Patent Publication Number: US-2010118909-A1

Title: Miniature high-power laser diode device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a laser diode device, and more particularly to a miniature high-power laser diode device. 
     2. Description of the Related Art 
     In the prior art, generally, a high-power laser diode is packaged in a package housing so as to form a butterfly package, and then an optical fiber is fixed by a saddle mechanism, and then the optical fiber and the chip are optically coupled and oriented by using a laser welding machine (a laser hammering process). 
     A conventional laser welding machine mainly includes a power supply, a clamping and orienting device, and a controller.  FIG. 1  is a schematic view of a conventional saddle mechanism for clamping and orienting an optical fiber. As shown in  FIG. 1 , in the prior art, an optical fiber  11  is disposed in and through an optical fiber guider  12 , and then the optical fiber guider  12  is placed into a saddle mechanism  13 , thereby facilitating the laser spot welding, optical coupling, and alignment. In this case, the following three steps need to be performed: placing the optical fiber guider  12  into the saddle mechanism  13 , fixing the optical fiber guider  12  at the saddle mechanism  13  by laser spot welding (at welding spots P 1  and P 2 ), and moving, positioning, and aligning the optical fiber  11  in three-dimensional (X-Y-Z) directions. 
     However, the prior art has the following disadvantages. A butterfly type high-power laser diode device requires a thermoelectric cooler (TE-cooler) to ensure the stability of the laser chip, so the package housing thereof is large in volume, which hampers the miniaturization of the system. The optical fiber guider  12  needs to meet a precise positioning requirement when being placed into the saddle mechanism  13 , as does the laser spot welding process, so as to achieve a high coupling efficiency. As a result, the high-power laser diode devices cannot be mass produced and the packaging cost is accordingly increased. 
     Therefore, there is a need to provide a miniature high-power laser diode device to solve the above problem. 
     SUMMARY OF THE INVENTION 
     The present invention provides a miniature high-power laser diode device, which includes a base, a laser chip, an optical fiber guider, and an optical fiber. The base has a groove and a disposing area, and the groove connects to the disposing area. The laser chip is disposed on the disposing area, and the optical fiber guider is disposed at the groove. The optical fiber is disposed in and through the optical fiber guider. The optical fiber has a first end connected to the laser chip. 
     As a result of the cooperation between the optical fiber guider and the groove, the orientation of the optical fiber is simple and precise. The conventional thermal deformation and residual welding stress can be reduced, and the soldering flux applied in a conventional soldering and packaging process of the optical fiber can be omitted, so that the coupling efficiency, the yield, the stability of high power laser output, and the lifetime of the laser diode device of the present invention can be improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a conventional saddle mechanism for clamping and orienting an optical fiber; 
         FIG. 2  is a schematic view of a miniature high-power laser diode device according to the present invention; 
         FIG. 3  is a schematic view of an optical fiber guider disposed at a V-shaped groove according to the present invention; 
         FIG. 4  is a schematic view of an optical fiber guider disposed at a U-shaped groove according to the present invention; 
         FIG. 5  is a schematic view of an optical fiber guider with flat-plate-shaped side fins according to the present invention; 
         FIG. 6  is a schematic view of an optical fiber with a grinding angle according to the present invention; 
         FIG. 7  is a schematic view of a mini-butterfly type high-power laser diode device according to the present invention; 
         FIG. 8  is a schematic view of a relation between the grinding angle and coupling efficiency of an optical fiber according to the present invention; and 
         FIG. 9  is a schematic view of a miniature high-power laser diode module according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 2  is a schematic view of a miniature high-power laser diode device according to the present invention. Referring to  FIG. 2 , a miniature high-power laser diode device  2  is shown which includes a base  21 , a laser chip  22 , an optical fiber guider  23 , a plurality of leads  24 , and an optical fiber  25 . The base  21  has a groove  211 , a disposing area  212 , a cathode electrode  213 , and an anode electrode  214 . The groove  211  connects the disposing area  212 . The laser chip  22  is disposed on the disposing area  212 . The optical fiber guider  23  is disposed at the groove  211 . 
     The groove  211  comprises with supporting portions  215  on two sides of a rabbet thereof. The cathode electrode  213  and the anode electrode  214  are disposed on the disposing area  212 . The cathode electrode  213  and the anode electrode  214  are respectively electrically connected to a cathode and an anode of the laser chip  22 . In this embodiment, the laser chip  22  is adhered and electrically connected to the anode electrode  214 . The leads  24  are electrically connected to the cathode of the laser chip  22  and the cathode electrode  213 . The leads  24  are preferably gold wires. 
     The base  21  and the optical fiber guider  23  may be made of a KOVAR alloy, an INVAR alloy, or a tungsten carbide (WC) alloy as required. In this embodiment, the base  21  is made of an electrically insulating material (for example, the WC alloy). It should be noted that, if the base  21  is made of a conductive material (for example, the KOVAR or INVAR alloy), an insulating material must be disposed between the base  21  and the anode electrode  214 , so that the base  21  is not electrically connected to the anode electrode  214 . 
