Structures that correct for thermal distortion in an optical device formed of thermally dissimilar materials

Abstract

Numerous novel structures and methods are presented for their ability to correct angular and offset alignment errors caused by thermal distortion of a device formed out of dissimilar materials, such as a movable platform and waveguide coupled to a fixed platform and another waveguide. A flexure connected between two platforms corrects offset alignment errors along the centerline axis of the flexure. Thermal distortion is corrected also by varying the relative size of the two platforms and the addition of slots and/or extraneous waveguides. A waveguide may be sandwiched between two matching materials, with or without an extra thermal compensation layer portion. A method uses simple processes to build a substrate with matching waveguides on each side of the substrate. Another simple method creates a suspended structure by using simple semiconductor processes.

1 . An optical device comprising: 
 a first structure;    a movable structure to move relative to the first structure and being disposed adjacent to the first structure;    a first light guiding structure on the first structure, the first light guiding structure comprising a different material than the first structure;    a second light guiding structure on the movable structure, the second light guiding structure comprising a different material than the movable structure, each of the first and second light guiding structures having an end portion such that the end portions of the first and second light guiding structures are aligned to propagate an optical signal between the first and second light guiding structures; and    the first structure including a base and an overhang portion which protrudes beyond the base, the overhang portion having dimensions such that when the optical device is subject to a thermal distortion, the end portions of the first and second light guiding structures maintain alignment with each other to be capable of propagating an optical signal.    
     
     
         2 . The optical device of  claim 1  wherein the dimensions of the overhang portion result in the first structure and the first light guiding structure being displaced under a thermal influence by the same amount that the movable structure and the second light guiding structure are displaced by the thermal influence.  
     
     
         3 . The optical device of  claim 1  wherein the first light guiding structure is a waveguide.  
     
     
         4 . The optical device of  claim 1  wherein the second light guiding structure is a waveguide.  
     
     
         5 . The optical device of  claim 3  wherein the second light guiding structure is a waveguide.  
     
     
         6 . The optical device of  claim 1  further comprising: 
 a second structure positioned adjacent the movable structure;    a third light guiding structure on the second structure, the third light guiding structure comprising a different material than the second structure; and    the second structure including a base and an overhang portion which protrudes beyond the base, the overhang portion having dimensions such that when the optical device is subject to a thermal distortion, the end portions of the second and third light guiding structures are aligned with each other to be capable of propagating an optical signal.    
     
     
         7 . The optical device of  claim 1  wherein the side of the overhang portion adjacent to the movable structure is narrower than the movable structure.  
     
     
         8 . An optical device for propagating an optical signal, the optical device comprising: 
 a first structure formed by a semiconductor process;    a movable structure formed by a semiconductor process to move relative to the first structure and being disposed adjacent to the first structure;    a first light guiding structure on the first structure, the first light guiding structure comprising a different material than the first structure; and    a second light guiding structure on the movable structure, the second light guiding structure comprising a different material than the movable structure, each of the first and second light guiding structures having an end portion such that the end portions of the first and second light guiding structures are aligned to propagate the optical signal between the first and second light guiding structures, the end portions of the first and second light guiding structures adapted to maintain alignment with each other in the presence of thermal distortion so that the first and second light guiding structures can propagate an optical signal.    
     
     
         9 . The optical device of  claim 8  further comprising a slot in the fixed or movable structure, the slot helping to maintain alignment of the ends of the first and second light guiding structures with each other in the presence of thermal distortion.  
     
     
         10 . The optical device of  claim 8  further comprising an optically extraneous waveguide adjacent to the first or movable structure, the extraneous waveguide helping to maintain alignment of the end portions of the first and second light guiding structures with each other in the presence of thermal distortion.  
     
     
         11 . The optical device of  claim 8  wherein the first light guiding structure is a waveguide.  
     
     
         12 . The optical device of  claim 11  wherein the second light guiding structure is a waveguide.  
     
     
         13 . The optical device of  claim 8  wherein the second light guiding structure is a waveguide.  
     
     
         14 . The optical device of  claim 8  wherein the end portions of the first and second light guiding structures bend substantially the same amount in order to maintain alignment with each other in the presence of thermal distortion so that the first and second light guiding structures can propagate an optical signal.  
     
     
         15 . The optical device of  claim 8  wherein the movable structure has a first side and a second side, the second light guiding structure being mounted on the first side of the movable structure, and a third structure formed on the second side of the movable structure, the third structure being configured to substantially cancel the thermal distortion of the second light guiding structure.  
     
