Magneto-optical Figure Of Merit Research Articles

Enhancement of the Faraday Effect and Magneto-optical Figure of Merit in All-Dielectric Metasurfaces

Enhancement of the Faraday Effect and Magneto-optical Figure of Merit in All-Dielectric Metasurfaces

Self-biased magneto-optical films based on CoFe2O4–silica nanocomposite

Composite thin films made of cobalt ferrite nanoparticles embedded in silica/zirconia sol-gel matrix are presented, and their versatility is illustrated through the impact of the nanoparticle features on the films’ final properties. The intrinsic magneto-optical potentiality of the nanoparticles is especially given by a peak around 1550 nm in the spectra of both the Faraday rotation and the magneto-optical figure of merit. These nanoparticles are inserted in the liquid preparation of a sol-gel host matrix, which is coated on a glass substrate at soft temperature. SEM and optical analysis show the absence of nanoparticle aggregates and defects into thin films and prove the ability of these films to be used as a guiding layer for photonic integration. The dispersion in the host matrix and the integration on a substrate do not affect the merit factor of the material. The specific Faraday rotation of the films is about 300°/cm for a volume fraction of nanoparticles of 1.5%, and it possesses a hysteresis loop. Its dependence on the nanoparticle mean size offers the possibility to achieve self-biased behavior. In addition, a magnetic field applied during the coating promotes an alignment of the magnetic easy axis of the nanoparticles along a preferential direction. It allows increasing even more the remanent magneto-optical effect and also reducing the birefringence and reaching a TE/TM phase matching of the film guided modes. It gives a way to tune these two parameters that play a crucial role in magneto-optical devices.

面向高功率激光隔离器的磁光材料（特邀）

As the key component of optical isolators, magneto-optic(MO) materials play an important role especially in high power laser system to ensure one-way light propagation, protect the laser sources and stabilize the laser output. The recent research progress of the MO materials used in near-infrared high power optical isolators was introduced. The key thermal-optic characteristics of MO materials under high power laser conditions and their effects on device performance were illustrated in detail. The studies and high power performance of several newly developed MO material candidates like TSAG crystal, TAG ceramic, and TGG ceramic were reviewed and compared with the commonly used TGG single crystal and Tb-doped glasses on aspects of Verdet constant, thermal conductivity, magneto-optic figure of merit and so on. Among them, TAG ceramics were discussed emphatically including the effects of ions doping and synthesis technology on its magneto-optic and thermal-optic properties. At last, the newest progress on the study of TAG ceramics was introduced, as well as the application prospect and research trend of MO materials used in the 3-5 μm mid-infrared region.

Dysprosium substituted Ce:YIG thin films with perpendicular magnetic anisotropy for silicon integrated optical isolator applications

In this report, dysprosium substituted Ce1Y2Fe5O12 (Ce:YIG) thin films (Dy:CeYIG) with perpendicular magnetic anisotropy (PMA) are successfully deposited on silicon and silicon-on-insulator waveguides by pulsed laser deposition. The structural, magnetic, and magneto-optical properties of Dy:CeYIG films are investigated. We find that increasing dysprosium concentration leads to a decreased out-of-plane magnetic saturation field. Dy2Ce1Fe5O12 and Dy2Ce1Al0.4Fe4.6O12 thin films show PMA dominated by magnetoelastic effects due to thermal mismatch strain. These films further exhibit high Faraday rotation and low optical loss. Our work demonstrates that Dy substitution is an effective way to induce PMA in Ce:YIG thin films without compromising their magneto-optical figure of merit, making this material promising for self-biased transverse electric mode optical isolator applications.

Properties of Ferrite Garnet (Bi, Lu, Y)₃(Fe, Ga)₅O12 Thin Film Materials Prepared by RF Magnetron Sputtering.

This work is devoted to physical vapor deposition synthesis, and characterisation of bismuth and lutetium-substituted ferrite-garnet thin-film materials for magneto-optic (MO) applications. The properties of garnet thin films sputtered using a target of nominal composition type Bi0.9Lu1.85Y0.25Fe4.0Ga1O12 are studied. By measuring the optical transmission spectra at room temperature, the optical constants and the accurate film thicknesses can be evaluated using Swanepoel’s envelope method. The refractive index data are found to be matching very closely to these derived from Cauchy’s dispersion formula for the entire spectral range between 300 and 2500 nm. The optical absorption coefficient and the extinction coefficient data are studied for both the as-deposited and annealed garnet thin-film samples. A new approach is applied to accurately derive the optical constants data simultaneously with the physical layer thickness, using a combination approach employing custom-built spectrum-fitting software in conjunction with Swanepoel’s envelope method. MO properties, such as specific Faraday rotation, MO figure of merit and MO swing factor are also investigated for several annealed garnet-phase films.

