What is the roughness of the etched structures?

Wet etched structures are extremely smooth and have a roughness in Angstrom range. The structures are fully optical transparent. 
Large roughness for structures in glass chips is typical observed for structures manufactured by use of laser assisted manufacturing techniques or abrasion-based techniques like powder blasting. Almost all catalogue products from Micronit are manufactured using wet etching to create full transparent channels without substantial roughness.