ABSTRACT
Abstract. An adiabatically waveguiding photodiode with thin absorption layer is introduced. The PD is capable of 40Gbps operation with responsivity of more than 1.0A/W. And the devices show low polarization dependency and high saturation input power, of which characteristics are suitable for 40Gbps optical communication systems. A cost-effective module with fiber or PLC is also possible because of its large alignment tolerance. 12
1. Introduction A surface-illumination photodiode (PD) has high coupling efficiency with an optical fiber. On the other hand, to fully absorb the incident beam, it should have thick absorption layer of ~3pm, which limits 3dB bandwidth because of carrier transit time. This limitation can be overcomed using side-illumination PD. Compared to surfaceillumination PD, however, side-illumination PD shows low responsivity resulting from low coupling efficiency with an optical fiber. To overcome low coupling efficiency of side-illumination PD, typically, SSC (Spot Size Converter) integrated PD was introduced. A SSC integrated PD, however, is complicated to fabricate and efficiency of SSC is limited. In this paper, 40Gbps adiabatically waveguiding PD without SSC, which shows compatible or superior features to a SSC integrated PD, is introduced.
