Tunable bragg grating and devices employing the same

Abstract

The present invention relates generally to electro-optically active waveguide segments, and more particularly to the use of a selective voltage input to control the phase, frequency and/or amplitude of a propagating wave in the waveguide. Particular device structures and methods of manufacturing are described herein.

1. A method for manufacturing an electro-optic waveguide segment having a core and a cladding; the method comprising the steps of:
 forming a Bragg grating in said waveguide segment;  
 removing a first selective portion of said cladding above at least a portion of said Bragg grating to form a first recess within said cladding, said first selective portion having an outer dimension which is less than an unmodified section of said cladding;  
 depositing a first electrically conductive material covering at least part of said first selective portion and in direct contact with a deepest portion of said first recess, thereby forming a first electrode, wherein there are substantially no air gaps between said first electrode and said first recess;  
 removing a second selective portion of said cladding to form a second recess within said cladding, said second selective portion having an outer dimension which is less than an unmodified section of said cladding, said first and second selected portions not contacting one-another;  
 depositing a second electrically conductive material covering at least part of said second selective portion and in direct contact with a deepest portion of said of said second recess, thereby forming a second electrode, wherein there are substantially no air gaps between said second electrode and said second recess; and  
 poling said waveguide segment using at least a electric field applied to either said first or second electrode to induce an non-linearity in said waveguide segment.  
 
     
     
       2. The method recited in  claim 1 , wherein said first recess is substantially filled with said first electrically conductive material. 
     
     
       3. The method recited in  claim 2 , wherein said first electrically conductive material is optically transparent. 
     
     
       4. The method recited in  claim 1 , wherein said second recess is substantially filled with a second electrically conductive material. 
     
     
       5. The method recited in  claim 4 , wherein said second electrically conductive material is optically transparent. 
     
     
       6. The method recited in  claim 1  wherein said poling step is performed using ultraviolet light injected into said waveguide segment in combination with said electric field. 
     
     
       7. The method recited in  claim 1 , wherein said poling step is performed using said electrical field in combination with heating said waveguide segment. 
     
     
       8. A method for manufacturing an electro-optic waveguide segment having a core and a cladding; the method comprising the steps of:
 forming a Bragg grating in said waveguide segment;  
 removing a first selective portion of said cladding above at least a portion of said Bragg grating to form a first recess within said cladding, said first selective portion having an outer dimension which is less than an unmodified section of said cladding;  
 depositing a first electrically conductive material covering at least part of said first selective portion and in direct contact with a deepest portion of said first recess, thereby forming a first electrode, wherein there are substantially no air gaps between said first electrode and said first recess;  
 removing a second selective portion of said cladding to form a second recess within said cladding, said second selective portion having an outer dimension which is less than an unmodified section of said cladding, said first and second selected portions not contacting one-another;  
 depositing a second electrically conductive material covering at least part of said second selective portion and in direct contact with a deepest portion of said second recess, thereby forming a second electrode, wherein there are substantially no air gaps between said second electrode and said second recess; and  
 poling said waveguide segment using ultraviolet light injected into said waveguide segment to induce an non-linearity in said waveguide.  
 
     
     
       9. A method for manufacturing an electro-optic waveguide segment having a core and a cladding; the method comprising the steps of:
 forming a Bragg grating in said waveguide segment; 
 removing a first selective portion of said cladding above at least a portion of said Bragg grating to form a first recess within said cladding, said first selective portion having an outer dimension which is less than an unmodified section of said cladding;  
 
 depositing a first electrically conductive material covering at least part of said first selective portion and in direct contact with a deepest portion of said first recess, thereby forming a first electrode, wherein there are substantially no air gaps between said first electrode and said first recess; 
 removing a second selective portion of said cladding to form a second recess within said cladding, said second selective portion having an outer dimension which is less than an unmodified section of said cladding, said first and second selected portions not contacting one-another;  
 
 depositing a second electrically conductive material covering at least part of said second selective portion and in direct contact with a deepest portion of said second recess; and  
 poling said waveguide segment by heating said waveguide segment in combination with ultraviolet light injected into said waveguide segment to induce an non-linearity in said waveguide segment.  
 
     
     
       10. A method for manufacturing an electro-optic waveguide segment having a core and a cladding; the method comprising the steps of:
 removing a first selective portion of said cladding to form a first recess within said cladding, said first selective portion having an outer dimension which is less than an unmodified section of said cladding;  
 removing a second selective portion of said cladding to form a second recess within said cladding, said second selective portion having an outer dimension which is less than an unmodified section of said cladding, said first and second selected portions not contacting one another;  
 depositing a first electrically conductive material within said first recess and in direct contact with a deepest portion of said first recess, thereby forming a first electrode, wherein there are substantially no air gaps between said first electrode and said first recess;  
 depositing a second electrically conductive material within said second recess and in direct contact with a deepest portion of said second recess, thereby forming a second electrode, wherein there are substantially no air gaps between said second electrode and said second recess; and  
 poling said waveguide segment using at least a electric field applied to said first and second selective portions to induce a non-linearity in said waveguide segment.  
 
     
     
       11. The method for manufacturing recited in  claim 10 , further comprising the step of forming a Bragg grating in said waveguide segment. 
     