Enhanced Faraday rotation and magneto-optical figure of merit in gold grating/graphene/silicon hybrid magneto-plasmonic devices

Graphene is a promising THz magneto-optical material. However, high Faraday rotation is only achievable at a low THz frequency range in single layer graphene. In this paper, we report simultaneous Faraday rotation and optical transmission enhancement in Au grating/graphene/silicon hybrid plasmonic structures across a wide frequency range from 0.43 to 24 THz using extraordinary transmission of THz spoof surface plasmons. In a broad frequency range up to 13.1 THz, the Faraday rotation and magneto-optical figure of merit in this hybrid structure can exceed the maximum value of single layer graphene at the low THz frequency range. Numerical analysis on the device dispersion relation indicates that the mechanism of simultaneous Faraday rotation and transmission enhancement is due to coupling of the TE waveguide mode with the TM hybrid waveguide-plasmon mode. Our work demonstrates the hybrid plasmonic structure as a promising candidate for THz nonreciprocal photonic device applications.

Thermo-optical and magneto-optical characteristics of CeF3 crystal

Thermo-optical and magneto-optical characteristics of a uniaxial CeF3 crystal have been investigated. Its optical anisotropy parameter, magneto-optical figure of merit, and the ratio of the thermo-optical constants P and Q have been measured. The found characteristics have been compared with the corresponding values for the TGG crystal. Based on the obtained results it has been concluded that, despite its anisotropy, the CeF3 crystal is promising material for the development of Faraday isolators for high-power lasers.

Optical and magneto-optical behavior of Cerium Yttrium Iron Garnet thin films at wavelengths of 200-1770 nm.

Magneto-optical cerium-substituted yttrium iron garnet (Ce:YIG) thin films display Faraday and Kerr rotation (rotation of light polarisation upon transmission and reflection, respectively) as well as a nonreciprocal phase shift due to their non-zero off-diagonal permittivity tensor elements, and also possess low optical absorption in the near-infrared. These properties make Ce:YIG useful in providing nonreciprocal light propagation in integrated photonic circuits, which is essential for accomplishing energy-efficient photonic computation and data transport architectures. In this study, 80 nm-thick Ce:YIG films were grown on Gadolinium Gallium Garnet substrates with (100), (110) and (111) orientations using pulsed laser deposition. The films had bulk-like structural and magnetic quality. Faraday and Kerr spectroscopies along with spectroscopic ellipsometry were used to deduce the complete permittivity tensor of the films in the ultraviolet, visible and near-infrared spectral region, and the magneto-optical figure of merit as a function of wavelength was determined. The samples showed the highest IR Faraday rotation reported for thin films of Ce:YIG, which indicates the importance of this material in development of nonreciprocal photonic devices.

Thermo-optical properties of terbium-aluminum garnet ceramics doped with silicon and titanium.

The Verdet constant and thermo-optical characteristics of a Si-doped and Ti-doped terbium aluminum garnet ceramics have been investigated. It is shown that the Verdet constant of the samples is ∼40% higher than that of TGG ceramics at 1064 nm. The best samples of Si:TAG have magneto-optical figures of merit more than 1.5 times greater than those of TGG ceramics. Si:TAG is better than TGG ceramics as a medium for high-power Faraday isolators.

Optical, magnetic susceptibilities and magneto-optical properties of neodymium doped Tb3Ga5O12 with meliorated properties for near-infrared optical isolators

High optical quality Tb3−xNdxGa5O12 (TNGG) single crystal has been grown by Czochralski technique. The absorption spectrum in the wavelength range of 300–1600 nm has been measured at room temperature, as well as the weak absorption at 1064 nm, and the spectral characteristics were analyzed in detailed. Results show a superior transparency in the near-infrared region. Thermal conductivity and laser induced damage threshold (LIDT) measurements were carried out to check its potential usage. Magnetic properties of the as-grown crystal were studied and showed paramagnetism. The magneto-optical properties were studied and the specific Faraday rotation of the as-grown crystal was measured at 1064 nm wavelength. The Verdet constant and magneto-optical figures of merit (V/α) calculated are 41 rad m−1 T−1 and 2.56 × 102 rad/T at 1064 nm, which are both larger than that of commercial TGG (2.44 × 102 rad/T). The results indicated that the TNGG shows a superior properties than that the commercial TGG and could be a promising candidate magneto-optical material in the wavelength of 900–1450 nm.

