The photodetector comprises a single 75 GHz waveguide-integrated photodiode, which shows an extremely flat frequency response, both in power and in phase. The on-chip integrated bias-network with an optimized RF design in particular, ensures an undisturbed frequency response from DC to the 3 dB cut-off frequency and saves costs for internal bias-tees. The module is especially designed for optimal RF performance and therefore the pulse response reveals virtually no ringing.
High-power behavior shows a linear response up to an optical input power of 10 dBm. An output voltage swing of more than 0.5 Vpp can be achieved for short pulses without any degradation of the pulse response. All photodetector devices are characterized in the frequency domain up to 75 GHz by using a heterodyne technique. In the time domain, a femtosecond pulse source and a 65 GHz sampling oscilloscope are used to measure the pulse response.