Optical heterodyne millimeter-wave generation using 1.55-μm traveling-wave photodetectors

Optical heterodyne millimeter-wave generation using traveling-wave photodetectors (TW-PDs) is examined both experimentally and theoretically. Ultrahigh-frequency InP-based 1.55-μm TW-PDs were fabricated and employed in an experimental setup for optical heterodyning. For the first time, optical heterodyne millimeter-wave generation in excess of 160 GHz is experimentally demonstrated in the frequency domain. The maximum electrical power delivered by the TW-PD to a 5052 impedance is -11.5 dBm at 110 GHz with a polarization penalty of only 1.3 dB. Furthermore, a theoretical analysis in frequency domain is presented describing the frequency response of TW-PD including effects of the photogenerated carrier dynamics as well as optical and electrical wave propagation phenomena. A broadband and flat frequency response is found indicating a total rolloff of about 13.1 dB for a frequency span from 25 GHz to 200 GHz. Finally, the detectors responsivity is theoretically investigated to differentiate between the physical phenomena associated with high-frequency limitations