Low Polarization Sensitive O-band SOA on InP Membrane for Advanced Photonic Integration

Managing insertion losses, polarizations and device footprint is crucial in developing large-scale photonic integrated circuits (PICs). This paper presents a solution to these critical challenges by designing a semiconductor optical amplifier (SOA) in the O-band with reduced polarization sensitivity, leveraging the ultra-compact InP Membrane on Silicon (IMOS) platform. The platform is compatible with close integration atop electronics, via densely populated vertical interconnects. The SOA incorporates a thin tensile-strained bulk active layer to mitigate polarization sensitivity. The developed 500 um long SOA has a peak gain of 11.5 dB at 1350 nm and an optimal polarization dependency of less than 1 dB across a 25 nm bandwidth, ranging from 1312 nm to 1337 nm. The device is practical for integrated circuits where multiple amplifiers work in cascades with a minimal 6.5 dB noise figure (NF) measured at the gain peak. The designed vertical active-passive transition, achieved through inverse tapering, allows for effective field coupling in the vertical direction resulting in a transmission efficiency of over 95% at the transition and minimal polarization sensitivity of less than 3%. The device yields significant gain at a small current density of less than 3 kA/cm2 as the result of minimalist gain medium structure, reducing joule heating and improving energy efficiency. This is especially relevant in applications such as optical switching, where multiple SOAs populate the PIC within a small area. Consequently, the simulated and fabricated low polarization sensitive O-band SOA is a suitable candidate for integration into large-scale, ultra-compact photonic integrated circuits.