Pulse control in laser systems

Abstract

A pulsed laser system includes a laser pump, a laser rod, a reflector interposed between the laser pump and the laser rod, through which energy from the laser pump enters the laser rod, an output reflector through which energy is emitted from the laser rod, a switch interposed between the laser rod and the output reflector, and a control device. The switch, when closed, causes energy to be stored in the laser rod and, when opened, allows energy to be emitted from the laser rod during an emission period. The control device allows a primary laser pulse emitted from the laser rod during the emission period to impinge on a workpiece and blocks from the workpiece secondary laser emission occurring during the emission period after emission of the primary pulse. The pulsed laser system is operated over a range of repetition rates, so as to cause laser energy to be emitted during a plurality of emission periods at each repetition rate. At least a portion of the laser energy emitted during the emission periods is directed toward the target structure in order to perform passive or functional trimming of the target structure. The switch is closed for a fixed, predetermined period of time prior to each emission period regardless of repetition rate of the primary laser pulse within the range of repetition-rates in order to store energy in the laser rod. The pump is operated continuously at constant power.

1 - 39 . (canceled)  
   
   
       40 . A method of providing a pulsed laser output, said method comprising the steps of: 
 providing a laser pump, a laser rod, a reflector interposed between the laser pump and the laser rod, and through which energy from the laser pump enters the laser rod, an output reflector through which energy is emitted from the laser rod, and a switch interposed between the laser rod and the output reflector configured to be closed to cause energy to be stored in the laser rod for a desired period of time, and to be opened to allow energy to be emitted from the laser rod during an emission period;    selecting a pulse shape to be produced by the laser source, based on known properties of a target material to be processed on a workpiece, said step of selecting a pulse shape being independent of a time interval between at least two successive transmissions of pulses onto the workpiece; and    causing the pulsed laser system to be pulsed, by causing the switch to be closed for a fixed, predetermined period of time prior to each emission period regardless of the time interval between the at least two successive transmissions of pulses onto the workpiece, so as to cause the laser source to process the target material on the workpiece, with the set time interval between the at least two successive transmissions of pulses onto the workpiece, while the pulse shape remains as preset regardless of the time interval, without setting of the time interval affecting the pulse shape.    
   
   
       41 . The method as  claim 40 , wherein the step of cause the laser source to process the target material on the workpiece involves causing micromachining of a target material on the workpiece.  
   
   
       42 . The method as claimed in  claim 41 , wherein the micromachining of the target material involves micromachining a semiconductor circuit on a silicon substrate.  
   
   
       43 . The method as claimed in  claim 41 , wherein the micromachining of the target material involves trimming a trimmable component.  
   
   
       44 . The method as claimed in  claim 41 , wherein the micromachining of the target material involves trimming a thick-film electrical element.  
   
   
       45 . The method as claimed in  claim 41 , wherein the micromachining of the target material involves trimming a thin-film electrical element.  
   
   
       46 . The method as claimed in  claim 41 , wherein the micromachining of the target material involves trimming a resistor.  
   
   
       47 . The method as claimed in  claim 41 , wherein the micromachining of the target material involves trimming a capacitor.  
   
   
       48 . The method as claimed in  claim 41 , wherein the micromachining of the target material involves laser marking the target material.  
   
   
       49 . The method as claimed in  claim 41 , wherein the micromachining of the target material involves micromachining a worksurface with a controlled laser pulse width.  
   
   
       50 . A method of providing a pulsed laser output, said method comprising the steps of: 
 providing a laser pump, a laser rod, a reflector interposed between the laser pump and the laser rod, and through which energy from the laser pump enters the laser rod, an output reflector through which energy is emitted from the laser rod, and a switch interposed between the laser rod and the output reflector configured to be closed to cause energy to be stored in the laser rod for a desired period of time, and to be opened to allow energy to be emitted from the laser rod during an emission period;    selecting a time interval between at least two successive transmissions of pulses onto a workpiece, based on known properties of a target material to be processed on a workpiece, said step of selecting a time interval being independent of a pulse shape to be produced by the laser source; and    causing the pulsed laser system to be pulsed, with the pulse shape set independently of the time interval, by causing the switch to be closed for a period of time prior to each emission period that is fixed and predetermined for the set pulse shape regardless of the time interval between the at least two successive transmissions of pulses onto the workpiece, so as to cause the laser source to process the target material on the workpiece, while the time interval remains as set regardless of the pulse shape, without setting of the pulse shape affecting the time interval.    
   
