2.4 GHz L-Band Passively Harmonic Mode Locked Er-Doped Fiber Laser Based on Carbon Nanotubes Film

Abstract

We experimentally demonstrate a passively harmonic mode locked (PHML) Er-doped fiber laser with pump power efficiency up to 17 MHz/mW operating at L-band based on single walled carbon nanotubes polyvinyl alcohol (SWCNTs-PVA) film. Under 233 mW pump power, the stable pulse train at 1594.97 nm with 40.5 dB side mode suppression ratio (SMSR) and 742 fs pulse duration is obtained at a repetition rate of 1.923 GHz, corresponding to 170 th harmonic of the fundamental frequency. Under optimized intracavity conditions, the pulses frequency is able to scale up to 2.415 GHz with a high level of 40 dB SMSR, which to the best of our knowledge, is the highest value yet reported from a L-band PHML fiber laser incorporating SWCNTs as saturable absorber (SA). Such high repetition rate and stable fiber laser operating at L band may be desirable for various applications. Index Terms-mode locked fiber lasers, mode locking, nanomaterials I. INTRODUCTION RESENT research activities on ultrashort pulse fiber lasers with up to GHz range repetition rate have been extensively explored on account of their potential applications in optical frequency metrology [1], high speed optical sampling [2] and modern optical communication system [3]. Especially, for the modern optical communication system, the conventional Cband telecommunication window has been incapable of supplying the demand of persistent increasing of communication capacity. For addressing the problem, extending optical telecommunication region to L band is a key issue. Therefore, there is no doubt that investigating L-band fiber laser with high repetition rate via PHML method is of great importance. It is already widely acknowledged that active mode locking [4], short cavity [5] as well as PHML [6] have been considered as effective methods to achieve high repetition rate pulses. In a PHML laser, when high pump light launches into the laser Manuscript received XXXXXX. We would like to express our gratitude to the National Natural Science Foundation of China (NSFC) (61605107,61975107) and the open fund (Grant No. IPOC2017B010

Dynamics of carbon nanotube-based mode-locking fiber lasers

“…Various operation regimes, including Q-switching [52,53,[66][67][68][69][70][71], Q-switched mode-locking [72], and mode-locking [9,37,50,[73][74][75][76], were reported. Pulse evolution and interaction dynamics, including various soliton types [9,37,55,[77][78][79], soliton molecule [74,80,81], harmonic mode-locking [58,75,82], vector solitons [83,84], dark soliton [85], and soliton rains [86,87], were observed based on SWCNT-SAs and MWCNT-SAs. Due to the technical advantages of high beam quality, high efficiency, high integration, high reliability, etc., of fiber lasers, in this section, we mainly focus on the CNT-SA-based ultrafast fiber lasers.…”

“…Due to the excellent properties for saturation absorption, CNT-SA has been widely used in Q-switched and modelocked lasers, including the solid-state lasers [45][46][47][48][49], semiconductor lasers [50], waveguide lasers [51], and fiber lasers. The excellent properties of CNT-SAs enable ultrastable, ultrashort, and compact fiber laser system working from the visible to the mid-infrared spectral region [52][53][54][55], with functionalized operations like gigahertz repetition rate [56][57][58], multi-wavelength output [36,59,60], pulse duration, and spectral bandwidth tunability [37,[61][62][63][64][65]. Various operation regimes, including Q-switching [52,53,[66][67][68][69][70][71], Q-switched mode-locking [72], and mode-locking [9,37,50,[73][74][75][76], were reported.…”

“…By means of the optoacoustic effect that induces a trapping potential, the acoustic resonance can stabilize the modelocking of laser at different harmonics (from the first to sixth order at the appropriate pumping strength) with perfect long-term stability [75]. Up to now, the repetition rate using HML has been increases to 2.415 GHz at 1594.97 nm with 40 dB side mode suppression ratio (SMSR), which corresponds to 213 rd harmonic of the fundamental cavity repetition rate [58] as shown in Figure 7(C)-(H).…”

Carbon nanotube mode-locked fiber lasers: recent progress and perspectives

“…We have carried out a systematic exploration on the effects of average cavity dispersion and spectral bandwidth on HML in L-band using similar laser scheme [203]. It was found that the single pulse energy was eventually determined by the product of the average cavity dispersion and spectral bandwidth (dispersion bandwidth product, DBP) if other parameters such as average nonlinearity parameter, the time bandwidth product and center wavelength were CNT film with lower modulation depth was incorporated [204]. The pulse performances were shown in Figure 5C-E, and the corresponding pulse energy was decreased to 2.41 pJ, which is the lowest pulse energy ever obtained in a PHML fiber laser using a CNT SA, indicating effective cavity management.…”

Wavelength-Tunable L-Band High Repetition Rate Erbium-Doped Fiber Laser Based on Dissipative Four-Wave Mixing

“…To achieve a high-repetition rate (HRR) pulse train, a variety of passive mode-locking mechanisms have been reported, such as harmonic mode locking [ 12 , 13 , 14 ], short cavity [ 15 , 16 ], and dissipative four-wave mixing (DFWM) [ 17 , 18 ]. Compared to harmonic mode locking and short cavity, DFWM is a simpler and more effective method to generate an HRR pulse train with a capability even up to terahertz.…”