Optimization of laser parameters to achieve desired performance

One example disclosed herein relates to a method of at least partially optimizing one or more output performance parameters of a laser die. The method includes an act of identifying one or more output performance parameters to be at least partially optimized, an act of identifying one or more design parameters associated with the one or more output performance parameters, an act of determining a subset of the one or more design parameters that should be varied so as to at least partially effect the one or more output performance parameters, an act of varying the subset of design parameters to produce one or more intermediate results, and an act of using the intermediate results to determine values for the one or more design parameters such that the one or more performance parameters are at least partially optimized.

BACKGROUND

Semiconductor lasers are currently used in a variety of technologies and applications, including communications networks. One type of semiconductor laser is the distributed feedback (“DFB”) laser. The DFB laser produces a stream of coherent, monochromatic light by stimulating photon emission from a solid state material. DFB lasers are commonly used in optical transmitters, which are responsible for modulating electrical signals into optical signals for transmission via an optical communication network.

Generally, a DFB laser includes a positively or negatively doped bottom layer or substrate, and a top layer that is oppositely doped with respect to the bottom layer. An active region, bounded by confinement regions, is included at the junction of the two layers. These structures together form the laser body. A grating is included in either the top or bottom layer to assist in producing a coherent light beam in the active region. The coherent stream of light that is produced in the active region can be emitted through either longitudinal end, or facet, of the laser body. DFB lasers are typically known as single mode devices as they produce light signals at one of several distinct wavelengths, such as 1,310 nm or 1,550 nm. Such light signals are appropriate for use in transmitting information over great distances via an optical communications network.

BRIEF SUMMARY

One example disclosed herein relates to a method of at least partially optimizing output performance for a laser die. The method includes an act of identifying a first design parameter, an act of identifying a second design parameter, the first and second design parameters configured to at least partially affect one or more output performance parameters of a laser die, an act of varying the first design parameter to produce first intermediate performance results, an act of varying the second design parameter to produce second intermediate performance results, and an act of using the first and second intermediate performance results to determine a value for the first and second design parameters that at least partially optimizes the one or more output performance parameters.

Another example disclosed herein relates to a method of at least partially optimizing one or more output performance parameters of a laser die. The method includes an act of identifying one or more output performance parameters to be at least partially optimized, an act of identifying one or more design parameters associated with the one or more output performance parameters, an act of determining a subset of the one or more design parameters that should be varied so as to at least partially effect the one or more output performance parameters, an act of varying the subset of design parameters to produce one or more intermediate results, and an act of using the intermediate results to determine values for the one or more design parameters such that the one or more performance parameters are at least partially optimized.

Additional features and advantages will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the teaching herein. The features and advantages of the teaching herein may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.

DETAILED DESCRIPTION

Reference will now be made to figures wherein like structures will be provided with like reference designations. It is understood that the drawings are diagrammatic and schematic representations of presently preferred embodiments of the invention, and are not limiting of the present invention nor are they necessarily drawn to scale.

Example Operating Environment

Reference is first made toFIG. 1, which depicts a perspective view of an optical transceiver module (“transceiver”), generally designated at100, for use in transmitting and receiving optical signals in connection with an external host that is operatively connected in one embodiment to a communications network (not shown). As depicted, the transceiver shown inFIG. 1includes various components, including a receiver optical subassembly (“ROSA”)10, a transmitter optical subassembly (“TOSA”)20, electrical interfaces30, various electronic components40, and a printed circuit board (“PCB”)50. In detail, two electrical interfaces30are included in the transceiver100, one each used to electrically connect the ROSA10and the TOSA20to a plurality of conductive pads18located on the PCB50. The electronic components40are also operably attached to the PCB50. An edge connector60is located on an end of the PCB50to enable the transceiver100to electrically interface with a host (not shown here). As such, the PCB50facilitates electrical communication between the ROSA10/TOSA20, and the host. In addition, the above-mentioned components of the transceiver100are partially housed within a shell70. Though not shown, the shell70can cooperate with a housing portion to define a covering for the components of the transceiver100.

