UTC-PD's optoelectronic mixing principle and optimal working condition

In this article, we illustrate the working principle of optoelectronic mixing for uni-traveling-carrier photodetector (UTC-PD). As a result of the combined influence of local oscillators (LO) and bias modulation signals (RF), the velocity and concentration of photogenerated electrons in the depletion region exhibit mixing components with frequencies of \(|{f}_{LO}\pm {f}_{RF}|\) $|f_{\mathit{LO}}\pm f_{\mathit{RF}}|$ . The optoelectronic mixing signal is primarily generated by these two components, and its peak value is determined by the concentration of photogenerated electron. Moreover, the cliff layer can greatly enhance the output power of the mixed frequency signal, since it allows more photogenerated electrons to be transmitted to the depletion region.