Terbium Scandium Aluminum Garnet Research Articles

1.01-W narrow-linewidth ultra-violet laser by Pr: YLF

We presented the first report of a high-power narrow-linewidth 261 nm laser. This laser relies on a diode-pumped Pr: YLF crystal and employs a ring cavity design that integrates TSAG (Terbium Scandium Aluminum Garnet) as the magneto-optical crystal. A double-ended pumping configuration is established through the utilization of two 10-W 444-nm blue diode laser arrays as pump sources. Through intracavity frequency doubling facilitated by a BBO (Beta-Barium Borate) crystal, we have achieved a final output of 1.01 W narrow-linewidth laser radiation at 261 nm.

Pulse Nd:YAG/Cr:YAG laser modulated by a TSAG magneto-optic crystal

A special pulse Nd:YAG/Cr:YAG laser is designed. A particular output mirror consists of a polarization coupled mirror and a terbium scandium aluminum garnet (TSAG) crystal. Using the Faraday magneto-optic effect in the TSAG crystal and a high reflectance mirror, the characteristic of the pulse laser can be actively modulated by adjusting the magnetic intensity. An optimal magnetic intensity (5090 Gs) is measured for output power, pulse energy, peak power, and pulse width. This provides a modern and special reference for the design and manufacture of pulse lasers.

Optical planar and ridge waveguides in terbium scandium aluminum garnet crystal fabricated by ion implantation and precise diamond blade dicing

Terbium scandium aluminum garnet crystal is a promising material which has excellent characteristics for magneto-optical devices. We report on the fabrication of optical planar and ridge waveguides in the terbium scandium aluminum garnet by using combination of helium ion implantation and precise diamond blade dicing. The conditions for the ion implantation are an energy of 400 keV and a fluence of 6 × 1016 ions/cm2. The rotating velocity and cutting speed of the diamond blade were set to be 20,000 rpm and 0.1 mm/s, respectively. The implantation depth and distributions of energy loss were calculated by the stopping and range of ions in matter 2013. The refractive index distribution and the dark-mode spectrum for the implanted planar waveguide were obtained by the reflectivity calculation method and the prism coupling system, respectively. The near-field intensity profiles of both the planar and ridge waveguides were measured by the end-face coupling technique. The optical guiding properties of the terbium scandium aluminum garnet waveguides suggest that they can serve as candidates for optical waveguide isolators.

Temperature-dependent terahertz dielectric modulation of a high-performance magneto-optic CeF3 crystal

We present experimental observations of the high-performance magneto-optic (MO) CeF3 crystal using terahertz time-domain spectroscopy (THz-TDS) in the temperature range 40–300 K for the first time. The complex refractive index strongly depends on temperature, which increases with increasing temperature. Intriguingly, the changes of complex refractive index values reach more than 0.1 between 40 K and 300 K, which is larger than terbium scandium aluminum garnet (TSAG) crystal. The weak loss tangent indicates that the crystal has a high potential as a high-dielectric-constant photovoltaic device in the terahertz domain.

Temperature-Dependent Dielectric Characterization of Magneto-Optical Tb3Sc2Al3O12 Crystal Investigated by Terahertz Time-Domain Spectroscopy**Supported by the National Natural Science Foundation of China under Grant Nos 11604202, 11674213, 61735010 and 51572275, the Shanghai Rising-Star Program under Grant No 18QA1401700, the ‘Chen Guang’ Project under Grant No 16CG45, the Shanghai Municipal Education Commission, and the Shanghai Education Development Foundation.

Terbium scandium aluminum garnet (TSAG) crystals have been widely used in magneto-optical systems. We investigate the complex refractive index of the TSAG crystal in the terahertz frequency range using terahertz (THz) time-domain spectroscopy in the temperature range 100–300 K. It is observed that the refractive index and the absorption coefficient increase with the THz frequency. The refractive index increases with the temperature. We measure the temperature coefficient of the refractive index of the TSAG crystal in the frequency range 0.4–1.4 THz. Furthermore, the loss tangent, i.e., the ratio of experimental values of the imaginary and real part of the dielectric permittivity, is found to be almost independent of frequency. TSAG is very promising for applications in THz optoelectronics because it has a high dielectric constant, low loss, and low thermal coefficient of the dielectric constant.

Realization of a 101 W single-frequency continuous wave all-solid-state 1064 nm laser by means of mode self-reproduction.

We realized a 101W single-frequency continuous wave (CW) all-solid-state 1064nm laser by means of mode self-reproduction in this Letter. Two identical laser crystals were placed into a resonator to relax the thermal lens of the laser crystals, and an imaging system was employed to realize cavity mode self-reproduced at the places of the laser crystals. Single-frequency operation of the resonator was realized by employing a new kind of high extinction ratio optical diode based on the terbium scandium aluminum garnet crystal to realize a stable unidirectional operation of the laser, together with introducing a large enough nonlinear loss to the resonator to effectively suppress the multi-mode oscillation and mode hopping of the laser. As a result, a 101W single-frequency 1064nm laser in a single-ring resonator was achieved with 42.3% optical efficiency. The measured power stability for 8h and the beam quality were better than ±0.73% and 1.2, respectively.

TSAG-based Faraday isolator with depolarization compensation using a counterrotation scheme.

