Due to eye safety regulations, the allowable transmitted power in an optical wireless communication system is limited. Maximization of the optical power collected at the receiver is required in order to achieve the link power budget needed for maximum-speed data transfer. A large optical aperture at the receiver yields efficient power collection. Large-area top-illuminated photodiodes can on the one hand collect much light, but on the other hand inherently have a large capacitance and, thus, a reduced electrical bandwidth. To completely break this optical-electrical tradeoff, we propose a new class of optical receivers, i.e., cascaded aperture optical receivers. Such an optical receiver decouples the light collection function from the light detection one by using two separate apertures: the first function is done by surface grating coupler(s) feeding the received light into a waveguide, and the second one by an ultrahigh speed waveguide-coupled photodiode. These two apertures can be engineered independently to optimize the overall optical and electrical properties of the receiver. Empowered by an integrated cascaded aperture optical receiver fabricated on our InP membrane platform, we successfully demonstrated an indoor optical wireless communication system with a 200 Gb/s (5λ × 40 Gb/s) capacity.
- Cascaded aperture optical receiver
- InP membrane
- optical wireless communication
- surface grating
- uni-traveling-carrier photodiode