Transparent material processing with an ultrashort pulse laser

Abstract

Methods for ultrashort pulse laser processing of optically transparent materials. A method for scribing transparent materials uses ultrashort laser pulses to create multiple scribe features with a single pass of the laser beam across the material, with at least one of the scribe features being formed below the surface of the material. Slightly modifying the ultrashort pulse laser processing conditions produces sub-surface marks. When properly arranged, these marks are clearly visible with side-illumination and not clearly visible without side-illumination. In addition, a method for welding transparent materials uses ultrashort laser pulses to create a bond through localized heating. The ultrashort pulse duration causes nonlinear absorption of the laser radiation, and the high repetition rate of the laser causes pulse-to-pulse accumulation of heat within the materials.

What is claimed is: 
     
         1 . A method for bonding transparent materials, comprising:
 focusing a beam of ultrashort laser pulses near an interface between said materials; and   producing said ultrashort laser pulses at a repetition rate in the range from 100 KHz to 100 MHz and with one or more zones of fluence sufficient to induce localized melting of said materials at said interface.   
     
     
         2 . The method of  claim 1 , wherein said bonding is carried out without a requirement for a supplemental bonding agent or an intermediate light absorbing layer. 
     
     
         3 . The method of  claim 1 , wherein a focused beam of ultrashort pulses induces non-linear absorption of energy in said transparent material(s). 
     
     
         4 . A microfluidic system comprising transparent material(s) bonded using the method of  claim 1 . 
     
     
         5 . A microfluidic system according to  claim 4 , wherein said bonded transparent material(s) are arranged without an intermediate light absorbing layer therebetween. 
     
     
         6 . A method for welding transparent materials, comprising:
 directing a beam of ultrashort laser pulses to near an interface between said materials, to induce non-linear absorption of energy proximate at least one high intensity region of said beam, to deposit and accumulate heat at said region with repeated pulses at a repetition rate sufficiently high to cause localized melting of said materials.   
     
     
         7 . A method for creating a raised ridge at the interface between two opposed surfaces to be welded to fill a gap that cannot be bridged by welding alone, comprising:
 focusing ultrashort laser pulses below one or both of the opposed surfaces on which the ridge is to be formed, to raise the ridge; and   subsequently laser welding the raised ridge and the opposite surface or ridge.   
     
     
         8 . An optical system for welding transparent materials, comprising:
 a laser system that produces a beam of femtosecond to picosecond ultrashort laser pulses having pulse widths in the range from about 50 fs to 500 ps; and   a focusing element for focusing said beam near an interface between said materials, wherein said laser system has a pulse repetition rate in the range from 100 kHz to 100 MHz, and said pulses have a zone of higher fluence, which are cumulatively sufficient to induce localized melting of said materials at said interface.   
     
     
         9 . A method for welding transparent materials, comprising:
 directing a beam of ultrashort laser pulses to near an interface between said materials; and optically controlling formation and spatial position of one or more areas of high intensity within a body of said materials, to induce melting of said materials only within said zone or zones.