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1.
Laser Feedback Technique for Precise Retardation Measurements   总被引:1,自引:0,他引:1       下载免费PDF全文
费立刚  张书练 《中国物理快报》2006,23(11):2974-2977
A simple and precise retardation measurement based on laser feedback is demonstrated. The measurement principle is based on polarization flipping induced by optical feedback from an external birefringence cavity. The measured wave plate is located in the external cavity. When the length of the external cavity is tuned, the polarization states of laser will flip between two eigenstates, and the position of polarization flipping in one period of intensity modulation will vary with retardation of the wave plate. The duty ratio of two eigenstates is used to determine the retardation. Main advantages of the technique are that it is compact, low cost, fast and flexible. Especially, it is insensitive to a fluctuation of laser intensity and is suitable for on-line measurement. The experimental results have shown that the measurement uncertainty is better than 0.03° in the range 30°-150°.  相似文献   

2.
We present a simple but effective method for small-angle measurement based on optical feedback interferometry (or laser self-mixing interferometry). The absolute zero angle can be defined at the biggest fringe amplitude point, so this method can also achieve absolute angle measurement. In order to verify the method, we construct an angle measurement system. The Fourier-transform method is used to analysis the interference signal. Rotation angles are experimentally measured with a resolution of 10^-6 rad and a measurement range of approximately from -0.0007 to +0.0007 rad.  相似文献   

3.
This paper presents the anisotropic optical feedback of a single frequency intra-cavity He-Ne laser.A novel phenomenon was discovered that the laser output an elliptical polarized frequency instead of the initial linear polarized one.Two intensities with a phase difference were detected,both of which were modulated in the form of cosine wave and a fringe shift corresponds to a λ/2 movement of the feedback mirror.The phase difference can be continuously modulated by the wave plate in the external cavity.Frequency stabilization was used to stabilize the laser frequency so as to enlarge the measuring range and improve the measurement precision.This anisotropic optical feedback system offers a potential displacement measurement technology with the function of subdivision of λ/2 and in-time direction judgment.The three-mirror Fabry-Perot cavity model is used to present the experimental results.Given the lack of need of lasing adjustment,this full intra-cavity laser can significantly improve the simplicity and stability of the optical feedback system.  相似文献   

4.
任成  谈宜东  张书练 《中国物理 B》2009,18(8):3438-3443
External-cavity birefringence feedback effects of the microchip Nd:YAG laser are presented.When a birefringence element is placed in the external feedback cavity of the laser,two orthogonally polarized laser beams with a phase difference are output.The phase difference is twice as large as the phase retardation in the external cavity along the two orthogonal directions.The variable extra-cavity birefringence,caused by rotation of the external-cavity birefringence element,results in tunable phase difference between the two orthogonally polarized beams.This means that the roll angle information has been translated to phase difference of two output laser beams.A theoretical analysis based on the Fabry-Perot cavity equivalent model and refractive index ellipsoid is presented,which is in good agreement with the experimental results.This phenomenon has potential applications for roll angle measurement.  相似文献   

5.
In many applications, it is important to know the waist of a laser beam. However, it is impossible to measure it directly because the intensity is high at the waist. We have used an optical fiber-scan system to characterize the Gauss/an intensity profile of a focused femtosecond laser beam. The measurement system employs a single-mode optical fiber that is fixed on a motorized three-dimensional translation stage to collect the laser energy and the other end is connected to an optical power meter to measure the intensity profile. Using the measure data and geometry formulas, one can calculate the beam waist and far-field divergence angle of a laser beam. The measured beam waist size is essentially consistent with the result of theoretical fit.  相似文献   

6.
External anisotropic feedback effects on the phase difference behaviour of output intensities in a microchip Nd:YAG laser are presented. By rotating a quarter wave plate placed in the external cavity, the angle between laser initial polarization direction and o-axis of the wave plate is tuned from -45°to 45°, which results in variable extra-cavity birefringence along two orthogonal detection directions. With only one optical path and one wave plate, laser intensities of the two orthogonal directions, both modulated by the external cavity length, are output with a tunable phase difference, which can be continuously changed from zero to twice as large as that of the waveplate. Experimental results as well as a theoretical analysis based on Fabry-Perot cavity equivalent model and the refractive index ellipsoid, are presented. The potential applications of this phenomenon are also discussed.  相似文献   

