Dielectric optical waveguides and technique for fabricating same

Claim 1

The method of claim 1 wherein said native oxide forming step (b) comprises the steps of bringing said major surface into contact with an electrolyte bath containing a solution of H2O2 in water, making said heterostructure an anode and a noble metal a cathode therein, applying a voltage between said anode and cathode for a time period sufficient to form on said major surface a native oxide layer of the desired thickness, removing said heterostructure from said bath and subsequently drying said heterostructure.

Claim 8

A method of fabricating a dielectric waveguide comprising the steps of: (a) epitaxially growing on a GaAs substrate a double heterostructure comprising at least one AlyGa1 yAs middle layer formed between and contiguous with a pair of AlGaAs outer layers comprising AlxGa1 xAs and AlzGa1 zAs, y < x and z, said middle layer being adapted for the propagation of light therethrough; (b) forming a native oxide layer on the topmost AlGaAs layer of said double heterostructure by submersing said double heterostructure in an electrolyte bath comprising a solution of H2O2 buffered with an acid, making said double heterostructure the anode and a noble metal the cathode across which a voltage is applied for a time period sufficient to grow a native oxide layer of the desired thickness, removing said double heterostructure from said bath and subsequently drying said heteroStructure by heating same; (c) removing selected portions of said oxide layer thereby forming from the remaining portions thereof a mask having a predetermined shape; (d) forming a mesa from said double heterostructure by bringing same into contact with a bromine methanol solution containing approximately 0.05 to 0.1 percent bromine by volume, thereby etching away at a relatively slow rate those portions of said heterostructure not covered by said mask, said etching being effective to form optically flat surfaces on opposite side walls of said mesa; and (e) bringing said mesa into contact with a solution of H2O2 having pH in the range of about 6 to 8 and simultaneously agitating said solution, said latter agitated solution being effective to differentially etch said middle layer at a faster rate than said outer layers, thereby to form a pedestal-like mesa structure in which the width of said middle layer is less than the corresponding width of said outer layers, so that said outer layers overhang said middle layer and form air gaps therebetween.