Ultra-long flashlamp-excited pulse dye laser for therapy and method therefor

Abstract

A flashlamp-excited dye laser generating light pulses for therapy has a circulator which circulates a gain media through a dye cell. A controller coordinates operation by triggering flashlamps to excite the laser gain media while the circulator is circulating the gain media. This operation enables the effective generation of laser light pulses with a duration of at least one millisecond. The laser pulse is formed from many subpulses. If the flow velocity of dye solution is great enough such that the new solution enters the resonant cavity before the solutions in the cavity are substantially spent, subsequent subpulses are not quenched, enabling the generation of ultra-long effective pulses with high fluences. Specifically, longer effective pulses of up to 50 msec are attainable with energies of up to 50 Joules. These energies enable reasonable spot sizes, which makes the invention relevant to cutaneous as well as deep tissue therapy, for example.

What is claimed is:  
     
         1 . A flashlamp-excited pulse dye laser, comprising: 
 an optical system defining a resonant cavity and providing at least a portion of light generated in the resonant cavity as an output laser light pulse;    a flashlamp for exciting the laser gain media contained in the cavity;    a circulator for circulating the gain media through the cavity; and    a controller for triggering the flashlamp to excite the laser gain media while the circulator is circulating the gain media through the cavity to generate a long effective laser light pulse, comprising a series of shorter-duration subpulses, where the circulator circulates the gain media such that at least half the gain media in the cavity is replaced with new gain media during the period defined by the beginning of one subpulse to the beginning of the subsequent subpulse.    
     
     
         2 . The laser of  claim 1 , wherein at least 90 percent of the gain media is replaced within the period defined by the beginning of one subpulse to the beginning of the subsequent subpulse.  
     
     
         3 . A method of operation for a flashlamp-excited pulse dye laser, the method comprising: 
 periodically exciting original dye solution in a resonant cavity with a flashlamp to generate a series of subpulses over an effective pulse duration;    replacing at least half of the at least partially exhausted original dye solution in the resonant cavity with new dye solution within the period defined by the beginning of a subpulse to the beginning of the subsequent subpulse to sustain lasing over the effective pulse duration.    
     
     
         4 . The method of  claim 3 , wherein at least 90 percent of the at least partially exhausted original dye solution in the resonant cavity is replaced with new dye solution within the period defined by the beginning of a subpulse to the beginning of the subsequent subpulse.