While discussed in some detail here, the optical transceiver100is described by way of illustration only, and not by way of restricting the scope of the invention. As mentioned above, the optical transceiver100in one embodiment is suitable for optical signal transmission and reception at a variety of per-second data rates, including but not limited to 1 Gbit, 2 Gbit, 2.5 Gbit, 4 Gbit, 8 Gbit, 10 Gbit, or higher rates. Furthermore, the principles of the present invention can be implemented in optical transmitters and transceivers of shortwave and long wave optical transmission and any form factor such as XFP, SFP and SFF, without restriction.

The TOSA20of the transceiver100is one example of an optical transmitter that can employ an optical source, such as a semiconductor laser, that is configured according to embodiments of the present invention. Briefly, in operation the transceiver100receives electrical signals from a host (not shown) or other data signal-producing device to which the transceiver is operably connected for transmission onto an optical fiber operably connected to the TOSA20. Circuitry of the transceiver100drives a laser (described below) within the TOSA20with signals that cause the TOSA to emit onto the optical fiber optical signals representative of the information in the electrical signal provided by the host. Accordingly, the TOSA20serves as an electro-optic transducer. Having described a specific environment with respect toFIG. 1, it will be understood that this specific environment is only one of countless architectures in which the principles of the present invention may be employed. As previously stated, the principles of the present invention are not intended to be limited to any particular environment.

Example Distributed Feedback Laser

A distributed feedback (“DFB”) laser is one example of a semiconductor optical device employed according to embodiments of the present invention. By way of general overview, a DFB laser contains a cavity having an active medium and a distributed reflector that operates in a wavelength range of the laser action. The DFB laser has multiple modes, including both longitudinal and transversal modes, but one of these modes will typically offer better loss characteristics relative to the other modes. This single mode typically defines a single-frequency operation of the DFB laser.

The following description provides various details regarding a ten gigabit/second (“10 G”) DFB laser configured for light emission at a wavelength of approximately 1310 nm. The following description includes both structural and functional characteristics of the 10 G DFB laser, together with certain details regarding the manufacturing processes used to build the laser. Note, however, that this description is meant to be exemplary only; indeed, lasers and other semiconductor optical devices having structural and/or functional aspects that differ from the present description can also benefit from the principles of embodiments of the present invention as disclosed herein. It is also appreciated that additional or alternative layers, layer thicknesses, or structures can be incorporated into the present laser device as will be understood by those of skill in the art. The following discussion is therefore not intended to limit the present invention in any way. In particular, the principles of the present invention may also be achieved in a 1310 nm 2.5 G DFB laser.

a. Base Epitaxial Layers

FIG. 2illustrates layers of a base epitaxial portion112of a 10 G DFB laser, generally designated at110, at a stage prior to etching of the grating layers. The DFB laser110is grown on an Indium Phosphide substrate (n-InP substrate)114.

A “mode modifier” layer (n-IGAP Mode Modifier)118is grown on top of the substrate114using Indium Gallium Arsenide Phosphide at an approximate thickness of 120 nm. This layer functions to reduce the power of second-order transversal modes that propagate within the laser structure. In particular, the mode modifier layer118effectively increases the loss associated with these second-order transverse modes and couples the modes away from the gain medium of the laser. This suppression of second-order transverse modes allows for wider mesa widths on the laser because the laser is less sensitive to these modes.

A buffer layer122is grown on top of the “mode modifier” layer118. This buffer layer provides a surface on which the n-layers of the laser are grown.

A first n-confinement layer126is grown on the buffer layer and is doped with silicon. A second n-confinement layer130is grown on the first n-confinement layer126layer and is also doped with silicon. Both of these layers are current confinement layers and effectively maintain electrons within the laser active region so that photons are produced. The second n-confinement layer130is graded to improve the confinement characteristics of the layer. The thicknesses of these n-layers were designed to be thin in order to optimize the thermal performance of the laser.

A multi-quantum well active region (MQW region)134is grown on the n-type confinement layers. The active region134is designed to have eight wells136with corresponding wavelengths of ˜1295 nm. Quantum barriers138between the wells have corresponding wavelengths of approximately 980 nm. Standard barrier wavelengths are in the range of 1060-1090 nm and thus have smaller barrier heights than the present multi-quantum-well design. The depth and width of the wells are designed to produce a 1310 nm photon. The active region is designed to be “strain compensated” which means that the barriers are designed to have opposing strain characteristics relative to the well strain characteristics. As a result, the strain generated from the barriers at least partially cancels the strain generated by the wells and reduces the overall strain on the layer. The present well design is intentionally manufactured so that a complete cancellation of strain does not occur, but a small amount of strain remains for performance reasons.

