Patent Publication Number: US-2023163561-A1

Title: Package self-heating using multi-channel laser

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of co-pending U.S. patent application Ser. No. 16/995,729 filed Aug. 17, 2020. The aforementioned related patent application is herein incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     Embodiments presented in this disclosure generally relate to optical devices, and more specifically, to techniques for fabricating and operating an optical device capable of self-heating using a multi-channel laser. 
     BACKGROUND 
     Optimal performance of semiconductor-based lasers occurs within a limited temperature range. For example, the laser efficiency (e.g., an emitted optical power for an electrical bias power) may be reduced at temperatures above the range, and spectral performance can degrade at temperatures below the range due to the emergence of out-of-band parasitic lasing modes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate typical embodiments and are therefore not to be considered limiting; other equally effective embodiments are contemplated. 
         FIG.  1    is a diagram illustrating a perspective view of an exemplary multi-channel laser die, according to one or more embodiments. 
         FIG.  2    is an exemplary method of fabricating an optical apparatus, according to one or more embodiments. 
         FIG.  3    is an exemplary method of operating an optical apparatus, according to one or more embodiments. 
         FIGS.  4 A- 4 F  illustrate an exemplary sequence of fabricating an optical apparatus, according to one or more embodiments. 
         FIG.  5    is a diagram illustrating exemplary alignment of an optical fiber, a lens, and a multi-channel laser die, according to one or more embodiments. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially used in other embodiments without specific recitation. 
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Overview 
     One embodiment presented in this disclosure is a method of fabricating an optical component. The method comprises electrically coupling different laser channels of a laser die to different electrical leads, testing a respective optical coupling of each of the different laser channels, optically aligning an optical fiber with a first laser channel of the different laser channels having the greatest optical coupling, and designating a second laser channel of the different laser channels as a heater element for the first laser channel. 
     Another embodiment presented in this disclosure is an optical component comprising a laser die and a housing component attached to the laser die. Different laser channels of the laser die are electrically coupled to different electrical leads of the housing component. The optical component further comprises an optical fiber that is optically aligned with a first laser channel of the different laser channels. A second laser channel of the different laser channels is designated as a heater element for the first laser channel. 
     Another embodiment presented in this disclosure is a method comprising transmitting light from a first laser channel of a laser die into an optical fiber, and operating a second laser channel of the laser die as a heater element for the first laser channel. 
     Example Embodiments 
     Semiconductor-based lasers such as distributed feedback (DFB) lasers may use a high reflectivity (HR) rear facet and an anti-reflectivity (AR) front facet. The phase of the rear facet is often defined by the cleaving or etching process, which causes a random phase relationship between the light reflected at the rear facet and the grating. In some cases, the random phase can correspond to unsuitably low values of a side mode suppression ratio (SMSR) indicating the presence of substantial parasitics affecting propagation of a modulated signal. These unsuitably low values of SMSR may result in the failure of a substantial percentage of laser dies. To improve the yield of laser dies, multiple laser channels may be formed in each laser die. Thus, even if one laser channel is determined to be faulty or otherwise out-of-spec during the burn-in of the laser die, the other laser channel(s) may still be within spec and the laser die may remain usable. 
     Optimal performance of semiconductor-based lasers occurs within a limited temperature range. For example, the laser efficiency (e.g., an emitted optical power for an electrical bias power) may be reduced at temperatures above the range, and spectral performance can degrade at temperatures below the range due to the emergence of out-of-band parasitic lasing modes. Techniques used for temperature control for the laser may include a thermo-electric cooler (TEC) combined with a temperature feedback loop (e.g., a thermistor), or alternatively a heater circuitry (e.g., a surface mount technology (SMT) or thin-film resistor) located proximate to the laser die combined with a temperature feedback loop (e.g., a thermistor). 
     According to embodiments described herein, an optical component comprises a laser die and a housing component attached to the laser die. Different laser channels of the laser die are electrically coupled to different electrical leads of the housing component. The optical component further comprises an optical fiber that is optically aligned with a first laser channel of the laser channels. A second laser channel of the laser channels is designated as a heater element for the first laser channel. 