A Faraday isolator (FI) with depolarization compensation using a counterrotation scheme has been realized in experiment for the first time, to the best of our knowledge. It is based on terbium scandium aluminum garnet crystals with negative optical anisotropy parameters. An order of magnitude advantage over the traditional FI scheme is achieved in this case. An isolation ratio of 35.7dB at a radiation power of 1440W has been obtained. According to the numerical estimates, an isolation ratio of 30dB can be provided up to a power of 5.5kW.

Investigation of the Thermal Conductivity Terbium Gallium and Terbium Scandium Aluminum Garnet Crystals

The thermal conductivity of terbium gallium and terbium scandium aluminum garnet crystals has been studied by the method of steady-state longitudinal heat flow in the temperature range of 50‒300 K. The effect of the impurity composition of terbium gallium garnet crystals and the formula composition of terbium scandium aluminum garnet crystals on their thermal conductivity is shown.

Faraday rotator based on TSAG crystal with orientation.

A Faraday isolator (FI) for high-power lasers with kilowatt-level average power and 1-µm wavelength was demonstrated using a terbium scandium aluminum garnet (TSAG) with its crystal axis aligned in the <001> direction. Furthermore, no compensation scheme for thermally induced depolarization in a magnetic field was used. An isolation ratio of 35.4 dB (depolarization ratio γ of 2.9 × 10-4) was experimentally observed at a maximum laser power of 1470 W. This result for room-temperature FIs is the best reported, and provides a simple, practical solution for achieving optical isolation in high-power laser systems.

TSAG-based cryogenic Faraday isolator

Thermooptical and magnetooptical properties of novel magnetoactive crystal terbium–scandium aluminum garnet were investigated at temperature range 80–300K. It is shown that Verdet constant increases inversely proportional to temperature, and thermally induced depolarization, and the optical power of the thermal lens is reduced significantly with cooling from 290K to 80K. According to estimates, TSAG crystals in [111] orientation allow to create a cryogenic Faraday isolator provides a degree of isolation of 30dB with the laser power exceeds ∼6kW, it is estimated that the transition to the [001] orientation allows to provide degree of isolation of 30dB at a laser power higher than 400kW.

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

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.

Faraday isolator based on a TSAG single crystal with compensation of thermally induced depolarization inside magnetic field

A Faraday isolator based on a terbium scandium aluminum garnet (TSAG) single crystal with compensation of thermally induced depolarization inside magnetic field was demonstrated. An isolation ratio of 32dB at 350W cw laser radiation power was achieved. Thermally induced depolarization and thermal lens were studied and compared with similar thermal effects arising in the widely used terbium gallium garnet crystal (TGG) for the first time.

Faraday isolator based on TSAG crystal for high power lasers.

A Faraday isolator based on a new magneto-optical medium, TSAG (terbium scandium aluminum garnet) crystal, has been constructed and investigated experimentally. The device provides an isolation ratio of more than 30 dB at 500 W laser power. It is shown that this medium can be used in Faraday isolators for kilowatt-level laser powers.

Dependence of Faraday effect on the orientation of terbium–scandium–aluminum garnet single crystal

To investigate the directional dependence of the Faraday effect in terbium–scandium–aluminum garnet (TSAG) single crystals, grown by the Czochralski method, the Verdet constant was measured at 〈111〉, 〈110〉, and 〈100〉 orientations. Extinction ratio and magnetic susceptibility were measured. From the linear dependence of the Verdet constant and inverse wavelength square 1/λ2, 〈111〉 direction shows the highest value of Verdet constant (for λ⋅ = 649.1 nm, Vav = 8.256 × 10−3 deg · Oe−1 · cm−1). Significant anisotropy of magnetic susceptibility was not observed. The extinction ratio of TSAG shows the highest value for 〈111〉 orientation 38.7 dB, which implies that it can be used as an optical isolator.

Annealing Effect in Terbium–Scandium–Aluminum Garnet Single Crystal

Terbium–scandium–aluminum garnet (TSAG) single crystal grown by the Czochralski method was annealed in a reducing or an oxidizing atmosphere. The oxidation state of terbium cations was studied using transmission spectra and magnetic susceptibility. By annealing in the reducing atmosphere, Tb4+ was reduced to Tb3+. In the case of annealing in the oxidizing atmosphere, some of Tb3+ ions were oxidized to Tb4+. Verdet constant and extinction ratios were measured after annealing in both atmospheres. The highest Verdet constant was obtained for the TSAG annealed in the reducing atmosphere (for λ=649.1 nm V=8.580×10-3 deg·Oe-1·cm-1). The extinction ratio of the sample annealed in the oxidizing atmosphere showed the highest value of 40.35 dB.

Microwave phonon attenuation in rare-earth garnets: Ion-phonon interactions

Significant deviations from the behavior usual for dielectrics are observed in the ultrasonic attenuation at gigahertz frequencies in Nd, Gd, and Tb garnets and are attributed to the rare-earth ions. Relaxation of low-lying electron states by Orbach processes satisfactorily explains attenuation peaks in neodymium gallium garnet and terbium scandium aluminum garnet near 60 K. Below 20 K the attenuation in all these garnets, irrespective of electronic structure, increases as the inverse of temperature and the square of frequency. Mechanisms that could explain these results based on the relaxation of low-lying states are proposed. The lack of knowledge about the parameters entering the theoretical models prevents a detailed comparison with experiment at this time.