Abstract:
An optical alignment mount for adjusting a height of an optical component includes a component mount adapted to receive an optical component. A height of the optical component in the mount can be adjusted and fixed as desired.

Description:
[0001]    The present application is based on and claims the benefit of U.S. provisional patent application Ser. No. 60/405,011, filed Aug. 20, 2002, and provisional patent application Ser. No. 60/404,865, filed Aug. 20, 2002, the contents of which are hereby incorporated by reference in their entirety. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to optical components. More specifically, the invention relates to alignment of optical components.  
           [0003]    Fiber optic communication systems allow data transfer at tremendous rates over long distances. For high performance, it is important to efficiently couple light between optical components used in these systems. Efficient coupling of light between optical components in fiber optic communication systems requires precision adjustment, alignment, and securing of the components, often to a tolerance level of less than 1 micron. Fiber alignment problems are appreciated in the art and substantial efforts have been made to address them. Numerous alignment mounts and securing methods are disclosed in the prior art. These methods include laser welding, soldering, and using adhesive to secure the alignment mounts.  
           [0004]    U.S. Pat. No. 5,619,609 discloses a clip and sleeve system that facilitates alignment and subsequent securing of an optical fiber by laser welding. U.S. Pat. No. 6,184,987 discloses a process for fine adjustment of the alignment of an optical fiber after the fiber has been initially secured by laser welding. Subsequent laser welds shift the position of the clip in a process known as “laser hammering” and allow fine adjustments of the optical fiber. Alternatively, after initial alignment and securing by laser welding, fine adjustments of the fiber may be made by mechanically deforming the clip.  
           [0005]    U.S. Pat. No. 6,222,579 discloses a method of aligning an optical component that uses a quantity of solder that exceeds the required adjustment range. The optical component is aligned while the solder is molten and secured by allowing the solder to solidify. U.S. Pat. No. 6,470,120 discloses a dual eccentric sleeve alignment system that is rotated to achieve epicyclic motion. U.S. Pat. No. 6,174,092 discloses a method for aligning optical fibers that uses a slanted, planar fiber adapter. The fiber adapter engages a similarly slanted, planar base member to minimize the amount of solder.  
           [0006]    Although there has been some success using prior art mounts and securing methods such as laser welding, soldering and using adhesive to secure alignment mounts, there still exists a need for an optical alignment mount that allows height adjustment and minimizes “post-bond shift” during the securing process. “Post-bond shift” occurs due to dimensional changes of the bonding material or mounting structures during the fixing or securing process. Accordingly, there is a need for an optical alignment mount that has height adjustability and minimizes post-bond shift errors.  
         SUMMARY OF THE INVENTION  
         [0007]    An optical alignment mount for adjusting a height of an optical component includes a component mount adapted to receive an optical component. A height of the optical component in the mount can be adjusted and fixed as desired. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a perspective view of an optical alignment mount.  
         [0009]    [0009]FIGS. 2A, 2B, and  2 C are front elevational views of the optical alignment mount of FIG. 1 showing height adjustment of an optical fiber.  
         [0010]    [0010]FIG. 3 is a top plan view of the optical alignment mount of FIG. 1 adjusted to couple light from a laser into an optical fiber.  
         [0011]    [0011]FIG. 4 is a side elevational view of the optical alignment mount of FIG. 1 adjusted to couple light from a laser into and optical fiber.  
         [0012]    [0012]FIG. 5 is a perspective view of a fiber optic laser source.  
         [0013]    [0013]FIG. 6 is a front elevational view of a laser welded optical alignment mount.  
         [0014]    [0014]FIG. 7 is an exploded perspective view of another aspect of an optical alignment mount.  
         [0015]    [0015]FIG. 8 is a front elevational view of the optical alignment mount of FIG. 7.  
         [0016]    [0016]FIG. 9 is a bottom plan view of the pivot support of FIGS. 7 and 8.  