7.
The interaction of an intense femtosecond laser field (~ 10^16 W/cm^2) with argon clusters in a dense jet has been studied by measuring the energy and angle distributions of emitted ions. A directional anisotropy in the ion explosion energies is observed. The experimental results indicate that the average ion energies are up to 40% in the detection direction parallel to the laser polarization higher than that perpendicular to it. The measured ion yield increases about 80%, correspondingly. The findings are interpreted by charge-dependent ion acceleration and explosion of elliptic microplasma spheres.  相似文献   

8.
High precision grating diffraction laser warning system is a photoelectric countermeasure equipment to judge and locate the incoming laser function. In order to improve the positioning accuracy, an improved algorithm for calculating and fitting the calculation parameters of the spot center was proposed. Firstly, the laser spot was preprocessed, and the center coordinates of the connected area were obtained by using the improved connected area marking algorithm and spot center extraction algorithm. Secondly, the azimuth angle and pitch angle were set, the images were collected and the spot center was calculated, and the pixel horizontal and vertical coordinates in x and y direction as well as fitting surfaces of laser parameters were fitted, so as to judge the azimuth angle, pitch angle and wavelength of the incoming laser. Finally, the improved connected area marking algorithm, spot center extraction algorithm and parameter fitting calculation results were compared with the traditional algorithm. The experimental results show that the pitch angle error between the fitting calculation results and the real data is less than 0.4°, and the azimuth angle error is less than 0.2°, which greatly improves the accuracy of laser direction recognition. Copyright ©2022 Journal of Applied Optics. All rights reserved.  相似文献   

9.
A method is proposed to solve the problem of direction discrimination for laser feedback interferometers.By vibrating the feedback mirror with a small-amplitude and high-frequency sine wave,laser intensity is modulated accordingly.The modulation amplitude can be extracted using a phase sensitive detector(PSD).When the feedback mirror moves,the PSD output shows a quasi-sine waveform similar to a laser intensity interference fringe but with a phase difference of approximately ±π/2.If the movement direction of the feedback mirror changes,the phase difference sign reverses.Therefore,the laser feedback interferometer offers a potential application in displacement measurement with a resolution of 1/8 wavelength and in-time direction discrimination.Without using optical components such as polarization beam splitters and wave plates,the interferometer is very simple,easy to align,and less costly.  相似文献   

10.
A sensitive method to determine the optic axis azimuth of the birefringence element is presented, which is based on laser feedback. The phase difference between the two intensities in birefringence feedback changes with the angle between the optic axis of the birefringence element and laser original polarization. The phase difference is highly sensitive to the relative position of the optic axis and the laser original polarization. This method is used to highly precisely determine the optic axis azimuth, and is able to distinguish between the fast axis and the slow axis of the birefringence element. Theoretical analysis and experimental results are both demonstrated.  相似文献   

11.
This paper reports that an experimental investigation of fast pitch angle scattering (FPAS) of runaway electrons in the EAST tokamak has been performed. From the newly developed infrared detector (HgCdTe) diagnostic system, the infrared synchrotron radiation emitted by relativistic electrons can be obtained as a function of time. The FPAS is analysed by means of the infrared detector diagnostic system and the other correlative diagnostic systems (including electron-cyclotron emission, hard x-ray, neutrons). It is found that the intensity of infrared synchrotron radiation and the electron-cyclotron emission signal increase rapidly at the time of FPAS because of the fast increase of pitch angle and the perpendicular velocity of the energetic runaway electrons. The Parail and Pogutse instability is a possible mechanism for the FPAS.  相似文献   

12.
An approach based on depth-sensitive skew-angle x-ray diffraction (SAXRD) is presented for approximately evalu- ating the depth-dependent mosaic tilt and twist in wurtzite c-plane GaN epilayers. It is found that (103) plane and (101) plane, among the lattice planes not perpendicular to the sample surface, are the best choices to measure the depth profiles of tilt and twist for a GaN epilayer with a thickness of less than 2 μm according to the diffraction geometry of SAXRD. As an illustration, the depth-sensitive (103)/(101) ω-scans of a 1.4-μm GaN film grown by metal-organic chemical vapor deposition on sapphire substrate are measured and analyzed to show the feasibility of this approach.  相似文献   

13.
In order to study the collisional quantum interference (CQI) on rotational energy transfer in atom-diatom system, we have studied the relation of the integral interference angle and differential interference angle in Naq-Na2 (A1 ∑u^+,v=8-b^3∏0u,v=14) collision system. In this paper, based on the first-Born approximation of timedependent perturbation theory and taking into accounts the anisotropic effect of Lennard-Jones interaction potentials, we present a theoretical model of collisional quantum interference in intramolecular rotational energy transfer, and a relationship between differential and integral interference angles.  相似文献   

