Beam Deflection Angle Research Articles

Beam deflection by an aperiodic binary diffraction grating

In this article we investigate the beam deflection by a one-dimensional binary diffraction grating. We propose a simple theoretical expression that can be used to predict the beam deflection angle due to both periodic and aperiodic binary grating profiles. We show that the theoretically calculated beam deflection angles agree well with the experimentally obtained deflection angles for various grating patterns. Thus the expression can be used to precisely position the deflected beam at a predetermined location. Further, we show that the theoretical expression can be used to construct a map between the spatial frequency of the grating and the deflection angle which can be employed to deflect the beam at equal intervals by sequentially changing the spatial frequency in accordance with the map. We also demonstrate the superior beam repeatability of a binary grating based beam scanner.

Studying integrated silicon-lens antennas for radio communication systems operated in the 60 GHz frequency band

We consider the development of an integrated lens antenna for LAN radio communication systems operated in the 60 GHz frequency band. The antenna is an extended hemispherical silicon lens. On its flat surface, a microstrip antenna element is located. The use of silicon, which has a dielectric permittivity e = 11.7, as the lens material ensures the maximum range of scanning angles for the minimum axial size of the lens. The approximate analytical formulas, which are used for initial calculations of the lens parameters, allow one to evaluate the basic parameters of the lens antenna integrated with the microstrip antenna element. For further optimizing the parameters of the lens and the antenna element, 3D simulation of the electromagnetic-field distribution was performed. Based on its results, we have developed and manufactured extended hemispherical silicon lenses, which had radii of 6 and 12 mm. The planar microstrip antenna element was manufactured by the low temperature co-fired ceramics (LTCC) technology. The results of simulation and experimental studies of the manufactured prototypes demonstrate that the developed lens antennas has directivities of 17.6 and 23.1 dBi for lenses with radii of 6 and 12 mm, respectively. In this case, the maximum beam deflection angle is achieved, which is equal to 55°, while the permissible decrease in the directivity is no more than 6 dBi compared with the case of a non-deflected beam. The obtained results show that the developed integrated lens antennas can find applications in high-speed radio communication systems operated in the millimeter-wave range.

A pseudo-rigid-body 2R model of flexural beam in compliant mechanisms

Based on the pseudo-rigid-body model (PRBM), a 2R PRBM that consists of three rigid links joined by two revolute joints and two torsion springs is proposed in this study. A method of parametric approximation to the deflection path and deflection angle of a flexural beam is developed for the 2R PRBM. A two-dimensional optimization for the characteristic radius factors and a linear regression for the spring stiffness coefficient are presented. Although the model parameters are dependent on the loading conditions, the 2R PRBM is useful in increasing the modeling accuracy of the 1R PRBM and reducing the computation time of the 3R PRBM. The advantage of the new model is also illustrated through a comparison of deformation energies among the various kinds of PRBM and the flexural beam. An application example of compliant mechanism is presented using the 2R PRBM. The 2R PRBM is significant to expand the applications of pseudo-rigid-body model in the analysis and design of compliant mechanisms, particularly in the further study on the dynamics of compliant mechanisms.

Analyzing the receiving power of rectilinear mobile/free-space optical links by considering the effect of laser beam divergence and deflection angles

For rectilinear mobile/free-space optical (RM-FSO) links, laser beam divergence and deflection angles are key factors to get highly accurate receiving power. The effective receiving area of the receiving-lens (R-lens) is presented and used to investigate receiving power under different circumstances. By comparing the optical spot size on the receiving plane with the R-lens diameter, the effects of laser beam divergence and deflection angles on receiving power are analyzed. The results show that the theoretical simulation is basically consistent with the experimental data, and the errors are given. Thus, given different moving situations of RM-FSO links, the solution can be used to analyze the receiving power more effectively by considering the effect of laser beam divergence and deflection angles.

