title: Low noise erbium fiber fs frequency comb based on a tapered-fiber carbon nanotube design.
abstract: We report on a low noise all-fiber erbium fs frequency comb based on a simple and robust tapered-fiber carbon nanotube (tf-CNT) design. We mitigate dominant noise sources to show that the free-running linewidth of the carrier-envelope offset frequency (fceo) can be comparable to the best reported performance to date for fiber-based frequency combs. A free-running fceo linewidth of ~20 kHz is demonstrated, corresponding to an improvement of ~30 times over previous work based on a CNT mode-locked fiber laser [Opt. Express 18, 1667 (2010)]. We also demonstrate the use of an acousto-optic modulator external to the laser cavity to stabilize fceo, enabling a 300 kHz feedback control bandwidth. The offset frequency is phase-locked with an in-loop integrated phase noise of ~0.8 rad from 10Hz to 400kHz. We show a resolution-limited linewidth of ~1 Hz, demonstrating over 90% of the carrier power within the coherent fceo signal. The results demonstrate that the relatively simple tf-CNT fiber laser design can provide a compact, robust and high-performance fs frequency comb.
authors: College of Optical Sciences, University of Arizona, 1630 East University Boulevard, Tucson, Arizona 85721, USA.
authors: Tsung-Han
authors: TH
authors: Wu
authors: K
authors: K
authors: Kieu
authors: N
authors: N
authors: Peyghambarian
authors: R J
authors: RJ
authors: Jones