Integrated-optic double-ring resonators with a wide free spectral range of 100 GHz

Integrated-optic double-ring resonators with a wide free spectral range (FSR) of 100 GHz are fabricated using GeO/sub 2/-doped silica waveguides with a high relative refractive index difference (/spl Delta/) of 1.5%. The resonators are composed of two ring resonators comprising small ring waveguides with radii of 1.75 and 2.0 mm. The double-ring resonator module exhibited a wide FSR of 98.0 GHz, a finesse of higher than 138, a low crosstalk of less than -11.7 dB, and a low insertion loss of 6.1 dB. The measured FSR of 98.0 GHz is wider than any previously reported ring resonator composed of optical waveguides.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>