Method and apparatus for laser induced thermo-acoustical streaming of liquid

Abstract

A laser induced thermo-acoustical system has a waveguide for propagating laser radiation to an absorbing layer of a tip. The tip has an absorbing layer serving to absorb the laser radiation propagating through the waveguide. The absorbing layer has such an absorption coefficient that upon absorbing the laser radiation the absorbing layer heats up to boil a quantity of a liquid when the tip is surrounded by the liquid. A laser induced thermo-acoustical method calls for providing a waveguide for propagating laser radiation to the absorbing layer of the tip to be at least partially absorbed by the absorbing layer and to boil a quantity of the liquid surrounding the tip and generating the stream of liquid. The laser induced thermo-acoustical streaming of the liquid is used, in particular, for the treatment of a root canal and periodontal pockets.

What is claimed is: 
     
         1 . A laser-induced thermo-acoustical system for generating a stream of liquid, the system comprising a laser source and a tip, the tip comprising a waveguide and an absorbing layer configured to be surrounded by a liquid, the waveguide configured to propagate laser radiation from the laser source to the absorbing layer of the tip and the absorbing layer configured to being heated while absorbing the laser radiation propagating through the waveguide, said absorbing layer having an absorption coefficient that allows boiling of the liquid, wherein upon heating the absorbing layer the liquid boils to generate bubbles of vapor and to generate acoustical pressure to generate the stream of liquid. 
     
     
         2 . The system of  claim 1 , wherein the tip is a thermo-optical tip. 
     
     
         3 . The system of  claim 1 , wherein the laser radiation is generated by a diode laser. 
     
     
         4 . The system of  claim 1 , wherein the absorbing material is selected from the group consisting of a semiconductor, metal, metal oxide, carbon, and doped optical material. 
     
     
         5 . The system of  claim 1 , wherein the absorption coefficient is selected from a range from about 0.5 to about 1.0. 
     
     
         6 . The system of  claim 1 , wherein the absorption coefficient is selected from a range from about 0.8 to about 1.0. 
     
     
         7 . The system of  claim 1 , wherein a thickness of the absorbing layer is selected from a range from about 0.01 mm to about 0.5 mm. 
     
     
         8 . The system of  claim 1 , wherein a thickness of the absorbing layer is selected from a range from about 0.05 mm to about 0.2 mm. 
     
     
         9 . The system of  claim 1 , wherein the absorbing layer is disposed on a distal end of the tip. 
     
     
         10 . The system of  claim 1 , wherein the absorbing layer is disposed on a side of the tip. 
     
     
         11 . The system of  claim 1 , wherein the absorption layer has a shape influencing diversion of streaming of the liquid. 
     
     
         12 . The system of  claim 1 , wherein a wavelength of the laser radiation is selected from a range corresponding to a lower absorption coefficient of a material of the waveguide and to the absorption coefficient of the absorbing material of the tip. 
     
     
         13 . The system of  claim 1 , wherein the laser radiation has a pulse width selected from a range of 0.001 ms to 100 ms, a repetition rate selected from a range of 1 Hz and 10000 Hz, energy per pulse from a range of 5×S J/cm 2  to 500×S J/cm 2 , wherein S is an area of a waveguide aperture, a laser power selected from a range of 20 W to 1000 W, and wherein incident fluence on the absorbing layer is from a range of 5 J/cm 2  to 500 J/cm 2 . 
     
     
         14 . The system of  claim 1 , wherein the laser radiation has a pulse width selected from a range of 0.05 ms to 10 ms, a repetition rate selected from a range of 1 Hz and 100 Hz, energy per pulse from a range of 10×S J/cm 2  to 100×S J/cm 2 , wherein S is an area of a waveguide aperture, a laser power selected from a range of 50 W to 250 W, and wherein incident fluence on the absorbing layer is from a range of 10 J/cm 2  to 100 J/cm 2 . 
     
     
         15 . A laser induced thermo-acoustical apparatus comprising:
 a source of laser radiation;   a tip comprising a waveguide and an absorbing layer configured to be surrounded by a liquid, said waveguide configured to propagate the laser radiation to the absorbing layer, the absorbing layer (1) absorbing the laser radiation propagating through the waveguide and (2) having an absorption coefficient that allows boiling of the liquid,   wherein upon the absorbing layer absorbing the laser radiation boils the liquid to generate bubbles of vapor and to generate acoustical pressure to generate a stream of the liquid; and   a water pump for pumping the liquid to the tip through a water channel.   
     
     
         16 . The apparatus of  claim 15 , wherein the laser radiation is generated by a diode laser. 
     
     
         17 . The apparatus of  claim 15 , further comprising a hand piece, and wherein the source is housed in the hand piece.