Carbon Nanotube Mode-locked Fiber Laser Research Articles

Dual-comb soliton rains based on polarization multiplexing in a single-walled carbon nanotube mode-locked Er-doped fiber laser

Dual-comb soliton rains based on polarization multiplexing in a single-walled carbon nanotube mode-locked Er-doped fiber laser

Observation of the extracavity propagation of amplified bound-state soliton pulses emitted from a SWNT mode-locked fiber laser

We have experimentally investigated the extracavity propagation of amplified bound-state soliton pulses from a passively single-wall carbon nanotube mode-locked fiber laser. Under proper configuration of pump power and state of polarization, bound-state pulses exhibit a modulated optical spectrum. Except for the two main center wavelengths of 1557.3 and 1560.5 nm, additional five sidelobes centered at 1548.9, 1552.8, 1565.5, 1569.0 and 1573.1 nm are observed. Besides, the propagation after the extracavity erbium-doped fiber amplification is also investigated. It is demonstrated the significant change of the pulse separation is experimentally obtained when adjusting the extracavity PC before the autocorrelator, which is attributed to the coherent nonlinear soliton-soliton interaction. In addition, when different lengths of single-mode fiber after extracavity amplifier is removed or added, the significant change of the pulse separation is also observed, which matches well with the simulated evolution of pulse separation with respect to the SMF length. The pulse separation change of amplified bound soliton pulses is experimentally and theoretically investigated. These results provide further physical understanding of the generation and extracavity propagation of bound-state soliton pulses.

Transient dynamics of pulsating polarization rotating dual solitons in an ultrafast fiber laser.

The state of polarization is essential for a full description of ultrashort pulses. We experimentally observe the transient vector dynamics of pulsating vector solitons with rotating polarizations in a single-wall carbon nanotube mode-locked fiber laser. We acquire the single-shot polarization evolution of two different dual soliton pulsations using a homemade real-time wavelength-resolved state of polarization measurement system. We identify experimentally two different types of dual-soliton pulsations with longer and shorter pulsating periods respectively, and we find that dispersive-caused wave-caused energy exchange may be the reason for the distinct single soliton polarization evolution in multi-soliton cases. Our results are crucial for understanding the essence of soliton behaviour and developing novel potential applications of ultrafast fiber lasers.

Intracavity-loss controlled wavelength-tunable bidirectional mode-locked erbium-doped fiber laser.

Bidirectional wavelength-tunable mode-locked fiber lasers have demands for many applications. In our experiment, two frequency combs from a single bidirectional carbon nanotube mode-locked erbium-doped fiber laser are obtained. Continuous wavelength tuning is demonstrated in the bidirectional ultrafast erbium-doped fiber laser for the first time. We utilized the microfiber assisted differential loss-control effect on both directions to tune operation wavelength and it presents different wavelength tuning performances in two directions. Correspondingly, the repetition rate difference can be tuned from 98.6 Hz to 32 Hz by applying strain on microfiber within 23 µm stretching length. In addition, a minor repetition rate difference variation of 4.5 Hz is achieved. Such technique may provide possibility to expand wavelength range of dual-comb spectroscopy and broad its application fields.

Analysis of various soliton pulsation spectro-temporal dynamics in anomalous dispersion fiber laser

In this paper, we studied the effects of the output ratio and small-signal gain on soliton pulsation by modeling the anomalous dispersion carbon nanotube mode-locked fiber laser. Under different parameters, in addition to the conventional soliton pulsation, we also observed the soliton pulsation with obvious Kelly sideband and the soliton pulsation with soliton splitting. And we found the explosive-like soliton pulsation, which exhibits the time shift caused by soliton explosion. Specially, we observed the novel creeping vibrating soliton molecules that has creeping behavior in time-domain but vibrating behavior in spectral evolution. These findings can shed new insights into the soliton complex nonlinear behavior in dissipative systems.

Formation and Evolution of Soliton in Two-Mode Fiber Laser

High-order mode fiber lasers are gathering the rising attentions from fundamental researches to practical applications due to their distinctive spatial and temporal properties. Here, we demonstrate a carbon nanotube mode-locked two-mode fiber laser and investigate the formation and evolution process of the soliton based on the time-stretch dispersive Fourier transform method. Stable single pulse and bound-state pulses are observed at pump powers of 32.0 and 41.3 mW, respectively. Attributing to the coexistence of fundamental mode and first group high-order modes, the optical spectrum exhibits slight intensity modulations and the autocorrelation trace shows additional small side lobes. Similar to that of single-mode fiber lasers, the buildup process of soliton includes the relaxation oscillation, beating behavior, and stable mode-locking state. However, owing to the interplay between two transverse modes in the two-mode fiber laser, the duration and fluctuation intensity of the relaxation oscillation are much larger than that of single-mode fiber lasers.

Nanotube mode-locked, wavelength and pulsewidth tunable thulium fiber laser.

Mode-locked oscillators with highly tunable output characteristics are desirable for a range of applications. Here, with a custom-made tunable filter, we demonstrate a carbon nanotube (CNT) mode-locked thulium fiber laser with widely tunable wavelength, spectral bandwidth, and pulse duration. The demonstrated laser's wavelength tuning range reached 300 nm (from 1733 nm to 2033 nm), which is the widest-ever that was reported for rare-earth ion doped fiber oscillators in the near-infrared. At each wavelength, the pulse duration can be regulated by changing the filter's bandwidth. For example, at ~1902 nm, the pulse duration can be adjusted from 0.9 ps to 6.4 ps (the corresponding output spectral bandwidth from 4.3 nm to 0.6 nm). Furthermore, we experimentally and numerically study the spectral evolution of the mode-locked laser in presence of a tunable filter, a topic that has not been thoroughly investigated for thulium-doped fiber lasers. The detailed dynamical change of the mode-locked spectra is presented and we observed gradual suppression of the Kelly sidebands as the filter's bandwidth is reduced. Further, using the polarization-maintaiing (PM) cavity ensures that the laser is stable and the output laser's polarization extinction ratio is measured to exceed 20 dB.

