Crystal Materials for Optical Circulators
Yttrium Iron Garnet and Bismuth-substituted Iron Garnets are the most common materials. The Verdet constant of the BIG is typically more than 5 times larger the YIG, so a compact device can be made using the BIG crystals. Photonic crystals (PCs) are periodic electromagnetic structures that enable the precise manipulation of optical wave propagation. While an isolator causes loss in the isolation direction, a circulator collects the light and directs it to a nonreciproca output port. By locally switching the direction of the magnetic field on chip, we can dynamic es nators; (230 o integrate in photonic integrated circuits. The function of an optical circulator is similar to that of a microwave circulator—to transmit a lightwave from one port to the next sequential port with a maximum intensity, but at the same time to block.
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