In addition, the layers of the MQW region134are intentionally doped with Zn, to maintain a low-level p-type doping. This is done to assure that the p-n junction of the laser diode always occurs in the same place, and is not made variable by unpredictable dopant diffusion processes.

A first p-confinement layer142is grown on the active region. A second p-confinement layer146is grown on the first p-confinement layer142layer. Both of the p-layers are confinement layers and effectively maintain holes within the active region so that photons are produced. The layer142is graded to improve the confinement characteristics of the layer. The thicknesses of these p-layers were designed to be thin in order to optimize the speed and thermal performance of the laser.

A spacer layer150is located above the p-confinement layers. This spacer layer is made of Indium Phosphide. The thinness of the spacer layer improves the coupling efficiency of the grating and improves the speed of the laser. In particular, the spacer layer effectively controls the degree to which lateral current spreading occurs between the bottom of the ridge mesa and the active region.

Various “above-active” grating layers are located above the spacer layer150. An etch stop layer152is grown on the spacer layer150. This etch stop layer is provided for stopping the mesa etch.

A second spacer layer156is provided to separate the etch stop layer152and the grating layer. A grating layer160is grown on the second spacer layer156. The grating layer is “above active” (as compared to other possible designs in which the grating is below the active region). Laser holography, wet etching, and subsequent InP regrowth, as explained further below, are used to create a uniform grating.

The laser cavity of the DFB laser110can support two degenerate longitudinal grating modes because the grating formed in the grating layer160is uniform (as opposed to, e.g., a quarter-wave shifted design). Selection of one or the other of these two modes is dependent upon the phase associated with the facet cleave, which is dependent upon the location of the cleave with respect to the grating period. Because the location of the cleave cannot be controlled with sufficient precision, all phase possibilities will be represented by any ensemble of devices of this design. As a result, there will always be a finite percentage of laser parts for which both grating modes are equally supported, resulting in inadequate single-mode behavior. These lasers are discarded and not sold.

A top layer162is provided above the grating layer on which regrowth of other layers is performed.

b. Grating Fabrication and Regrowth

FIG. 3illustrates various grating fabrication and subsequent regrowth stages employed in forming portions of the structure of the DFB laser110. In particular,FIG. 3shows a side view of the base epitaxial structure112ofFIG. 2, together with subsequent grating fabrication and regrowth of the DFB laser110. As described above and by way of brief overview, a wet etch is performed to etch periodic gaps within the grating layer. After the etch is completed and the grating teeth are created, thick Indium Phosphide is grown on the etched, base epitaxial structure, in order to fill the gaps with low-index InP and also to form the mesa layer. The regrowth is completed with an Indium Gallium Arsenide layer for electrical contact.

This regrowth Indium Phosphide is used to create a mesa on the epitaxial base that provides current confinement and also functions as a waveguide, by virtue of lateral optical confinement. This structure is also referred to herein as a “ridge waveguide” structure. Photoresist is used to etch ridges on the regrowth that creates ridges to define the mesa of the DFB laser. Both dry and wet etching may be used in creating the mesa ridges.

After the etching process, a dielectric layer is placed on the structure. In the present design, a “triple stack” of Silicon Nitride, Silicon Dioxide, and Silicon Nitride is used as the dielectric, although other dielectrics may be used. This layer is typically thick in order to reduce parasitic capacitance (and improve speed) and is used to confine the current within the mesa. The dielectric layer is removed from the top of the mesa to allow an electrical contact and metallic layer to be placed on the mesa.

Electrical contact is made by depositing metal onto the Indium Gallium Arsenide layer at the top of the mesa. This contact is both a non-alloy contact and a low penetration contact.

