Abstract:
A method and apparatus are provided for freeing laser bars stuck in a facet coating fixture. A roller device is provided that rolls into a facet coating fixture channel and applies a downward force to a stuck laser bar. The roller device provides an uncomplicated and reliable system for handling the bars.

Description:
This application is a divisional of application Ser. No. 09/225,269, filed Jan. 5, 1999, now U.S. Pat. No. 6,125,530, which is hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a method and apparatus for handling a laser bar or laser bars and relates to a system for loosening a bar or bars stuck in a channel of a facet coating fixture. 
     BACKGROUND OF THE INVENTION 
     Laser diodes are manufactured from laser bars that are in turn manufactured from substrates. A laser bar, also referred to as a bar of diodes, is formed by cleaving a section from a semiconductor substrate. The substrate has a number of contiguous diodes in a pattern. The laser bars are facet coated prior to separating into individual laser diodes. 
     Laser bars are coated by placing the bar on its edge in a coating fixture such as that disclosed in copending U.S. patent application Ser. No. 08/844,455, the contents of which are incorporated herein by reference. Various coatings may be applied to the bar&#39;s facets that effect the operation of the individual laser diodes. Regardless of the type of coating used, the laser bars can get stuck in the facet coating fixture. When this happens the laser bars must be loosened to be removed. 
     A facet coating fixture is comprised of multiple channels each of which hold individual bars. When the coating process is finished, the holding mechanism retracts and the bars are meant to fall through exit channels, with the assistance of a vacuum or other means. Even under these conditions the bars do not always release and some stick to one side or the other of the channel. The bars are fragile. Since the ends of a bar have no devices, the ends are the only places it can be safely handled without damaging it. 
     Prior art systems have failed to provide an efficient method for freeing stuck laser bars in a reliable manner. 
     SUMMARY OF THE INVENTION 
     The present invention solves these and other problems by providing a method and apparatus for loosening laser bars from a facet coating fixture and other devices containing channels. The present invention is directed to the loosening of any form of laser bar that is stuck in a channel of a coating fixture. 
     The laser bars have two ends. The ends contain alignment marks for processing. There are no devices on the ends. Consequently, the ends can be handled without damaging the laser bar. The ends are approximately twenty (20) mils wide and can be touched. The present invention takes advantage of this fact by using a two part roller device to apply pressure to the end areas. The pressure is applied to both ends of the bar so that the bar is released without causing breakage. 
     The roller device can be guided by grooves that already exist on the coating fixture. The roller device can be readily positioned in the grooves and traversed up and down the length of the coating fixture, from channel to channel, releasing all stuck bars in a single action. The roller may be used with or without an alignment fixture. 
     The roller device must have a diameter that is larger than the lateral width of the channel. This permits the roller device to roll into the channel and back out. The diameter of the roller device, relative to the channel width, permits the roller device to penetrate inside the channel a sufficient distance to contact the stuck bar. In addition, the diameter of the roller device is sufficiently large such that the majority of the downward movement that the roller device is capable of achieving is concentrated on the outside edge, the non-sticking side, of the bar. 
     In an alternate embodiment, the roller device can be integrated with a spring or actuator assembly so that the force can be adjusted or fixed. 
     With these and other objects, advantages and features of the invention that may become apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims, and to the several drawings attached herein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of a roller device constructed in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is a side view of the roller device of FIG. 1; 
     FIG. 3 is a side view of a laser bar; 
     FIG. 4 is a top view of the laser bar of FIG. 3; 
     FIG. 5 is a top view of a facet coating fixture, with two stuck laser bars, constructed in accordance with a preferred embodiment of the present invention; 
     FIG. 6 is a partial cross sectional view of the facet coating fixture of FIG. 5, taken along the line  6 — 6 , with a roller device in a channel; 
     FIG. 7 illustrates an adjustable force device constructed in accordance with the invention; 
     FIG. 8 illustrates another force device constructed in accordance with the invention; and 
     FIG. 9 illustrates another force device constructed in accordance with the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1 and 2 show a roller device  1  which has two rollers  1   a ,  1   b . The two rollers  1   a ,  1   b  are maintained in axial alignment through the use of a holder, shown schematically as  1   c . The holder  1   c  is operated through the use of a handle means, schematically shown as  1   c . The rollers  1   a ,  1   b  are cylindrical. 
