Jizhao Zang

Photonic Generation of High-Power Pulsed Microwave Signals

Photonic generation of high-power pulsed microwave signals is demonstrated using charge-compensated modified unitraveling-carrier photodiodes. The impulse response without RF modulation achieved unsaturated peak voltage of 33.5 V and full-width at half-maximum of 50 ps. The peak power levels for gated modulation at 1 and 10 GHz were 41.5 dBm (14.2 W) and 40 dBm (10 W), respectively.

Characterization of Amplitude Noise to Phase Noise Conversion in Charge-Compensated Modified Unitravelling Carrier Photodiodes

The phase noise, i.e., amplitude modulation to phase modulation (AM-PM) in the photodetector. In general, AM-PM of charge-compensated modified uni-travelling carrier (CC-MUTC) photodiodes originates from the combined nonlinearities of the detector impedance and carrier transit times, which depend on the electric field distribution and the velocity-field characteristics of carrier transport. In this work, we report measurements of AM-PM in transit-time-limited CC-MUTC photodiodes. A Crosslight-based simulation of the photodetection process is used to quantitatively estimate the AM-PM of CC-MUTC photodiodes. Simulated AM-PM of a 15-GHz microwave signal shows good agreement with experimental results. The measured and simulated AM-PM versus photocurrent exhibit a null point that originates from the competition between hole deceleration due to the collapsed electric field in the depleted absorption region and electron acceleration in the self-induced electric field in the undepleted absorption region.

Hybrid integration of modified uni-traveling carrier photodiodes on a multi-layer silicon nitride platform using total reflection mirrors

We demonstrate hybrid integration of modified uni-traveling carrier photodiodes on a multi-layer silicon nitride platform using total reflection mirrors etched by focused ion beam. The hybrid photodetectors show external responsivity of 0.15 A/W and bandwidth of 3.5 GHz for devices with a diameter of 80 µm. The insertion loss of the waveguide is 3 dB and the coupling efficiency of the total reflection mirror is -3 dB. The highest RF output power is -0.5 dBm measured at 3 GHz with 9 mA photocurrent and -9 V bias.

Heterogeneously integrated waveguide-coupled photodiodes on silicon-on-diamond (SOD)

We report on InP-based high power modified uni-traveling carrier (MUTC) photodiodes heterogeneously integrated on silicon on diamond (SOD) waveguides. Typical dark currents of MUTC photodiodes on SOD waveguides are 20 nA at - 5 V bias voltage. A 50-μm long photodiode has an internal responsivity of 1.07 A/W at 1550 nm wavelength. The bandwidths of photodiodes with active areas of 14×25 μm2, 14×50 μm2, 14×100 μm2 and 14×150 μm2 are 22 GHz, 16 GHz, 10 GHz and 7 GHz, respectively. The maximum output RF powers of 14×100 μm2 photodiodes are 13 dBm, 14.4 dBm and 15.3 dBm at 10 GHz, respectively. The maximum DC dissipated power is 0.67 W. To our knowledge, this is the first demonstration of III-V photodiodes integrated on SOD waveguides.