Crack resistant sol-gel wafer coatings for integrated optics

1. A method of preparing a multi-layer, crack resistant sol-gel glass derived coating on a substrate by the steps of

spin coating a first sol-gel layer on said substrate;

removing an outer peripheral portion of said spin-coated layer;

curing said spin coated layer;

depositing at least one additional spin-coated layer;

removing from each said additional spin-coated layer an additional outer peripheral portion beyond the edge of said first removed outer peripheral portion; and

curing each said additional deposited layer.

2. A method according to claim 1 wherein a layer of sol-gel is formed of a viscous mixture of methyl trimethoxysilane and tetraethyl orthosilicate in the presence of diluted hydrochloric acid.

3. A method of making a crack resistant sol-gel film in layers sufficiently thick to be useful for forming optical waveguide structures, comprising the steps of:

a. spin-coating a substrate selected from the group consisting of glass and silicon to deposit a buffer layer of sol-gel;

b. removing the outer periphery of said buffer layer of spin-coated sol-gel from said substrate;

c. curing said buffer layer;

d. spin-coating a core layer of sol-gel on top of said buffer layer;

e. removing more of the outer periphery of core layer than has been removed from said buffer layer;

f. curing said core layer;

g. spin-coating a cladding layer of sol-gel on top of said core layer;

h. removing more of the outer periphery of said cladding layer than has been removed from said buffer and core layers; and

i. curing said cladding layer.

4. A method according to claim 3 wherein the spin-coated sol-gel substrate is cured by baking.

5. A method according to claim 3 wherein said outer periphery of said sol-gel is removed by spraying a solvent at said outer periphery.

6. A method according to claim 3 wherein a layer of sol-gel is formed of a viscous mixture of methyl trimethoxysilane and tetraethyl orthosilicate in the presence of diluted hydrochloric acid.