Carbon Nanotube Mode-Locked Fiber Laser Generating Cylindrical Vector Beams with a Two-Mode Fiber Bragg Grating

We propose and demonstrate a compact all-fiber laser generating cylindrical vector beam (CVB) using carbon nanotubes as the saturable absorber for mode-locking and a two-mode fiber Bragg grating (TM-FBG) as the mode discriminator. Both radially and azimuthally polarized beams with a polarization purity of 90% were obtained by simply adjusting the polarization controllers. The CVB mode-locked fiber laser operates at 1552.9 nm with a 3-dB line width of less than 0.02 nm, generating ns CVB pulses. The all-fiber CVB laser may have potential applications from fundamental research to practical applications, such as particle capture, high-resolution measurement and material processing.

基于碳纳米管锁模光纤激光器的偏振锁定和偏振进动矢量孤子的研究进展

基于碳纳米管锁模光纤激光器的偏振锁定和偏振进动矢量孤子的研究进展

Large anomalous-dispersion mode-locked fiber laser based on a chirped fiber Bragg grating pair

A carbon-nanotube mode-locked erbium fiber laser with large net anomalous dispersion is presented. A chirped fiber Bragg grating (CFBG) pair is incorporated to increase the net-cavity anomalous dispersion and soliton splitting threshold. Self-started mode-locked laser produces stable pulses with repetition rate of 9.26 MHz. Laser spectrum is centered at ~1560 nm with 3 dB bandwidth of 0.43 nm. The typical output pulse energy and duration is 0.21 nJ and 8.05 ps, respectively.

Widely-pulsewidth-tunable ultrashort pulse generation from a birefringent carbon nanotube mode-locked fiber laser.

We demonstrate the generation of soliton pulses covering a nearly one order-of-magnitude pulsewidth range from a simple carbon nanotube (CNT) mode-locked fiber laser with birefringence. A polarization-maintaining-fiber-pigtailed, inline polarization beam splitter and its associated birefringence is leveraged to either enable additional nonlinear polarization evolution (NPE) mode-locking effect or result in a bandwidth-tunable Lyot filter, through adjusting the intracavity polarization settings. The large pulsewidth tuning range is achieved by exploiting both the nonlinear CNT-NPE hybrid mode-locking mechanism that narrows the pulses and the linear filtering effect that broadens them. Induced vector soliton pulses with pulsewidth from 360 fs to 3 ps can be generated, and their time-bandwidth products indicate they are close to transform-limited.

Nonlinear pulse shaping and polarization dynamics in mode-locked fiber lasers

We review our recent progress on the study of new nonlinear mechanisms of pulse shaping in passively mode-locked fiber lasers. These include a mode-locking regime featuring pulses with a triangular distribution of the intensity, and spectral compression arising from nonlinear pulse propagation. We also report on our recent experimental studies unveiling new types of vector solitons with processing states of polarization for multi-pulse and tightly bound-state soliton (soliton molecule) operations in a carbon nanotube (CNT) mode-locked fiber laser with anomalous dispersion cavity.

High-power sub-picosecond all-fiber laser source at 1.56 lm

We demonstrate an all-fiber, high-power, and high stability ultrafast laser source operating at 1563 nm. A highly stable, self-starting carbon nanotube (CNT) mode-locked femtosecond fiber laser is used as the seed source. The amplifier stage uses a fiber chirped pulse amplification configuration. The main power amplifier is based on a cladding-pumped Er-Yb co-doped fiber with 10 µm active single-mode core diameter. The laser source provides 3.4 W average output power at 75 MHz repetition rate. The pulses are compressed to 765 fs by a low-loss transmission grating pair. The robust, compact, and high-power 1560 nm fiber laser source can be used for eye surgery and solar cell micromachining.

Pulse-state Switchable Fiber Laser Mode-locked by Carbon Nanotubes

We proposed a carbon nanotube (CNT) mode-locked fiber laser delivering chirp-free soliton (CFS) and chirped pulse (CP) simultaneously or separately based on a circulator and chirped fiber Bragg grating (CFBG). The CFS reflected by the CFBG exhibits spectral sidebands with a bandwidth of 0.27 nm, whereas the CP has a smooth spectrum with a bandwidth of 4.1 nm. The durations of the CFS and CP are 9.6 and 1.3 ps, respectively. Due to the large anomalous dispersion and spectral filtering of CFBG, the CFS maintains low intensity and accumulates high energy without wave breaking. Numerical simulations agree well with the experiment and confirm the strong pulse shaping ability of CNT. The operation-switchable fiber laser may facilitate the practical applications where multitype pulses are necessary.

Vector solitons with locked and precessing states of polarization

We demonstrate experimentally new families of vector solitons with locked and precessing states of polarization for fundamental and multipulse soliton operations in a carbon nanotube mode-locked fiber laser with anomalous dispersion laser cavity.

Generation of Few-Cycle Pulses From an Amplified Carbon Nanotube Mode-Locked Fiber Laser System

We report a simple femtosecond fiber laser system based on a carbon nanotube saturable absorber that is capable of generating 14-fs pulses (containing less than four optical cycles) with optical spectrum extending from 1000 nm to around 1500 nm.