a new methodology that obtains, in an analytical way, the complex electric field of ultrashort pulses. This methodology is based only on Fourier analysis of the frequency components of spectrally resolved interferometric collinear autocorrelations. We present an experimental demonstration of this technique and the results are compared with the conventional second-harmonic generation frequency-resolved optical gating technique. 相似文献
18.
Photodegradation of melanin thin films is investigated for a UVA wavelength of 355 nm and a UVC wavelength of 244 nm. The technique involves interferometric exposure of melanin with two coherent beams from a low-power UV laser. The periodic photodegradation-grating pattern is monitored by diffraction of a second low-power He-Ne laser. Dependence of the photodegradation rate on UV intensity as well as the effect of ambient humidity is investigated and explained with a simple model. The technique has promise for investigating photo-induced effects in other biomolecular substrates as well. 相似文献
19.
A theoretical treatment for multiple-beam fringe visibility taking into consideration the profile of the spectral source is derived for (a) a Gaussian profile; and (b) a Lorentzian profile. A comparative study between the visibility of the two profiles is presented. Expressions for the intensity distribution for Doppler and Voigt cases are given. The fringe visibility dependence on the half-width of the spectral profile of the light illuminating the interferometer for the two cases, namely Lorentzian and Gaussian, is presented. This leads to the view that the coherence length for a Voigt profile is less than it is in the absence of Doppler or pressure broadening. Multiple-beam Fabry-Perot fringes in transmission have been utilized for the determination of the coherence length of the two spectral lines emitted from 198Hg at wavelengths of 5461 Å and 4358 Å. The method for determination is based on the variation of the visibility of the recorded interference fringes with path difference. 相似文献
20.
Y. Li Y. Song J. Yang K. Yang X. Zhang Y. Wang 《Applied physics. B, Lasers and optics》2008,92(2):253-257
A unique phase object (PO) with both positive and negative phase retardation is used in the nonlinear-imaging technique with
a phase object (NIT-PO) to measure the nonlinear refractive index of materials. Using positive–negative PO, one can increase
the sensitivity of the NIT-PO compared with the conventional uniform PO. The improvement of sensitivity is especially significant
at negative nonlinear shift regions, and can reach an order of magnitude near the nonlinear phase shift ΔϕNL=-π. The sensitivity increase of the NIT-PO with positive–negative PO is from 1.7 to 3.0 times greater when compared with
the Z-scan technique within ΔϕNL≤|π|. An empirical expression is obtained which allows for direct calculation of the Kerr coefficient from measured the nonlinear
image. CS2 is used to demonstrate the measurement using a positive–negative PO.
PACS 42.65.-k; 42.30.Kq 相似文献