A metallic layer is placed on the electrical contact to which electrical current may be provided to the laser structure. In the present embodiment, the metallic layer is made of three sub-layers of titanium, platinum and gold, although other materials could be used. A titanium layer is placed directly on the electrical contact layer, then a platinum layer and a gold layer is applied. This metallic layer provides sufficient conductivity to the Indium Gallium Arsenide layer so that current can be properly provided to the laser structure. Bottom electrical contacts are generated by thinning the InP substrate and placing an n-type metallic layer on the bottom.

A DFB laser is removed from a wafer using common techniques such as cleaving and breaking the wafer both horizontally and laterally to separate each laser. After this process, AR and HR coating is performed to encapsulate the active region of the laser and provide the requisite reflectivity characteristics of the laser cavity as may be seen inFIG. 3Bas refectivities R1and R2. The reflectivity characteristics define the optical power emitted from the back of the laser and the front of the laser. In uniform grating designs, a majority of the optical power is emitted from the front of the laser which couples into optical fiber. A minority of the optical power is emitted from the back of the laser which may couple with a photodetector (not shown) that is used to monitor the laser performance.

In one embodiment, the coating is made of layers of Silicon Oxide and Silicon. The reflectivity of the AR coating is designed to be less that 1% and the HR coating is designed to be greater than 96%. Once the coating process is complete, a testing process may be performed in which the power characteristics and optical spectrum are tested.

The example DFB laser110and photodetector are packaged into an optical sub-assembly, which is subsequently packaged into an optical module along with driver and control integrated circuits such as transceiver100.

Although the above description was specifically tailored to a DFB laser, the examples disclosed herein may also be used in other high-speed lasers, such as a 1310 nm 10 G Fabry-Perot (FP) laser. The Fabry Perot laser, as is known in the art, is also grown on a substrate with various layers, a mesa and an active.

Aspects of Laser Design

Reference is now made toFIG. 4, which illustrates a laser400. Laser400may correspond to laser110previously described or it may correspond to other DFB or FP lasers. As illustrated, laser400includes at least a mode modifier level410, an active region420, an InP spacer layer430, an etch stop layer440, and a mesa450. As will be appreciated and as is illustrated with respect to the embodiment ofFIG. 2, laser400may also include additional layers to those illustrated.

While designing laser400, a designer typically has several output performance parameters that should be met. In other words, the designer must account for these output performance parameters and often will make trade-offs among one or more output performance parameters in order to achieve a design with the most optimized performance possible. Of course, there may be circumstances when the most optimized performance may not be achievable. These typical performance parameters are listed below in Table 1. Note that other performance parameters may also be utilized.

TABLE 1Linearity of output power vs. current curveModulation efficiencySpeed at a certain currentThreshold current over temperature

As mentioned, the designer often will make trade-offs between the various output performance parameters. To make these trade-offs, there are several variable design parameters that a designer may use as listed below in Table 2. Of course, it will be appreciated that several other design parameters may also be used.

TABLE 2Number of wellsDistance between etch stop and active region (p-InP spacer thickness)Distance to mode modifierThickness of mode modifierComposition of mode modifierMesa widthCavity lengthMirror reflectivities, R1 and R2

Referring again toFIG. 4, the various design parameters of Table 2 are illustrated in relation to the various layers previously described. For example the InP spacer layer430thickness is designated at460, the distance from the active region420to the mode modifier layer410is designated at470, the number of wells is designated at480, the composition of the mode modifier layer410is designated at495, the thickness of the mode modifier layer410is designated at485, and the width of the mesa450is designated at490. As mentioned above, the mirror reflectivities R1and R2are shown inFIG. 3B.

As will be appreciated, the distance470between the active region420and the mode modifier layer410is comprised of the one or more layers that separate the mode modifier layer from the active region. In the example discussed in relation toFIG. 2above, this distance may include one or more of the buffer layer122, the first confinement layer126, and the second confinement layer130.

Likewise, in some examples the InP spacer layer430and its thickness460may comprise one or more layers. For instance, in the example discussed in relation toFIG. 2above, in some instances the first and second confinement layers142and146in addition to spacer layer150may comprise the thickness460, while in other instances the spacer layer150alone may comprise the thickness460.

