Broadband Optical Isolator or Circular Polarizer

Abstract

An optical device can be used for circularly polarizing light and/or removing reflected light from an optical system (optical isolation). The optical device can have a polarizing-cube including a pair of prisms and a polarizer. Each prism can have two ends linked by an inner face and two outer faces. The prisms can be attached together at the inner face of each with the polarizer sandwiched between the prisms. Fresnel rhomb(s) can be attached to outer face(s) of the prisms.

What is claimed is: 
     
         1 . An optical device comprising:
 a polarizing-cube including a polarizer and a pair of prisms defining a first prism and a second prism, each prism having two ends linked by an inner-face and two outer-faces, the prisms are attached together at the inner-face of each with the polarizer sandwiched between the prisms;   one outer-face of the first prism defines an entry-face and the other outer-face of the first prism defines a reflection-face;   one outer-face of the second prism, located opposite of the entry-face of the first prism, defines an exit-face, and the other outer-face of the second prism, located opposite of the reflection-face of the first prism defines an elimination-face;   a Fresnel rhomb, defining an exit-rhomb, having a proximal-end attached to the exit-face of the second prism and having a distal-end spaced apart from the exit-face and opposite of the proximal-end; and   an angle (θ 1 ) between a plane of the entry-face of the first prism and a plane of the exit-face of the second prism is at least 3°.   
     
     
         2 . The optical device of  claim 1 , wherein the exit-rhomb is attached to the second prism by an adhesive-free, optical-bond. 
     
     
         3 . The optical device of  claim 1 , wherein the pair of prisms and the exit-rhomb are made of the same material. 
     
     
         4 . The optical device of  claim 1 , wherein an angle-of-rotation of the exit-rhomb is between 44 degrees and 46 degrees, where the angle-of-rotation is an angle between a plane parallel to at least one of the ends of the prisms and an edge of the exit-rhomb at the exit-face. 
     
     
         5 . The optical device of  claim 1 , wherein: the exit-rhomb has four sides extending between the proximal-end and the distal-end, the four sides including: an acute-angle-side having an acute-angle that is an internal angle between the acute-angle-side and the exit-face of the second prism; an opposite-side that is opposite of the acute-angle-side; and two adjacent-sides that are adjacent to and extend between the acute-angle-side and the opposite-side; and
 the acute-angle of the exit-rhomb, and a length of the exit-rhomb between the proximal-end and the distal-end, are configured for two internal reflections of a wavelength of light in the wavelength range of intended use.   
     
     
         6 . The optical isolator of  claim 5 , wherein an internal angle, between each of the two adjacent-sides of the exit-rhomb and the exit-face of the second prism is between 89 degrees and 91 degrees. 
     
     
         7 . The optical isolator of  claim 1 , wherein the exit-rhomb has a length for circular polarization of light. 
     
     
         8 . The optical isolator of  claim 1 , wherein the exit-rhomb covers at least 35% of the exit-face of the second prism. 
     
     
         9 . The optical device of  claim 1 , further comprising another Fresnel rhomb, defining an elimination-rhomb, having a proximal-end attached to the elimination-face of the second prism and a distal-end spaced apart from the elimination-face and opposite of the proximal-end. 
     
     
         10 . The optical device of  claim 1 , further comprising another Fresnel rhomb, defining a reflection-rhomb, having a proximal-end attached to the reflection-face of the first prism and a distal-end spaced apart from the reflection-face and opposite of the proximal-end. 
     
     
         11 . The optical device of  claim 1 , wherein θ 1  is at least 6°. 
     
     
         12 . The optical device of  claim 1 , wherein θ 1  is between 4.5° and 13°. 
     
     
         13 . The optical device of  claim 1 , wherein θ 1  is between 6° and 11°. 
     
     
         14 . The optical device of  claim 1 , wherein an angle between the entry-face of the first prism and a plane of the distal-end of the Fresnel rhomb is <2°. 
     
     
         15 . The optical device of  claim 1 , wherein an angle between the entry-face of the first prism and a plane of the distal-end of the Fresnel rhomb is <1°. 
     
     
         16 . The optical device of  claim 1 , wherein an angle between the entry-face of the first prism and a plane of the distal-end of the Fresnel rhomb is <0.5°. 
     
     
         17 . The optical device of  claim 1 , wherein an angle between the entry-face of the first prism and a plane of the distal-end of the Fresnel rhomb is <0.1°. 
     
     
         18 . An optical device comprising:
 a polarizing-cube including a polarizer and a pair of prisms defining a first prism and a second prism, each prism having two ends linked by an inner-face and two outer-faces, the prisms are attached together at the inner-face of each with the polarizer sandwiched between the prisms;   one outer-face of the first prism defines an entry-face and the other outer-face of the first prism defines a reflection-face;   one outer-face of the second prism, located opposite of the entry-face of the first prism, defines an exit-face, and the other outer-face of the second prism, located opposite of the reflection-face of the first prism defines an elimination-face;   a Fresnel rhomb, defining an exit-rhomb, having a proximal-end attached to the exit-face of the second prism and having a distal-end spaced apart from the exit-face and opposite of the proximal-end;   a Fresnel rhomb, defining an elimination-rhomb, having a proximal-end attached to the elimination-face of the second prism and a distal-end spaced apart from the elimination-face and opposite of the proximal-end; the Fresnel rhombs are attached to the second prism by an adhesive-free, optical-bond; and   an angle (θ 1 ) between a plane of the entry-face of the first prism and a plane of the exit-face of the second prism is at least 3°.   
     
     
         19 . An optical device comprising:
 a polarizing-cube including a polarizer and a pair of prisms defining a first prism and a second prism, each prism having two ends linked by an inner-face and two outer-faces, the prisms are attached together at the inner-face of each with the polarizer sandwiched between the prisms;   one outer-face of the first prism defines an entry-face and the other outer-face of the first prism defines a reflection-face;   one outer-face of the second prism, located opposite of the entry-face of the first prism, defines an exit-face, and the other outer-face of the second prism, located opposite of the reflection-face of the first prism defines an elimination-face;   a Fresnel rhomb, defining an exit-rhomb, having a proximal-end attached to the exit-face of the second prism and having a distal-end spaced apart from the exit-face and opposite of the proximal-end;   a Fresnel rhomb, defining a reflection-rhomb, having a proximal-end attached to the reflection-face of the first prism and a distal-end spaced apart from the reflection-face and opposite of the proximal-end;   the Fresnel rhombs are attached to the second prism by an adhesive-free, optical-bond; and   an angle (θ 1 ) between a plane of the entry-face of the first prism and a plane of the exit-face of the second prism is at least 3°.   
     
     
         20 . The optical device of  claim 19 , wherein the pair of prisms, the exit-rhomb, and the reflection-rhomb are made of the same material.