Linear and nonlinear optical properties in an asymmetric double quantum well under intense laser field: Effects of applied electric and magnetic fields

In the present study, the effects of electric and magnetic fields on the linear and third-order nonlinear optical absorption coefficients and relative change of the refractive index in asymmetric GaAs/GaAlAs double quantum wells under intense laser fields are theoretically investigated. The electric field is oriented along the growth direction of the heterostructure while the magnetic field is taken in-plane. The intense laser field is linear polarization along the growth direction. Our calculations are made using the effective-mass approximation and the compact density-matrix approach. Intense laser effects on the system are investigated with the use of the Floquet method with the consequent change in the confinement potential of heterostructures. Our results show that the increase of the electric and magnetic fields blue-shifts the peak positions of the total absorption coefficient and of the total refractive index while the increase of the intense laser field firstly blue-shifts the peak positions and later results in their red-shifting.     

Nonlinear Faraday rotation for optical limitation

The possible use of the nonlinear Faraday effect for optical limitation of the laser power is investigated in a resonant Faraday medium placed between two crossed polarizers. The results are comparable with those obtained at strong magnetic fields as a result of the linear Faraday effect. Advantages of the method are the narrow bandwidth and the wide field of view. The investigations are interesting from the viewpoint of applications for optical sensor protection and automation of the experiment. All measurements are performed at the F(g) = 2 --> F(e) = 1 hyperfine structure transition of the 87Rb D1 line.     

Accurate magneto-optic sensitivity measurements of some diamagneticglasses and ferrimagnetic bulk crystals using small applied AC magneticfields

Many materials exhibit a relatively large Faraday effect. A plane polarized optical beam passing through these materials has its plane of polarization rotated by a measurable amount proportional to the applied magnetic field strength parallel to the propagation direction of the beam. Some of the most sensitive materials of this kind are diamagnetic glasses and ferrimagnetic crystals. We have made accurate measurements of the magneto-optic sensitivity of a variety of diamagnetic glasses and ferrimagnetic bulk optic crystals using small applied ac magnetic fields in contrast to the more common technique involving very strong applied dc magnetic fields     

Magnetooptic spectroscopy of EuS, EuSe, and EuTe

The absorption Coefficient and the interband Faraday rotation of EuS, EuSe, and EuTe thin films have been measured as a function of the photon energy (1-6 eV), the temperature (2.7-300 K), and the applied magnetic field (0.1-11.5 kOe). From the Faraday rotation (FR) we compute the circular magnetic dichroism and from both and the optical constantsnandkwe derive the imaginary part of the off-diagonal elements of the complex conductivity tensor Im σxy. Integral values of the latter depend on the spin polarization of electronic states and permit a distinction between pd and fd transitions.     

法拉第滤光器在法拉第激光器领域研究进展

法拉第激光器是一种利用法拉第反常色散原子滤光器作为选频元件的新型外腔半导体激光器,原理上法拉第激光的输出波长随着激光二极管驱动电流及工作温度的变化,始终与原子跃迁谱线相对应,可以将激光频率有效地锁定至原子跃迁谱线,实现窄线宽的激光输出信号,并且短期与长期频率稳定性均较好。本文详细介绍了自1845年法拉第旋光效应提出以来,法拉第反常色散原子滤光器的发展历程,法拉第激光器的工作机理、发展历程以及性能优越性,并结合国内外的研究进展,介绍了法拉第激光发展各个阶段的技术瓶颈及相应的解决办法,同时展望了法拉第激光器未来在量子领域特别是量子精密测量领域的重要价值。     

Unidirectional single-mode Nd:YAG laser with a planar semimonolithic ring cavity

Unidirectional single-mode operation of a diode-pumped Nd:YAG laser with a planar semimonolithic ring cavity has been demonstrated at 1064 nm. The semimonolithic cavity consists of a laser active medium placed in a magnetic field, a crystal quartz plate, and an output coupling mirror, which form an optical diode by acting as a Faraday rotator, a reciprocal polarization rotator, and a partial polarizer, respectively. A single-mode output power of 155 mW and a slope efficiency of 17% were obtained with a 1.2-W diode laser at 809 nm. A laser linewidth of less than 100 kHz is inferred from a beat note frequency spectrum between two identical laser systems and continuous tuning to greater than 2 GHz was observed.     