     
       12. An optical frequency modulator, comprising:
   a first optical fiber having first and second ends;        a mirror optically coupled to the first optical fiber first end, the mirror having a first surface configured to receive a light input signal and a second surface to reflect light from the first optical fiber first end back into the first optical fiber first end; and        a tunable Bragg grating waveguide having an optical input, an optical output and a control input, the optical input being optically coupled to the first optical fiber second end and the optical output configured to produce an output light signal, wherein the control input is configured to receive a control signal that controls the tunable Bragg grating waveguide, wherein the tunable Bragg grating comprises a second optical fiber having an electro - optically active core, and a cladding, wherein the control input comprises a pair of electrodes, each electrode disposed in one of a pair of grooves in the cladding, the pair of grooves opposed across the core and wherein each of the electrodes comprises electrically conductive material deposited in the groove by vapor deposition or sputtering.     
     
     
       13. The modulator of  claim 12  wherein the Bragg grating waveguide is configured to reflect light of selected wavelengths back into the fiber optical fiber second end and thereby form a laser with the mirror and the first optical fiber, the output light signal being a laser light output signal. 
     
     
       14. The modulator of  claim 12  wherein the Bragg grating waveguide is integrally formed within the first optical fiber. 
     
     
       15. The modulator of  claim 12  wherein the control input of the Bragg grating waveguide is configured to receive the control signal and the Bragg grating waveguide is adapted to pass selected wavelengths in dependence on the control signal applied to the control input. 
     
     
       16. The modulator of  claim 15  wherein the control input is configured to receive a voltage and the Bragg grating waveguide is adapted to pass the selected wavelengths in dependence on the voltage applied to the control input. 
     
     
       17. The modulator of  claim 15  wherein the control input is configured to receive a time- varying control signal and the Bragg grating waveguide is adapted to pass selected wavelengths that vary in dependence on the time - varying control signal applied to the control input.   
     
     
       18. The modulator of  claim 15  wherein the control input is configured to receive a non- time - varying control signal and the Bragg grating waveguide is adapted to pass selected wavelengths that are fixed in dependence on the non - time - varying control signal applied to the control input.   
     
     
       19. A method for optical frequency modulation, comprising:
   providing light to a first optical fiber first end through a mirror having a reflective side facing the first optical fiber first end to reflect light from the first optical fiber first end back into the first optical fiber first end;        positioning a tunable Bragg grating waveguide to receive light from a second end of the first optical fiber, wherein the tunable Bragg grating comprises an optical fiber with an electro - optically active core, and a cladding and a pair of electrodes, each electrode disposed in one of a pair of grooves in the cladding, the pair of grooves opposed across the core, wherein each of the electrodes comprises electrically conductive material deposited in the groove by vapor deposition or sputtering; and controlling the tunable Bragg grating waveguide to allow light of selected wavelengths to pass through the tunable Bragg grating waveguide to an output.     
     
     
       20. The method of  claim 19  wherein controlling the tunable Bragg grating waveguide comprises applying a control signal to a control input wherein the selected wavelengths passed through the tunable Bragg grating waveguide are dependent on the control signal. 
     
     
       21. The method of  claim 20  wherein the control signal is a time- varying control signal and the selected wavelengths passed through the tunable Bragg grating waveguide are varied in dependence on the time - varying control signal applied to the control input.   
     
     
       22. The method of  claim 20  wherein the control signal is a non- time - varying control signal and the selected wavelengths passed through the tunable Bragg grating waveguide are fixed in dependence on the non - time - varying control signal applied to the control input.   
     
     
       23. The modulator of  claim 12  wherein the Bragg grating waveguide has a refractive index that is configured to change in response to the control signal. 
     
     
       24. The modulator of  claim 12  wherein the mirror is configured to receive the light input signal having a broad bandwidth and to reflect light having a broad bandwidth from the first optical fiber first end back into the first optical fiber first end. 
     
     
       25. The modulator of  claim 24  wherein the Bragg grating waveguide is configured to receive the light from the first optical fiber second end having a broad bandwidth and to pass light having a bandwidth more narrow than the bandwidth of the input light signal to thereby produce the output light signal. 
     
     
       26. The modulator of  claim 12  wherein the first optical fiber is a rare- earth doped optical fiber.   
     
     
       27. The modulator of  claim 12  wherein the Bragg grating waveguide is a poled waveguide. 
     
     
       28. The method of  claim 20  wherein the control signal is a voltage and the selected wavelengths passed through the tunable Bragg grating waveguide are dependent on the voltage applied to the control input. 
     
     
       29. The method of  claim 19  wherein controlling the tunable Bragg grating waveguide comprises altering a refractive index of the tunable Bragg grating waveguide. 
     
     
       30. The method of  claim 19  wherein the tunable Bragg grating waveguide is integrally formed within the first optical fiber. 
     
     
       31. An optical frequency modulator, comprising:
   a first optical fiber having first and second ends;        a mirror optically coupled to the first optical fiber first end, the mirror having a first surface configured to receive a light input signal and a second surface to reflect light from the first optical fiber first end back into the first optical fiber first end; and        an electro - optic tunable Bragg grating waveguide having an optical input, an optical output and a control input, the optical input being optically coupled to the first optical fiber second end and the optical output configured to produce an output light signal, wherein the control input is configured to receive a control signal that controls the tunable Bragg grating waveguide, wherein the tunable Bragg grating comprises a second optical fiber having an electro - optically active core, a cladding, wherein the control input comprises a pair of electrodes, each electrode disposed in one of a pair of grooves in the cladding, the pair of grooves opposed across the core and wherein each of the electrodes comprises cono - fusical projections of electrically conductive material deposited in the groove by vapor deposition or sputtering.