Athermal integrated optical waveguide device

Abstract

An athermalized integrated optical waveguide device in which thermal spectral shifts are inhibited is provided and in which the light transmitting properties are insensitive to temperature variations and fluctuations. The athermalized integrated optical waveguide device has at least two waveguide core arms, preferably comprised of a silica glass, with the core arms cladded with a waveguide cladding composition, preferably a silica glass that has a boron concentration different than the cores. The first waveguide arm and the second waveguide arm have a difference in an effective index thermal slope in order to provide an athermalized device such as an intereferometer on a substantially planar substrate. In addition the at least two waveguide core arms are comprised of path segments having different waveguide core dimensions.

What is claimed is:  
     
         1 . An athermalized integrated optical waveguide device comprising: 
 a planar substrate;    a first waveguide core arm formed on said planar substrate;    a second waveguide core arm formed on said planar substrate; and    a waveguide cladding which optically clads said first waveguide core arm and said second waveguide core arm, wherein said first waveguide core arm and said second waveguide core arm have a difference in an effective index thermal slope d(N 1 −N 2 )/dT.    
     
     
         2 . The athermalized integrated optical waveguide device of  claim 1  further comprising: 
 a plurality of waveguide core arms in addition to the first waveguide core arm and the second waveguide core arm.  
 
     
     
         3 . The athermalized integrated optical waveguide device of  claim 1  wherein the first waveguide core arm and the second waveguide core arm each include a core composition, and wherein the waveguide cladding includes a cladding composition.  
     
     
         4 . The athermalized integrated optical waveguide device of  claim 3  wherein the core composition and the cladding composition have a difference in thermal spectral index shift slope (nm/° C.).  
     
     
         5 . The athermalized integrated optical waveguide device of  claim 3  wherein the core composition is a silica glass.  
     
     
         6 . The athermalized integrated optical waveguide device of  claim 5  wherein the core composition includes GeO 2 , B 2 O 3 , P 2 O 5 , and SiO 2 .  
     
     
         7 . The athermalized integrated optical waveguide device of  claim 3  wherein the cladding composition is a silica glass.  
     
     
         8 . The athermalized integrated optical waveguide device of  claim 7  wherein the cladding composition includes B 2 O 3 , P 2 O 5 , and SiO 2 .  
     
     
         9 . The athermalized integrated optical waveguide device of  claim 3  wherein the core composition or the cladding composition or both include a dopant for controlling thermal spectral index shift slope (nm/° C.) at a concentration, and there is a difference in the concentration of said dopant for controlling thermal spectral index shift slope (nm/° C.) between the core composition and the cladding composition.  
     
     
         10 . The athermalized integrated optical waveguide device of  claim 9  wherein the dopant includes boron, and the difference in concentration of the dopant for controlling thermal spectral index shift slope (nm/° C.) is a difference in boron concentration.  
     
     
         11 . The athermalized integrated optical waveguide device of  claim 10  wherein the difference in the concentration of the core composition and the cladding composition is between about 3 wt. % B 2 O 3  and about 11 wt. % B 2 O 3 .  
     
     
         12 . The athermalized integrated optical waveguide device of  claim 10  wherein the difference in the concentration of the core composition and the cladding composition is between about 5 wt. % B 2 O 3  and about 9 wt. % B 2 O 3 .  
     
     
         13 . The athermalized integrated optical waveguide device of  claim 10  wherein the difference in the concentration of the core composition and the cladding composition is between about 6 wt. % B 2 O 3  and about 8 wt. % B 2 O 3 .  
     
     
         14 . The athermalized integrated optical waveguide device of  claim 10  wherein the difference in the concentration of the core composition and the cladding composition is approximately 7 wt. % B 2 O 3 .  
     
     
         15 . The athermalized integrated optical waveguide device of  claim 10  wherein the difference in concentration of the dopant for controlling thermal spectral index shift slope (nm/° C.) provides a first d 2 N/(dTdB) value between the core composition and the cladding composition that is greater than a second d 2 N/(dTdB) value between the core composition and the cladding composition that has a difference in the concentration of boron.  
     
     
         16 . The athermalized integrated optical waveguide device of  claim 1  wherein the first waveguide core arm defines a path segment having a waveguide core dimension of w 1 , and the second waveguide core arm defines a path segment having a waveguide core dimension of w 2 , wherein w 1  is not equal to w 2 .  
     
     
         17 . The athermalized integrated optical waveguide device of  claim 16  wherein the first waveguide core arm is a first waveguide core composition, the second waveguide core arm is a second waveguide core composition, and the waveguide cladding is a cladding composition.  
     
     
         18 . The athermalized integrated optical waveguide device of  claim 16  wherein the waveguide core dimension w 1  and the waveguide core dimension of w 2  are each a waveguide core width.  
     
     
         19 . The athermalized integrated optical waveguide device of  claim 16  wherein the waveguide core dimension w 1  and the waveguide core dimension w 2  are each a waveguide core thickness.  
     
