論文

High repetition rate ultrafast fiber lasers are essential for both scientific research and industrial applications. Here, we report the first, to the best of our knowledge, all-fiber ring laser with a fundamental repetition rate exceeding 1 GHz, by integrating all necessary functions into one single device with commercial active fiber pigtails. Low-threshold self-starting mode-locking is achieved by using a carbon nanotube (CNT) saturable absorber that directly deposits on the Er-doped fiber connector. The laser operates at 1562 nm, delivering 682 fs pulses with 1.028 GHz fundamental repetition rate with good stability, low intensity/phase noise, and high signal-to-noise ratio. The proposed compact source is promising for high repetition rate applications and provides a reference for fiber lasers with different mode-locking mechanisms or in various wavelength ranges. We also provide in-depth discussions on the key challenges and future directions for fiber lasers mode-locking at GHz rates using real saturable absorbers.

Nonreciprocity of traditional filters severely limits their tunability. To tap alternatives, here we propose hybrid wavelength manipulation with enhanced ambient-thermal-drift adaptability in an all-polarization-maintaining fiber laser. A multifunctional 2-in-1 device, which is based on a CNTs-coated tapered panda fiber and a specially designed PMMA (polymethyl methacrylate) package, is fabricated and applied to induce nonlinear saturable absorption and hybrid spectral filtering. In particular, hybrid tuning is enabled by the combination of mechanical and non-mechanical mechanisms, thus greatly prompting flexibility and efficiency. As wide as 40-nm tuning range in C- and short L-band is covered, with coefficients of 0.0116 nm/μϵ and 0.77 nm/°C respectively via stretching and heating the tapered fiber. Meanwhile, twisting induces steady dual-wavelength mode-locking. Required amount of adjustment is also cut nearly in half in contrast to previously reported works. Besides, great thermal expansion of PMMA introduces adaptative compensation towards ambient thermal fluctuation, resulting in over 4.7 times improvement. Numerical analysis is also studied for optimal design of filters. This work explores promising solutions for advanced tunable ultrafast lasers.

THz technology is positioned as a key enabler for next-generation wireless links due to the extensive untapped bandwidth and inherent compatibility with silicon photonics. Here, the phase noise of THz sources is modeled to characterized its impacts on a QAM-based wireless communication system. Particularly, common and instantaneous phase errors are unveiled and presented via constellation diagrams. In addition, tolerance of phase noise under different M-ary modulation formats is explored. Meanwhile, a linear correlation between instantaneous component and EVM is revealed to define the errorfree boundary, where microcomb-driven scheme is highlighted as a highly promising candidate for error-resilient THz links under advanced M-QAM formats. The results intuitively illustrate the impacts of phase noise and offer practical insights for refining technical details on physical-layer protocols.

For the first time, to the best of our knowledge, in the soliton regime, we demonstrate an L-band fiber laser mode-locked by all polarization-maintaining (all-PM) nonlinear polarization rotation (NPR). A numerical study suggests that lengthening the NPR section boosts modulation depth and lowers saturation power of the artificial saturable absorber (SA). With the longest NPR section to date (21 m), the laser emits 1.25-ps soliton pulses at 1584.2 nm and a 3.9-MHz repetition rate. Our laser provides a promising L-band seed source, exhibiting improved repeatability and stability compared with non-PM L-band pulse fiber lasers.

For the first time, we introduce a rapid wavelength-swept L-band tunable mode-locked fiber laser, boasting an exceptional wavelength sweeping rate of up to 19 kHz, enabled by external modulation of the pump current.

For the first time, we introduce a rapid wavelength-swept L-band tunable mode-locked fiber laser, boasting an exceptional wavelength sweeping rate of up to 19 kHz, enabled by external modulation of the pump current.

We achieved the first demonstration of a wavelength-tunable mode-locked fiber laser in the L-band using all-polarization-maintaining (all-PM) nonlinear polarization rotation (NPR). The all-PM configured laser features excellent repeatability and reliability. By increasing the pump power from 82.5 mW to 135 mW, a center wavelength-tuning from 1576.2 nm to 1592.2 nm is obtained. This non-mechanical tuning mechanism opens new possibilities for L-band wavelength-tunable lasers and their applications.

High repetition rate laser pulses are important for applications such as laser micromachining, bioimaging and optical frequency comb-based metrology. So far, no report on GHz-level fundamental repetition rate generation from an all-fiber ring laser. Here, we demonstrate the first all-fiber ring laser with GHz fundamental repetition rate. The laser produces ultrafast pulses at 1562 nm, with a pulse width of 682 fs, and a fundamental repetition rate of 1.028 GHz. The stable mode-locking is characterized by the low relative intensity noise and the high signal-to-noise ratio of the radiofrequency signal. The laser is mode-locked by carbon nanotubes (CNTs) with self-starting under a relatively low pump power. The proposed compact all-fiber ring laser could be used as the seed source where high repetition rate stable optical pulses are needed.

Mode-locked fiber lasers delivering ultrafast and intense optical pulses with picosecond or femtosecond pulse widths are powerful tools for nonlinear science and applications such as optical frequency comb-based metrology, bioimaging or high-precision micromachining [1]. Most of the previous works focus on the generation and development of wideband, narrow pulse width laser pulses. However, narrow-bandwidth optical pulses seem to be neglected. Such optical pulses with narrow bandwidth/long pulse duration, play important role for quantum optics, and has gained increasing attention in recent years [2]. Here, we present a carbon nanotube (CNT)-mode-locked fiber laser with all-PM format, capable of generating ultranarrow-bandwidth pulses down to 12.1 pm (equivalent to 1.49 GHz) while offering large tunability in both wavelength and pulse width.

Nonlinear saturable absorption threshold of a fast saturable absorber for stable mode-locking is numerically investigated, which reveals distinct patterns within different dispersion managements. Meanwhile, the impacts of saturable absorber parameters on mode-locking dynamics are analyzed.

We report numerical study on spectral ripple effects in a mode-locked fiber laser towards steady single-pulse states. Maps of nonlinear saturable absorption threshold required for stable mode-locking generation are explored. Ripple cancellation is also demonstrated.

We report numerical study on spectral ripple effects in a mode-locked fiber laser towards steady single-pulse states. Maps of nonlinear saturable absorption threshold required for stable mode-locking generation are explored. Ripple cancellation is also demonstrated.

Numerical exploration of nonlinear spectral analysis for measuring saturable absorption recovery time demonstrates monotonic relationship between it and difference spectra. The results also reveal a certain tolerance to self-phase modulation effects, allowing all-fiber system configurations.

For the first time in the soliton regime, we demonstrated a bound-state pulse generated in an Erbium-doped mode-locked fiber ring laser based on all polarization-maintaining nonlinear polarization rotation.

For the first time in the soliton regime, we demonstrated a bound-state pulse generated in an Erbium-doped mode-locked fiber ring laser based on all polarization-maintaining nonlinear polarization rotation.

For the first time in the soliton regime, we demonstrated a bound-state pulse generated in an Erbium-doped mode-locked fiber ring laser based on all polarization-maintaining nonlinear polarization rotation.

For the first time in the soliton regime, we demonstrated a bound-state pulse generated in an Erbium-doped mode-locked fiber ring laser based on all polarization-maintaining nonlinear polarization rotation.

We report the first demonstration of stably coexistent dual-wavelength bound states, where the temporal distributions of soliton molecules at two lasing wavelength components can be changed among different intra- and inter-molecule structures independently.

We report the first demonstration of stably coexistent dual-wavelength bound states, where the temporal distributions of soliton molecules at two lasing wavelength components can be changed among different intra- and inter-molecule structures independently.