Referring now toFIGS. 5A and 5B, two graphs of the output performance of a laser such as laser400are shown.FIG. 5Aillustrates far field angle spectra of a laser such as laser400. The figure on the left is at a current, I=25 mA and figure on the right is at I=90 mA. The presence of a side lobe is clearly seen (marked by the circles) at large currents and not at lower current levels. This is the cause of the significant non-linearity in the output power vs. current curve shown inFIG. 5B.

Suppressing this side lobe (aka second order mode) without compromising the performance of the laser (threshold current, slope efficiency, high speed performance) may be challenging. Advantageously, the principles of the present invention provide a solution to this challenge. By altering the design parameters shown in Table 2, the non-linearity of the LI curve (output power vs. injected current) can be significantly reduced, as seen inFIG. 5C. In addition, the other three output performance parameters as shown in Table 1 may at least be partially optimized.

Accordingly, the principles of the present invention allow a designer to vary one or more of the design parameters of Table 2 in order to at least partially optimize one or more of the output performance parameters of Table 1 to thereby at least partially optimize output performance of laser400. For instance, in one example, a designer may be interested in optimizing the gain margin of the laser400. Optimizing the gain margin of laser400may help to improve the linearity of the output power versus current curve as well as the other three output performance parameters listed in Table 1. Accordingly, the designer may vary one or more of the design parameters to achieve the desired result.

For instance,FIG. 6illustrates the effects on gain margin when varying the thickness460of the InP spacer layer430, the distance470between the active region420and the mode modifier layer410, and the thickness485of the mode modifier layer410. As illustrated,FIG. 6shows the gain margin on the Y-axis versus the InP spacer thickness460on the X-axis. InFIG. 6, the width490of the mesa450is kept constant at 2.1 micro-meters (μm). In addition, the thickness485of the mode modifier410is kept constant at 0.14 μm when the mode modifier is present.

Referring first to line610, the performance results are shown when the thickness460of the InP spacer layer430is varied and the distance470between the active region420and the mode modifier layer410is kept constant at 1.4 μm. The ridge width490and the thickness485of the mode modifier are also kept constant as previously described. For example, as InP spacer thickness460is increased from approximately 0.02 μm to approximately 0.15 μm, the gain margin increases.

Likewise, line630illustrates the performance results when thickness460of the InP spacer layer430is varied, the distance470between the active region420and the mode modifier layer410is kept constant at 0.7 μm, and the mesa width490and the thickness485of the mode modifier are also kept constant as previously described. In this case, as InP spacer thickness460is increased from approximately 0.02 μm to approximately 0.15 μm, the gain margin also increases. Line620illustrates that when keeping the mesa width490constant and removing the mode modifier layer410, as InP spacer thickness460is increased from approximately 0.04 μm to approximately 0.15 μm, the gain margin also increases.

In another example, the designer may vary the mode modifier layer410and the width490of the mesa450. For example,FIG. 7illustrates the effects on gain margin when the thickness460of the InP spacer layer430is kept constant at 0.03 um, the distance470between the active region420and the mode modifier layer410is kept constant at 1.4 um, and the mesa width490and mode modifier layer410are varied.

Referring first to line710, it is shown that when a mode modifier layer410with a thickness485of 0.14 um is included in laser400, the gain margin will decrease as the mesa width490is increased. Likewise, line720shows that when the mode modifier layer410is not included, the gain margin will also decrease as the mesa width490is increased.

However, line730shows that if 60% is the lowest acceptable gain margin, then mesa width490may be 0.4 microns wider when the mode modifier layer410is included to have the same acceptable results (i.e., gain margin 60% or higher) as when mode modifier layer410is not included. In other words, in those circumstances where a smaller mesa width490is necessary, the designer may remove the mode modifier layer410and still achieve an acceptable gain margin. Conversely, in those circumstances where a larger mesa width490is necessary, the designer may include in the mode modifier layer410to allow for a wider mesa while still achieving an acceptable gain margin. A larger mesa width is more easily manufacturable and hence leads to a lower chip cost. A good designer will incorporate manufacturability and cost into consideration in addition to the items in Table 1.

