A system for encoding energy peaks of an identifier comprises an encoder. The encoder is configured to define a readable spectral range of an identifier. The identifier comprises a rugate microtag. The encoder is configured to divide the readable spectral range into a plurality of bins. The encoder is configured to encode in a center of a bin near one end of the readable spectral range a reference peak. The encoder is configured to encode in a center of each of a set of bins a set of peaks of a data pattern within the readable spectral range.