   
       51 . A method of providing a pulsed laser output, said method comprising the steps of: 
 providing a laser pump that is operable continuously at constant power, a laser rod, a reflector interposed between the laser pump and the laser rod, and through which energy from the laser pump enters the laser rod, an output reflector through which energy is emitted from the laser rod, and a switch interposed between the laser rod and the output reflector configured to be closed to cause energy to be stored in the laser rod for a desired period of time, and to be opened to allow energy to be emitted from the laser rod during an emission period;    selecting a pulse energy characteristic to be produced by the laser source, based on known properties of a target material to be processed on a workpiece, said step of selecting a pulse energy characteristic being independent of a time interval between at least two successive transmissions of pulses onto the workpiece; and    causing the pulsed laser system to be pulsed, while the laser source is continuously pumped at constant power, so as to cause the laser source to process the target material on the workpiece, with the set time interval between the at least two successive transmissions of pulses onto the workpiece, while the selected pulse energy characteristic remains as set regardless of the time interval, without setting of the time interval affecting the pulse energy characteristic.    
   
   
       52 . A method of providing a pulsed laser output, said method comprising the steps of: 
 providing a laser pump, a laser rod, a reflector interposed between the laser pump and the laser rod, and through which energy from the laser pump enters the laser rod, an output reflector through which energy is emitted from the laser rod, and a switch interposed between the laser rod and the output reflector configured to be closed to cause energy to be stored in the laser rod for a desired period of time, and to be opened to allow energy to be emitted from the laser rod during an emission period;    selecting a time interval between at least two successive transmissions of pulses onto a workpiece, based on known properties of a target material to be processed on a workpiece, said step of selecting a time interval being independent of a pulse energy characteristic to be produced by the laser source; and    causing the pulsed laser system to be pulsed, with the pulse energy characteristic set independently of the time interval, by causing the switch to be closed for a period of time prior to each emission period that is fixed and predetermined for the set pulse energy characteristic regardless of the time interval between the at least two successive transmissions of pulses onto the workpiece, so as to cause the laser source to process the target material on the workpiece, while the time interval remains as set regardless of the pulse energy characteristic, without setting of the pulse shape affecting the time interval.    
   
   
       53 . A method of providing a pulsed laser output, said method comprising the steps of: 
 providing a laser pump that is operable continuously at constant power, a laser rod, a reflector interposed between the laser pump and the laser rod, and through which energy from the laser pump enters the laser rod, an output reflector through which energy is emitted from the laser rod, and a switch interposed between the laser rod and the output reflector configured to be closed to cause energy to be stored in the laser rod for a desired period of time, and to be opened to allow energy to be emitted from the laser rod during an emission period;    selecting a pulse width to be produced by the laser source, based on known properties of a target material to be processed on a workpiece, said step of selecting a pulse width being independent of a time interval between at least two successive transmissions of pulses onto the workpiece; and    causing the pulsed laser system to be pulsed, while the laser source is continuously pumped at constant power, so as to cause the laser source to process the target material on the workpiece, with the set time interval between the at least two successive transmissions of pulses onto the workpiece, while the selected pulse width remains as set regardless of the time interval, without setting of the time interval affecting the pulse width.    
   
   
       54 . The method of  claim 53  wherein the laser source is a continuously pumped laser source and wherein the method further includes closing the switch to cause energy to be stored by the laser source for a desired period of time, and opening the switch to allow energy to be emitted from the laser source during an emission period.