Thermo-Optical and Magneto-Optical Characteristics of Terbium Scandium Aluminum Garnet Crystals

Abstract

Magnetoactive materials are of considerable current interest, primarily for applications in nonreciprocal Faraday devices used for polarization control, optical isolation, optical switching, and modulation. The need for such devices is growing with laser power enhancement. They reduce risk of self-excitation of the amplifiers and optical elements damage and are a handy tool for organizing multipass schemes. However, at high average power of radiation these devices are subject to thermally induced effects that impair their operability and lead to increased losses and to the formation of phase distortions in the transmitted radiation. One of the methods to reduce thermally induced effects is to use in Faraday devices new magnetoactive materials with better thermo-optical properties. This paper is devoted to the study of thermo-optical and magneto-optical characteristics of a unique magnetoactive material-a terbium scandium aluminum garnet (TSAG) crystal. The TSAG has an extraordinary value of optical anisotropy parameter ξ , a Verdet constant 25% higher than the traditionally used terbium gallium garnet crystal and the highest magneto-optical figure-of-merit known in magnetoactive materials at the moment.Index Terms-Magneto-optical materials, Faraday effect, thermo-optic effects.

Sinterability of nanopowders of terbia solid solutions with scandia, yttria, and lutetia

“…Further experiments confirmed the possibility of replacing the single crystal material with ceramics without a loss of functionality. In recent years some works have been published on the production of magneto-optical ceramics based on terbium-aluminum garnet Tb 3 Al 5 O 12 (TAG) [3,4] and terbium scandium aluminum garnet crystals (TSAG) [5,6], possessing a higher Verdet constant value and better thermo-optical properties in comparison with TGG. However, the use of these materials is limited by the maximum possible concentration of terbium in the structural unit (37.5 at%), which determines the Verdet constant.…”

Faraday effect measurements of holmium oxide (Ho2O3) ceramics-based magneto-optical materials

“…Recently, there has been an increasing trend in investigating new materials which could supersede TGG, as it is limited by increasing absorption losses, and large-aperture TGG elements are difficult to manufacture [19] . In this manner, a terbium scandium aluminum garnet (TSAG) crystal [20] , terbium aluminum garnet (TAG) ceramics [21] , cerium-doped TAG ceramics [22] , or rare-earth (RE) elements-doped TGG crystals [23,24] In this work we report measurements of the Faraday effect in Ho 2 O 3 ceramics-based magneto-optical materials, advancing the analysis from the previous work [27] . Section 2 is dedicated to a laser measurement of the Verdet constant temperature dependence of Ho 2 O 3 ceramics at 1.064 µm, which was, to the best of our knowledge, yet-unknown.…”

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

“…The Q, P, ξ parameters are dependent on a large set of material parameters incorporating optical, thermo-optical, thermo-mechanical and elasto-optical properties [16][17][18]. However, it was reported multiple times, how these constants may be evaluated indirectly using different measurement methods (see, e.g., [39][40][41][42][43]). Within the scope of this manuscript, we cover in detail:…”

“…Equation (13) is used in the vast majority of the reported Verdet constant investigations at room temperature since the needed criteria for its use are usually very well met (e.g., [41,46,[58][59][60]). However, when the investigated spectral range contains additional resonance lines, they should be included in the model function, especially when the resonance strongly affect the overall Verdet constant dependence.…”

“…The largest piece of the TGG ceramics, a 100 mm × 100 mm slab, was reported in [111], greatly overcoming the manufacturing limits of the TGG crystal. Another material, which could be used as an advantageous alternative to the TGG crystal, is the terbium scandium aluminium crystal (TSAG) [112,113], which possesses ∼25% higher Verdet constant [114,115], lower thermo-optical constant Q and negative optical anisotropy parameter [41]. All of these properties ensure that the TSAG scores much higher in the FOM parameter than TGG, which has marked this material as one of the prime candidates of several other scientific investigations [37,[116][117][118].…”