     
         16 . The optical device of  claim 15  wherein the first light guiding structure is a waveguide.  
     
     
         17 . The optical device of  claim 16  wherein the second light guiding structure is a waveguide.  
     
     
         18 . The optical device of  claim 15  wherein the second light guiding structure is a waveguide.  
     
     
         19 . An optical device for propagating an optical signal, the optical device comprising: 
 a stationary structure formed by a semiconductor process;    a movable structure formed by a semiconductor process to move relative to the stationary structure and being disposed adjacent to the stationary structure;    a first light guiding structure on the stationary structure, the first light guiding structure comprising a different material than the stationary structure;    a second light guiding structure on the movable structure, the second light guiding structure comprising a different material than the movable structure; and    a third structure comprising the same material as the movable structure and located on the second light guiding structure so that the second light guiding structure is positioned between the movable structure and the third structure;    each of the first and second light guiding structures having an end portion such that the end portions of the first and second light guiding structures are aligned to propagate the optical signal between the first and second light guiding structures, the end portions of the first and second light guiding structures maintaining alignment with each other in the presence of thermal distortion so that the first and second light guiding structures can propagate an optical signal.    
     
     
         20 . The optical device of  claim 19  wherein the first light guiding structure is a waveguide.  
     
     
         21 . The optical device of  claim 20  wherein the second light guiding structure is a waveguide.  
     
     
         22 . The optical device of  claim 19  wherein the second light guiding structure is a waveguide.  
     
     
         23 . The optical device of  claim 19  wherein the third structure is configured to maintain the end portions of the first and second light guiding structures in alignment with each other in the presence of thermal distortion.  
     
     
         24 . An optical device comprising: 
 a substrate including a suspended structure adapted to move relative to the substrate, the suspended structure having a first surface and a second surface, the first and second surfaces being on opposite sides of the suspended structure;    a light guiding structure disposed on the first surface of the suspended structure; and    a thermal distortion offset structure formed on the second surface of the suspended structure, the thermal distortion offset structure configured to offset a thermal distortion applied to the first surface of the suspended structure.    
     
     
         25 . The optical device of  claim 24  wherein the light guiding structure is a first waveguide.  
     
     
         26 . The optical device of  claim 25  wherein the first and second surfaces are top and bottom surfaces of the suspended structure.  
     
     
         27 . The optical device of  claim 25  wherein the thermal distortion offset structure is made of the same material as the first waveguide.  
     
     
         28 . The optical device of  claim 27  wherein the thermal distortion offset structure includes a second waveguide.  
     
     
         29 . The optical device of  claim 28  wherein the thermal distortion offset structure is a second waveguide whose configuration differs from the configuration of the first waveguide.  
     
     
         30 . The optical device of  claim 25  wherein the first and second surfaces are side surfaces of the suspended structure, the side surfaces being generally orthogonal to the top surface of the suspended structure.  
     
     
         31 . The optical device of  claim 30  further comprising a top layer disposed on the suspended structure, the top layer covering the first waveguide.  
     
     
         32 . A method of manufacturing an optical device for propagating an optical signal, the method comprising: 
 providing a first substrate having a first side and a second side;    forming a first light guiding structure on the first side of the first substrate, the first light guiding structure comprising a different material than the first substrate;    forming an insulator on the first or second substrate;    etching a cavity to remove a portion of the insulator and a portion of the second substrate;    bonding the first substrate to the second substrate such that the insulator is located between the first and second substrates and the first light guiding structure resides in the cavity;    decreasing the thickness of the second side of the first substrate;    depositing a second material on the second side of the first substrate such that in the presence of thermal stress, the deposited second material substantially cancels the effect of the thermal stress on the first light guiding structure; and    processing the first substrate to form a suspended structure which is adapted to move relative to the second substrate, the suspended structure having the first light guiding structure.    
     
     
         33 . The method of  claim 32  wherein the first light guiding structure is a waveguide.  
     
     
         34 . The method of  claim 32  wherein the deposited second material forms at least a component of a second light guiding structure.  
     
     
         35 . The method of  claim 33  wherein the deposited second material forms at least a component of a second light guiding structure.  
     
     
         36 . The method of  claim 33  wherein the first light guiding structure includes a plurality of waveguides.  
     
     
         37 . The method of  claim 32  wherein the insulator is a dielectric layer.