Abstract
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. Photodetector 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 corroborate and expand upon the physical understanding of how the broadband, complex impedance of the circuit following the photodiode modifies the linearity - in some cases quite 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. This represents a 1000-fold improvement over state-of-the-art photodiodes and significantly extends the attainable microwave power by a factor of four. As such, we eliminate the long-standing requirement in ultrashort pulse detection of precise tuning of the photodiode's operating parameters to coincide with a nonlinearity minimum. These results should also apply more generally to reduce nonlinear distortion in a range of other microwave photonics applications.
Highlights
High-speed photodiodes are key components of a wide range of photonic systems such as microwave-photonic links [1, 2], opto-electronic oscillators (OEOs) [3, 4], photonic-based radar [5], photonic signal processing [6, 7], high speed waveform generation [8], and the generation of low-noise microwaves via optical frequency division (OFD) [9, 10]
As the optical-toelectrical converter, high fidelity operation of the high-speed photodiode is critical in limiting excess noise and signal distortion that would otherwise largely undermine the advantages of employing photonic techniques in microwave signal generation, dissemination, and processing
With the development of high saturation power photodiodes capable of generating microwave power approaching 2 W [11], increased signal-to-noise ratio (SNR) and all photonic gain [12] have become more feasible to a wider range of microwave photonic systems
Summary
High-speed photodiodes are key components of a wide range of photonic systems such as microwave-photonic links [1, 2], opto-electronic oscillators (OEOs) [3, 4], photonic-based radar [5], photonic signal processing [6, 7], high speed waveform generation [8], and the generation of low-noise microwaves via optical frequency division (OFD) [9, 10]. This can be accomplished by way of a Sagnac interferometer containing an electro-optic modulator that compares the optical pulse time of arrival to the zero-crossings of the microwave oscillator While this technique has demonstrated AM rejection as large as 60 dB [21], the output frequency is limited to the microwave oscillator’s capture range, and it hasn’t demonstrated the extremely low phase noise capabilities of direct optical pulse detection [23]. We show that charge-compensated modified uni-traveling carrier (CC-MUTC) photodiodes under short pulse illumination support 10 GHz generation with AM-to-PM coefficients below -50 dB over a photocurrent range of 40 mA, an improvement of several orders of magnitude over standard and advanced p-i-n photodiode designs [16, 17], as well as previous MUTC designs [24, 25] This level of AM-to-PM rejection enables the utilization of these photodiodes without additional stabilization schemes and at higher microwave output powers than previously reported. This scheme can be readily adopted by other systems using high linearity photodiodes, including those that do not utilize ultrashort optical pulses [4]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
