Abstract
Passive harmonic mode-locking in soliton fiber laser is presented with excellent noise characteristics by employing a single-walled carbon nanotubes saturable absorber designed to interact with evanescent wave of the laser field. The 34(th) harmonic mode-locking pulses at 943.16 MHz repetition rate were stably generated with 18 mW output power, >50 dB side-mode suppression and -140 dB/Hz relative intensity noise. Soliton energy control with polarization controller further increased the harmonic order to 61st, 1.692 GHz, but with compromised performance. Scaling to higher-order harmonic mode-locking is discussed for practical application in optical communication system.
Highlights
After its introduction 6 decades ago [1], research activities on carbon nanotubes (CNTs) have increased significantly since early 90’s [2] to exploit their unique mechanical, chemical and electronic characteristics [3,4,5]
Passive harmonic mode-locking in soliton fiber laser is presented with excellent noise characteristics by employing a single-walled carbon nanotubes saturable absorber designed to interact with evanescent wave of the laser field
The 34th harmonic mode-locking pulses at 943.16 MHz repetition rate were stably generated with 18 mW output power, >50 dB side-mode suppression and 140 dB/Hz relative intensity noise
Summary
After its introduction 6 decades ago [1], research activities on carbon nanotubes (CNTs) have increased significantly since early 90’s [2] to exploit their unique mechanical, chemical and electronic characteristics [3,4,5]. There have been a number of reports on mode-locking in fiber lasers and solidstate lasers using SWCNTs as a SA [9,10,11,12,13] with the advantages of fast recovery time (around 1 ps), wide operation wavelengths (780 nm ~1.9 μm) and easy fabrication compared to the commonly used semiconductor saturable absorber mirror (SESAM). While typical fiber lasers have tens of MHz repetition rate, its passive harmonic mode-locking can exhibit GHz repetition without extra active modulator. Since the first demonstration of this kind of frequency multiplication [20], 1.1 W over 2 GHz from the 95.5 MHz fundamental repetition rate was reported through the nonlinear polarization evolution (NPE) method [22]. The limited nonlinear interaction of the ferrule-type CNT SA restricts its key performances such as repetition rate
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