Chemical etching of fiber probe

A method of etching a fiber, comprising:

• providing an etchant solution which is chemically reactive to the fiber;
• forming a layer of a protective solvent that is chemically inert to the fiber on top of said etchant solution and having a density smaller than said etchant solution,
• selecting said etchant solution and said protective solvent to have predetermined densities and viscosity coefficients to form a substantially flat meniscus on the interface between said etchant solution and protective solvent around the fiber when immersed;
• immersing a portion of the fiber in said etchant solution and said protective solvent;
• and
• maintaining convective flows surrounding said immersed portion within said etchant solution so that said immersed portion is broken away by etching to form a tapered tip within said etchant solution.

A method of forming a chalcogenide fiber probe by chemical etching, comprising:

• processing a fiber having a chalcogenide fiber core to expose the fiber core at one end;
• providing an etchant solution which is chemically reactive to said fiber core and has a first interfacial energy with respect to said fiber core;
• forming a layer of a protective solvent chemically inert to said fiber core on top of said etchant solution, said protective solvent having a density smaller than said etchant solution and a second interfacial energy with respect to said fiber core, wherein said first interfacial energy is substantially equal to said second interfacial energy;
• immersing said fiber core in said etchant solution and said protective solvent;
• and
• maintaining convective flows surrounding said immersed fiber core within said etchant solution so that a portion of said fiber core is broken away by etching at a location below interface between said protective solvent and etchant to form a tapered probe tip within said etchant solution.