         [0017]    [0017]FIG. 10 is a front elevational view of an optical alignment mount where a pivot surface engages a base directly. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    The present invention relates to the precision alignment of optical components. More specifically, the present invention provides an improved optical alignment mount with height adjustment. As used herein, “height” is a distance in a direction away from a support structure which may in some embodiments, comprise a substrate. Optical components such as a fibers, lenses, collimators, and detectors may be raised or lowered during alignment by rotating, pivoting, or tilting an appropriate optical component mount within the optical alignment mount. Solid support between the various elements of the optical alignment mount is maintained during this height adjustment as well as the alignment of the optical component in other degrees of freedom. Accordingly, alignment errors caused by post-bond shifting, that invariably occur during securing due to dimensional changes of the bonding material are substantially reduced. In another aspect, very thin layers of bonding material are applied between the various elements of the optical alignment mount. Due to the thinness of the bonding material, post-bond shifts that occur during securing are again reduced substantially.  
         [0019]    [0019]FIG. 1 is a perspective view of optical alignment mount  10 . Example optical component, fiber  18 , is attached to component mount  14 . Component mount  14  has a cylindrically shaped pivot surface  15  that engages v-shaped socket  28  of pivot support  12 . Gripping features  26  in component mount  14  may comprise holes or other shapes that aid a gripper or manipulator to position and align component mount  14 . Gripping features  24  in pivot support  12  may comprise holes or other shapes that aid a gripper or manipulator to position and align pivot support  12 .  
         [0020]    [0020]FIGS. 2A, 2B, and  2 C illustrate how the height of fiber  18  may be raised or lowered in the Y direction by rotating component mount  14  in the θ Z  direction. In FIG. 2A the core of fiber  18  is at height Y 0  and offset from the pivot position P of component mount  14 . Pivot position P is a line extending in and out of the plane of FIGS. 2A, 2B, and  2 C and is at the center of curvature of pivot surface  15 . By rotating component mount  14  in the positive θ Z  direction as shown in FIG. 2B, component mount  14  pivots about pivot position P and the core of fiber  18  is raised to height Y 1 . By rotating component mount  14  in the negative θ Z  direction as shown in FIG. 2C, the core of fiber  18  is lowered to height Y 2 . The core position of fiber  18  may be adjusted in the X and Z directions by translating pivot support  12  with respect to base  16  in the X and Z directions, respectively. The θ Y  alignment of fiber  18  may be adjusted by rotating pivot support  12  with respect to base  16  about the Y axis. V-groove  30  in component mount  14  supports fiber  18 . The θ Z  alignment of fiber  18  may be adjusted by rotating fiber  18  in the v-groove  30  about the Z axis before fiber  18  is secured to component mount  14 .  
         [0021]    Pivot surface  15  of component mount  14  engages v-shaped socket  28  along two contact lines  20 . As component mount  14  rotates about pivot position P, contact lines  20  are maintained as shown in FIGS. 2A, 2B, and  2 C. Contact lines  20  support component mount  14  and a solid support is formed between socket  28  and pivot surface  15 . Bonding material, such as epoxy or solder may be applied in gap  32  between component mount  14  and socket  28 . Since pivot surface  15  engages socket  28  at contact lines  20 , any shrinkage of bonding material acts to tightly secure component mount  14  to socket  28 . However, the shrinkage of the bonding material has a negligible affect on the alignment of fiber  18  since there is already solid support between pivot surface  15  and v-groove  28 .  
         [0022]    Pivot support  12  contacts base  16  at two contact planes  22  maintaining solid support between pivot support  12  and base  16 . Bonding material, such as epoxy or solder may be applied in gap  34  between pivot support  12  and base  16 . Since pivot support  12  is supported on base  16  at contact planes  22 , any shrinkage of bonding material acts to tightly secure pivot support  12  to base  16 . However, the shrinkage of the bonding material has a negligible affect on the alignment of fiber  18  since there is already solid support between pivot support  12  and base  16 . In another aspect, base  16  may have raised protrusions to support pivot support  12  and still maintain gap  34 . In a further aspect, three small, flat pedestals or three small spherical protrusions may be formed in either pivot support  12  or base  16  to maintain gap  34  and support pivot support  12  on base  16 .  