In a further example, the designer may be interested in optimizing the confinement of a first mode. To accomplish this, the designer may use the variable design parameters. For example,FIG. 8illustrates the effects on confinement of the first mode where the mesa width490is kept constant at 2.1 um and the mode modifier layer410thickness485is kept constant at 0.14 um. As is shown in lines810,820, and830, when the thickness460of the InP spacer layer430is varied from 0.02 μm to approximately 0.15 μm, the confinement decreases as InP spacer thickness increases.

Lines810,820, and830also show that making the distance470between the active region420and the mode modifier layer410smaller also decreases confinement. For instance, confinement is better across all InP spacer thicknesses when the distance470is 1.4 μm than when the distance470is 0.7 μm. In addition, having no modifier layer410provides better confinement than having a small distance470.

As mentioned previously, a designer may also be interested in at least partially optimizing modulation efficiency, speed at a certain current, and threshold current over temperature, which are some of the performance parameters listed in table 2. Accordingly, the designer may also vary one or more of the variable design parameters of table 1 in order to at least optimize these performance parameters.

Referring first toFIG. 9, a plot is shown of modulation efficiency when varying the distance470between the active region420and the mode modifier layer410. For example, line910shows that when the thickness460of the InP spacer layer430is kept constant at 0.07 μm, modulation efficiency increases as the distance470is increased. Likewise, line920shows that when the thickness460of the InP spacer layer430is kept constant at 0.15 μm, modulation efficiency increases as the distance470is increased.

Referring now toFIG. 10, a plot is shown of speed at a certain current, in this case the threshold current+36 mA, when varying the distance470between the active region420and the mode modifier layer410. For example, line1010shows that when the thickness460of the InP spacer layer430is kept constant at 0.07 μm, speed at a certain current increases as the distance470is increased. Likewise, line1020shows that when the thickness460of the InP spacer layer430is kept constant at 0.15 μm, speed at a certain current increases as the distance470is increased.

Referring now toFIG. 11, a plot is shown of threshold current at 85 degrees Celsius, which can be used to approximate threshold current over temperature, when varying the distance470between the active region420and the mode modifier layer410. For example, line1110shows that when the thickness460of the InP spacer layer430is kept constant at 0.07 μm, the threshold current decreases as the distance470is increased. Likewise, line1120shows that when the thickness460of the InP spacer layer430is kept constant at 0.15 μm, the threshold current decreases as the distance470is increased.

As previously mentioned, the designer may also vary the number of wells in the active region, the length of the active region cavity, and the facet or mirror reflectivities. For example, varying the number of wells in the active region and/or the length of the cavity may affect the performance parameters previously described. In like manner, varying the amount of reflective material applied to the facet edges as described above may also affect the performance parameters.

Accordingly, based onFIGS. 5C-11, it is seen that it is desirable for the designer to improve the gain margin between the fundamental or first order mode (the mode the laser should operate in) and the second order mode (the mode which should be suppressed). However, the designer must be careful not to adversely impact the confinement for the fundamental mode, threshold current, slope efficiency, and high speed performance. In other words, the designer will make trade-offs between the various design parameters in order to at least partially optimize the laser. For example, as shown inFIG. 6, increasing the spacer thickness460tends to improve the gain margin. However,FIG. 8shows that decreasing the spacer thickness460tends to improve the confinement. Accordingly, the designer will need to pick a spacer thickness460that provides both acceptable gain margin and acceptable confinement. In other words, the designer will need to trade-off between desired gain and confinement and pick a value for the spacer thickness460that provides both acceptable gain margin and acceptable confinement. The designer will also need to make trade-offs between the other design parameters as illustrated in the figures to arrive at values of the design parameters that produce desirable output performance parameter levels and thus provide acceptable laser400performance.

Turning now toFIG. 12, a flowchart of a method1200for at least partially optimizing output performance for a laser die is illustrated. Method1200will be explained in relation to the other figures previously described above, although method1200is not limited to such examples.

Method1200includes an act of identifying a first design parameter (act1202) and an act an act of identifying a second design parameter (act1204). The first and second design parameters are configured to at least partially affect one or more output performance parameters of a laser die. For example, a designer may identify one or more of the design parameters listed in Table 2 above. As previously described, these design parameters are configured to at least partially affect the output performance parameters listed in Table 1. The designer would typically identify those design parameters most closely associated with the output performance parameter of interest. Note that in some examples, the designer may also identify third and fourth design parameters as circumstances warrant. Further, in other examples the first and second design parameters may be the same parameter and the third and fourth design parameters may be the same parameters.