Nonlinear and magneto-optical transmission studies on magnetic nanofluids of non-interacting metallic nickel nanoparticles

Oxide free stable metallic nanofluids have the potential for various applications such as in thermal management and inkjet printing apart from being a candidate system for fundamental studies. A stable suspension of nickel nanoparticles of ～ 5 nm size has been realized by a modified two-step synthesis route. Structural characterization by x-ray diffraction and transmission electron microscopy shows that the nanoparticles are metallic and are phase pure. The nanoparticles exhibited superparamagnetic properties. The magneto-optical transmission properties of the nickel nanofluid (Ni-F) were investigated by linear optical dichroism measurements. The magnetic field dependent light transmission studies exhibited a polarization dependent optical absorption, known as optical dichroism, indicating that the nanoparticles suspended in the fluid are non-interacting and superparamagnetic in nature. The nonlinear optical limiting properties of Ni-F under high input optical fluence were then analyzed by an open aperture z-scan technique. The Ni-F exhibits a saturable absorption at moderate laser intensities while effective two-photon absorption is evident at higher intensities. The Ni-F appears to be a unique material for various optical devices such as field modulated gratings and optical switches which can be controlled by an external magnetic field.     

用于高性能光隔离器的复合稀土铁石榴石ReYbBiIG单晶材料研究

通过加速旋转坩埚技术和Bi₂O₃/B₂O₃助溶剂生长技术研制新型磁光复合稀土铁石榴石单晶ReYbBiIG(Re:Tb³⁺、Ho³⁺、Y³⁺。从理论上解释了将两种具有相反符号法拉第温度和波长系数的掺铋稀土铁石榴石复合可以显著优化磁光性能,并成功制得具有大磁光优值、低饱和磁化强度、低近红外吸收、极小法拉第温度和波长系数的系列优质磁光单晶(如:Ho_0.85Yb_1.12Bi_1.03Fe₅O₁₂和Tb_2.06Yb_0.46Bi_0.48Fe₅O₁₂等)。研究表明,以新型磁光复合稀土铁石榴石单晶ReYbBiIG作为法拉第转子材料制得的新型光隔离器更适用于WDM光纤通讯系统对宽波段和温度稳定性的要求。     

Polarization-independent optical circulator for high accuracy Faraday depolarization lidar

A high precision, polarization-independent optical circulator was developed for high accuracy Faraday depolarization lidar. Glan laser prisms and other novel optics were utilized in the circulator optics, resulting in a high extinction ratio of polarization of >30 dB. High accuracy is needed to detect a small rotation angle in the polarization plane of the propagating beam. It is generated by the Faraday effect due to the lightning discharge. The developed circulator delivered high performance of insertion loss and isolation as laser transmitter and echo receiver in the inline lidar optics.     

Weak value amplification of an optical Faraday differential refraction effect

In the presence of a longitudinal magnetic field B, a beam of linearly polarized light incident from a Faraday medium of Verdet constant V refracts at its interface with a medium of negligible Verdet constant and emerges as two opposite circularly polarized beams that are separated by a small divergence angle δ that is proportional to the product BV. Judicious postselection of the polarization state of the emergent light can be used to amplify the measured value of δ by several orders of magnitude. This technique makes it possible to optically measure either very small V values when B is known or small magnetic fields when V is known.     

An optical faraday rotation technique for the determination of magnetic relaxation times

A technique is described for the measurement of macroscopic magnetic relaxation times in crystals using the optical Faraday rotation as a monitor of the magnetization. The method is applied to the paramagnetic Eu²⁺ion in CaF2:Eu²⁺at cryogenic temperatures. In this experiment the crystal is placed between a crossed polarizer and analyzer and subjected to a pulsed magnetic field. The transmitted light from a CW argon-ion laser gives a direct indication of the relaxation time.     

磁性材料在同步辐射及自由电子激光中的应用

同步辐射与自由电子激光都是相对论高能电子束产生的电磁辐射光, 在国民经济、科学技术研究和国防军事等领域中有着广泛应用。各种永磁插入件是同步辐射光源及自由电子激光装置的关键设备之一, 磁性材料特别是永磁体磁特性及质量对插入件的磁场品质、磁场峰值、磁场稳定性和运行方案等都有着重要影响。本文综述了同步辐射及自由电子激光特征, 介绍了磁性材料在同步辐射及自由电子激光插入件中的应用情况。     

Optical operation of a magnetic bubble

A magnetic bubble domain is generated on liquid-phase epitaxial (LPE) garnet film by focusing laser light. It is possible to write with only a few milliwatts light power on a thin film with a low anisotropy field. Because the Bi-containing LPE films used have a high Faraday rotation angle, a written bit or bubble can be read out with a high contrast ratio. Because of its low coercivity, the bubble moves along the temperature gradient to the region heated by the light beam and is then stabilized at a corner of a square formed on the film by etching or ion-implantation. Erasure is possible selectively or all together by increasing the bias field. These optical operations of a magnetic bubble are discussed in connection with the material parameters.     