Proton irradiation of liquid crystal based adaptive optical devices

To assess its radiation hardness, a liquid crystal based adaptive optical element has been irradiated using a 60 MeV proton beam. The device with the functionality of an optical beam steerer was characterised before, during and after the irradiation. A systematic set of measurements on the transmission and beam deflection angles was carried out. The measurements showed that the transmission decreased only marginally and that its optical performance degraded only after a very high proton fluence ( 10 10 p / cm 2 ) . The device showed complete annealing in the functionality as a beam steerer, which leads to the conclusion that the liquid crystal technology for optical devices is not vulnerable to proton irradiation as expected in space.

Aero-optical wavefront measurement technique based on BOS and its applications

A collimated light beam will be refracted if it propagates through a flow-field with index-of-refraction variations, and its wavefront will be distorted. If we measure the deflection angle of the light beam, the gradient of the wavefront can be obtained using the Malus law, and the wavefront aberration can be computed with a reconstruction algorithm. Two characteristics of background oriented schlieren (BOS) are conducive to wavefront aberration measurement: BOS can be used to measure the deflection angle of a light beam by measuring the displacement field between the reference image and the experiment image. Moreover, in a BOS system of Schlieren mode, only the ray perpendicular to the background image can be captured with a camera. This is helpful to measure wavefront aberrations that occur after a planar wavefront has passed through the flow-field. Based on these characteristics of BOS of Schlieren mode, a new wavefront measurement technique, which is called the BOS-based wavefront technique (BOS-WT), is proposed in this paper. It works by constructing the relationship between the displacement of the background image and the aero-optical wavefront gradient and uses the Southwell wavefront reconstruction algorithm. A BOS-WT system was assembled, and its temporal resolution was found to be 6 ns, and its temporal-correlation resolution reached 0.2 μs. A BOS-WT can measure the time-correlation transient wavefront quantitatively. It is simple and easy to operate. In this paper, we also present a study of the aero-optical performance of supersonic mixing layer based on our BOS-WT transient wavefronts at an interval of 5 μs. The results showed the wavefront was transient and distorted after it had passed through the mixing layer. Through the analysis of the data at the 5 μs interval, the temporal evolution of wavefront can be obtained.

Direct measurement of the beam deflection angle using the axialB-dot field

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Beam steering of external cavity diode laser by an intracavity electro-optic ceramic deflector

A novel beam-steering external cavity diode laser using an intracavity lead lanthanum zirconate titanate (PLZT) electro-optic ceramic deflector is proposed and demonstrated experimentally. The laser consists of a semiconductor laser with single mode fiber coupled output, polarization controller, PLZT electro-optic ceramic deflector, and output concave mirror. By applying proper driven electrical signals on the PLZT electro-optic deflector, the beam deflection angle achieves 5.8 mrad at 1 000 V. A high-speed beam-steering property with less than 120-ns switching time is also observed. Moreover, a good beam quality with Gaussian spatial profile and a linear polarization state are obtained.

High‐power potassium‐titanyl‐phosphate laser fibres for endovaporization of benign prostatic hyperplasia: how much do they deteriorate during the procedure?

• To assess the residual power delivered at the tip of a high-power (80 W) potassium-titanyl-phosphate (KTP) laser (80 W Green Light PV(TM), Laserscope(®); American Medical Systems, Minnetonka, MN, USA) at the end of a photoselective vaporization of the prostate (PVP) procedure, as well as the deflection angle of the laser beam. • In total, 65 laser fibres were collected at the end of PVP procedures indicated for symptomatic benign prostatic hyperplasia over a period of 17 months. PVP was performed by two senior urologists. • The power of laser beam at tip exit was measured for each fibre at the end of the procedures using a photodiode whose signal was amplified, and then quantified by a volt multimeter. • The deflection angle was measured using a graduated sphere. • Approximately 70% of fibres delivered less than 40 W at the end of the procedure, which is less than the vaporization threshold. • Some 9% of fibres had lost their diffraction capacity with a significant alteration of laser beam angulation. These values were not operator dependent. • The data show that a large proportion of laser fibers deliver a significantly underpowered beam at the end of the procedures. • This seems to be caused by peroperative destruction of the fibers, which results in a progressive loss of efficacy of PVP during procedures.