Method1200also includes an act of varying the first design parameter to produce first intermediate performance results (act1206) and an act of varying the second design parameter to produce second intermediate performance results (1208).

For instance, usingFIG. 6as an example, in one example, the designer may vary a first design parameter such as the spacer thickness460to produce intermediate results that show how gain margin is affected by varying the spacer thickness. The designer may also vary a second design parameter such as the distance470between the active region and the mode modifier layer to produce second intermediate results that show how gain margin is affected by varying the distance470or having no mode modifier layer at all.

In another example, act1206is performed when the designer varies a first design parameter to produce first intermediate results about a first output performance parameter. Act1208is then performed when the designer varies a second design parameter to produce second intermediate results about a second output performance.

For instance, usingFIGS. 6 and 8as an example, the designer may vary a first design parameter such as the spacer thickness460to produce intermediate results that show how gain margin is affected by varying the spacer thickness. The designer may then vary a second designer variable such as spacer thickness460to produce intermediate results that show how confinement is affected by varying the spacer thickness. It should be noted that this is an example of where the first and second design parameters are the same. It will be appreciated that in other examples the first and second design parameters may be different. For instance the first design parameter may be spacer thickness460and the second design parameter may be mesa width490as shown inFIG. 7.

In some examples, a third design parameter may be varied and may be used in conjunction with the first design parameter to produce the first intermediate results. Referring again toFIG. 6, the distance470between the active region and the mode modifier layer may be varied while also varying the spacer thickness460to produce the first intermediate results as shown in the figure.

A fourth design parameter may also be varied and may be used in conjunction with the second design parameter to produce the second intermediate results. Referring again toFIG. 8, the distance470between the active region and the mode modifier layer may be varied while also varying the spacer thickness460to produce the second intermediate results as shown in the figure. It should be noted that this is an example of where the third and fourth design parameters are the same. It will be appreciated that in other examples the third and fourth design parameters may be different.

Turning again toFIG. 12, method1200further includes an act of using the first and second intermediate performance results to determine a value for the first and second design parameters that at least partially optimizes the one or more output performance parameters (act1210). For example, the designer may use the intermediate results to determine which value or set of values for the design parameters will cause the one or more output performance parameters to be at least partially optimized. In some embodiments, the designer will need make trade-offs based on the intermediate results. It should be noted that the term value as used in claims need not be limited to a single value, but may also include a set of more than one value.

For instance, usingFIGS. 6 and 8as an example, the designer will have to determine, based on the intermediate results previously discussed, what value or set of values of spacer thickness460will provide both acceptable gain margin and confinement. As previously discussed, a larger spacer layer thickness460provides better gain margin while a smaller spacer thickness460provides better confinement. Accordingly, the designer will need to make trade-offs between desired gain margin and confinement and then determine what value or set of values of spacer thickness460will provide both an acceptable gain margin and confinement. The same process will have to be accomplished for the other design parameters and performance parameters until values of all the design parameters are determined that provide an overall optimized laser400performance.

Turning now toFIG. 13, a flowchart of a method1300for at least partially optimizing one or more output performance parameters of a laser die is illustrated. Method1300will be explained in relation to the other figures previously described above, although method1300is not limited to such examples.

Method1300includes an act of identifying one or more output performance parameters to be at least partially optimized (act1302) and an act of identifying one or more design parameters associated with the one or more output performance parameters (act1304). For example, one or more of the output performance parameters listed in Table 1 and one or more of the design parameters listed in Table 2 are identified.

Method1300also includes an act of determining a subset of the one or more design parameters that should be varied so as to at least partially effect the one or more output performance parameters (act1306) and an act of varying the subset of design parameters to produce one or more intermediate results (act1308). As previously described, the various design parameters are varied to produce intermediate results.

Method1300further includes an act of using the intermediate results to determine values for the one or more design parameters such that the one or more performance parameters are at least partially optimized (act1310). As previously described, trade-offs may be made based on the intermediate results to achieve values or sets of values for one or more of the design parameters that at least partially optimize one or more of the performance parameters.