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The sensing mechanism of our Mid - IR waveguide sensor is based on evanescent wave absorption by functional groups of the surrounding chemical molecules , which selectively absorb specific wavelengths in the mid - IR , depending on the nature of their chemical bonds .
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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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