EQUIVALENT-CIRCUIT ANALYSIS OF HARMONIC DISTORTIONS IN PHOTODIODE

We report a simple method to obtain a p-i-n photodiode's harmonic dist ortion levels at different frequencies from the microwave reflection c oefficient S-11 of the photodiode under de illumination. This approach is based upon the tracking of the photodiode's microwave impedance wi th S-11 at different incident optical powers before severe saturation occurs at low bias or at high optical power. The second-harmonic disto rtions measured from a waveguide photodiode agree closely with those p redicted from the S-11 data.