         [0023]    Pivot surface  15  may be secured to socket  28  and pivot support  12  may be secured to base  16  by appropriate bonding materials such as adhesive or solder. Component mount  14 , pivot support  12  and base  16  may be transparent to allow appropriate radiation to secure pivot surface  15  to socket  28  and pivot support  12  to base  16  such as with adhesive or by laser soldering. Component mount  14 , pivot support  12 , and base  16  may be of appropriate materials or a combination of materials, such as metal, glass, ceramic, semiconductor, or plastic and have coatings to facilitate bonding. Pivot support  12  could include a curved pivot surface and component mount  14  could be configured with a socket that allows component mount  14  to pivot and allow height adjustment of fiber  18 . Component mount  14 , pivot support  12 , and base  16  may also be made by molding.  
         [0024]    In another aspect, a very thin layer of bonding material may be applied at contact lines  20  and contact planes  22 . The thin layer of bonding material may act as a lubricant between pivot surface  15  and socket  28 , and pivot support  12  and base  16 , respectively, to promote ease of adjustment. The layer of bonding material should be thin so that dimensional changes of the bonding layer during curing or fixing are smaller than the final alignment accuracy requirement. In this aspect, the thickness of the bonding layer is much smaller than the range of Y direction height adjustability of optical alignment mount  10 .  
         [0025]    An example fiber optic laser source that advantageously employs the optical alignment mount  10  is illustrated in FIGS. 3-5. However, the present invention is applicable to other optical devices and other types of optical components.  
         [0026]    [0026]FIG. 3 is a top plan view of base  16  and FIG. 4 is a side elevational view of base  16 . Laser  40 , monitor photodiode  42 , and thermistor  44  are also mounted to base  16 . For high coupling efficiency of laser  40  output into optical fiber  18 , laser  40  may be energized and the core of fiber  18  may be actively aligned with respect to the emission facet of laser  40 . The output of fiber  18  is sensed by a detector (not shown) and fiber  18  may be aligned in the X, Y, Z, θ Y  and θ Z  directions as discussed above in reference to FIGS. 2A, 2B, and  2 C in order to optimize light coupling between laser  40  and fiber  18 . The tip of fiber  18  may also be shaped to form a lens in order to improve coupling efficiency.  
         [0027]    A perspective view of fiber optic laser source  58  is shown in FIG. 5. Base  16  is mounted in package  50 . Electrical leads  52  provide connections to external electrical circuitry needed to operate laser source  58 . Wire bond pads  51  in package  50  allow wire bonds to electrically connect laser  40 , monitor photodiode  44 , and thermistor  46  to electrical leads  52 . Fiber  18  is fed through ferrule  54 . Holes  56  allow for mounting of laser source  58 . A lid may soldered, welded, or adhesive bonded to seal the top of package  50  and a seal of glass, solder, or adhesive may be formed between fiber  18  and ferrule  54 .  
         [0028]    In a further aspect, component mount  14 , pivot support  12 , and base  16  may be made of appropriate materials such as stainless steel or Kovar and laser welded together, such as with a pulsed Nd:YAG laser. Fillet welds may be formed at weld locations  23  and  25  as shown in FIG. 6. Preferably, weld locations  23  are made simultaneously and equal energy and energy density is applied to weld locations  23 . This reduces any shifting of component mount  14  relative to pivot support  12  as the weld pools cool. Preferably, weld locations  25  are also made simultaneously and equal energy and energy density is applied to weld locations  25 . This reduces any shifting of pivot support  12  relative to base  16  as the weld pools cool.  
         [0029]    As discussed above, the position of optical fiber  18 , or other optical elements, may be adjusted in the X, Y, Z, θ Y , and θ Z  directions using optical alignment mount  10  to maintain solid support. Another embodiment of the present invention is shown in FIGS. 7-9 that additionally allows an optical element, such as a fiber optic collimator, to be adjusted in the θ X  direction and maintain solid support. FIG. 7 is an exploded perspective view of optical alignment mount  60  and FIG. 8 is a front elevational view of optical alignment mount  60 . Example optical component, fiber optic collimator  66 , is secured to component mount  64  using v-groove  76  or other suitable mounting technique. Fiber optic collimator  66  is offset from pivot position P of component mount  64 . Component mount  64  has a spherically shaped pivot surface  65  that engages pivot support  62  and allows component mount  64  to swivel or rotate about pivot position P in the θ Y , θ Y , and θ Z  directions. In this aspect, pivot position P is a point at the center of curvature of pivot surface  65 . Pivot support  62  is shown having a hole-shaped socket  74  that engages pivot surface  65 . Socket  74  may also be chamfered or a conical shaped depression that allows component mount  64  to swivel in the θ X , θ Y , and θ Z  directions. Pivot surface  65  makes a circular line contact with pivot support  62 . FIG. 9, which is a bottom plan view of pivot support  62 , shows three small pedestals  68  on the bottom of pivot support  62  that contact base  72 .  
