Characterization of Phase Noise Effects in the Photodetection of Ultrashort Optical Pulses (Briefing charts)
NATIONAL INST OF STANDARDS AND TECHNOLOGY BOULDER CO TIME AND FREQUENCY DIV
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Very-low-noise microwave signals are desirable for many state-of-the-art applications, including many types of radar and imaging systems, as well as secure communication. However, even state-of-the-art rf oscillator technology for producing signals into the tens of gigahertz range does not generate signals with low enough phase noise for these important systems to work to their full potential. A new approach for achieving microwave signals with ultra-low phase noise involves using an optical frequency divider that has as its reference a narrow-line width CW laser. Femtosecond laser frequency combs provide an effective and efficient way to take an ultra-stable optical frequency reference and divide the signal down into the microwave region. In order to convert optical pulses into a usable rf signal, one must use high-speed photodetection unfortunately, excess phase noise from both technical and fundamental sources can arise in the photodetection process. In order to ultimately minimize the noise effects of the photodetector, we must first characterize some of the known sources for noise inside these devices. In this paper, we describe two of these effects power-to-phase conversion and shot noise within three different test diodes. The noise performance of each diode reveals the nature of the noise sources, their effect on the output signal, and what design features of the photodiode minimize these noise effects.
- Electrooptical and Optoelectronic Devices