Magneto-optic Modulator Research Articles

方波磁光调制测量在无机械连接的设备间方位传递中的应用

方波磁光调制测量在无机械连接的设备间方位传递中的应用

基于正弦波磁光调制的空间方位失调角传递技术的改进

To enlarge the transmission scale and improve the transmission precision of an azimuth transmission system based on sine wave magneto-optic modulation,a new method of transmitting the azimuth in a large-scale and high-precision was established.The principle of the current azimuth transmission system was analyzed,and a double-angle formula was introduced to enlarge the transmission scale.A model to measure the azimuth was established according to analyzing the relationship between the azimuth and the extremum of the modulated light,and the measurement model was expatiated by comparing the extremums.A integrated method combined the approximation in little-scale with the looking-up table in large-scale was presented to calculate the arc tangent function in the model.Simulation results indicate that the theoretic transmission scale is widened obviously and the precision is improved.Experiment results show that the actual transmission scale is-64-64° and the transmission error is under 10″,which is better than those of the current methods.The method provides a new way to transmit the spatial azimuth in large-scales and high-precision.

方波磁光调制测量在航天器对接中的应用

To measure the roll angle between two spacecrafts at the last-phase of spacecraft-docking accurately,a roll angle measurement system based on square wave magneto-optic modulation was present.A model of the modulated signal was present according to the Faraday effect and Malous law,and the relationship equation between the modulated signal and the roll angle was established according to the character of modulated signal.The combination of the variation trend of the modulated signal was used to delete the extraneous roots of the equation,then the roll angle measurement model based on square wave magneto-optic modulation was acquired.Simulation results indicate that the new method has higher measurement precision,and the measurement scale is-90~90°,wider than that of the traditional method.Furthermore,the new method shows advantage on data acquisition and data process.In conclusion,the method can provide a new reference for measuring the roll angle between spacecrafts in higher precision and wider scale for spacecraft docking.

基于正弦波磁光调制的方位失调角精确测量方法

基于正弦波磁光调制的方位失调角精确测量方法

An Experimental Research on Faraday Effect of Magneto-Optical Medium

The Verdet constant is the essential parameter of Faraday Effect. Study on Verdet constant of magnetic optical medium is very important in Faraday Effect research and application. In this paper, Verdet constant of liquid and solid medium were investigated with light extinction method with the help of photoelectric detector. Using the square wave magneto-optic modulation method which we established, Verdet constant of air was measured. Variation of Verdet constant of these materials with changes of light wavelength and temperature was investigated. These experimental data may provide reference for research and application of magneto-optic effect. Meanwhile, the experiment in this paper is also one of the key works of magnetic rotation imaging method for geomagnetic field measurement which we proposed. It will provide experimental support for this new geomagnetic field measurement method.

Theoretical Simulation and Preparation of Magneto-Optical Modulator

Magneto-Optical modulation technology has become key component in many optical information systems. However, due to the abstract theoretical knowledge, many textbooks do not introduce the properties of circular anisotropy, so it is difficult for most students to understand the polarization properties of light accurately and in depth. In this paper, the processes of Magneto-Optical modulation are Three-Dimensionally dynamically simulated by using MATLAB software first. These simulations make the complex and abstract light propagation processes become visual, which are effective aids for optics’ teaching. These simulations can enhance the understanding of the concept and the interactions with media of polarized lights and the principles of Magneto-Optical modulation. Second, a magnetic rotation glass is used to produce Magneto-Optical modulator, and finally the optical communication simulation experiment is realized and the effect is good. Experimental results show that the magneto-optical modulator has advantages like low power requirements, low modulation voltage, simple device, flexible, long life-time and small affect to the external temperature etc.

Efficient direct magneto-optical phase modulation of light waves in spun microstructured fibres

We have proposed a phase modulator of optical radiation for an interferometric electric-current sensor. The modulator takes advantage of the Faraday effect in spun microstructured optical fibres. Such fibres enable small-diameter multiturn fibre coils to be produced, which is necessary for achieving a preset phase modulation amplitude at a moderate drive current. The principal characteristics of the modulator have been studied experimentally: frequency response, magneto-optical sensitivity and output signal contrast. The results demonstrate that the modulator ensures high efficiency, approaching the theoretical one, provided the modulation period exceeds the time it takes light to pass through the fibre. We have examined the influence of spun fibre parameters on the performance of the modulator.

Magnetic tunnel junctions using Co/Pt multilayered free layers with perpendicular magnetic anisotropy

Co/Pt multilayered films with perpendicular magnetic anisotropy have a large magneto-optical Kerr effect. To use the films with a submicron magneto-optical light modulator driven by spin transfer switching, we fabricated two types of magnetic tunnel junctions (MTJs) with Co/Pt multilayered films for the free layers. One is an fcc-based MTJ, another is a bcc-based MTJ with CoFeB/MgO/CoFeB junction. The fcc-based MTJ with a Ag buffer layer on the bottom electrode showed a large coercive force of the pinned layer, a large Kerr rotation angle of 0.3 degree in the free layer and a tunnel magnetoresistance (TMR) ratio of 3.8%. In the CoFeB/MgO/CoFeB junction, an X-ray diffraction pattern of an MgO layer showed a large MgO(002)-orientation. However, the TMR ratio was less than 3 %. An MTJ with a Ta buffer layer between the CoFeB layer and the Co/Pt multilayered films in the free layer was prepared. The Ta buffer was used to alleviate a lattice mismatch between bcc-CoFeB/MgO/CoFeB and fcc-Co/Pt multilayer. The peak intensity of the MgO(002)-orientation was increased up to 2 times. This result suggests that the crystalline texture of the bcc-CoFeB/MgO/CoFeB junction is strongly influenced by the fcc-Co/Pt multilayered films.