     Beneficially, including multiple laser stripes on the laser die provides a redundancy that significantly improves the yield of the laser die. The laser stripes are arranged proximate to each other such that standard packaging techniques may be used. In some embodiments, the multiple laser stripes share a lens and are spaced apart such that optical energy from the first laser channel is coupled into the core of optical fiber while optical energy from the second laser channel (e.g., the heater element) is not coupled into the core. In some embodiments, a greatest optical coupling of the laser channels is determined during testing, and the laser channel having the greatest optical coupling is determined to be the first laser channel. 
       FIG.  1    is a diagram  100  illustrating a perspective view of an exemplary multi-channel laser die  105 , according to one or more embodiments. 
     The multi-channel laser die  105  (also referred to as a laser die  105 ) comprises a substrate  110  and a plurality of laser channels  115 - 1 ,  115 - 2 . The substrate  110  may be formed of one or more layers of any suitable semiconductor material(s). As shown, the substrate  110  comprises an optical waveguide layer  135  arranged above a cladding layer  140 , which is arranged above a conductive contact layer  145 . The laser channels  115 - 1 ,  115 - 2  are spaced apart (e.g., a pitch) by a distance d, and respectively include an optically active layer  130 - 1 ,  130 - 2 . The multi-channel laser die  105  further comprises a cladding layer  125 - 1 ,  125 - 2  arranged above the optically active layer  130 - 1 ,  130 - 2 , and a conductive contact layer  120 - 1 ,  120 - 2  arranged above the cladding layer  125 - 1 ,  125 - 2 . 
     In one example, the cladding layers  140 ,  125 - 1 ,  125 - 2  comprise an indium phosphide (InP) semiconductor material, and the optical waveguide layer  135  may be formed of gallium indium arsenide phosphide (GaInAsP), aluminum gallium indium arsenide (AlGaInAs), or another suitable quaternary compound semiconductor material. In another example, the cladding layers  140 ,  125 - 1 ,  125 - 2  comprise an aluminum gallium arsenide (AlGaAs) semiconductor material, and the optical waveguide layer  135  may be formed of gallium arsenide (GaAs), AlGaAs with a lower proportion of aluminum, and so forth. The optically active layer  130 - 1 ,  130 - 2  may comprise regions of any suitable optically active material(s), such as quantum wells, quantum dots, and quantum wires. Further, the optically active material(s) may be electrically pumped and/or optically pumped. 
     The multi-channel laser die  105  comprises a front facet  150  having an anti-reflectivity film or coating, and a rear facet  155  having a high-reflectivity film or coating. Each of the laser channels  115 - 1 ,  115 - 2  extends between the front facet  150  and the rear facet  155 . 
     In some embodiments, the laser channels  115 - 1 ,  115 - 2  have a same phase at the rear facet  155 . In other embodiments, the laser channels  115 - 1 ,  115 - 2  have a predetermined phase difference at the rear facet  155  to decorrelate any deleterious phases of the laser channels  115 - 1 ,  115 - 2 . 
     In general, yielding of the multi-channel laser die  105  requires only one of the laser channels  115 - 1 ,  115 - 2  to be functional. Assuming that both laser channels  115 - 1 ,  115 - 2  are functional, the “non-preferred” laser channel  115 - 1 ,  115 - 2  (e.g., having a lesser optical coupling and/or having degraded spectral performance and/or showing signs of early failure (burn-in fail)) may be designated and operated as the heater element for the “preferred” laser channel  115 - 1 ,  115 - 2  that is operated as the laser element. The heater element may be operated to raise the operating temperature of the laser and extend the operational range of the laser element. Further, using one of the laser channels  115 - 1 ,  115 - 2  as the heater element provides a simpler implementation as additional components such as a TEC are not required. 
       FIG.  2    is an exemplary method  200  of fabricating an optical apparatus, according to one or more embodiments. The method  200  may be used in conjunction with other embodiments, such as the multi-channel laser die  105  of  FIG.  1   . 