An optical polarization-bistable element based on the Faraday effect

An optical polarization-bistable element scheme based on an He-Ne laser (λ = 3.39 μm) with a Faraday cell in the cavity is considered for the first time. A sample of such cavity having the shape of a parallelepiped has been manufactured from an yttrium iron garnet single crystal and a theoretical analysis of this element in terms of the Jones matrices has been performed. It is established that the polarization bistability can be observed for a single-trip Faraday rotation of 45°. Experiments with the device based on a hybrid bistability scheme showed that, under certain conditions, the circular polarization is reversibly switched between σ⁺ and σ^?.     

Basic research and applications in magnetism

Several brief case histories are recounted, to show how basic scientific discoveries of new materials and phenomena are used as necessary background for the design of modern devices. The essential elements in the follow-through from the discoveries to the useful devices are listed for six subjects used as examples: 1) rare earths for permanent magnets, 2) orthoferrite domain "bubbles" for memory, 3) Faraday rotation of polarized microwave radiation, 4) magnetic properties of grain-oriented silicon steel, 5) optical properties of magnetic materials, and 6) superconducting magnets.     

Evolution of the polarization state in material media with uniform linear birefringence and an applied nonhomogeneous external magnetic field: application to bulk-type Faraday current sensors

In this work we find the exact solution for the evolution of the polarization state of a light wave that propagates in a material medium with uniform linear birefringence and a nonuniform external magnetic field. The obtained results could be used to improve the precision of existing Faraday current sensors.     

Optical bistability and multistability driven by external magnetic field in a dielectric slab doped with nanodiamond nitrogen vacancy centres

Abstract

The theoretical investigation of controlling the optical bistability (OB) and optical multistability (OM) in a dielectric medium doped with nanodiamond nitrogen vacancy centres under optical excitation are reported. The shape of the OB curve from dielectric slab can be tuned by changing the external magnetic field and polarization of the control beam. The effect of the intensity of the control laser field and the frequency detuning of probe laser field on the OB and OM behaviour are also discussed in this paper. The results obtained can be used for realizing an all-optical bistable switching or development of nanoelectronic devices.     

Faraday compensator of reciprocal optical anisotropy utilizing a polarization ring interferometer

It is shown that a polarization ring interferometer containing a Faraday cell can be used to compensate the reciprocal anisotropy in round-trip optical circuits. It is established theoretically and experimentally that, unlike the case of conventional Faraday mirrors, the quality of the restoration of the polarization in a compensator based on a polarization ring interferometer is practically independent of the Faraday rotation angle. A deviation of the Faraday rotation angle from 45° leads only to an additional power loss. The novel compensators can be used in fiber-optic circuits with a wideband light source or with several sources having different wavelengths. Pis’ma Zh. Tekh. Fiz. 25, 57–63 (May 26, 1999)     

Analytical investigation of eddy currents in nonlinear ferromagnetic media for weak magnetic fields

Electromagnetic field diffusion into a nonlinear ferromagnetic conducting half-space is analytically investigated for weak magnetic fields. For these fields a "nth power" approximation for magnetization curves is used. The exact analytical solutions to the non-linear partial differential equations of electromagnetic field theory are found for circular polarization of incident waves. The case of noncircular polarization is treated as a perturbation of circular polarization. Linear equations for perturbations are then derived and their analytical solutions are found. The analytical theory is illustrated by the computational results for surface impedances and third harmonics of electromagnetic fields.     

High sensitivity optical fiber current sensor based on polarization diversity and a Faraday rotation mirror cavity

A novel high sensitivity optical fiber current sensor (OFCS) based on polarization diversity and a Faraday rotation mirror cavity is proposed and demonstrated. Comparing with single-channel detection in a conventional OFCS, a signal power gain of 6?dB and a signal-to-noise ratio improvement of over 30?dB have been achieved in the new scheme. The cavity amplifies magnetic field-induced nonreciprocal phase modulation, while the Faraday rotation mirrors suppress the reciprocal birefringence. A linear response is obtained for current amplitude as low as several mA at an AC frequency of 1?kHz.