Patent ID: 8565561

Claim:
A polarization independent optical isolator comprising: a pair of wedge-shaped birefringent crystal plates placed on an optical path; a Faraday rotator which is placed, on the optical path, between the wedge-shaped birefringent crystal plates and which is made of a magnetic garnet single crystal; collimator lenses which are placed, on the optical path, at positions outside the respective wedge-shaped birefringent crystal plates in relation to the Faraday rotator taken as a center; and sapphire single crystal plates bonded to light transmitting surfaces of the Faraday rotator, respectively, wherein the pair of wedge-shaped birefringent crystal plates are each made of a YVO 4 single crystal, a light transmitting surface of each of the sapphire single crystal plates is formed in such a manner as to be parallel to a non-inclined light transmitting surface of a corresponding adjacent one of the wedge-shaped birefringent crystal plates, and to be offset from a c-plane of the sapphire single crystal plate, and the polarization independent optical isolator is set to satisfy the following conditions: an incident angle θa of imaginary light on each of the sapphire single crystal plate is 6.06 to 9.61 degrees, the imaginary light being represented by a bisector of an angle formed by optical axes of an ordinary ray and an extraordinary ray separated by each of the wedge-shaped birefringent crystal plates; an offset angle θoff of the light transmitting surface from the c-plane of each sapphire single crystal plate is 3.05 to 5.67 degrees; and 3 mm≧f≧18.21/θa (mm), where f represents a focal length of each of the collimator lenses.