Vacuum annealed cerium-substituted yttrium iron garnet films on non-garnet substrates for integrated optical circuits

Polycrystalline cerium-substituted yttrium iron garnet (CeYIG) showing large Faraday rotation (FR) in the near-IR region was grown on non-garnet (synthetic fused silica, Si, and Si-on-insulator) substrates by sputtering followed by thermal annealing in vacuum. The FR of the films is comparable to the single crystal value. Structural characterization, magnetic properties, refractive index, extinction coefficient, surface topography, and FR vs. wavelength were measured and the magnetooptical figure of merit was compared with that of CeYIG films on garnet substrates.

Growth and Magneto-Optical Properties of Li2MoO4·1.8Tb2(MoO4)3 Crystal

Li2MoO4·1.8Tb2(MoO4)3 crystal, a kind of solid solution crystal, was grown in air by the top seeded solvent growth method in a Li2Mo2O7 flux. The lattice parameters of the crystal were determined by X-ray diffraction analysis. The absorption coefficient of the crystal was investigated at wavelengths from 400 to 1500 nm at room temperature. Valence states of Tb ions in Li2MoO4·1.8Tb2(MoO4)3 crystal were analyzed by X-ray photoelectron spectroscopy measurement. Verdet constants for the Li2MoO4·1.8Tb2(MoO4)3 crystal at 532, 633 and 1064 nm wavelengths were measured by the extinction method. They are −341, −239 and −75 rad m−1 T−1, respectively. The results show that the crystal has a larger magneto-optical figure of merit than terbium gallium garnet at wavelength of 633 nm.

Faraday rotation and magneto-optical figure of merit for the magnetite magnetic fluids

In the present paper, using magnetite magnetic fluids as examples, we consider the optical and magneto-optical properties of magnetic fluids based on particles of magnetic oxides, for the optical constants of the material of which, n and k , the relation 22 kn  holds. In this work the Faraday rotation is represented within the theoretical Maxwell-Garnett model. A theoretical analysis has shown that Faraday rotation for magnetic fluids is related to the Faraday rotation on the material of particles by the simple relation. According to this result in specific experimental conditions the values of the Faraday rotation prorate to q , which is the occupancy of the volume of the magnetic fluid with magnetic particles and spectral dependences of effect in magnetic fluid and in the proper bulk magnetic are similar. We also show that the values of the magneto-optical figure of merit for ultrafine medium and for the bulk material are equal.

Magneto-optics in Diluted Magnetic Semiconductors and in Ferromagnetic-Metal/Semiconductor Hybrids

ABSTRACTThe optical isolator made of diluted magnetic semiconductor and the isolator made of a ferromagnetic-metal/semiconductor hybrid have been developed aiming to integrate nonreciprocal optical devices, such as an optical isolator and optical circulator, into the semiconductor-made optoelectronic integrated circuits,. The Cd1-xMnxTe exhibits a huge Faraday effect and can be grown on a semiconductor substrate. For Cd1-xMnxTe waveguide with a Cd1-xZnxTe/ Cd1-xMnxTe quantum well grown on GaAs substrate we achieved a high Faraday rotation of 2000 deg/cm, a high isolation ratio of 27 dB, a low optical loss of 0.5 dB/cm, and a high magneto-optical figure-of-merit of 2000 deg/dB/kG in a wide 25-nm wavelength range. It was predicted theoretically and proved experimentally the effect of non-reciprocal loss in hybrid semiconductor/ferromagnetic metal waveguides. This effect can be use for new design of waveguide optical isolator. Because of its simplicity and technological compatibility, this design is attractive for the integration into optoelectronic integrated circuits. The magneto-optical figure-of merit of 7% was demonstrated for the AlGaAs passive optical waveguide covered by Co.

