Low-cost edge-illuminated refracting-facet photodiode module with large bandwidth and high responsivity

We have demonstrated a low-cost, high-speed and high-responsivity photodiode module utilizing an edge-illuminated refracting-facet photodiode (RFPD), in which the incident light parallel to the up-side surface is refracted at an angled facet and absorbed in a thin absorption layer. Since the incident light refracted at an angled facet penetrates at a definite angle to the absorption layer, the absorption length is effectively longer, resulting in high responsivity. In addition, since the RFPD chip has a large tolerance to optical-axis misalignment, the module can be produced with a simple single-lens alignment configuration, which enables low-cost fabrication. The fabricated RFPD module has a large-bandwidth (38 GHz) and high-responsivity (1 A/W). The measured polarization dependence of responsivity is less than 0.2 dB at a wavelength of 1.55/μm.