Dynamic Analysis of Cascaded Laser Power Converters for Simultaneous High-Speed Data Detection and Optical-to-Electrical DC Power Generation

We analyze the dynamic behaviors of a novel device, i.e., cascaded high-speed laser power converters (LPCs), which can detect the direct-current (dc) component of an incoming high-speed optical data stream and efficiently convert its dc component to dc electrical power. By utilizing a p-type photoabsorption layer in our LPC, the problem of slow-motion holes can be eliminated, and only the electrons act as the active carriers. We can thus achieve high-speed performance with the LPC under forward-bias operation with a small electric field inside. Furthermore, according to our modeling and measurement results, there are a significant alternating-current capacitance reduction and an electron-trapping effect at the interface between the absorption and collector layers with a significant degradation in the carrier drift velocity. These become more serious with the increase in optical pumping power and forward-bias voltage and truly limit the net optical-to-electrical (O-E) bandwidth of the device. In order to overcome such a transient-time-limited bandwidth and further increase the maximum dc output voltage of the LPC, we connect two single LPCs in series (cascade). Error-free data detection of 10-Gb/s and an O-E dc power-generation efficiency of 21.1% can be achieved simultaneously at a wavelength of 850 nm by the use of such two cascaded LPCs.