Wavelength dependence of magneto-optic properties of terbium gallium garnet ceramics

High-Verdet Constant and Low-Optical Loss Tb3+ Doped Magnetite Nanoparticles

Magneto-optical (MO) polymer nanocomposites have emerged as alternatives to conventional MO crystals, particularly in nanophotonics applications, thanks to their better processing flexibility and superior Verdet constants. However, a higher Verdet constant commonly comes with excessive optical loss due to increased absorption and scattering, resulting in a constant or reduced figure-of-merit (FOM) defined as the Verdet constant over optical loss. By doping magnetite (Fe3O4) nanoparticles with Tb3+ ions, we report a new strategy to enhance the Verdet constant without increasing the optical loss. The Fe3O4:Tb3+ nanocomposite is one of a kind that simultaneously achieves a state-of-the-art Verdet constant of 5.6 × 105 °/T·m and a state-of-the-art FOM of 31°/T in the near-infrared region.

High Verdet Constant Glass for Magnetic Field Sensors

Due to the high transparency, high Verdet constant, as well as easy processing properties, rare-earth ion-doped glasses have demonstrated great potential in magneto-optical (MO) applications. However, the variation in the valence state of rare-earth ions (Tb³⁺ to Tb⁴⁺) resulted in the decreased effective concentration of the paramagnetic ions and thus degraded MO performance. Here, a strategy was proposed to inhibit the oxidation of Tb³⁺ into Tb⁴⁺ as well as improve the thermal stability by tuning the optical basicity of glass networks. Moreover, the depolymerization of the glass network was modulated to accommodate more Tb ions. Thus, a record high effective concentration (14.19 × 10²¹/cm³) of Tb ions in glass was achieved, generating a high Verdet constant of 113 rad/(T·m) at 650 nm. Lastly, the first application of MO glass for magnetic field sensors was demonstrated, achieving a sensitivity of 0.139 rad/T. We hope our work provides guidance for the fabrication of MO glass with high performance and thermal stability and could push MO glass one step further for magnetic sensing applications.

Thermo-Optical Studies of Laser Ceramics

A cycle of works on manufacturing and studying laser and magnetooptical ceramics with a focus on their thermo-optical characteristics performed by the research team is analyzed. Original results that have not been published before such as measurements of the Verdet constant in the Zr:TAG, Re:MgAl₂O₄, and ZnAl₂O₄ ceramics are also presented.

Solution-Processed Faraday Rotators Using Single Crystal Lead Halide Perovskites

Lead halide perovskites (LHPs) have become a promising alternative for a wide range of optoelectronic devices, thanks to their solution-processability and impressive optical and electrical properties. More recently, LHPs have been investigated in magneto-optic studies and have exhibited spin-polarized emission, photoinduced magnetization, and long spin lifetimes. Here, the viability of methylammonium lead bromide (MAPbBr3) single crystals as solution-processed Faraday rotators is demonstrated. Compared to terbium gallium garnet, the industry standard in the visible, it is found that MAPbBr3 exhibits Verdet constants (i.e., strength of Faraday effect) of similar or greater magnitude (up to 2.5x higher), with lower temperature dependence. Due to its low trap absorption, it is calculated that an optical isolator made from MAPbBr3, with appropriate antireflection coatings, should reach ≈95% transmission and achieve 40 dB isolation for incoming powers of over 2 W. It is also shown that the Verdet constant of MAPbBr3 can be calculated accurately from its dispersion in refractive index, allowing the possibility to predict similar effects in other perovskite materials.

Verdet Constant of Magneto-Active Materials Developed for High-Power Faraday Devices

We review the progress in the investigation of the Verdet constant of new magneto-active materials for the Faraday-effect-based devices used in high-power laser systems. A practical methodology for advanced characterization of the Verdet constant of these materials is presented, providing a useful tool for benchmarking the new materials. The experimental setup used for the characterization is a flexible and robust tool for evaluating the Faraday rotation angle induced in the magneto-active material, from which the Verdet constant is calculated based on the knowledge of the magnetic field and the material sample parameters. A general model for describing the measured Verdet constant data as a function of wavelength and temperature is given. In the final part of this review, we present a brief overview of several magneto-active materials, which have been to-date reported as promising candidates for utilization in the Faraday devices. This overview covers room-temperature investigations of the Verdet constant of several materials, which could be used for the ultraviolet, visible, near-infrared and mid-infrared wavelengths.

Magneto-optic pyrochlore ceramics of Tb2Hf2O7 for Faraday rotator

In the first demonstration of the Faraday effect in an optical-grade Tb₂Hf₂O₇ (THO) ceramic, its optical properties and the Verdet constant's wavelength dependence were evaluated at room temperature. The transmittance loss of this material was equally low as for the terbium gallium garnet, a well-known magneto-optic material. The Verdet constant at 1064 nm was 50.4 rad/Tm, which was 1.4 times greater than that of the terbium gallium garnet. THO ceramics show great potential for use in Faraday devices in near-infrared laser applications.