Spurious-Free Dynamic Range in Photonic Integrated Circuit Filters With Semiconductor Optical Amplifiers

Among other advantages, radio-frequency (RF) signal processing in the optical domain using photonic integrated circuits (PICs) offers unprecedented bandwidth and tunability. However, modern RF-photonic link applications demand PICs with high spurious-free dynamic range (SFDR). The SFDR of active PICs integrating semiconductor optical amplifiers (SOAs) is limited by amplified spontaneous emission noise and distortion caused by four-wave mixing. Here, we derive an analytical model for the SFDR of SOAs, and extend it to PICs with arbitrary transfer functions integrating many SOAs. The model is general and applicable to any photonic signal-processing circuit operating in the linear amplification regime below saturation. We show analytically the importance of SFDR-driven photonic design over noise-figure-driven design. Using this model, we explore the SFDR of coupled-ring bandpass filters integrated on a high saturation power integration platform and show SFDR as high as 117.0
${\rm dB}\cdot{\rm Hz}^{2/3}$
for filters with bandwidths in the 1–2 GHz range. We show how the material parameters and PIC design determine the SFDR. Tradeoffs between SFDR and filter bandwidth, extinction, and stopband roll-off are investigated.