Transmission of an object azimuth on distance with the help of magnetooptical modulator

This work is devoted to development and analysis of optoelectric method of an object azimuthal location transmission on distance with the help of magnetooptical modulator.

Magneto-optic fiber Sagnac modulator based on magnetic fluids

A magneto-optic modulator with a magnetic fluid film inserted into an optical fiber Sagnac interferometer is proposed. The magnetic fluid exhibits variable birefringence and Faraday effect under external magnetic field that will lead to a phase difference and polarization state rotation in the Sagnac interferometer. As a result, the intensity of the output light is modulated under the external magnetic field. Moreover, the modulator has a high extinction ratio and can easily be integrated in a single-mode fiber system. The performance of the modulator is not affected by ambient temperature variation from room temperature to 40 °C.

Spatial light phase modulators with one-dimensional magnetophotonic crystals driven by piezoelectric films

We demonstrate a novel spatial light phase modulator composed of a one-dimensional magnetophotonic crystal driven by a piezoelectric film. With the application of a constant magnetic bias field perpendicular to the film plane, the magneto-optic Kerr rotation angle of the modulator was subject to continuous change from 3.8–2.4° with the voltage up to 50 V and hence a continuous phase modulation for rays with circular polarization. Surprisingly, the magneto-optical response of the modulator showed nonvolatile behavior and the light phase was maintained at a designated value without applying any stress. Based upon the above experimental results, magneto-optic spatial light phase modulators with a 64 × 64 array of magnetic pixels were constructed. The fabricated device had a dimension of 15 μm2 and demonstrated two-dimensional optical modulation of the phase of reflected rays.

基于磁光调制偏振光的空间方位失调角高精度测量新方法

基于磁光调制偏振光的空间方位失调角高精度测量新方法

Hybrid organic–inorganic materials for integrated optoelectronic devices

AbstractA device containing a microcavity organic light‐emitting diode (OLED) and a magnetooptically active bismuth iron garnet (BIG) Bi3Fe5O12 waveguide combines a planar source for polarized light generation with the material exhibiting the highest known Faraday rotation at room temperature. To build such a device an optimization of garnets and OLEDs has to be done. For a good functionality of the device it is essential to maximize the light coupled from the OLED into the waveguide and to seperate s‐ and p‐polarized emitted light. To optimize the OLED emisson numerical simulations have been performed where material and thickness of the metal anode, as well as the thickness of the hole and the electron conducting layers were varied. The stacks with the best separation of s‐ and p‐polarized light and the highest coupling into the waveguide were determined, fabricated, and characterized regarding their electrical and optical properties. OLEDs have to be deposited on plane surfaces for exhibiting low leakage currents and thus being functional. In order to get plane and crack free BIG surfaces the garnet growth and surface formation were examined on various gadolinium gallium garnet (GGG) Gd3 Ga5 O12 and buffered non‐garnet substrates. GGG substrates with different cuts and lattice constants were characterized as well as yttrium iron garnet (YIG) Y3Fe5O12 and GGG buffered sapphire, silicon, and fused silica substrates. The garnet had to be structured to fabricate a planar waveguide. Therefore laser structuring and plasma etching techniques were utilized. The structured garnets were characterized regarding the wall roughness. The optical constants of YIG and BIG were determined from films deposited on silicon using ellipsometric measurements. The combination of microcavity OLED and garnet waveguide resulted in an integrated magnetooptical modulator whose functionality has been proven by applying an external magnetic field and measuring the rotation of the polarized light.

Submicron Magneto-Optical Spatial Light Modulation Device for Holographic Displays Driven by Spin-Polarized Electrons

We have proposed a spin transfer switching (STS MO-SLM) device, based on Magneto-optical (MO) spatial light-modulation and driven by spin-polarized current flow, and confirmed its basic operation and characteristics experimentally. The proposed SLM device can be operated without active-matrix devices, has a spatial resolution as small as several hundred nanometers and possesses the potential for being driven at ultra-high speed of several tens of nanoseconds. Unlike existing SLM devices, this device satisfies both the size and speed requirements of SLMs for use in displaying holographic three-dimensional (3D) moving images. To improve the light modulation characteristics of SLM device, we carried out studies on magnetic films with perpendicular magnetic anisotropy to obtain large magneto-optical signals, which enabled us to realize enhanced light modulation performance. In addition, we measured a MO signal that was about twenty-times larger than that possible with in-plane anisotropy. We conclude that the MO-SLM device that we are developing is suitable for displaying future super-high definition, holographic three-dimensional moving images.

