Highly stable optoelectronic oscillator with a 10⁵ finesse etalon as a photonic filter

摘要

Low noise microwave signals are important for many applications in communications, radar, and navigation. The optoelectronic oscillator (OEO) design allows for creation of stable signals by taking advantage of optical elements for their long energy storage time and very low loss. High-Q elements include long fiber delay lines [1] and photonic filters [2] such as Fabry-Perot etalons (FPE) and whispering gallery mode resonators. Photonic filters also serve as mode selectors for the RF oscillation frequency, eliminating the need for RF bandpass filters which eliminate higher harmonic oscillations. Presented here is an optoelectronic oscillator system utilizing a high finesse FPE for both a photonic filter and optical frequency reference. By referencing the laser source to the etalon through Pound-Drever-Hall (PDH) frequency stabilization, a narrow linewidth, long term stable optical source is created [3], reducing output frequency drifts due to the source. The RF output of the OEO shows fractional frequency instability of 3.3×10⁻¹⁰ at 1 s. This result displays an improvement of more than two orders of magnitude over previous results using photonic filtering with a lower finesse etalon[4].