     The method  200  begins at block  205 , where different channels of the laser die are electrically coupled to different electrical leads. The electrical leads may be included in a package for the optical apparatus. In some embodiments, a header of the package comprises the electrical leads, and electrically coupling the different channels to different electrical leads comprises attaching the laser die to the header. In some embodiments, the different channels of the laser die may be electrically coupled to a same electrical lead (e.g., a common cathode that is shared by the different channels) so long as each channel is also electrically coupled with different electrical leads (e.g., each of the different channels is electrically coupled with a different anode). 
     At block  215 , an optical coupling of each of the laser channels is tested. In some embodiments, testing the respective optical coupling is performed using a monitor photodiode (e.g., a large area monitor photodiode) shared by the laser channels. In some embodiments, the monitor photodiode is included in the package (e.g., included in the header). 
     In other embodiments, the monitor photodiode may external to the packaging of the optical component. In some embodiments, testing the respective optical coupling includes disposing a lens between the laser die and the monitor photodiode. For example, the method  200  may further comprise contacting a cap of the package to the header, where the lens is arranged at an opening of the cap. 
     At block  225 , an optical fiber is optically aligned with a first laser channel of the laser channels having the greatest optical coupling. In some embodiments, optically aligning the optical fiber comprises moving the cap relative to the header. In this way, optically aligning the optical fiber is performed through the lens. The method may further comprise rigidly attaching the cap to the header. 
     In some embodiments, optically aligning the optical fiber comprises arranging the optical fiber at a first distance from the lens. The first distance is based on a magnification of the lens and is selected to match a mode size of the laser channels to a mode size of the optical fiber. 
     At block  235 , a second laser channel of the laser channels is designated as a heater element for the first laser channel. The method  200  ends following completion of block  235 . 
       FIG.  3    is an exemplary method  300  of operating an optical apparatus, according to one or more embodiments. The method  300  may be used in conjunction with other embodiments, such as operating the optical apparatus formed using the method  200  of  FIG.  2   . 
     The method  300  begins at block  305 , where light is transmitted from a first laser channel of a laser die into an optical fiber. In some embodiments, the light is transmitted through a lens into a core of the optical fiber. At block  315 , temperature measurements are acquired. In some embodiments, the temperature measurements are acquired using a thermistor coupled with the laser die. In some embodiments, the laser die is arranged within a package, and the temperature measurements are acquired external to the package. 
     At block  325 , a second laser channel of the laser die is operated as a heater element for the first laser channel. In some embodiments, the second laser channel is operated based on the temperature measurements. In some embodiments, the light from the second laser channel is transmitted through the lens and is not coupled into the core. For example, the spacing between the laser die, the lens, and the optical fiber may be determined such that the light from the second laser channel is offset from the light from the first laser channel by a predetermined amount at the optical fiber (e.g., several microns) to minimize coupling from the second laser channel into the core. The spacing may further be based on a pitch between the first laser channel and the second laser channel and a magnification of the lens. The method  300  ends following completion of block  325 . 
       FIGS.  4 A- 4 F  illustrate an exemplary sequence of fabricating an optical apparatus, according to one or more embodiments. The sequence illustrated in  FIGS.  4 A- 4 E  may be used in conjunction with other embodiments, e.g., one possible implementation of the method  200  of  FIG.  2   . 
     Diagram  400  of  FIG.  4 A  represents a top view of the multi-channel laser die  105 . The laser channels  115 - 1 ,  115 - 2  are disposed on a substrate  110 . The laser channels  115 - 1 ,  115 - 2  extend parallel to each other and are spaced apart (e.g., a pitch) by a distance d. The diagram  400  thus represents a pre-bond chip or bar testing stage for the multi-channel laser die  105 . 
     In  FIG.  4 B , the multi-channel laser die  105  is bonded with a substrate  410  to form an assembly  405 .  FIG.  4 B  thus represents die bonding, testing, and/or burn-in stages for the multi-channel laser die  105 . 
