Silicon Nitride-Based Compact Double-Ring Resonator Comb Filter With Flat-Top Response

A novel double-ring resonator comb filter structure with flat-top response is proposed and fabricated. In this letter, we discuss its function theoretically and present results from devices fabricated on silicon nitride. The measured results show a flat-top response profile for the transverse-magnetic mode over
C
- and
L
-band, with the channel isolation ~15 dB, the free spectral range ~3 nm, and the total insertion loss ~ -7.5 dB. The footprint of the device is ~ 450
mu
m x 250
mu
m.