     
         20 . The athermalized integrated optical waveguide device of  claim 16  wherein the first path segment of the first waveguide core arm having the waveguide core dimension w 1  is substantially parallel with the fourth path segment of the second waveguide core arm having the waveguide core dimension w 2 .  
     
     
         21 . The athermalized integrated optical waveguide device of  claim 16  wherein the first waveguide core arm defines a fifth path segment having a waveguide core dimension w 3  and the second waveguide core arm defines a sixth path segment having a waveguide core dimension w 3 .  
     
     
         22 . The athermalized integrated optical waveguide device of  claim 21  wherein the first waveguide core arm defines an adiabatic taper between the fifth path segment having a waveguide core dimension w 3  and the sixth path segment having a waveguide core dimension w 1 .  
     
     
         23 . The athermalized integrated optical waveguide device of  claim 16  wherein the length of the first path segment of the first waveguide core arm having the waveguide core dimension w 1  is substantially equal to the length of the fourth path segment of the second waveguide core arm having the waveguide core dimension w 2 .  
     
     
         24 . The athermalized integrated optical waveguide device of  claim 1  wherein the first waveguide core arm defines a first path segment having a waveguide core dimension w 1  and a second path segment having a waveguide core dimension of w 2 , the second waveguide core arm defines a third path segment having a waveguide core dimension w 1  and a fourth path segment having a waveguide core dimension w 2 , wherein the length of the first path segment of the first waveguide core arm having a waveguide core dimension w 1  is not equal to the length of the third path segment length of the second waveguide core arm having a waveguide core dimension w 1 .  
     
     
         25 . The athermalized integrated optical waveguide device of  claim 24  wherein the length of the first path segment of the first waveguide core arm having a waveguide core dimension w 2  is not equal to the length of the fourth path segment of the second waveguide core arm having a waveguide core dimension w 2 .  
     
     
         26 . The athermalized integrated optical waveguide device of  claim 1  wherein the athermalized integrated optical waveguide device is an interferometer.  
     
     
         27 . The athermalized integrated optical waveguide device of  claim 1  wherein the athermalized integrated optical waveguide device is a filter.  
     
     
         28 . The athermalized integrated optical waveguide device of  claim 1  wherein the athermalized integrated optical waveguide device is a wavelength division multiplexer or a wavelength division demultiplexer.  
     
     
         29 . The athermalized integrated optical waveguide device of  claim 1  wherein the athermalized integrated optical waveguide device is a phased array.  
     
     
         30 . The athermalized integrated optical waveguide device of  claim 1  wherein the length of said the waveguide core arm has a first length and the said second waveguide core arm has a second length not equal to said first length.  
     
     
         31 . The athermalized integrated optical waveguide device of  claim 1  wherein the athermalized integrated optical waveguide device further comprises: 
 a first coupler; and  
 a second coupler.  
 
     
     
         32 . A method for making an integrated optical waveguide device comprising the steps performed either sequentially or nonsequentially of: 
 providing a planar substrate;    forming a first waveguide core arm of a silica glass core composition on said planar substrate, said first waveguide core arm defining a first path segment having a waveguide core dimension w 1 , a second path segment having a waveguide core dimension w 3 , and a first optical path length;    forming a second waveguide core arm of said silica glass core composition, said second waveguide core arm including a third path segment having a waveguide core dimension w 2 , a fourth path segment having a waveguide core dimension w 3 , and a second optical path length not equal to said first optical path length of said first waveguide core arm so as to define a difference in optical path lengths ΔL equal to the difference between the optical path length of said first waveguide core arm and the optical path length of said second waveguide core arm;    cladding said first waveguide core arm and said second waveguide core arm with a silica glass cladding composition;    providing said silica glass core composition with a boron concentration B core ; and    providing said silica glass cladding composition with a boron concentration B clad , wherein said boron concentration B clad  is different from said boron concentration B core  of said core composition    
     
     
         33 . The method of  claim 32  wherein the steps of forming the first waveguide core arm and the second waveguide core arm include the step of: 
 depositing a core layer of the silica glass core composition over the planar substrate and exposing said core layer with an image containing a pattern corresponding to the first waveguide core arm and the second waveguide core arm.  
 
     
     
         34 . The method of  claim 32  wherein the first path segment of the first waveguide core arm having a waveguide core dimension w 1  is substantially parallel to the fourth path segment of the second waveguide core arm having a waveguide core dimension w 2 .  
     
     
         35 . The method of  claim 32  wherein the first path segment of the first waveguide core arm having a waveguide core dimension w 1  has a length L w , and the fourth path segment of the second waveguide core arm having a waveguide core dimension w 2  has a substantially equal length L w .  
     
     
         36 . The method of  claim 35  wherein the method further comprises the step of: 
 optimizing the difference in optical path lengths ΔL, waveguide core dimension w 1 , waveguide core dimension w 2 , length L w , and the difference between the boron concentration B core  in the core composition and the boron concentration B clad  in the cladding composition to produce an athermal interferometer.  
 
