Reduction of Flicker Phase Noise in High-Speed Photodetectors Under Ultrashort Pulse Illumination

Abstract

High-fidelity photodetection enables the transfer of the low noise inherent to optical oscillators to the microwave domain. However, when photodetecting optical signals of the highest timing stability, photodiode flicker (1/f) noise can dominate the resulting timing jitter at timescales longer than ∼1 ms. With the goal of improving femtosecond-level timing fidelity when transferring from the optical to microwave domain, we vary the duty cycle of a train of optical pulses and show that the photodetector flicker phase noise on a photonically generated 1 GHz microwave signal can be reduced by ∼10 dB under ultrashort pulse illumination, reaching as low as −140/f dBc/Hz. In addition, a strong correlation between amplitude and phase flicker noise is found, implying a single baseband noise source can modulate both quadratures of the microwave carrier. These findings expand the limits of the ultimate timing stability that can be transferred from optics to electronics.

Keywords

• 1/f noise
• microwave phase noise
• photodiodes