     Referring to  FIGS. 3 and 4 , the groove  211  may be a V-shaped groove (as shown in  FIG. 3 ) or a U-shaped groove (as shown in  FIG. 4 ). The optical fiber guider  23  comprises two side fins  231 . Preferably, the shape of the side fins  231  matches that of the supporting portions  215 . The groove  211  of the base  21  is quite small, and each of the supporting portions  215  has an arc-shaped structure when viewed under a microscope, so the side fins  231  are preferably arc shaped. In other applications, the side fins  231  may be flat-plate shaped (as shown in  FIG. 5 ). Preferably, a bonding material  26  is disposed between the supporting portions  215  and the side fins  231 , so as to enhance the bonding between the supporting portions  215  and the side fins  231 . The bonding material  26  is a gold-tin sheet (soldering), BAg-8 silver-copper sheet (brazing), a silver paste, or a polymer material containing copper/silver particles. 
     The optical fiber  25  is disposed in and through the optical fiber guider  23 . The optical fiber  25  may be a single-mode optical fiber or a multimode optical fiber. The optical fiber  25  has a first end  251  connected to the laser chip  22 . The first end  251  of the optical fiber  25  is formed with a grinding angle θ at a periphery thereof (as shown in  FIG. 6 ). Preferably, the grinding angle θ is 20° to 30°. 
       FIG. 7  is a schematic view of a mini-butterfly type high-power laser diode device according to the present invention. As shown in  FIGS. 2 and 7 , in other applications, a package housing  27  (for example, a mini-butterfly package housing) may be used to package the base  21 , the laser chip  22 , the optical fiber guider  23 , and the optical fiber  25 , so as to form a mini-butterfly type high-power laser diode device. 
     A process for manufacturing the miniature high-power laser diode device of the present invention is illustrated below by taking the mini-butterfly type high-power laser diode device as an example. Firstly, the base  21  is placed into the package housing  27 , and connected to the package housing  27  through soldering process. Next, the laser chip  22  is adhered and electrically connected to the anode electrode  214 . Afterwards, the leads  24  are connected to the cathode of the laser chip  22  and the cathode electrode  213  through wire bonding, and the cathode electrode  213  and the anode electrode  214  are each connected to corresponding electrodes of the package housing  27  (conducted to pins  271  at an exterior of the package housing  27 ). Then, the optical fiber  25  is placed into the optical fiber guider  23 , and then the optical fiber guider  23  is placed into the groove  211 . Then, the laser spot welding is performed on the optical fiber guider  23  (a laser hammering process), so as to adjust the coupling efficiency of the optical fiber  25  to the laser chip  22 . Finally, a parallel resistance rolled welding process or a laser welding process is performed to seal the package housing  27  by seam welding, thereby completing the mini-butterfly type high-power laser diode device. 
     As shown in  FIGS. 3 and 4 , in the step of performing the laser spot welding on the optical fiber guider  23 , firstly, a laser energy is applied to the side fins  231  to cause a slight deformation of the side fins  231 , and thus, the angle and position of the side fins  231  are adjusted in such a way that the side fins  231  more tightly cooperate with the supporting portions  215  on two sides of the rabbet of the groove  211 . Afterwards, the laser energy is applied between the side fins  231  and the supporting portions  215  or directly applied to the side fins  231  so as to heat and melt the bonding material  26 , thereby bonding the supporting portions  215  and the side fins  231 . Thus, through the present invention, the thermal deformation and residual welding stress of the conventional saddle mechanism and the optical fiber guider can be reduced, and the soldering flux applied in a conventional soldering and packaging process of the optical fiber can be omitted, thereby improving the coupling efficiency of the optical fiber and the lifetime of the laser diode device. 
       FIG. 8  is a schematic view of a relation between the grinding angle and coupling efficiency of an optical fiber according to the present invention. As shown in  FIGS. 3 ,  6  and  8 , after the angle and position of the side fins  231  are adjusted in the laser spot welding step and the supporting portions  215  and the side fins  231  are bonded together through heating and melting the bonding material  26 , the grinding angle of the optical fiber  25  is also changed accordingly, so as to achieve the highest coupling efficiency. It can be clearly seen in the distribution of data points shown in  FIG. 8  that, when the grinding angle falls between 20° and 30°, the miniature high-power laser diode device of the present invention has the highest coupling efficiency (up to about 85%), which proves that the miniature high-power laser diode device of the present invention does have an excellent coupling efficiency. 
       FIG. 9  is a schematic view of a miniature high-power laser diode module according to the present invention. As shown in  FIGS. 2 and 9 , in this embodiment, a plurality of miniature high-power laser diode devices  2  is disposed on a supporting substrate  3  (for example, a heat-dissipating substrate or a circuit board). The optical fibers  25  of the miniature high-power laser diode devices  2  are connected to a combiner  4 , so that the lasers generated by the miniature high-power laser diode devices  2  are converged and output by the combiner  4 , thereby meeting the requirements for setting the laser power. 
     To sum up, as a result of the cooperation of the optical fiber guider  23  and the groove  211 , the orientation of the optical fiber  25  is simple and precise. The conventional thermal deformation and residual welding stress can be reduced, and the soldering flux applied in a conventional soldering and packaging process of the optical fiber can be omitted, so that the coupling efficiency, the yield, the stability of high power laser output, and the lifetime of the laser diode device of the present invention are improved. 
     While the embodiments of the present invention have been illustrated and described, various modifications and improvements can be made by those skilled in the art. The embodiments of the present invention are therefore described in an illustrative but not restrictive sense. It is intended that the present invention may not be limited to the particular forms as illustrated, and that all modifications that maintain the spirit and scope of the present invention are within the scope as defined in the appended claims.