     
     
         37 . A method for making an integrated optical waveguide device for use in an environment having a temperature which changes, said method comprising the steps performed either sequentially or non-sequentially of: 
 providing a planar substrate;    providing a first waveguide arm and a second waveguide arm on said planar substrate, said first waveguide arm and said second waveguide arm each having a length defining a difference in lengths of −L, said first waveguide arm and said second waveguide arm each including a core composition having a high index of refraction and a boron concentration B core , said first waveguide arm defining a first segment having a length L w  and a waveguide dimension w 1 , a remainder of said first waveguide arm having a waveguide dimension w 3 , said second waveguide arm defining a second segment having a length L w  and a waveguide dimension w 2 , the remainder of said second waveguide arm having a waveguide dimension w 3 ;    cladding said first waveguide arm and said second waveguide arm with a cladding composition having a low index of refraction, and a boron concentration B clad  different from said boron concentration B core  of said core composition so as to define a difference −B between said boron concentration B core  of said core composition and said boron composition B clad  of said cladding composition; and    athermalizing said integrated optical waveguide device by optimizing said difference in lengths −L, said length L w , said waveguide dimension w 1 , said waveguide dimension w 2 , said waveguide dimension w 3 , and said difference −B between said boron concentration B core  of said core composition and said boron composition B clad  of said cladding composition to provide a zero or near-zero thermal spectral shift when said integrated optical waveguide device is subjected to a change in the temperature.    
     
     
         38 . The method of  claim 37  wherein the first segment having the length L w  and the waveguide dimension w 1  has a mode field effective index N 1  dependent on the waveguide dimension w 1 , the second segment having a length L w  and a waveguide dimension w 2  has a mode field effective index N 2  dependent on the waveguide dimension w 2 , and the remainder of the first waveguide arms and the remainder of the second waveguide arm each having a waveguide dimension w 3  have a mode field effective index N 3 , wherein  
       
         
           
             
               
                 
                   
                     
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         39 . An integrated optical waveguide interferometer for use in an environment in which a temperature changes, said integrated optical waveguide interferometer comprising: 
 a first channel waveguide arm having a first length and a second channel waveguide arm having a second length, said first length and said second length defining a difference in length ΔL, said first channel waveguide arms and said second channel waveguide arm having a core composition, said first channel waveguide arm including a first segment of length L w , a channel waveguide width w 1  and a mode field effective index N 1  dependent upon said channel waveguide width w 1 , said first channel waveguide arm including a second segment having a channel waveguide width w 3 , and a mode field effective index N 3  dependent upon said channel waveguide width w 3 , said second channel waveguide arm having a third segment of length L w , a channel waveguide width w 2  and a mode field effective index N 2  dependent upon said channel waveguide width w 2 , said second channel waveguide arm having a fourth segment having a channel waveguide width w 3 , and a mode field effective index N 3  dependent upon the channel waveguide width w 3 , a waveguide cladding composition, said waveguide cladding composition optically cladding said first channel waveguide arm and said second channel waveguide arm, at least said core composition or said cladding composition or both having a concentration of a dopant for controlling thermal spectral index shift slope (nm/° C.) and defining a difference ΔB between said concentration of said dopant in said core composition and in said cladding composition, said integrated optical waveguide interferometer being substantially insensitive to a change in the temperature when                         N   3            T          Δ                 L     +              (       N   2     -     N   1       )            T            L   w         ≅     O   .                       
     
     
         40 . The integrated optical waveguide interferometer of  claim 39  wherein the cladding composition and the core composition include silica glass.  
     
     
         41 . The integrated optical waveguide interferometer of  claim 39  wherein the dopant for controlling thermal spectral index shift slope (nm/° C.) includes boron.  
     
     
         42 . The athermalized integrated optical waveguide device of  claim 41  wherein the difference ΔB in the concentration of the dopant between the core composition and the cladding composition is between about 5 wt. % B 2 O 3  and about 9 wt. % B 2 O 3 .  
     
     
         43 . The athermalized integrated optical waveguide device of  claim 41  wherein the difference ΔB in the concentration of the dopant between the core composition and the cladding composition is between about 6 wt. % B 2 O 3  and about 8 wt. % B 2 O 3 .  
     
     
         44 . The athermalized integrated optical waveguide device of  claim 41  wherein the difference ΔB in the concentration of the dopant between the core composition and the cladding composition is about 7 wt. % B 2 O 3 .  
     
     
         45 . The integrated optical waveguide interferometer of  claim 39  wherein the concentration of the dopant for controlling thermal spectral index shift slope (nm/° C.) in the either the core composition or the cladding composition or both is not equal to zero.  
     
     
         46 . The integrated optical waveguide interferometer of  claim 45  wherein the dopant for controlling thermal spectral index shift slope (nm/° C.) includes boron.