     FIGS. 3 and 4 show a laser bar  2  in cross-section and top view respectively. The laser bar  2  has a rectangular substrate that is notched to form devices defined between the marks  4 . FIG. 3, the cross-section, shows the facet  204  of the laser bar. The end sections  2   a  and  2   b  are contacted by roller release device. For illustrative purposes, the marks  4  show the repeated patterns that define the individual laser diodes, prior to separation. The center portion  3  should not be handled. The ends  2   a ,  2   b  of the laser bar  2  are free of devices. The end sections  2   a ,  2   b  can be handled without damaging the laser diodes in the center section  3 . 
     Referring now to FIG. 5, a facet coating fixture  10  is shown with two laser bars  2  stuck in channels  12 . Two roller devices  1  are provided. There is one roller device  1  for each channel  12 . The following discussion refers to only a single roller device  1  and a single stuck bar  2 . The application of the other roller devices  1  may be the same. In an alternative embodiment of the invention, a single roller device  1  may be used to release both laser bars  2 . That is a single facet coating fixture  10  may have one roller device  1  for all channels  12  or one roller device  1  for each channel  12 . The laser bars  2  may be about four mils wide. 
     The roller device  1  is designed to come into contact with the two ends of the laser bar  2   a ,  2   b . The distance  100  (FIG. 1) between the rollers  1   a ,  1   b  depend on the length of the laser bar center portion  3  (that is, the distance between the bar ends  2   a ,  2   b ). The diameter  15  of the circular roller ends  1   a ,  1   b  must be greater than the width  16  of the channel  12 . In a preferred embodiment, the roller diameter  15  is one hundred and sixty percent (160%) of the channel&#39;s width  16 . 
     The roller device  1  is designed to roll on the top surface  10   a  of the facet coating fixture  10 , as shown in FIGS. 5 and 6. The facet coating fixture  10  is more fully described in U.S. patent application Ser. No. 08/844,455 the contents of which are incorporated herein by reference. 
     The facet coating fixture  10  is used to coat the laser bars  2 . The laser bars  2  are placed in channels  12  and held in place during the coating process. After the coating process is finished, the laser bars  2  are released and are removed in the direction represented by arrow  200  in FIG. 6, and through a removal channel by a vacuum (not shown). The laser bars  2  however can get stuck in the channels  12 . 
     The roller device  1  is designed to roll into the channels  12  to remove the stuck laser bars  2 . The roller device  1  exerts a force on the ends  2   a ,  2   b  to effectuate the removal of a stuck laser bar  2 . The roller device  1  pivots on edge  13  and partially penetrates into the channel  12 . The diameter  15  of the roller  1  is greater than the width  16  of the channel  12 . 
     As the diameter  15  of the roller device  1  is larger than the width  16  of the channel  12 , the roller device  1  penetrates the farthest in the center of the channel  12 . Thus, the laser bar  2  is pushed downward to the greatest extent possible on its non-stuck edge  17 . The roller device  1  can be rolled into the channel  12  from either side so as to free or loosen a laser bar  2  that is stuck to either side of the channel  12 . As such, the roller device  1  may contact the non-stuck edge  17  at the beginning of the removal process or at the end of the removal process. 
     In addition, the cylindrical surfaces  202  of the roller device  1  permit the pressure to be applied across the top surface  204  of the stuck bar  2 . Other shapes may be used for the rollers  1   a ,  1   b  that accomplish approximately the desired application of force. 
     FIG. 7 shows a profile of a variable force roller  60 . A roller  1   a  is attached to an arm  62  through a connection means  61 . The arm  62  is connected to an actuator arm  63  that is in turn connected to an actuator  64 . The actuator  64  is connected to a control device (not shown) that can control the downward force of the roller  1   a.    
     FIG. 8 shows a profile of another variable force roller device  70 . A roller  1   a  is connected to a first arm  72  through a connection means  71 . The first arm  72  is connected to a weight arm  73 . The weight arm  73  is connected to the first arm  72  at an angle, such that a weight  74  placed on the end of the weight arm  73 , changes the downward force of the roller  1   a  a predetermined amount. The weight arm  73  and first arm  72  comprise a connection point  75  that is used to pull or push the roller  1   a  across the facet coating fixture  10 . 
     FIG. 9 shows a profile of a variable force roller device  80 . A roller  1   a  is connected to an arm  82  through a connector means  81 . The arm  82  is provided with a top plate  83 . A container  84  is provided that permits vertical movement of the top plate  83 . A spring  85  is provided in the container  84  between a bottom  86  and the top plate  83 . The spring  85  assists in reducing the force applied by the roller  1   a . Alternately, the spring  85  may be positioned to increase the force applied by the roller  1   a.    
     The invention herein described and claimed may be modified and is not limited to the specific embodiments herein described.