Generation of efficient solid-state laser pulse trains

Abstract

A device and method for generating laser pulse trains for delivery to a target including the use of a single laser generator which produces a plurality of pulse groupings of two or more individual laser pulses within each laser pulse train, generated at selected time intervals. The laser pulse train has a pulse width of at least about 30 microseconds and a pulse repetition rate of 1 to about 1,000 Hertz. The time intervals between the individual pulses within each of the pulse groupings along with the intervals between pulse groupings themselves are selected and controlled by a controller in reference to several variables including the emission and energy storage lifetimes of the lasing medium, the thermal diffusion time constant of the target, the time required to cool the target after the application of laser pulses to its ambient temperature, and the dissipation time of acoustic waves generated by the pulses.

1 . A device for generating laser pulse trains for delivery to a target comprising: 
 a single laser generator for generating and delivering a plurality of laser pulse groupings as a laser pulse train to a target at selected time intervals wherein each of the laser pulse groupings comprises two or more individual successive pulses generated at selected time intervals wherein the laser pulse train has a pulse width of at least about 30 microseconds and a pulse repetition rate of 1 to about 1,000 Hertz; and    a controller operably associated with the generator for selecting and controlling the time intervals between each of the pulse groupings and each of the individual pulses.    
   
   
       2 . The device of  claim 1  wherein the controller is adapted to select and control amplitude, duration and shape of each of the individual pulses in each of the laser pulse trains.  
   
   
       3 . The device of  claim 2  wherein the controller is a central processing unit.  
   
   
       4 . The device of  claim 1  further comprising a sampling monitor operably associated with the controller for sampling and monitoring the characteristics of the individual pulses generated by the generator.  
   
   
       5 . The device of  claim 1  wherein the generator is a resonator.  
   
   
       6 . The device of  claim 1  wherein the generator is an oscillator having of a pump chamber housing a solid-state lasing medium having an energy storage lifetime of at least 100 microseconds, and a flash lamp.  
   
   
       7 . The device of  claim 1  further comprising a feedback monitor operably associated with the controller for monitoring and controlling the characteristics of the pulses delivered to the target.  
   
   
       8 . The device of  claim 1  wherein the generator is a continuous-wave pump for pumping a solid-state medium by a semiconductor laser diode source and a Q-switch.  
   
   
       9 . The device of  claim 1  further including an aiming beam generator.  
   
   
       10 . The device of  claim 1  wherein pulse spacing within a laser pulse grouping is 0.1 to 10 milliseconds.  
   
   
       11 . The device of  claim 1  wherein the pulse width is in the range of about 50 microseconds to about 2,500 microseconds.  
   
   
       12 . A method of generating laser pulse trains for delivery to a target comprising the steps of: 
 providing a single laser generation source;    generating a plurality of laser pulse groupings within a laser pulse train at selected time intervals wherein each of the laser pulse groupings comprises two or more individual successive laser pulses generated at selected time intervals; and    delivering the laser pulse train to the target.    
   
   
       13 . The method of  claim 12  wherein the selected time intervals between the plurality of laser pulse groupings is greater than the selected time intervals between the individual pulses in each of the pulse groupings.  
   
   
       14 . The method of  claim 12  wherein the selected time intervals between each of the individual pulses in each of the pulse groupings is less than the thermal diffusion time of the target.  
   
   
       15 . The method of  claim 12  wherein the selected time interval between each of the laser pulse groupings is greater than the thermal diffusion time of the target.  
   
   
       16 . The method of  claim 12  wherein the selected time interval between each of the laser pulse groupings is equal to the time required to cool the target back to its ambient temperature.  
   
   
       17 . The method of  claim 12  wherein the selected time intervals between each of the individual pulses in each of the pulse groupings is less than ten milliseconds.  
   
   
       18 . The method of  claim 12  wherein the selected time interval between each of the pulse groupings is fixed.  
   
   
       19 . The method of  claim 12  wherein the selected time interval between each of the pulse groupings is variable.  
   
   
       20 . The method of  claim 12  wherein the selected time interval between each of the individual pulses in each of the pulse groupings is less than the dissipation time of an acoustic shock wave generated by the preceding pulse in the respective pulse grouping.  
   
   
       21 . The method of  claim 12  wherein the selected time interval between each of the individual pulses in each of the pulse groupings is greater than the dissipation time of an acoustic shock wave generated by the preceding pulse in the respective pulse grouping.  
   
   
       22 . The method of  claim 12  wherein the selected time interval between each of the individual pulses in each of the pulse groupings is greater than the dissipation time of an acoustic shock wave generated by the preceding pulse in the respective pulse grouping and less than the thermal diffusion time of the target.  
   
   
       23 . The method of  claim 12  further comprising the step of sampling the characteristics of each of the generated pulses.  
   
   
       24 . The method of  claim 12  further comprising the step of sampling the characteristics of the pulses delivered to the target.  
   
   
       25 . The method of  claim 12  further comprising the step of controlling the time intervals between each of the pulse groupings and each of the individual pulses in each of the pulse groupings.  
   
   
       26 . The method of  claim 12  further comprising the step of controlling the shape, amplitude and duration of each of the individual pulses in each of the pulse groupings.  
   
   
       27 . The method of  claim 26  wherein each of the pulse groupings comprises first, second and subsequent pulses and the amplitude and duration of the second and subsequent pulses is less than the amplitude and duration of the first pulse in each of the pulse groupings.  
   
   
       28 . The method of  claim 26  wherein first and second pulses are generated in each of the pulse groupings, and the amplitude and duration of the second pulse in each of the pulse groupings is of an order of magnitude less than the amplitude and duration of the first pulse.