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Interestingly , minute geometry asymmetry and surface roughness are clearly revealed by far - field analysis , demonstrating that second harmonic generation is a promising tool for the sensitive optical characterization of plasmonic nanostructures .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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