     In  FIGS.  4 C and  4 D , the assembly  405  is attached to a submount  425  of a header  420  to respective form an assembly  415 ,  432 . The header  420  may be formed of any suitable material, such as a metal. The header  420  further comprises a plurality of electrical leads  430 - 1 ,  430 - 2 ,  430 - 3 . In some embodiments, the electrical lead  430 - 1  is an anode for the laser channel  115 - 1 , the electrical lead  430 - 3  is an anode for the laser channel  115 - 2 , and the electrical lead  430 - 2  is a common cathode for the laser channels  115 - 1 ,  115 - 2 . In other embodiments, the laser channels  115 - 1 ,  115 - 2  may be electrically coupled to different cathodes. 
     In some embodiments, testing is performed on the multi-channel laser die  105  to determine the optical and spectral performance and reliability of each of the laser channels  115 - 1 ,  115 - 2 . For example, a large area monitor photodiode may be shared by the laser channels  115 - 1 ,  115 - 2 . In some embodiments, the testing is performed prior to attaching the assembly  405  to the submount  425 . In other embodiments, the testing is performed after attaching the assembly  405  to the submount  425 . 
     In some embodiments, a first laser channel  115 - 1  having the showing the superior performance is designated as the laser element of the assembly  405 , and a second laser channel  115 - 2  is designated as the heater element for the laser channel  115 - 1 . In some embodiments, and as shown in  FIG.  4 D , attaching the assembly  405  to the submount  425  comprises aligning the first laser channel  115 - 1  with a center axis C of the header  420 , which in some cases corresponds to an optical axis of the optical apparatus. This may occur in cases where the multi-channel laser die  105  has been tested and burned-in prior to its attachment to the header  420 . In other embodiments, the optical axis of the optical apparatus may not correspond to the center axis C, and the first laser channel  115 - 1  is aligned with the optical axis. 
     In some embodiments, and as shown in  FIG.  4 C , the first laser channel  115 - 1  and the second laser channel  115 - 2  are offset from a center axis C of the header  420  (which in some cases corresponds to an optical axis of a lens of the optical apparatus). However, the offset distances of the laser channels  115 - 1 ,  115 - 2  from the center axis C are relatively small when compared with the distances between the laser die and the lens, and between the optical fiber and the lens, such that the offset distances contributes only negligible aberration without degrading optical coupling, when compared with an on-axis optical system. This may occur in cases where the multi-channel laser die  105  is tested and burned-in after its attachment to the header  420  (e.g., for a Transistor Outline (TO) header). 
     In  FIG.  4 E , a cap  440  of the package is contacted to the header  420  to form an assembly  435 , where the laser die is arranged in an interior space formed by the cap  440  and the header  420 . The cap  440  may be formed of any suitable material, such as a metal. A lens  445  is arranged at an opening of the cap  440 . In some embodiments, the lens  445  may have a positive magnification that images the mode size of the optical signals exiting the laser die onto the mode size of the core of the optical fiber. By translating the cap  440  relative to the header  420 , the lens  445  may be aligned to the first laser channel  115 - 1  in two spatial dimensions. Once the lens  445  is aligned to the facet, the cap  440  may be rigidly attached to the header  420  (e.g., through welding). 
     In some embodiments, the testing is performed on the multi-channel laser die  105  through the lens  445 . In these embodiments, a large area monitor photodiode  455 - 1  is external to the packaging of the optical component and is shared by the laser channels  115 - 1 ,  115 - 2 . In other words, optical energy from the laser channels  115 - 1 ,  115 - 2  is directed through the lens  445  onto the large area monitor photodiode  455 - 1 . In other embodiments, a large area monitor photodiode  455 - 2  is included in the package (e.g., included in the header  420 ) and is shared by the laser channels  115 - 1 ,  115 - 2 . 
     In  FIG.  4 F , an optical connector  465  is contacted to the cap  440  at an interface  470  to form an assembly  460 . The optical connector  465  may have any suitable implementation, such as a fiber pigtail or a receptacle. An optical fiber  480  is rigidly attached to the optical connector  465 . In some embodiments, a ferrule  475  surrounds the optical fiber  480  and ensures alignment of the optical fiber  480  during connector mating. The ferrule  475  may be formed of any material having suitable rigidity, such as ceramic, stainless steel, plastic, or tungsten carbide. The ferrule  475  and the optical fiber  480  may be rigidly attached to each other using any suitable techniques, such as adhesive or crimping. In some cases, an end of the ferrule  475  may be polished after rigidly attaching the optical fiber  480 , e.g., to provide an improved optical interface. 
