論文

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.

In this paper, laser cleaning of the 5083 alloy was used to remove the native oxide film and modify the morphological defects. The effects of oxygen content changes and surface morphology evolution on weld porosity after pretreatment with different energy densities (E) was studied. After laser cleaning, the oxygen element first decreases and then increases. With 3.5–35 J/cm2, the surface oxygen content drops by more than 60% compared with the untreated sample. It is the lowest with 17.5 J/cm2, a decrease of 75%. The main oxide are Al2O3 before and after laser cleaning. Untreated specimens have morphological defects such as scratches, superficial damage, and bulge. As E increased, the morphological defects were modified by the crater, gradually for fusion, and finally formed a striation morphology. The micromorphology after laser cleaning did not significantly affect the penetration and weld width. However, observation of the keyhole behavior reveals the micromorphology can affect the keyhole stability to regulate the process porosity. The change trend of the hydrogen porosity of the weld is consistent with the oxygen content. With 17.5 J/cm2, the hydrogen porosity of the weld is 0.9%.

THz wireless communications have garnered significant attention due to their unprecedented data rates enabled by the abundant untapped spectrum. However, advanced modulation formats beyond 64-QAM remain largely unexplored, as phase errors introduced during up/down-conversion severely limit system performance. Particularly, OFDM transmission is highly susceptible to aggravated ICI induced by phase noise, undermining the orthogonality of subcarriers. While PLLs and pilot-assisted compensation can mitigate phase errors, excessive pilot overhead compromises spectral efficiency and energy consumption, and white phase noise remains unrecoverable. Therefore, quantifying phase noise tolerance is essential for practical physical layer protocols. Here, we reveal the impact of phase noise in a 64-QAM, 2048-subcarrier OFDM THz transmission system. 3σ-error estimation is proposed to quantify phase noise tolerance, indicating an intuitive EVM threshold of approximately 5%. This threshold further delineates the tradeoffs among phase noise levels, SNR requirements, and pilot overhead. Moreover, by benchmarking representative oscillators with distinct phase noise spectra, microring resonators (MRRs) are identified as indispensable enablers for low-pilot-overhead OFDM THz links operating beyond 64-QAM.

We demonstrate a bidirectional polarization-multiplexed fiber laser and explore its potentials towards self-referenced dual-comb generation with tunable repetition rates. Regardless of ambient temperature fluctuations, the absolute deviation of dual-comb frequencies' difference is within 0.52 Hz.

We demonstrate a bidirectional polarization-multiplexed fiber laser and explore its potentials towards self-referenced dual-comb generation with tunable repetition rates. Regardless of ambient temperature fluctuations, the absolute deviation of dual-comb frequencies' difference is within 0.52 Hz.

Soliton complexes highlight the particle-like dynamics of dissipative pulses. However, simple and reliable manipulation of bound solitons remains challenging, particularly for all-polarization-maintaining (PM) configurations that are free from random polarization perturbations. Here, we report controllable pulse patterns of robustly coexisting dichromatic soliton complexes in an all-PM fiber laser based on a twistable tapered-fiber filter. According to the twist angle, dichromatic pulses are switched between different patterns, and components at each wavelength can be independently manipulated, extending encodings from the time to the frequency domain. To the best of our knowledge, it is the first experimental demonstration of dual-wavelength soliton complexes that different pulse patterns coexist at separated wavebands.

We demonstrate the pump-controlled mode-locking switching in an all-polarization-maintaining, CNT-mode-locked fiber laser. By simply changing the injected pump power, the mode-locking can be switched between two wavelengths, or built up at both wavelengths.

We demonstrate the pump-controlled mode-locking switching in an all-polarization-maintaining, CNT-mode-locked fiber laser. By simply changing the injected pump power, the mode-locking can be switched between two wavelengths, or built up at both wavelengths.

We demonstrate the pump-controlled mode-locking switching in an all-polarization-maintaining, CNT-mode-locked fiber laser. By simply changing the injected pump power, the mode-locking can be switched between two wavelengths, or built up at both wavelengths.

Mode-locked fiber lasers with wavelength tunability and dual-wavelength mode-locking capability have wide applications in nonlinear imaging, precision metrology and photonic sensing. Here, for the first time, we propose and experimentally demonstrate an environmentally stable all-polarization-maintaining (all-PM) fiber mode-locked laser without any intracavity filter and attenuator, whose mode-locking wavelength is switchable with the injected pump power. By increasing the pump power, the mode-locking wavelength switches from 1560-nm band to 1560/1530-nm dual-wavelength mode-locking, and finally to the 1530-nm band. The mechanism behind the phenomenon is well explained by the reverse saturable absorption induced intracavity loss variation. The proposed laser has a very concise configuration with only one integrated wavelength-division-multiplexer and a carbon nanotubes/polydimethylsiloxane (CNT/PDMS) saturable absorber (SA). The compact size, simple wavelength switching scheme as well as environmental stability makes it promising for practical applications.

We present for the first time, to the best of our knowledge, the pump-power-controlled, all-polarization-maintaining (all-PM), all-fiber configured, wavelength-tunable mode-locked fiber laser in the L-band (1565 to 1625 nm). A tuning range over 20 nm (1568.2 to 1588.9 nm) is attained simply by varying the pump power between 45 and 115 mW. Our work represents the first demonstration of wavelength tuning in all-PM configured nonlinear polarization evolution (NPE) lasers. The non-mechanical and electrically controllable tuning method offers ease of use and cost efficiency within an advanced all-PM, all-fiber design, indicating promising adaptability to diverse wavelength bands.

