Self-Seeded Programmable Parametric Fiber Comb Source

Coherent light consisting of multiple-frequency combs is commonly used in metrology. Various methods of generating combs exist which are suited for different applications. Mode-locked lasers naturally output a train of phase-locked spectral lines and are a very simple way of generating a comb. These lasers do not operate in the continuous wave regime and the generated comb has very limited flexibility. Such features make mode-locked lasers ill suited for certain applications like differential absorption LIDAR or ranging. One interesting method for comb generation uses a frequency-shifting element to repeatedly shift re-circulating optical fields. The method has a rich set of operating modes, including the possibility for the comb frequencies to shift in time creating an effective chirp. However, the bandwidth and noise characteristics of the signal are limited by the Erbium-doped-fiber amplifiers used in the loop. Parametric nonlinearities can lead to a wide range of interesting effects such as phase-sensitive amplification which, unlike typical phase-insensitive amplifiers, can amplify a signal without adding noise. Other properties of parametric amplification can include the generation of additional frequency components, a huge gain bandwidth (>200nm) with engineerable spectral shape, and an ultrafast (sub-ps) response allowing nearly instantaneous control of the process. We propose to investigate the use of parametric amplification for generating agile optical frequency combs. We will combine techniques used in communications, sensing and standard optical comb generation to suggest possible designs and evaluate their use in real-world applications.