Lens-free alignment-free optical isolators integrated into a fiber array

We demonstrate lens-free optical isolators integrated into a thermally expanded core fiber array. The isolators are constructed without any optical alignment. The isolator chip is composed of two birefringent wedges, a birefringent plate and a Faraday rotator which is sandwiched between a pair of thermally expanded core (TEC) fibers. The optical performance is promising and suggests the configuration is useful for low-cost isolators.