Determining thermal properties of thin coatings using the “thermal mirror” method

We suggest a photothermal method for measuring thermal properties of opaque coatings. The coating–substrate assembly is irradiated by the repetitive pulse power laser which causes a nonstationary buckling of the coating. Thermal properties of the coating are determined by comparing the measured phase shift in the wave component of the temporal dependence of beam deflection angle of the low power laser with theoretical predictions obtained by solving equations of thermal elasticity.

Planar integrated optical sensors based on the mirage effect

The modulation of the deflection of a 2D guided optical beam in a planar waveguide is analyzed for sensing applications. The deflection is caused by a gradual change in the depth of the planar waveguide transversal to the direction of propagation. The beam deflection angle could be used for sensing the refractive index of the external medium among other variables. We present numerical results to evaluate the possibility of developing a glass-integrated structure for refractive index sensing.

Development of an adjustable beam flattening system for modification of passive beam delivery technique in proton therapy

The purpose of this work is to introduce a simple method for the maximization of beam intensity on the target volume in proton therapy based on passive beam delivery system. In this method, the treatment area of the lateral beam profile is adjusted with the lateral size of the target to maximize the contribution of protons in target bombarding in order to achieve a more effective treatment. For this aim, an adjustable beam flattening system was designed to modify dose delivery by creating any arbitrary lateral homogeneous dose profile, using multi-foil scattering and beam wobbling systems. The multi-foil scattering system includes several uniform scatterer foils with different thicknesses. By this system the proper scatterer foil is automatically inserted in front of the incident proton beam for each treatment. The adjustable beam flattening system is controlled by a computer program developed with several options. This program allows the user to create the desired flat beam profile by providing the best scatterer thickness and an appropriate beam deflection angle, where both are fundamental parameters in the flat dose profile generation.

Refractive error correction for in situ curvature measurement using laser beam deflection method

Stoney’s equation allows one to calculate the internal stress in a thin film deposited on a thick substrate from the curvature of the bilayer beam. The curvature measurement is thus critical in the bending beam method, which is based on this equation. When an optical technique is used in curvature measurement, the refraction at optical boundaries needs to be corrected. An approximate correction to Stoney’s equation accounting for refractive error in the bending beam method in electrochemical applications was reported previously. This paper revisits the derivation. A set of diagrams for optical paths in in situ curvature measurement using the laser beam deflection method are presented. These diagrams allow us to establish the triangular relationships among the incident angles of the light beam and the deflection angle of the cantilever beam. Correction solutions are derived for three possible optical arrangements with the consideration of the travel distance of the light beam in liquid and in the container wall. In its approximated form, the correction derived in this paper differs from the previous formula by a factor of 2. It was discovered that an incorrect relationship for curvature was used in the previous derivation.

新颖的微流控电调谐空间光开关

A novel space optical switch device of optofluidic is proposed to solve the problems of electrical controlling without mechanical device.The basic structure of the switch includes a core exchange space sandwiched between two optical arrays.The basic unit of array is made from liquid prism as a beam control unit including three kinds of immiscible liquids(water / oil / water).Through the electro-wetting effect,the beam deflection angle of the liquid prism can be adjusted about -15 °~15 °continuously in a specific voltage range(30 ~ 110 V).Thus one can construct a variety of two-dimensional or even three-dimensional optical switch array.

