Precise force measurement method by a Y-shaped cavity dual-frequency laser

A novel precise force measurement based on a Y-shaped cavity dual-frequency laser is proposed.The principle of force measurement with this method is analyzed,and the analytic relation expression between the input force and the change in the output beat frequency is derived.Experiments using a 632.8-nm Y-shaped cavity He-Ne dual-frequency laser are then performed;they demonstrate that the force measurement is proportional to a high degree over almost five decades of input signal range.The maximum scale factor is observed as 5.02×109 Hz/N,with beat frequency instability equivalent resolution of 10-5 N.By optimizing the optical and geometrical parameters of the laser sensor,a force measurement resolution of 10-6 N could be expected.     

A novel orthogonal polarized dual-frequency laser using a Y-shaped cavity

In this paper, we propose and demonstrate a novel dual-frequency He-Ne laser based on a Y-shaped cavity. The laser uses a polarization beam splitter to produce two orthogonal polarized beams that oscillate simultaneously in different sub-cavities. The different optical lengths of the cavities produce two longitudinal mode series with different mode spacing. In our experiments, a frequency difference between two orthogonal polarized lights ranging from 26 to 665 MHz was observed by changing the voltage applied to the piezoelectric transducer attached to the mirror of P polarized sub-cavity. The lock-in frequency difference is about 26 MHz. The competing processes were also investigated.     

A novel active optical approach for acceleration measurement based on a Y-shaped cavity dual-frequency laser

A novel active optical approach for acceleration measurement based on a Y-shaped cavity dual-frequency laser is presented and demonstrated. Applied acceleration causes a change in the refractivity of sensing gas in one of the two cavities, resulting in a beat frequency variation between two orthogonal polarized lights. As a result, this approach produces a modulation of beat frequency strictly proportional to the input acceleration. Preliminary experiments with a 632.8 nm Y-shaped cavity He–Ne dual-frequency laser confirm the validity of the laser sensor. The experimental results show that the laser sensor in this approach characterizes a nearly linear response to the input acceleration, which is a projection of gravitational acceleration. The experimental values of the scale factors are mostly in good agreement with theoretical ones. By optimizing the optical and geometrical parameters of the laser sensor, an acceleration measurement resolution of 10^?5–10^?6 gravitational acceleration (within ±5 g measurement range) could be expected. Furthermore, we investigate the principle about the sign of the scale factor in detail, and propose a simple but efficient method to distinguish the direction of the acceleration acted on the laser sensor.     

Optical feedback characteristics in a dual-frequency laser during laser cavity tuning

The optical feedback characteristics in a Zeeman-birefringence dual-frequency laser are studied during the laser cavity tuning in three different kinds of optical feedback conditions: (i) only // -light is fed back; (ii) only ⊥-light is fed back; (iii) both lights are fed back.A compact displacement sensor is designed using the experimental result that there is a nearly 90 degrees phase delay between the two lights' cosine optical feedback signals when both lights are fed back into the laser cavity.The priority order that the two lights' intensity curves appear can be used for direction discrimination. The resolution of the displacement sensor is at least 79 nm, and the sensor can discriminate the target's moving direction easily.     

Experimental study of an argon laser discharge in a transverse magnetic field

Summary The influence of a static magnetic field orthogonal to the axis of an argon laser discharge is investigated. The enhancement of the small-signal gain at 488 nm is measured as a function of the magnetic field at different values of the parameters of the discharge. The data about the gain compared with the measurement of the fluorescence from the upper level of the 488 nm line give information about the excitation mechanisms. A strong enhancement of the ionization rate of Ar⁺ is detected.     

Suppression of magnetic relaxation by a transverse alternating magnetic field

The evolution of the spatial distribution of the magnetic induction in a superconductor after the action of the alternating magnetic field perpendicular to the trapped magnetic flux has been analyzed. The observed stabilization of the magnetic induction profile is attributed to the increase in the pinning force, so that the screening current density becomes subcritical. The last statement is corroborated by direct measurements.     

Breakdown in the transverse magnetic field

The breakdown between coaxial cylindrical electrodes in the homogeneous axial magnetic field in the pressure range around the Paschen minimum is studied. On the right of this minimum the breakdown voltage is not practically influenced by a weak magnetic field. On the left of this minimum the breakdown U-B curves can be divided into two branches: the upper ones can be approximated by the magnetron cut-off parabola, the lower ones correspond qualitatively in some cases to the second solution of the equation for breakdown in the inhomogeneous electric field corrected with respect to the losses of electrons caused by recapturing on the cathode.     

Focusing of electrons by a transverse magnetic field

The foundations of the focusing of electrons by a transverse magnetic field proposed by V.S. Tsoi in 1974 have been reviewed. The kinetics of electrons in condensed media and interactions of conduction electrons with interfaces has been studied by means of the focusing of electrons. Various applications of the focusing of charge carriers in low-dimensional, including two-dimensional, electron systems have been demonstrated.     

