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Optimizing linearity in high-speed photodiodes



Josue Davila-Rodriguez, X. Xie, J. Zang, Christian J. Long, Tara M. Fortier, Holly F. Leopardi, Takuma Nakamura, J. C. Campbell, Scott A. Diddams, Franklyn J. Quinlan


Analog photonic links require high fidelity, high speed optical-to-electrical conversion for applications such as radio-over-fiber, synchronization at kilometer-scale facilities, and low- noise electronic signal generation. Nonlinearity is a particularly vexing problem, causing signal distortion and excess noise, especially in systems utilizing ultrashort optical pulses. Here we show that photodetectors designed for high power handling and high linearity can perform optical-to-electrical conversion of ultrashort optical pulses with unprecedented linearity over a large photocurrent range. We also show that the broadband, complex impedance of the circuit following the photodiode modifies the linearity significantly. By externally manipulating the circuit impedance, we extend the detector's linear range to higher photocurrents, with over 50 dB rejection of amplitude-to-phase conversion for photocurrents up to 40 mA - more than 1000-fold improvement at the peak of the nonlinear response over other state-of-the-art photodiodes and a significant extension of the attainable microwave power with high linearity by a factor of 4. These results indicate the elimination of the long-standing requirement of precise tuning of the average photocurrent to coincide with a nonlinearity minimum, impacting many microwave photonics applications. Using our technique optical-to- electrical conversion can be performed free of excess phase noise from amplitude-to-phase conversion, opening the door to further understanding of the fundamental limitations to photodetection of optical signals.


Low noise microwaves, Photodiodes


Davila-Rodriguez, J. , Xie, X. , Zang, J. , Long, C. , Fortier, T. , Leopardi, H. , Nakamura, T. , Campbell, J. , Diddams, S. and Quinlan, F. (2018), Optimizing linearity in high-speed photodiodes, Optica, [online], (Accessed July 13, 2024)


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Created November 7, 2018, Updated February 22, 2019