Growth and characteristic of Sr 3Tb(BO 3) 3 crystal

A new borate single crystal of Sr 3Tb(BO 3) 3 with dimension Ф20×25 mm 2 has been grown by the Czochralski method. The grown crystal was characterized by DTA–TGA, FTIR and X-ray powder diffraction analysis. The results showed the crystal with [BO 3] 3− is congruently melting at 1351.35 °C which belongs to hexagonal structure. The hardness of Sr 3Tb(BO 3) 3 crystal is 422.5 VDH, and is equal to 5.0 moh. The thermal expansion coefficients were determined to be 2.08×10 −5/°C along (1 0 0) direction and 7.43×10 −6/°C along (0 0 1) direction and the transmission spectrum was measured in 320–1800 nm at room temperature. The magnetic properties of the single crystal were studied which showed its paramagnetism and magnetic anisotropy. The specific Faraday rotation of single crystal was measured at room temperature in 532, 633, and 1064 nm wavelength. The Verdet constants and magneto-optical figures of merit were investigated. The primary emphasis is laid to explore a new magneto-optical material, all the magneto-optical properties of Sr 3Tb(BO 3) 3 are comparing to the ones of TGG.

Growth and magneto-optical properties of LiTb(MoO4)2 crystal

Lithium terbium molybdate (LiTb(MoO4)2) single crystal was grown by the Czochralski method. The lattice parameters of the crystal were determined by X-ray diffraction analysis. The absorption coefficient and the Faraday rotation spectrum (B=1.07 T) were investigated at wavelengths of 400–1500 nm at room temperature. Verdet constants of LiTb(MoO4)2 crystal at 532-, 633- and 1064-nm wavelengths were measured by the extinction method. The results show that LiTb(MoO4)2 crystal has a larger magneto-optical figure of merit than that of terbium gallium garnet at wavelengths of 600–1500 nm.

Dependence of Faraday rotation and magneto-optical figure of merit on dielectric tensor elements in materials with uniaxial symmetry

Dependence of Faraday rotation and magneto-optical figure of merit on dielectric tensor elements in materials with uniaxial symmetry

Bi$_{3}$Fe$_{4}$Ga$_{1}$O$_{12}$ Garnet Properties and Its Application to Ultrafast Switching in the Visible Spectrum

We have synthesized Bi3Fe4Ga1O12 (BIGG) films on Gd3Ga5O12 and Gd3(ScGa)5O12 substrates by a pulsed laser deposition technique. X-ray diffraction and rocking curve analyses confirm the epitaxial quality of the films with a lattice constant close to 12.61 plusmn 0.01 Aring. Compared with that of a bismuth iron garnet Bi3Fe5O12 (BIG) film, the bandwidth of the BIGG transmittance (T) spectrum is extended and its left edge shifted down in wavelength by approximately 50 nm. This enables its Faraday rotation and switching speed to be tested at a wavelength of 532 nm. While BIGG film has a Faraday rotation angle slightly less than that of BIG film, its magnetooptical figure of merit, 2|thetasFd|/-ln(T%), is greatly improved to a typical value ~1.8 times larger than that of the BIG film. Further, the high-speed pulse response time of the BIGG film reaches 2.4 ns with a 1 mm aperture size at the wavelength of 532 nm.

Optimization of magneto-optical response of FeF2∕Fe∕FeF2 sandwiches for microwave field detection

We report on optimizing the magneto-optical (MO) response of dielectric/Fe/dielectric sandwich structures for microwave B-field sensor applications. We have performed experimental MO spectroscopic and simulation studies of FeF2∕Fe∕FeF2 sandwiches with varying both top and bottom FeF2 layer thicknesses. We evaluate the performance of the sensor with MO figure of merit (off-diagonal reflection coefficient) rather than with MO polarization state (MO azimuth rotation and ellipticity). Our simulations indicate that an increase in the modulus of the MO signal by a factor of 17 is feasible compared to the bulk Fe. However, the corresponding enhancement of the figure of merit, which is the relevant parameter, is only threefold. These simulations were carried out for the operating wavelength of sensors at 810nm. We show, contrary to the general belief, that in order to enhance the MO performance of the sensor it is more important to optimize the bottom dielectric layer rather than the top layer.

Growth and characterization of Tb 3Ga 5−xAl xO 12 single crystal

Growth conditions for pure and Al 3+-doped Tb 3Ga 5O 12 garnet crystals by the Czochralski method have been established. The growth protective atmosphere, changes in the lattice parameters with various dopant concentrations, segregation coefficient of Al 3+ in Tb 3Ga 5− x Al x O 12 crystal, absorption and transmission spectra in the wavelength range of 400–1100 nm as well as the Faraday rotation and magneto-optical figure of merit in 532 nm are investigated.