Bismuth-substituted Rare-earth Iron Research Articles

Development of an Optical Probe Current Sensor for Local and Narrow Area Measurement Using Magnetic Domain Reversal in Bismuth-Substituted Rare-Earth Iron Garnet Crystal

Development of an Optical Probe Current Sensor for Local and Narrow Area Measurement Using Magnetic Domain Reversal in Bismuth-Substituted Rare-Earth Iron Garnet Crystal

Liquid phase epitaxy growth of (GdYbBi)3(FeGe)5O12 films for magneto-optical applications

As an important component in magneto-optical devices, bismuth-substituted rare-earth iron garnet films play a significant role in guarantying a unidirectional light propagation in optical communication system. In this study, (GdYbBi)3(FeGe)5O12 film with a thickness of 120 μm was successfully grown by liquid phase epitaxy (LPE) technology. Lattice mismatch and internal stress between the epitaxial film and substrates were discussed in detail. Tested results shown that (GdYbBi)3(FeGe)5O12 films exhibit high crystal quality and large specific faraday rotation angle, which indicate that the prepared (GdYbBi)3(FeGe)5O12 films have a great potential to be used in optical communication system.

Structural and compositional inhomogeneities in Bismuth-Substituted rare earth iron garnet epitaxial films

Structural and compositional inhomogeneities in the free-standing epitaxial films of rare earth iron garnet films are characterized using high-resolution X-ray diffraction and energy dispersive X-ray fluorescence. These analyses show a variation in the lattice parameters as well as in chemical compositions, displaying inconsistency from the top and the bottom of the film, suggesting an inhomogeneous distribution of rare earth content. With these variations, intricate changes often occur in the magneto-optics properties. While with conventional X-ray diffraction techniques, the films appeared to be free of gross defects, our high-resolution rocking curves reveal variations in defect density and multiple lattice parameters. These results suggest that epitaxial films presumed to be homogeneous based on conventional X-ray diffractometry, may not be so. Therefore, films found to exhibit exotic physical properties should be carefully examined for the presence of structural and compositional anomalies to optimize the magneto-optic response. If such defects are present, the experimental results may be compromised due to sample imperfections, rather than intrinsic phenomena.

Thin-film magnetless Faraday rotators for compact heterogeneous integrated optical isolators

This report describes the fabrication, characterization, and transfer of ultra-compact thin-film magnetless Faraday rotators to silicon photonic substrates. Thin films of magnetization latching bismuth-substituted rare-earth iron garnets were produced from commercially available materials by mechanical lapping, dice polishing, and crystal-ion-slicing. Eleven-μm-thick films were shown to retain the 45° Faraday rotation of the bulk material to within 2° at 1.55 μm wavelength without re-poling. Anti-reflection coated films evince 0.09 dB insertion loses and better than –20 dB extinction ratios. Lower extinction ratios than the bulk are ascribed to multimode propagation. Significantly larger extinction ratios are predicted for single-mode waveguides. Faraday rotation, extinction ratios, and insertion loss tests on He-ion implanted slab waveguides of the same material yielded similar results. The work culminated with bond alignment and transfer of 7 μm-thick crystal-ion-sliced 50 × 480 μm2 films onto silicon photonic substrates.

Tuning of the transverse magneto-optical Kerr effect in magneto-plasmonic crystals

The spectral properties of the transverse magneto-optical Kerr effect (TMOKE) in periodic metal–dielectric hybrid structures are studied, in particular with respect to the achievable magnitude. It is shown that the TMOKE is sensitive to the magneto-optical activity of the bismuth-substituted rare-earth iron garnet, which is used as a dielectric material in the investigated structures. For samples with larger Bi substitution level and, consequently, larger gyration constant, the magnitude of the TMOKE increases and reaches 13% in the case of a Bi1.8Lu1.2Fe3.6Al1.4O12 magnetic film. Further, it is demonstrated that the TMOKE vanishes at the high-symmetry points of the Brillouin zone (at the Γ and X points). The main enhancement of the TMOKE takes place near the resonances of the surface plasmon polaritons (SPPs) at the metal/magnetic–dielectric interface. However, near the degenerate resonances of the SPPs at the air/metal and metal/magnetic–dielectric interfaces the TMOKE is increased by the air/metal SPPs as well. This phenomenon is explained in terms of a coupled oscillator model.