14.
蓝鼎  王育人  张荫民  王维  吴忠华 《中国物理 C》2009,33(11):1016-1018
The monodisperse polystyrene spheres are assembled into the colloidal crystal on the glass substrate by vertical deposition method, which is aimed at the so-called photonic crystal applications. The structural information of the bulk colloidal crystal is crucial for understanding the crystal growth mechanism and devel- oping the various applications of colloidal crystal. Small-angle X-ray scattering (SAXS) technique was used to obtain the bulk structure of the colloidal crystal at Beamline lW2A of BSRF. It is found that the SAXS pattern is sensitive to the relative orientation between the colloidal sample and the incident X-ray direction. The crystal lattice was well distinguished and determined by the SAXS data.  相似文献   

15.
吕磊  王雯宇  熊兆华 《中国物理 C》2010,34(12):1791-1796
Subject to neutrino experiments, the mixing matrix of ordinary neutrinos can still have small vi-olation from unitarity. We introduce a quasi-unitary matrix to interpret this violation and propose a natural scheme to parameterize it. A quasi-unitary factor △QF is defined to be measured in neutrino oscillation exper-iments and the numerical results show that the improvement in experimental precision may help us figure out the secret of neutrino mixing.  相似文献   

16.
The two-dimensional barrier passage is studied in the framework of Langevin statistical reactive dynamics. The optimal incident angle for a particle diffusing in the dissipative non-orthogonal environment with various strengths of coupling between the two degrees of freedom is systematically calculated. The optimal diffusion path of the particle in a non-Ohmic damping system is revealed to have a probability to return to the potential valley under the combined influence of the off-diagonal system tensors.  相似文献   

17.
Data were taken at the energy 2E = 990 MeV to search for multibody events, with the same large solid angle detector which has been used for the measurement of the , ω andφ production by e+e annilations. Assuming a π+ππ0π0 production by the quasi two-body process e+e → → ωπ0 we give the correspondi ng cross section σ(e+e → π+ππ0π0) = (1.1 ± 0.5) 10−32 cm2. Since no events with 3 and 4 charged pions have been observed σ(e+e → π+ππ0π) 1.5 × 10−33 cm2.  相似文献   

18.
The purpose of the present paper is to study the entropy hs(Ф) of a quantum dynamical systems Ф = ( L, s, Ф), where s is a bayessian state on an orthomodular lattice L. Having introduced the notion of entropy hs( Ф, A) of partition A of a Boolean algebra B with respect to a state s and a state preserving homomorphism Ф, we prove a few results on that, define the entropy of a dynamical system hs(Ф), and show its invariance. The concept of sufficient families is also given and we establish that hs (Ф) comes out to be equal to the supremum of hs (Ф,A), where A varies over any sufficient family. The present theory has then been extended to the quantum dynamical system ( L, s, Ф), which as an effect of the theory of commutators and Bell inequalities can equivalently be replaced by the dynamical system (B, s0, Ф), where B is a Boolean algebra and so is a state on B.  相似文献   

19.
The atomic and electronic structures of T1 and In on Si(111) surfaces are investigated using the firstprinciples total energy calculations. Total energy optimizations show that the energetically favored structure is 1/3 ML T1 adsorbed at the T4 sites on Si(111) surfaces. The adsorption energy difference of one T1 adatom between (√3 × √3) and (1 × 1) is less than that of each In adatom. The DOS indicates that TI 6p and Si 3p electrons play a very important role in the formation of the surface states. It is concluded that the bonding of TI adatoms on Si(111) surfaces is mainly polar covalent, which is weaker than that of In on Si(111). So T1 atom is more easy to be migrated than In atom in the same external electric field and the structures of T1 on Si(111) is prone to switch between (√3 × √3) and (1 × 1).  相似文献   

20.
鲁重贤 《中国物理》2007,16(3):635-639
The Eotvos experiment on the verification of equivalence between inertial mass and gravitational mass of a body is famous for its accuracy. A question is, however, can these experimental results be applied to the case of a physical space in general relativity, where the space coordinates could be arbitrary? It is pointed out that it can be validly applied because it has been proven that Einstein's equivalence principle for a physical space must have a frame of reference with the Euclidean-like structure. Will claimed further that such an overall accuracy can be translated into an accuracy of the equivalence between inertial mass and each type of energy. It is shown that, according to general relativity, such a claim is incorrect. The root of this problem is due to an inadequate understanding of special relativity that produced the famous equation E=mc^2, which must be understood in terms of energy conservation. Concurrently, it is pointed out that this error is a problem in Will's book, ‘Theory and Experiment in Gravitational Physics'.  相似文献   

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