     The ferrule  475  and the optical fiber  480  are inserted into an interior space of the optical connector  465  and are retained by the optical connector  465  using any suitable means, such as an adhesive, a friction fit, and so forth. In some embodiments, an optical isolator  485  is arranged in the interior space and is aligned with the optical fiber  480  when inserted. By translating the optical connector  465  relative to the cap  440 , the optical fiber  480  may be aligned, through the optical isolator  485  and the lens  445 , to the first laser channel  115 - 1  in three spatial dimensions. Once the optical fiber  480  is aligned to the first laser channel  115 - 1 , the optical connector  465  may be rigidly attached to the cap  440  (e.g., through welding). In this way, aligning the optical fiber  480  to the laser die comprises attaching the optical connector  465  with a housing component (e.g., attached with the header  420  through the cap  440 ). 
     In some embodiments, operating the second laser channel  115 - 2  is based on temperature measurements acquired using a thermistor  490  coupled with the multi-channel laser die  105 . The thermistor  490  supports an active feedback loop for operating the second laser channel  115 - 2  as the heater element. 
     In other embodiments, operating the second laser channel  115 - 2  is based on temperature measurements acquired external to the package (e.g., external to the assembly  460 ). During calibration, the performance of the laser element (i.e., the first laser channel  115 - 1 ) may be determined relative to the current delivered to the second laser channel  115 - 2  and the temperature measurements. The calibration data may be stored in memory (e.g., in a look-up table), and during operation the current delivered to the second laser channel  115 - 2  may be selected based on the temperature measurements to achieve optimal performance of the first laser channel  115 - 1 . 
       FIG.  5    is a diagram  500  illustrating exemplary alignment of an optical fiber, a lens, and a multi-channel laser die, according to one or more embodiments. The features illustrated in the diagram  500  may be used in conjunction with other embodiments. For example, diagram  500  represents one possible implementation of the optical apparatus shown in  FIG.  4 E . 
     In the diagram  500 , an inset portion  505  shows optical signals  450 - 1 ,  450 - 2  exiting the laser channels  115 - 1 ,  115 - 2  at a facet  515  of the laser die  105 . The optical signals  450 - 1 ,  450 - 2  are incident on the lens  445  and directed toward an endface  520  of the optical fiber  480 . An inset portion  510  shows the optical signals  450 - 1 ,  450 - 2  being received at the endface  520 . Although not shown here, an optical isolator may be arranged between the lens  445  and the endface  520 . 
     The optical signals  450 - 1 ,  450 - 2  exit along a length of the facet  515  having a distance d 1 , and the optical signals  450 - 1 ,  450 - 2  are received along a length of the endface  520  having a distance d 2 . In some embodiments, the endface  520  of the optical fiber  480  and the facet  515  of the laser die  105  are parallel, and adjacent ones of the optical signals  450 - 1 ,  450 - 2  are equidistant at the endface  520  and at the facet  515 . 
     The lens  445  provides a given magnification imaging the mode size of the optical signals  450 - 1 ,  450 - 2  exiting the facet  515  of the laser die  105  onto the mode size of the core at the endface  520 . In some embodiments, the magnification of the lens  445  is positive. 
     The magnification of the lens  445  also affects the spacing between the optical signals  450 - 1 ,  450 - 2  at the endface  520 . In some embodiments, the spacing between the optical signals  450 - 1 ,  450 - 2  (i.e., the distance d 2 ) is greater than about 10 microns to minimize cross-talk from the optical signal  450 - 2  onto the optical signal  450 - 1  received at the core of the optical fiber  480 . For example, the spacing between the laser channels  115 - 1 ,  115 - 2  (i.e., the distance d 1 ) may be between about 20 microns and about 70 microns, and the distance d 2  may be between about 50 microns and 150 microns. Other values and ratios of the distances d 1 , d 2  are also contemplated. 
