Design and Fabrication of Low Polarization Dependent Bulk SOA Co-Integrated with Passive Waveguides for Optical Network Systems

Low polarization-dependent semiconductor optical amplifiers (SOA) co-integrated with passive circuits via an easy fabrication process are highly demanded in optical communication systems. However, despite several SOAs have been reported, co-integration of polarization-independent bulk SOA with passive waveguides in the InP platform to generate complex systems remains an issue. In this work, we design, simulate, fabricate and characterize a low polarization-dependent SOA based on a bulk active layer that is co-integrated with passive waveguides and exhibits its potential application to realize photonic integrated circuits. Simulation results are in good agreement with the experimental results. Based on the simulation results, the designed SOAs with the length of 300 μm, 750 μm, and 1500 μm cover broadband with 3-dB bandwidth of around 65 nm, 40 nm, and 37 nm, respectively. Characterization of SOAs with different lengths between 300 μm and 1500 μm co-integrated with passive waveguide has been performed. Broadband gain and polarization-dependent gain (PDG) less than 2 dB is measured for 300 μm SOA. Also, at 1550 nm, output saturation power of 12.8 dBm is achieved at the current density of 11.6 kA/cm2. For the longest SOA with 1500 μm length, the higher gain of 16 dB with PDG lower than 2.5 dB and saturation power of 7.4 dBm at the wavelength of 1588 nm and current density of 4.1 kA/cm2 are achievable. Thus, one could design SOA based photonic circuits with higher gain and saturation power and low PDG by exploiting different SOA lengths and design at the wavelength of interest, opening to potential application in photonic integrated circuits like low-loss and polarization-insensitive switches.