Improvement of confinement in tokamaks by weakening of poloidal magnetic field near boundary

Theory of turbulent equipartition and experiment indicate that density, pressure, and temperature profiles follow the poloidal magnetic field profile. Therefore, it is suggested to change the magnetic geometry between core and boundary by toroidal conductors and/or plasma current. As a result, density and temperature gradients will become steeper, and stored energy will be higher with low boundary plasma parameters. The suggested new mode of confinement may substantially simplify achieving of ignition.     

Net acceleration of high-energy electrons by net inverse Bremsstrahlung of a laser wave in a uniform magnetic field and a transverse undulating magnetic field

The nonzero net dc force acting on relativistic beam electrons traveling in a uniform magnetic field, a laser wave, and transverse undulating magnetic field (magnetic wiggler) is calculated by using quantum-kinetics in accordance with the correspondence principle. It is found that the average of this force can be as strong as the Lorentz force of the laser wave in an electron energy region beyong energies for free electron lasing, and decreases linearly with the inverse of the electron energy far beyond this energy region.     

Thin ferromagnetic nanodisk in transverse magnetic field

The magnetization of a ferromagnetic nanodisk is studied using micromagnetic modeling. It is demonstrated that, under an external magnetic field applied perpendicular to the disk surface, magnetic phase transitions can occur between uniform states, between uniform and vortex states, and between vortex states with different directions of polarization. A simple variation model is proposed describing the observed magnetic states quantitatively.     

Frequency doubled diode laser in alternative extended cavity

We report on an alternative extended cavity scheme used with a 180 mW quantum well GaAlAs diode laser, operating near 850 nm. A dispersing prism and a thin glass plate are employed to enforce stable single-mode operation in the strong feedback regime, with no need for laser AR coatings. Compared to other configurations where a grating is used, the lower loss in the extended cavity allows higher fundamental power available for second harmonic generation. For example, by frequency doubling using potassium niobate in a power enhancement cavity, enough power can be generated from a single diode laser to decelerate and trap calcium atoms with radiation at 423 nm.     

Ultrasonic attenuation of aluminium in transverse magnetic field

The attenuation of longitudinal sound wave in Al single crystal in high transverse magnetic field has been calculated by 4-OPW approximation. The wave vector of the sound wave is parallel to [1$\text{1}$0] axis. In general, the result agrees well with Berre's experiment. The attenuation plotted against the magnetic field direction has 3 peaks which are explained in terms of the geometry of the Fermi surface of Al.     

The correlation between frequency difference and mode polarization in an intracavity birefringent dual-frequency laser

We discuss the correlations between the measured lasing-mode frequency difference and the mode polarization angle in an intracavity birefringent dual-frequency laser. The frequency difference and polarization are adjusted by rotating an intracavity quartz crystal through a large angular range. We propose two kinds of frequency difference: the equal-order frequency difference and the adjacent frequency difference. By measuring the equal-order frequency difference versus the quartz crystal rotation angle, the real physical process behind frequency splitting is revealed. Based on this, the adjacent frequency difference curve is also obtained. The emitted laser beam polarization angle is also measured for large rotations of the intracavity quartz crystal. These measurements reveal the complete process of optical activity in frequency splitting and allow us to predict the trends of frequency difference and polarization angle for large quartz crystal rotation angles. We analyze the correlations between the equal-order frequency difference and the polarization angle based on the experimental results, which show that the certain points on the two curves are inter-related. The principal results agree well with the optical theory of crystals.     

Zeeman双频激光器频率分裂与纵模间隔变动一致性分析

激光谐振腔内相位各向异性会引起频率分裂,两分裂模的频差大小由表现出的相位延迟所决定.对于腔内相位延迟较小的He-Ne激光器,两分裂模很接近,处于烧孔重叠区,存在模式竞争而不能同时振荡,形成隐频率分裂.同时,使得激光器两正交偏振方向上的相邻级纵模产生固定的变动量,其大小等于隐频率分裂量的2倍.如果沿激光偏振方向施加横向磁...     

Simulation of optical field in laser resonators cavity by eigenvector method

In this paper, an Eigenvector method (EM) for the calculation of optical resonator modes and beam propagation is introduced, in which the transit matrix of an optical resonator is obtained by dividing the mirror into finite grids based on the Fresnel–Kirchoff diffractive integral equation. Then, the eigenvectors, representing the multimode characteristics of the resonator, can be calculated by solving the integral matrix eigenequation. The merits of EM include that the considerably simpler procedure of solution of eigenvectors of the matrix eigenequation replaces the complicated iteration in traditional methods, and there is no dependence on the initial field distribution, and a number of modes can be derived once and the discrimination capability of the resonator can be evaluated easily. The examples using EM to simulate con-focal resonators with small or large Fresnel numbers are given, and the calculated results, well matched with Fox–Li method or Lagueree–Gaussian approximation analytical solution, prove that EM is highly feasible and reasonable.