Anisotropy and Field-Sensing Bandwidth in Self-Biased Bismuth-Substituted Rare-Earth Iron Garnet Films: Measurement by Ferromagnetic Resonance Spectroscopy

The high-frequency response of magneto-optic ferrites for field-sensing applications is dictated by the ferromagnetic resonance (FMR) frequency. The FMR frequency can be increased by applying an external biasing field or by tuning the internal anisotropies of the material to provide a self-bias. We report the angular dependence of FMR spectra of bismuth-substituted rare-earth iron garnet thin films to extract their uniaxial and cubic anisotropies. These measurements allow us to estimate the characteristic resonant frequency in the self-bias regime, which is equivalent to the high-frequency limit for magnetic field-sensing in these materials when no external field is applied. We find that the frequency limit estimated by FMR agrees with the measured frequency limit of a magneto-optic field sensor utilizing the same garnet composition.

Fast magneto-optic switch based on nanosecond pulses

The paper studies an all fiber high-speed magneto-optic switch which includes an optical route, a nanosecond pulse generator, and a magnetic field module in order to reduce the switching time of the optical switch in the all optical network. A compact nanosecond pulse generator can be designed based on the special character of the avalanche transistor. The output current pulse of the nanosecond pulse generator is less than 5 ns, while the pulse amplitude is more than 100 V and the pulse width is about 10 to 20 ns, which is able to drive a high-speed magnetic field. A solenoid is used as the magnetic field module, and a bismuth-substituted rare-earth iron garnet single crystal is chosen as the Faraday rotator. By changing the direction of current in the solenoid quickly, the magnetization of the magneto-optic material is reversed, and the optical beam can be rapidly switched. The experimental results indicate that the switching time of the device is about 100 to 400 ns, which can partially meet the demand of the rapid development of the all optical network.

Faraday rotation spectra of bismuth-substituted rare-earth iron garnet crystals in optical communication band

Bismuth-substituted rare-earth iron garnet (REBIG) crystals are used in optical isolators for optical communication. However, the Faraday rotation (FR) spectra of REBIG crystals in the wavelength region of 1.3–1.6 μm have not yet been theoretically studied. To interpret the spectra, we assumed that the FR in this wavelength range was dominated by the contribution of the electric dipole transitions, and calculated the FR spectra. REBIG bulk crystals were grown from the Bi2O3 self-fluxed melt by the top-seeded solution growth method. The experimental results agreed with the theoretical calculation of FR in (HoBi)3Fe5O12, (YbBi)3Fe5O12, (YYbBi)3Fe5O12, and (TbBi)3Fe5O12. The results indicate that the theoretical analysis method of the FR spectra of REBIG in the visible range of wavelengths can be applied in the optical communication band.

Preparation of bismuth-substituted rare-earth iron garnet films for magneto-optical recording media by pulsed laser ablation

Preparation of bismuth-substituted rare-earth iron garnet films for magneto-optical recording media by pulsed laser ablation

Growth-induced magnetic and optic anisotropy in bismuth-substituted iron garnet films

The growth-induced uniaxial magnetic anisotropy constant Kgu and the growth-induced birefringence Δng of (111) oriented epitaxial iron garnet films of composition R3−xBixFe5−yAlyO12 with R=Y, Gd, Sm have been investigated as a function of supercooling temperature ΔTs. The uniaxial anisotropy constant Kgu increases linearly with increasing ΔTs (0≤ΔTs≤100 K) in agreement with results reported for other bismuth-substituted rare-earth iron garnets. Δng turns out to be a linear function of Kgu and ΔTs. Δng is independent of the rare-earth species R in contrast to Kgu. The optical anisotropy arises primarily from the iron ions on the octahedral and tetrahedral sites as could be shown by the strong influence of diamagnetic dilution of the iron sublattices in the garnet crystal.

Faraday rotator materials for lasers (invited) (abstract)

Materials exhibiting strong Faraday rotation are of interest for components in laser systems. These include optical isolators, circulars, modulators, and switches in sizes ranging from microdevices for integrated optics to 30-cm-diam rotators for Nd:glass lasers used in inertial confinement fusion research. Properties of diamagnetic, paramagnetic, ferromagnetic, dilute magnetic semiconductors and free carrier rotators have been evaluated for various laser applications and for operation in the spectral range from the infrared to the ultraviolet and at various temperatures. Both crystalline and amorphous materials are considered; forms include bulk materials, fibers, and thin films. The characteristics of selected materials, including bismuth-substituted rare-earth iron garnets, Cd1−xMnxTe, and rare-earth doped glasses and crystals, are discussed. Relative figures of merit based on specific rotation, losses, cost, and special properties such as the nonlinear refractive index are also given.