Method of fabricating sub-micron structures in transparent dielectric materials

A method of fabricating a microstructure in a transparent dielectric material having a bottom surface, comprising:

• focusing femtosecond laser pulses having an energy-per-pulse of less than 3 μJ into said dielectric at a sufficient peak power, intensity and energy dosage to create a highly tapered modified zone having a length:width ratio ≧4:1 with modified etch properties, said tapered modified zone having a base with a diameter greater than about 1 μm and a tip having a diameter less than about 250 nm, which is less than the wavelength of the laser pulses, said tip being proximate said bottom surface;
• and
• selectively etching into said modified zone from said tip so that as said selective etching proceeds longitudinally into said modified zone, the progressively increasing width of said modified zone compensates for lateral etching occurring at said tip so as to produce a generally cylindrical hole at least partially extending into said modified zone.

A method of fabricating a microstructure in a transparent dielectric material, comprising:

• focusing femtosecond laser pulses into said dielectric at a sufficient peak power, intensity and energy dosage to create a highly tapered modified zone having a length:width ratio ≧4:1 with modified etch properties, said tapered modified zone having a central region with a central wider portion tapering to opposed tips;
• and
• selectively etching into said modified zone.