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te o ed N of led, res wing terresonator coupling has yet to be confirmed. 456 OPTICS LETTERS / Vol. 31, No. 4 / February 15, 2006In this Letter we present amplitude and group-delay measurements of CROWs based on chains of high-order and weakly coupled (1%) microring reso-nators fabricated in polymer materials. The experi-ment is also the first demonstration of such high-order coupled resonators in optical polymers to our knowledge. Our results illustrate the possibility of achieving large optical delays 100 ps in CROWs. The microring resonators were fabricated with electron-beam lithography in polymethylmeth-acrylate (PMMA, n=1.49, Microchem) with a perfluo-ropolymer, Cytop (n=1.34, Asahi Glass), as a lower cladding. Cytop was used because it provided suffi-cient index contrast for the fabrication of microrings. The combination of PMMA and Cytop has been used Fig. 1. (a) Optical micrograph of a CROW consisting of 12 microring resonators fabricated in PMMA on Cytop. (b) Scanning electron micrograph of the coupling region of the microring resonators. The radius of the microrings isTransmission and gro coupled-resonato