Uni-traveling-carrier balanced photodiode with tunable MMI coupler for optimization of source laser RIN suppression

A balanced uni-traveling-carrier (UTC) waveguide photodiode (PD) has been fabricated and characterized. The balanced PD incorporates a multimode interference (MMI) coupler as a light combiner/splitter with tunability of the output power splitting ratio. The individual UTC-PDs demonstrate a 1 dB compression current of 80.5 mA and a third-order output intercept point of 46.1 dBm at 60 mA, both representing the highest reported for a waveguide PD. The ability to fine tune the output power splitting of the MMI coupler allows for optimization of source laser relative-intensity noise suppression.