Terahertz wireless communications offer abundant untapped spectrum and are regarded as a promising playground for next-generation high-throughput links. Yet oscillator phase noise becomes the dominant impairment at such high frequencies, severely limiting the reliability of high-order QAM transmission. While photonic approaches, such as microcombs, are known to realize ultralow phase noise, the quantitative level of suppression required to sustain reliable high-order QAM transmission has not been clarified. Here, phase noise is reconstructed from measured spectra and embedded into a single-carrier link model to evaluate its impact. Distinct distortion mechanisms are identified, with slow common phase error and instantaneous phase jitter, where the latter remains as the residual impairment after carrier phase recovery. We further adopt a 3×EVM error margin, which maps residual distortions onto the constellation, providing a clear and practical indicator of system robustness. The results indicate that modest improvements in oscillator stability translate into significant BER gains without proportional power increase. These findings provide intuitive tolerance of phase noise in M-QAM systems and emphasize the importance of integrating low-noise photonic oscillators such as microcombs.

Repetition-rate-tunable fiber lasers are practical in addressing aliasing issue and exploring optimization parameters for dual-comb metrology and 3D surface profilometry. However, the tuning speed of typical delay lines is not very high, which limits the frame rate. Meanwhile, wide-range tunability is desired to extend non-ambiguity distances and eliminate dead zones. Here, we developed a dual-comb fiber laser based on a resonate piezoelectric motorized delay line that shows a tuning speed up to 493.5 kHz/s over 329-kHz tuning range, which is the fastest to the best of our knowledge. Benefiting from the mechanically shared polarization-maintaining oscillator, the proposed laser is stable with low crosstalk in full free-running, while this bidirectional polarization multiplexing configuration endows good flexibility and tunability. Consequently, the 1-hour variation of repetition rate difference is 0.52 Hz, with a standard deviation of 0.10 Hz. The dual combs are further pulled closer to 184.5 Hz by roughly compensating for fiber length. These results demonstrate a promising solution for developing accordion-comb seed light sources that can contribute to dual-comb metrology and 3D surface profilometry.

We experimentally demonstrate the minimization of relative intensity noise (RIN) in an all-polarization-maintaining (all-PM) ultrafast fibre laser mode-locked by carbon nanotube (CNT), which will benefit for high-precision applications requiring low RIN of laser.

Abstract: The thermal oxide layer formed of TA15 alloy has poor corrosion resistance. In this paper, the changes of the elements and components on the surface after laser ablation with different energy densities (E) were researched. The formation process and corrosion behavior of laser-generated oxide layer were clarified. As E increases, the oxygen content decreases from 8.52% to 5.43% and then increases to 11.89%. The surface oxide layer changes from TiO2(R) (i.e., rutile) to Ti2O3 + TiO2(R) and finally becomes TiO2(R) + TiO2(A) (i.e., anatase). The TiO2(R) gasification was confirmed by calculating the surface temperature rise. The surface reoxidation process was illustrated by a thermodynamically calculated ∆G-T(i.e., the Gibbs free energy changes with temperature). When E ≥ 17.5 J·cm−2, the oxide layer exhibits an agitated morphology, and oxide falls off at the bottom. As E increases, the corrosion rate decreases first and then increases. With energy density of 8.75 J·cm−2, the surface corrosion rate was 20.43 times slower than that of the untreated sample. The impedance spectrum and equivalent resistance results also prove the best corrosion resistance at 8.75 J·cm−2. The corrosion behavior of the oxide layer is analyzed from the properties of the oxide layer components and the reaction products with the electrolyte. Graphic abstract: [Figure not available: see fulltext.]

Single cavity dual-comb fiber lasers adopting different multiplexing configurations are benefited from the natures of common-mode noise suppression and superior coherence. Particularly, repetition-rate-tunable dual-combs enable non-ambiguous ranging and aliasing-free spectroscopy. However, their sampling rate and spectral resolution are severely restricted by the mechanical delay line (DLL). In a previous work, as rapid as 500 kHz/s tuning rate was realized to address this issue, while the minimum comb-frequency difference remained large under the inaccuracy of mechanical DLL. In this work, a polarization-multiplexing dual-comb fiber laser incorporated with a thermally controlled bidirectional Lyot filter is demonstrated with 870-times enhanced tuning precision compared with mechanical schemes. Linear correlation between temperature and repetition-rate-difference of this tuning mechanism is revealed. We achieve a tuning efficiency of 4.4 Hz/K and a control accuracy of 0.44 Hz, denoting a significant advance in operating Hz-scale differential comb lines. This design offers a robust platform for extending non-ambiguous distance in dead-zone-free dual-comb ranging and eliminating aliasing in spectroscopy.

A repetition-rate-tunable dual-comb laser is critical for alias-free ranging, yet delay lines consistently introduce errors by travel uncertainty. Here, we demonstrate bidirectional polarization-multiplexed Lyot filtering with only 0.11% error compared with the previous PZT solution reported.