Deposition of high fluorine content silica soot

A method of making a fluorine doped soot comprising:

• delivering a silicon containing precursor to a first opening in a burner face, said first opening being substantially free of an oxygen source;
• delivering a fluorine precursor to a second opening in said burner face, wherein said second opening spaced apart from said first opening;
• and
• delivering a fuel to a third opening of said burner face, said third opening spaced apart from said first opening.

A method of making a fluorine doped soot comprising:

• delivering a silicon containing precursor to a first opening in a burner face, said first opening substantially free of oxygen;
• delivering a fluorine precursor to a second opening in said burner face, wherein said second opening spaced apart from said first opening;
• and
• delivering a fuel to a third opening of said burner face, said third opening spaced apart from said first opening;
• wherein a relationship of alignment among said first, second, and third openings sufficient so that said fluorine and said fuel reacts to form HF in a concentration greater than a concentration of SiF4 formed from a reaction of said fluorine precursor with said silicon containing precursor.