Waveguide sandwich source of polarization entangled photons

Abstract

The disclosure is directed at a waveguide sandwich which comprises a pair of host materials, each of the host materials housing a component waveguide. The component waveguides are then placed in physical contact with each other to form a composite waveguide thereby producing a waveguide sandwich.

1 - 19 . (canceled) 
     
     
         20 . A device comprising:
 a sandwich source comprising first and second crystals, the sandwich source configured to produce polarization entangled photons in response to light pumped into the sandwich source at an interface between the first and second crystals, the interface extending from an input end of the sandwich source to an output end of the sandwich source;   a beam displacer at one or more of the input end or the output end.   
     
     
         21 . The device of  claim 20 , wherein the first crystal is physically bonded to the second crystal at the interface. 
     
     
         22 . The device of  claim 20 , wherein the first crystal comprises a first component waveguide, the second crystal comprises a second component waveguide, and the sandwich source comprises a composite waveguide formed by the first component waveguide and the second component waveguide. 
     
     
         23 . The device of  claim 20 , wherein the first crystal comprises a first bulk material, the second crystal comprises a second bulk material, and the interface comprises an interface between the first bulk material and the second bulk material. 
     
     
         24 . The device of  claim 20 , comprising:
 an input optically coupled to the input end of the sandwich source to pump light into the sandwich source at the interface; and   an output optically coupled to the output end of the sandwich source to collect the polarization entangled photons produced by the sandwich source.   
     
     
         25 . The device of  claim 20 , wherein the first crystal comprises a first down conversion crystal and the second crystal comprises a second down conversion crystal. 
     
     
         26 . The device of  claim 25 , wherein the first crystal and the second crystal have the same phase matching conditions. 
     
     
         27 . The device of  claim 25 , wherein the first down conversion crystal facilitates Type-I down conversion, the second down conversion crystal facilitates Type-I down conversion, and the polarization entangled photons are produced via Type-I down conversion in the first and second down conversion crystals. 
     
     
         28 . The device of  claim 25 , wherein the first down conversion crystal facilitates Type-II down conversion, the second down conversion crystal facilitates Type-II down conversion, and the polarization entangled photons are produced via Type-II down conversion in the first and second down conversion crystals. 
     
     
         29 . The device of  claim 20 , wherein at least one of the first crystal or the second crystal comprises at least one of Lithium Niobate (LiNbO3), Potassium Titanyl Phosphate (KTiOPO4), Potassium Titanyle Arsenate (KTiOAsO4), Lithium Iodate (LiIO3), Lithium Tantalate (LiTaO3), Gallium Arsenide (GaAs) or Aluminium Gallium Arsenide (AlGaAs). 
     
     
         30 . A method comprising:
 producing polarization entangled photons in a sandwich source comprising first and second crystals, the polarization entangled photons produced in response to light pumped into the sandwich source at an interface between the first and second crystals, the interface extending from an input end of the sandwich source to an output end of the sandwich source;   communicating the polarization entangled photons from the sandwich source.   
     
     
         31 . The method of  claim 30 , wherein the polarization entangled photons are produced in the sandwich source by down conversion in the first crystal and the second crystal. 
     
     
         32 . The method of  claim 30 , wherein producing polarization entangled photons comprises producing a polarization entangled biphoton state. 
     
     
         33 . The method of  claim 30 , wherein the first crystal comprises a first component waveguide in a first host material, the second crystal comprises a second component waveguide in a second host material, and the sandwich source comprises a composite waveguide formed by the first component waveguide and the second component waveguide. 
     
     
         34 . The method of  claim 30 , wherein the first crystal comprises a first bulk material and the second crystal comprises a second bulk material, and the interface comprises an interface between the first bulk material and the second bulk material. 
     
     
         35 . The method of  claim 30 , comprising:
 pumping light into the input end through an input fiber optically coupled to the input end; and   collecting the polarization entangled photons through an output fiber optically coupled to the output end.   
     
     
         36 . A system comprising:
 a means for producing polarization entangled photons, the means for producing polarization entangled photons comprising first and second crystals mated at an interface;   an input optically coupled to the means for producing polarization entangled photons to pump light into the means for producing polarization entangled photons at the interface; and   an output optically coupled to the means for producing polarization entangled photons to collect the polarization entangled photons.   
     
     
         37 . The system of  claim 36 , further comprising a beam displacer at one or more of an input end or an output end of the means for producing polarization entangled photons. 
     
     
         38 . The system of  claim 37 , comprising a beam displacer at the input end configured to facilitate coupling between the input and the means for producing polarization entangled photons. 
     
     
         39 . The system of  claim 37 , comprising a beam displacer at the output end configured to facilitate coupling between the output and the means for producing polarization entangled photons.