     The size of the lens  445 , the spacing between the lens  445  and the optical fiber  480 , and the spacing between the lens  445  and the facet  515  may be selected based on the distances d 1 , d 2 . In some embodiments, aligning the optical fiber  480  to the laser die  105  through the lens  445  comprises arranging the optical fiber  480  at a distance d 4  from the lens  445 . The distance d 4  is based on a magnification of the lens  445  and is selected to (i) match a mode size of the laser channels  115 - 1 ,  115 - 2  to a mode size of the core of the optical fiber  480 . 
     In some embodiments, the distance d 4  between the lens  445  and the optical fiber  480  (i.e., the endface  520 ) is between about two (2) times and about five (5) times a distance d 3  between the lens  445  and the facet  515 . In one non-limiting example, the distance d 4  is about 3000 microns, and the second distance is about 1000 microns. For this combination of distances d 3 , d 4 , a relatively large aperture of the lens  445  is capable of supporting the multiple channels. When compared with the distances d 3 , d 4 , the relatively small offset of the optical signals  450 - 1 ,  450 - 2  from an optical axis of the lens  445  contributes only negligible aberration without degrading optical coupling, when compared with an on-axis optical system. 
     Various techniques have been described for fabricating and operating an optical device capable of self-heating using a multi-channel laser. In some embodiments, prior to optical alignment of a laser die with an optical fiber, the laser die may be bonded to a submount and packaged onto a TO header. In some embodiments, each of the laser channels is tested to identify a superior laser channel to operate as the laser element. With the multiple laser channels, the partially-packaged assemblies may be divided into four (4) bins, of which only a single bin is yielded out when both laser channels fail burn-in, electrical, power, and spectral screening. The other laser channel may be operated as a heating element inside the laser die, and provides greater efficiency due to its proximity to the laser element, provides an extended power handling capability of the laser, and reduces component costs (e.g., not requiring an external heater or a TEC). 
     The multiple laser channels are arranged in proximity to each other, such that the laser may be implemented within a same mechanical package as a single-channel package. The optical alignment of an optical fiber to a selected laser channel may be performed without design modifications, as the required optical fiber offset for either laser channel falls within standard assembly tolerances. 
     Regardless of which laser channel is selected, the design of the optical apparatus may remain the same, as the offset of the laser channels from the optical axis of a lens may be relatively small when compared with the distances between the laser die and the lens, and between the optical fiber and the lens, such that the offset distances contributes only negligible aberration without degrading optical coupling, when compared with an on-axis optical system. 
     During the fabrication process, the individual laser channels may be toggled independently for testing, and both laser channels may use a same large area monitor photodiode. Once the designation of the laser channels as the laser element and the heater element is completed, optical alignment may occur with the laser element turned on and the heater element turned off. Other than testing of the individual laser channels, the fabrication of the optical apparatus may be completed without significant changes to the process flow, equipment, or test plan. 
     Despite the laser channels sharing a same coupling lens, the laser channel designated as the heater element will not couple light into the optical fiber so long as the laser channel is separated at least several microns from the laser channel designated as the laser element. In some embodiments, the light from the heater element is focused outside the main package cavity (e.g., beyond an optical isolator) such that no stray light is expected within the main package cavity, which could interfere with operation of the laser element. 
     In the preceding, reference is made to embodiments presented in this disclosure. However, the scope of the present disclosure is not limited to specific described embodiments. Instead, any combination of the described features and elements, whether related to different embodiments or not, is contemplated to implement and practice contemplated embodiments. Furthermore, although embodiments disclosed herein may achieve advantages over other possible solutions or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the scope of the present disclosure. Thus, the preceding aspects, features, embodiments and advantages are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s). 
     Aspects of the present disclosure are described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments presented in this disclosure. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks. 
     The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     The flowchart and block diagrams in the Figures illustrate the architecture, functionality and operation of possible implementations of systems, methods and computer program products according to various embodiments. In this regard, each block in the flowchart or block diagrams may represent a module, segment or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions. 
     In view of the foregoing, the scope of the present disclosure is determined by the claims that follow.