Laser-directed microcavitation

Abstract

Methods and systems for the controlled generation of microcavitation bubbles in a medium having a liquid phase are generally provided. Laser pulses having a time-dependent pulse parameter controllable over their duration are generated. The medium is irradiated with the laser pulses with a radiant exposure sufficient to initiate microcavitation within the medium during each laser pulse. The time-dependent pulse parameter of each laser pulse is controlled according to a generally positive variation over the pulse duration such that the medium absorbs a greater quantity of energy from the laser pulse at an end of the pulse duration than at a beginning thereof. Such methods and systems may be used for various applications such as biology, medicine or material processing.

1 . A method for the controlled generation of microcavitation bubbles in a medium having a liquid phase, comprising:
 generating one or more laser pulses, each laser pulse having a pulse duration and having a time-dependent pulse parameter controllable over the pulse duration;   irradiating the medium with the laser pulses with a radiant exposure sufficient to initiate microcavitation within the medium during each laser pulse; and   controlling the time-dependent pulse parameter of each laser pulse according to a generally positive variation over the pulse duration such that the medium absorbs a greater quantity of energy from the laser pulse at an end of the pulse duration than at a beginning thereof.   
     
     
         2 . The method according to  claim 1 , wherein the time-dependent pulse parameter is an amplitude of the laser pulses. 
     
     
         3 . The method according to  claim 1 , wherein the time-dependent pulse parameter is a spectral content of the laser pulses. 
     
     
         4 . The method according to  claim 1 , wherein the time-dependent pulse parameter is a spatial profile of the laser pulses. 
     
     
         5 . The method according to  claim 1 , wherein the generally positive variation of the time-dependent pulse parameter defines a sawtooth-like shape having a positive slope. 
     
     
         6 . The method according to  claim 1 , wherein the generally positive variation of the time-dependent pulse parameter defines first phase of regularly increasing amplitude, followed by a second phase of sharply decreasing amplitude. 
     
     
         7 . The method according to  claim 1 , wherein the generally positive variation of the time-dependent pulse parameter defines a low initial step followed by a sharp increased amplitude phase and a sharp decrease amplitude phase, sequentially. 
     
     
         8 . The method according to  claim 1 , wherein the generally positive variation of the time-dependent pulse parameter defines a sequence of sub-pulses of gradually increasing peak amplitude. 
     
     
         9 . A laser system for generating microcavitation bubbles in a controlled manner in a medium having a liquid phase, comprising:
 a laser pulse generating assembly for generating one or more of laser pulses, each laser pulse having a pulse duration and a time-dependent pulse parameter controllable over the pulse duration, the laser pulses having a radiant exposure sufficient to initiate microcavitation within the medium during each laser pulse when impinging on said medium; and   a pulse shaping mechanism configured to control the time-dependent pulse parameter of each laser pulse according to a generally positive variation over the pulse duration such that the medium absorbs a greater quantity of energy from the laser pulse at an end of the pulse duration than at a beginning thereof.   
     
     
         10 . The laser system according to  claim 9 , wherein the laser pulse generating assembly comprises a seed light source and at least one optical amplifier. 
     
     
         11 . The laser system according to  claim 9 , wherein the time-dependent pulse parameter is one of an amplitude, a spectral content or a spatial profile of the laser pulses. 
     
     
         12 . The laser system according to  claim 9 , wherein the pulse shaping mechanism comprises a digital pulse shaping module providing control signals to the laser pulse generating assembly. 
     
     
         13 . A method for selectively altering an organism having a liquid phase comprising the step of: generating microcavitation bubbles in said organism in a controlled manner by:
 generating one or more, each laser pulse having a pulse duration and having a time-dependent pulse parameter controllable over the pulse duration;   irradiating the organism with the laser pulses with a radiant exposure sufficient to initiate microcavitation within the organism during each laser pulse; and   controlling the time-dependent pulse parameter of each laser pulse according to a generally positive variation over the pulse duration such that the organism absorbs a greater quantity of energy from the laser pulse at an end of the pulse duration than at a beginning thereof.   
     
     
         14 . The method according to  claim 13 , wherein said organism is selected from the group consisting of: a prokaryotic cell, a eukaryotic cell and a virus. 
     
     
         15 . The method according to  claim 14 , wherein said organism is suspended in a fluid. 
     
     
         16 . The method according to  claim 13 , wherein said organism is a tissue, an organ or an organelle having a liquid phase. 
     
     
         17 . The method according to  claim 13 , carried out in vitro, in vivo or ex vivo. 
     
     
         18 . The method of  claim 16 , for laser ablation of an organ or a tissue, tumor destruction, microsurgery, or for selective photothermolysis. 
     
     
         19 . The method of  claim 18 , for tattoo or hair removal. 
     
     
         20 . The method according to  claim 17 , wherein said irradiating is carried out in vivo on a tissue, organ, or biological fluid for the treatment of a disease or a condition necessitating selectively destroying an affected tissue, organ or biological fluid having a liquid phase of a subject in need thereof 
     
     
         21 . The method of  claim 20 , wherein said disease or condition is selected from the group consisting of: kidney stones, bezoars or gallstones, cancer or an ophthalmologic condition 
     
     
         22 . The method of  claim 21 , wherein said ophthalmologic condition is selected from: floaters, retinal disease, ametropia, cataracts and glaucoma. 
     
     
         23 . The method of  claim 21 , for lithotripsy, selective retina therapy, selective laser trabeculoplasty, refractive surgery, capsulotomy or laser vitreolysis. 
     
     
         24 . A method for selectively altering a cell having a liquid phase, comprising the step of injecting a light absorber in said cell, irradiating said light absorber with laser pulses produced by the laser system of  claim 9 , so as to increase permeability of said cell. 
     
     
         25 . The method of  claim 24 , further comprising transfecting a genetic material or a drug to said cell. 
     
     
         26 . A method for detecting a presence of a light absorber in a medium having a liquid phase, said method comprising the step of irradiating said light absorber with laser pulses produced by the laser system of  claim 9 , thereby generating detectable microcavitation bubbles in said medium indicative of the presence of the light absorber. 
     
     
         27 . The method of  claim 26 , wherein the light absorber comprises a nanoparticle or a dye. 
     
     
         28 . A method for processing a material using microcavitation, the material comprising a medium having a liquid phase or being in contact with a medium having a liquid phase, said method comprising the step of irradiating said medium with laser pulses produced by the laser system of  claim 9 .