Fibre-optic micro-ring-resonator with 2 mm diameter

The authors report on the manufacturing and measurement of a fibre micro-ring absorption resonator for lambda =1.55 mu m with a biconical reduced fibre diameter down to 8.5 mu m. The small ring diameter of 2 mm exhibits a large free spectral range (FSR) of 30 GHz. From the optical frequency response, a finesse of 4.7 and an insertion loss of 1.2 dB were measured and the power coupling coefficient was calculated to be 0.28. To the authors´ knowledge this is the smallest optical ring resonator reported so far.