         [0030]    The height of collimator  66  is adjusted in the Y direction by rotating component mount  64 , about pivot position P, in the θ Z  direction. Collimator  66  is adjusted in the X and Z directions by translating pivot support  62  relative to base  72  in the X and Z directions, respectively. Adjustment in the θ X  and θ Y  directions is accomplished by rotating component mount  64  in the θ X  and θ Y  directions, respectively. Collimator  66  may be adjusted in the θ Z  direction by rotating collimator  66  in v-groove  76  before collimator  66  is secured to component mount  64 .  
         [0031]    Pivot surface  65  may be secured to socket  74  and pivot support  62  may be secured to base  72  by appropriate bonding material such as adhesive or solder. Component mount  64 , pivot support  62 , and base  72  may be transparent to allow appropriate radiation to secure pivot surface  65  to socket  74  and pivot support  62  to base  76  such as with adhesive or by laser soldering. Component mount  64 , pivot support  62 , and base  72  may be of appropriate materials, or a combination of materials, such as metal, glass, ceramic, semiconductor, or plastic and have coatings to facilitate bonding. Component mount  64 , pivot support  62 , and base  76  may also be made by molding. Pivot support  62  could include a curved pivot surface and component mount  64  could be configured with a socket that allows component mount  64  to pivot and allow height adjustment of fiber optic collimator  66 . A very thin layer of bonding material may be optionally applied at the support location between pivot surface  65  and socket  74  and support location  70  between pedestals  68  and base  72 . The thin layer of bonding material may act as a lubricant to promote ease of adjustment. The layer of bonding material should be thin so that dimensional changes of the bonding layer during curing or fixing are smaller than the final alignment accuracy requirement. The thickness of the bonding layer is much smaller than the range of Y direction height adjustability of optical alignment mount  60 .  
         [0032]    In another aspect, a pivot surface may engage the base directly. This is shown in FIG. 10. Optical alignment mount  80  includes component holder  84  and spherically shaped pivot  86 . Pivot  86  engages base  88 . Example optical component, lens  82 , is secured to component holder  84 . The height of lens  82  in the Y direction is adjusted by pivoting component holder  84  in the θ Z  direction. The position of lens  82  may also be adjusted in the X, Z, θ X , and θ Y  directions by moving component holder  84  in the X, Z, θ X , and θ Y  directions, respectively. Pivot  86  may be secured to base  88  by appropriate bonding material such as adhesive or solder. Pivot  86  and base  88  may be of appropriate materials, or a combination of materials, such as metal, glass, ceramic, semiconductor, or plastic and have coatings to facilitate bonding. In a further aspect, pivot  86  and base  88  are made of metal such as stainless steel, Kovar, or Invar. Pivot  86  may then be secured to base  88  by resistance welding or laser welding.  
         [0033]    Although the present invention has been described with reference to the preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the sprit and scope of the invention. Other optical components such as lenses, detectors, and light sources may be accurately aligned with the present invention. A number of optical components may be pre-assembled together and then aligned as a single unit with the present invention. Other optical devices such as fiber optic demultiplexers and optical amplifiers may use the optical alignment mount of the present invention. Pivot surfaces need not be spherical or cylindrical, but should be curved to allow the height of an optical component to be adjusted as the component mount is pivoted. Component mounts may have sockets and pivot supports may have pivot surfaces. Sockets may be made by anisotropically etching properly oriented single crystal silicon.  
         [0034]    The present invention enables optical components to be raised or lowered during alignment by pivoting the optical component mount. Solid support between the pivot surface and socket is maintained during this height adjustment as well as the alignment of the optical component in other degrees of freedom. Accordingly, alignment errors caused by post-bond shifts are substantially reduced.