| CPC G02B 6/305 (2013.01) [G02B 6/1228 (2013.01); G02B 6/136 (2013.01)] | 20 Claims | 

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               1. A method of fabricating a structure, comprising: 
            forming a waveguide having a core layer and a cladding layer over a substrate; 
                forming a masking element over the substrate, wherein the masking element has a first opening defining a cavity and a plurality of second openings defining a plurality of release holes; 
                etching the cladding layer under the first opening and the plurality of second openings to concurrently form the plurality of release holes and an upper portion of the cavity; and 
                etching the substrate under the plurality of release holes to form an isolation space. 
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