Total Performance of Magneto-Optical Ceramics with a Bixbyite Structure.

Akio Ikesue,Akira Yahagi,Yan Aung,Shinji Makikawa

doi:10.3390/ma12030421

Abstract

High-quality magneto-optical ceramics (TbxY1−x)2O3 (x = 0.5–1.0) with a Bixbyite structure were extensively investigated for the first time. The total performances of these ceramics were far superior to those of commercial TGG (Tb3Ga5O12) crystal, which is regarded as the highest class of Faraday rotator material. In particular, the Verdet constant of Tb2O3 (when x = 1.0) ceramic was the largest—495 to 154 rad·T−1·m−1 in the wavelength range of 633 to 1064 nm, respectively. It was possible to further minimize the Faraday isolator device. The insertion loss of this ceramic was equivalent to that of the commercial TGG single crystal (0.04 dB), and its extinction ratio reached more than 42 dB, which is higher than the value for TGG crystal (35 dB). The thermal lens effect (1/f) was as small as 0.40 m−1 as measured by a 50 W fiber laser. The laser damage threshold of this ceramic was 18 J/cm2, which is 1.8 times larger than that of TGG, and it was not damaged during a power handling test using a pulsed laser (pulse width 50 ps, power density 78 MW/cm2) irradiated at 2 MHz for 7000 h.

Highlights

In 1995, highly efficient laser oscillation using a polycrystalline Nd:YAG (Y3 Al5 O12 ) ceramic material was reported for the first time [1]
Tb4 O7 (Shin-Etsu, RU, 99.99%) and Y2 O3 (Shin-Etsu, RU, 99.999%) powders were used as starting materials; they were mixed in ethanol solvent for 10 h, the dried premixed powders were pressed in a CIP (Cold Isostatic Press) machine at 196 MPa
Single-crystal materials have been put into practical use until now, but this does not necessarily mean that Faraday rotator materials are only limited to single crystals

Summary

Introduction

In 1995, highly efficient laser oscillation using a polycrystalline Nd:YAG (Y3 Al5 O12 ) ceramic material was reported for the first time [1]. Research and development on various types of ceramic laser materials and laser oscillation has been successively reported [2]. Ceramic materials are influenced by Mie scattering and Rayleigh scattering [3,4,5,6] as they contain many grain boundaries which degrade the oscillation efficiency and laser beam quality when they are used as a laser gain medium. Recent studies have revealed that certain types of ceramic materials can provide novel characteristics that cannot be achieved in single crystals [7,8,9]. Polycrystalline ceramics are anticipated to be widely applied to the field of photonics in addition to laser applications.

Results

Discussion

Conclusion