Spin Transfer Switching and MR Properties of Co/Pt Multilayered Free Layers for Submicron Sized Magneto-Optical Light Modulation Device

Co/Pt multilayered films show strong perpendicular magnetic anisotropy and have a large magneto-optical Kerr effect in the short wavelength side. To use these films with submicron spatial light modulators driven by spin transfer switching (STS), we fabricated current perpendicular to plane giant magnetoresistance (CPP-GMR) and tunnel magnetoresistance (TMR) devices with Co/Pt multilayers for free layers and investigated the MR properties, the STS characteristics, and the Kerr effects. A Kerr hysteresis loop was clearly observed in the CPP-GMR device, which was 125 × 180 nm2. Full magnetization reversal of the Co/Pt multilayered film by spin transfer torque was demonstrated for a CPP-GMR device with a Cu-based top electrode. On the other hand, there was hardly any resistance change in a CPP-GMR with a transparent top electrode due to the low MR ratio of the device. A TMR stack with a Ag buffer layer showed a strong perpendicular magnetic anisotropy. An MR curve was detected for a TMR device with a transparent top electrode.

Fabrication and characteristics of one-dimensional magnetophotonic crystals for magneto-optic spatial light phase modulators

We prepared the reflection type magnetophotonic crystals (R-MPC) to enhance the magneto-optic property of magneto-optic spatial light phase modulator (MOSLM). Magnetophotonic crystals have a localized wavelength by using a defect layer in which the magneto-optic property can be increased tremendously. By the calculation, it was revealed clearly that Kerr rotation can be enhanced with increasing the repetition number (k) which is the number of dielectric layer. In this study, Dy1.0Bi1.5Y1.0Fe3.8Al1.2O12 (DyBi:YIG) garnet material, of which Faraday rotation angle is about −3 deg/μm, was utilized as a defect layer. At the designed wavelength of 532 nm and k=5, SGGG/[SiO2/Ta2O5]2/DyBi:YIG/[SiO2/Ta2O5]k structure fabricated with garnet thickness of 347.6 nm showed Kerr rotation angle of 26° and reflectivity of 0.2% which is coincident considerably with the results (θk=30° and R=0.59%) calculated by the matrix approach method. The fabricated R-MPC-MOSLM structure exhibited the magneto-optic property of about 25 times higher than single garnet film in consideration of the thickness of magneto-optic material.

双轴晶体锥光效应光盘径向寻迹研究

A new method of optical control is put forward based on conical effect in biaxial crystal.When the incident light spread along optical axis direction,the propagation direction will change with the polarization direction.By controlling the magnetic field on the magneto-optic modulator,the polarization direction can be changed,thus the laser beam direction control is realized.The fundamental of disk tracking is analyzed and overall plan is also designed,the relationship between polarizing angle and tracking displacement is obtained by numerical simulations,so this plan is reasonable.Compared with traditional tracking means of machine-electricity,this kind of plan has the following advantages:light weight,small volume and fast transient response.A new method for optical switch and scanning is provided meanwhile.

Fiber-Based Magneto-Optic Sagnac Optical Modulator

In this paper, a fiber-based, magneto-optic (MO) optical modulator based on Sagnac interferometry is proposed. The system uses a Faraday rotator to produce optical modulation with low magnetic fields. The Sagnac geometry allows for increased modulation at lower fields than traditional MO modulators. A formulation of the system is provided using Jones calculus. Experimental results at 1550 nm using single mode fiber are reported, including a discussion of dynamic range and effect of magnetic field strength. Theoretical and practical advantages and limitations are discussed. Methods for improving modulation speed, dynamic range, and performance are presented.

Phase sensitive Brillouin scattering measurements with a novel magneto-optic modulator

A recently reported phase sensitive Brillouin light scattering technique is improved by use of a magnetic modulator. This modulator is based on Brillouin light scattering in a thin ferrite film. Using this magnetic modulator in time and space Brillouin light scattering measurements, we have increased phase contrast and excluded influence of optical inhomogeneities in the sample. We also demonstrate that the quality of the resulting interference patterns can be improved by data postprocessing using the simultaneously recorded information about the reference light.

Magneto-optical modulation of a triple-mirror laser beam

Based on calculations and experiments, a He-Ne laser has been developed with effective intracavity magnetooptical modulation at λ = 1.15 μm. A polarization-anisotropic element — a magnetic diffraction grating made of yttrium iron garnet — is mounted in a matched passive arm of the triple-mirror cavity of the laser and serves as the modulator element. Modulation is produced using the Faraday effect, which simultaneously leads to efficient diffraction of the laser radiation on the asymmetric strip domain structure of a magnetic diffraction grating and to rotation of the E vector. The Jones matrix method is used to calculate the frequency and polarization characteristics. These, along with the modulation characteristics, were also studied experimentally. It is shown that amplitude modulation at frequencies up to 180 kHz takes place for small single-pass Faraday rotation angles (θ F ). The threshold frequency is determined by the response time of the magnetizing Helmholtz coil. The depth of modulation is 50%. For θ F > θ t (where θ t is the threshold), frequency modulation takes place with a deviation of up to several megahertz.