Polarization-maintaining optical circulator

A polarization-maintaining optical circulator, the polarization-maintaining optical circulator transmits the light input from port one to port two in the first direction and the light input from port two to port three in the second direction, the first direction and second direction being opposite to each other;

• the polarization-maintaining optical circulator comprising:
• a dual-core waveguide configured to provide port one and port three, a first birefringent crystal, a first Faraday rotator, a second birefringent crystal, a lens and a port two that are successively arranged along the first direction;
• the first birefringent crystal, the first Faraday rotator, and the second birefringent crystal are all parallel plate structures;
• wherein,
• the port one is a polarization-maintaining port and configured to input divergent linearly polarized light and the light input from port one enters the first birefringent crystal as o-light or e-light;
• the first birefringent crystal is configured to form a first crystal forward displacement of the light input from port one, and then output it to the first Faraday rotator;
• the first Faraday rotator is configured to rotate the polarization direction of the light input from port one by an angle of α in the first rotation direction and then output it to the second birefringent crystal, where α=45°;
• the second birefringent crystal is configured to form a second crystal forward displacement of the light input from port one, and then output it to the lens;
• the lens is configured to optically shape the light input from port one and output it to the port two;
• the port two is configured to output the light input from port one to realize the transmission from port one to port two;
• the port two is further configured to input light and then output it to the lens;
• the lens is further configured to optically converge the light input from port two and output it to the second birefringent crystal;
• the second birefringent crystal is further configured to form a second crystal backward displacement of the light input from port two, and then output it to the first Faraday rotator;
• the first Faraday rotator is further configured to rotate the polarization direction of the light input from port two by an angle of α in the first rotation direction and then output it to the first birefringent crystal;
• the first birefringent crystal is further configured to form a first crystal backward displacement of the light input from port two, and then output it to the port three;
• wherein, the polarization state of the light input from port two undergoes a 90° rotation in the first birefringent crystal relative to the light input from port one, causing the light input from port two to deviate from the light input from port one due to the transformation of the o-light and e-light in the first birefringent crystal;
• the walk-off between the light input from port one and the light input from port two being equal to the separation of two cores of the dual-core waveguide, allowing the light input from port two to couple into port three;
• the port three is configured to output the light input from port two to realize the transmission from port two to port three.