Method and apparatus reducing electrical and thermal crosstalk of a laser array

Abstract

Active compensation techniques are used for control of temperature, wavelength, and other characteristics of lasers within a laser array. The laser array includes a plurality of lasers and a plurality of dissipation elements. The dissipation elements can be interstitial to the lasers and can be implemented as non-lasing diodes. The dissipation elements are selectively activated (i.e., turned “on” to dissipate power) to adjust the temperature at the laser junctions. The change in junction temperature allows the lasers to operate at their specified wavelengths. The dissipation elements can be individually controlled and two or more bits of resolution can be provided. Active compensation can be used to adjust (i.e., to compensate) the temperature of selected lasers when one or more lasers are deselected. Active compensation can also be used to adjust (i.e., “tweak”) the wavelengths of the lasers within the laser array to be within their specified wavelengths.

1 . A semiconductor laser array comprising: 
 a plurality of lasers fabricated on a semiconductor substrate; and    a plurality of dissipation elements located within the laser array, at least one of the dissipation elements having independent control.    
   
   
       2 . The laser array of  claim 1  wherein the lasers are capable of being selected or deselected.  
   
   
       3 . The laser array of  claim 2  wherein at least one of the dissipation elements is activated when at least one of the lasers is deselected.  
   
   
       4 . The laser array of  claim 2  wherein selective ones of the dissipation elements are activated to maintain operating temperatures of the selected lasers.  
   
   
       5 . The laser array of  claim 2  wherein selective ones of the dissipation elements are activated to maintain operating wavelengths of the selected lasers to within specified values.  
   
   
       6 . The laser array of  claim 1  wherein the dissipation elements are implemented as non-lasing diodes.  
   
   
       7 . The laser array of  claim 1  wherein the dissipation elements are implemented as resistive elements.  
   
   
       8 . The laser array of  claim 1  wherein the dissipation elements are interstitial to the lasers.  
   
   
       9 . The laser array of  claim 1  wherein the dissipation elements are disposed adjacent to the lasers.  
   
   
       10 . A semiconductor laser array comprising: 
 at least one laser fabricated on a semiconductor substrate, each of the at least one laser capable of being selected or deselected; and    at least one dissipation element located within the laser array, at least one of the dissipation elements having independent control, at least one of the dissipation elements is activated to maintain an operating characteristic of selected lasers.    
   
   
       11 . A compensation circuit for maintaining an operating characteristic of lasers within a laser array, the laser array including a plurality of lasers and a plurality of dissipation elements, the circuit comprising: 
 a table to store compensation values;    drive circuits coupled to the table to receive the compensation values and generate drive signals for the dissipation elements.    
   
   
       12 . The laser array of  claim 11  wherein the drive signals maintain laser junction temperatures of selected lasers.  
   
   
       13 . The laser array of  claim 11  wherein the drive signals maintain operating wavelengths of selected lasers.  
   
   
       14 . The laser array of  claim 11  wherein the drive signals adjust operating wavelengths of selected lasers to within specified values.  
   
   
       15 . The laser array of  claim 11  wherein the compensation values correspond to drive current for the dissipation elements.  
   
   
       16 . The laser array of  claim 11  wherein the compensation values have at least two bits of resolution.  
   
   
       17 . The laser array of  claim 11  wherein the drive circuits include at least one digital-to-analog converter (DAC) to receive the compensation values and generate the drive signals.  
   
   
       18 . The laser array of  claim 11  wherein the drive circuits maintain temperature profiles of lasers that are turned “off” so that chirping of the lasers is reduced when the lasers are subsequently turned “on.” 
   
   
       19 . (canceled)  
   
   
       20 . (canceled)  
   
   
       21 . (canceled)  
   
   
       22 . (canceled)  
   
   
       23 . A method for fabricating a laser array comprising: 
 fabricating a plurality of lasers on a semiconductor substrate; and    fabricating a plurality of dissipation elements on the laser array, at least one of the dissipation elements having independent control.    
   
   
       24 . The method of  claim 23  wherein the dissipation elements are interstitial to the lasers.  
   
   
       25 . The method of  claim 23  wherein the dissipation elements are located adjacent to the lasers.  
   
   
       26 . The method of  claim 23  wherein the dissipation elements are non-lasing diodes.  
   
   
       27 . (canceled)  
   
   
       28 . (canceled)  
   
   
       29 . (canceled)  
   
   
       30 . (canceled)  
   
   
       31 . (canceled)  
   
   
       32 . (canceled)  
   
   
       33 . (canceled)  
   
   
       34 . (canceled)  
   
   
       35 . (canceled)  
   
   
       36 . (canceled)  
   
   
       37 . (canceled)  
   
   
       38 . (canceled)  
   
   
       39 . (canceled)  
   
   
       40 . The method of  claim 38  wherein the determining compensation values comprises: 
 determining temperature-to-wavelength coefficients of the lasers;    determining thermal coupling coefficients of the dissipation elements to the lasers; and    calculating the compensation values based on the wavelength errors, the temperature-to-wavelength coefficients, and the thermal coupling coefficients.    
   
   
       41 . A laser module comprising: 
 a laser array fabricated on a semiconductor substrate, the laser array including a plurality of lasers and a plurality of dissipation elements, at least one of the dissipation elements having independent control; and    a substrate coupled to the laser array.    
   
   
       42 . The laser module of  claim 41  wherein the substrate includes transmission lines for the plurality of lasers, the transmission lines configured to reduce electrical crosstalk.  
   
   
       43 . The laser module of  claim 41  wherein the substrate includes tapered transmission lines for the plurality of lasers, the tapered transmission lines configured to reduce return loss.  
   
   
       44 . The laser module of  claim 41  wherein the substrate includes transmission lines for the plurality of lasers and metallized via holes, the transmission lines and metallized via holes configured to reduce electrical crosstalk.  
   
   
       45 . The laser module of  claim 41  wherein the substrate includes transmission lines for the plurality of lasers and metallized via holes, the transmission lines and metallized via holes configured to reduce thermal and electrical crosstalk.  
   
   
       46 . A selectable and switchable semiconductor laser array comprising: 
 at least one laser fabricated on a semiconductor substrate, each of the at least one laser capable of being selected or deselected; and    at least one dissipation element located within the laser array, at least one of the dissipation elements having independent control,    wherein temperature of the at least one laser within the laser array is adjusted to predetermined value(s), and wherein the wavelength of the laser array is switched substantially contemporaneous upon receiving a control signal while the laser temperature remains at the predetermined value(s).