Method of manufacturing a ridge-shaped three dimensional waveguide

A method of manufacturing a ridge-shaped 3-dimensional waveguide, comprising the steps of:

• preparing a substrate made of a first ferroelectric oxide non-linear crystal of K3Li2−xNb5+x−yTayO15−2x(−0.4≦x≦0.20, 0≦y≦0.33);
• forming a crystal film made of a second ferroelectric oxide non-linear crystal of K3Li2−xNb5+x−yTayO15+2x(−0.4≦x≦0.20, 0≦y≦0.33) having a refractive index higher than that of the first ferroelectric oxide non-linear crystal on said substrate through a metal-organic chemical vapor phase deposition process which includes the steps of:
• providing organic gases of starting raw materials containing K, Li, Nb and Ta respectively;
• and introducing individually the organic gases together with an oxygen gas onto the substrate placed in a reaction chamber of a metal-organic chemical vapor phase deposition apparatus, thereby epitaxially growing the crystal film;
• forming a metal film on said crystal film;
• forming a mask by etching said metal film;
• and
• forming a ridge portion by selectively removing said crystal film through said mask by a dry etching method, wherein said crystal film is etched by the dry etching method using an etching gas of a mixture comprising CF4 and O2.