Large size rare earth iron garnet single crystals grown by the flux–Bridgman method

Rare earth garnet (R3Fe5O12, RIG) single crystals are the most ideal magneto-optical medium for optical isolators for wavelength longer than 1.1 μm, which has been commercially used in optical fiber communications. However, it is still a great challenge to grow large size RIG single crystals. In this work, high-quality Y3Fe5O12 (YIG) and Bi0.9Tb2.1Fe5O12 (Bi:TIG) single crystals were successfully grown by the flux–Bridgman method for the first time. The as-grown crystals up to 20 mm in diameter was obtained using the PbO–B2O3 flux. The transmittance of YIG crystals is over 75% in the region of 1100–2500 nm. TIG crystals also have good transmittance in the range of 1100–1700 nm, and show typical Tb absorption from 1700 to 2500 nm. The specific Faraday rotations of YIG and Bi0.9Tb2.1Fe5O12 crystals are 185 (°)/cm and –1250 (°)/cm at 1550 nm, which are comparable to the commercial RIG crystals grown by LPE method. The present results indicate that flux–Bridgman method shows great potential to grow large size and high-quality RIG magneto-optical crystals.