Theory of Photothermal Displacement Method for Determining Physical Properties of Multilayered Coatings

In this study theoretical principles underlying the photothermal method for determining thermal properties of opaque multilayered and functionally graded coatings are analyzed. The method is based on irradiation of the assembly by the repetitive pulse of focused laser radiation that is absorbed in the subsurface region and causes non-uniform heating and buckling of a coating. The irradiated surface of a coating is monitored by a low power beam of a second laser that is reflected from the specimen. The deflection angle of the monitoring beam, as a function of time, contains the relaxation and the “wave” components. It is shown that the phase of the “wave” component depends on the thermophysical properties (e.g., thermal diffusivity or thermal conductivity) of a coating. These properties can be determined by comparing experimentally measured values of the phase shift of the “wave” component with the theoretical values obtained from the analytical solution of the two-dimensional thermal elasticity problem for a multilayered coating–substrate assembly.

A Cantilever Force Sensor Combined With a Spherical Reflecting Mirror for Sensitivity Enhancement of an Optical Detection System

By fabricating a microspherical reflecting mirror (MSRM) on the tip of a cantilever, the deflection angle of the laser beam is significantly magnified. Therefore, the sensitivity of an optical sensing system is enhanced. The curvature of the spherical reflecting mirror determines the system sensitivity. Given a certain bending amount and a fixed distance between the cantilever and the position-sensing detector, the cantilever combined with an MSRM with a smaller radius of curvature produces a larger optical deflection, i.e., better system sensitivity. Also, under a given radius of curvature of the MSRM, the system sensitivity can be adjusted by changing the incident angle. A larger incident angle exhibits better system sensitivity/responsivity.

Achieving Nanorad Level Stability of Beam Deflection with Scanning Pentaprisms

A movable pentaprism is a key element in deflectometric profilers, where it directs the beam of an angle measuring device towards the surface under test and enables at the same time the flexible lateral displacement of the beam footprint on the surface. The beam deflection angle of the pentaprism is robust with regard to changes in its angular orientation. Optimal stability is achieved, however, only when the angle measuring device, the pentaprism, and the surface have initially been properly aligned. A newly developed procedure enables the rapid and accurate in-situ adjustment of all angles of the optical components in deflectometric set-ups with an uncertainty of several microrad. In combination with precision mechanical stages, variations in the prism’s deflection angle (caused by changes in its angular orientation) can then be limited to the nanorad level.

Optical switching based on high-speed phased array optical beam steering

We present a high-speed optical switching scheme based on phased array optical beam steering, and analyze the trade-off between the switch power efficiency, signal-to-noise-ratio, number of output channels, and switching speed. For the proof of concept, a two-channel optical switch has been fabricated, using a high-speed GaAs∕AlGaAs multiple quantum well phase modulator. We demonstrate a beam deflection angle of 100mrad at the fastest ever reported speed of 18GHz, consuming 1.8mW. A signal-to-noise ratio of 8dB is measured at each output channel. The relatively low signal-to-noise ratio can be further improved by increasing the number of phased arrays.

EXPERIMENTAL TECHNIQUE USING AN INTERFERENCE PATTERN FOR MEASURING DIRECTIONAL FLUCTUATIONS OF A LASER BEAM CREATED BY A STRONG THERMAL TURBULENCE

In the view of measuring directional fluctuations of a thin laser beam sent through a heated turbulent jet, an optical method using interference and diffraction with the out coming beam is proposed. The experimental set-up is described. A new technique for separating directional fluctuations of the laser beam is explained. From the measurement of the interference pattern perturbations, are deduced the Rms of the laser beam deflection angle, the spectrum of directional fluctuations of the laser beam, and the value of a scattering coefficient characterizing the heated turbulent jet. The measured spectrum reveals a −8/3 power law and the value obtained for that coefficient is nearly equal to that found in previous works. This agreement enables to conclude that the experimental technique used is efficient and satisfactory.

Region-of-interest imaging in differential phase-contrast tomography

Differential phase-contrast tomography, also known as beam-deflection tomography, is a method for reconstructing an object's refractive index distribution from knowledge of differential projection data that describe beam deflection angles. We describe and demonstrate an approach to determining regions of interest within an object from truncated differential projection data.