Polarization-maintaining Fiber Laser Research Articles

High-power polarization-maintaining LP11-mode fiber laser based on long-period fiber grating for precise welding.

An LP11-mode output all-fiber laser was presented, utilizing long-period fiber gratings (LPFGs) and polarization-maintaining optical fiber (PMF). The LPFG was designed and fabricated, achieving a 90.56% efficiency in LP01 to LP11 mode conversion. Furthermore, the transmission stability of LP11-mode in the PMF was also explored, with the spatial mode overlap ratio exceeding 0.95. Ultimately, the high-power polarization-maintaining (PM) fiber laser, capable of the LP11 mode output, was constructed, with the output power of 600 W and the beam quality M2 of 2.84. During the process of welding a thick Al-plate, the LP11 fiber laser exhibits a notable 1.88 times greater depth of fusion compared to the commercial single-mode fiber laser, when operating at the laser welding head speed of 100 mm/s. For applications demanding non-circular symmetric high-order modes, this research holds substantial potential for widespread adoption within the field of industrial processing.

1200-W all polarization-maintaining fiber GHz-femtosecond-pulse laser with good beam quality

In this work, we demonstrate a 1200-W average power all polarization-maintaining (PM) fiber ultrafast laser system operating at 1.0 µm. In accordance with the numerical modeling, the PM fiber laser system is designed and it delivers linearly-polarized femtosecond pulses at a 1.39-GHz fundamental repetition rate, with a maximum output power of 1214 W — to the best of our knowledge, the highest average power from all PM fiber ultrafast laser at 1.0 µm to date. The pulse width can be compressed to ∼800 fs with a beam quality of M2 < 1.1. This kilowatt-class all PM fiber laser system is expected to open new potential for high energy pulse generation through temporal coherent combination and laser ablation using GHz burst fs laser.

Multiple Bound State Soliton Pulses in the All Polarization Maintaining Fiber Laser.

The bound state soliton pulse, a novel mode-locked output state of fiber lasers, has been studied extensively to gain a better understanding of soliton interactions and to explain the mechanism behind the generation of mode-locked pulses. In this particular research, we utilized a self-made saturable absorber (SA) consisting of single-walled carbon nanotubes (SWCNT) in a fully polarization maintaining (PM) erbium-doped fiber optical path. Through this setup, we observed various bound state pulse phenomena, including the double bound state with different phase differences, the bound state formed by two double pulse bound states, the multi-pulse bound state, etc. The abundant bound soliton pulse states demonstrated the excellent nonlinear absorption characteristics of the SA as well as the excellent optical properties of the all-PM fiber laser. It contributed to exploring the relationship between sub pulses and mode-locked pulses in the future. Additionally, due to the strong interaction between bound state solitons and the inherent stability of the PM optical path, there was potential for utilizing this setup as a seed source to enhance the stability of high-power fiber lasers.

Power scaling of high-power linearly polarized fiber lasers with <10 GHz linewidth

In this work, an all-fiberized polarization-maintained (PM) fiber laser has been demonstrated with a near-top-hat-shaped spectrum. By optimizing the modulation signal to generate near-top-hat-shaped spectrums, a 3-kW PM fiber laser has been achieved at <10 GHz linewidth with the polarization extinction ratio of 96% and beam quality of 1.156, which is the highest output power ever reported with approximately 10 GHz linewidth, and further scaling of output power is limited by stimulated Brillouin scattering. By decomposing the mode content, the proportion of the fundamental mode in the output laser is above 97%. The stimulated Raman scattering suppression ratio reaches 62 dB at the maximal output power.

A 2 kW, 8 GHz-Linewidth Yb-Doped Polarization-Maintained Fiber Laser with Quasi-Flat-Top Pseudo Random Binary Sequence Phase Modulation for SBS Suppression.

We demonstrated a narrow-linewidth high-power Yb-doped polarization-maintaining (PM) fiber laser with near-diffraction-limited beam. The laser system consisted of a phase-modulated single-frequency seed source and four-stage amplifiers in the master oscillator power amplifier configuration. A quasi-flat-top pseudo random binary sequence (PRBS) phase-modulated single-frequency laser with a linewidth of 8 GHz was injected into the amplifiers for suppressing stimulated Brillouin scattering. The quasi-flat-top PRBS signal was readily generated from the conventional PRBS signal. The maximum output power was 2.01 kW with polarization extinction ratio (PER) of ~15 dB. The beam quality (M2) was less than 1.3 over the power scaling range.

Dynamics of frequency detuning in a hybrid Er-doped mode-locked fiber laser

Frequency detuning of mode-locked fiber lasers displays many remarkable nonlinear dynamical behaviors. Here we report for the first time the evolution of pulses from mode-locking through period pulsation to Q -switched mode-locking for three fundamental cases. Our experiments are performed in a hybrid actively and passively amplitude-modulated all-fiber polarization-maintaining mode-locked fiber laser, where the amplitude modulation frequency artificially deviates from the fundamental frequency of the cavity. We design and numerically simulate the laser with coupled Ginzburg–Landau equations. The experimentally observed dynamics of the mode detuning process is discussed with the assistance of the fitted model and numerical simulations, showing the generalizability of the optical mode detuning variation process. Our work provides fundamental insights for understanding perturbations in nonlinear optical resonant cavities and expands the ideas for studying chaotic path theory in hybrid mode-locked fiber lasers.

Wavelength and pulse width programmable mode-locked Yb fiber laser.

To the best of our knowledge, this study is the first demonstration of a mode-locked polarization-maintaining Yb fiber laser that incorporates a liquid-crystal-on-silicon-based electrically programmable filter into the cavity. The intracavity filter continuously tunes pulse characteristics, such as a wavelength tunable range of 1018-1065 nm and pulse width tunable range of 0.3-2.6 ps. Further, numerical simulations of the laser oscillator results were consistent with the experimental results and confirmed the mode-locked pulse generation regime. The proposed technique is expected to have great potential as a seed laser for multifunctional ultrashort-pulse lasers.

Single and Multiple Pulse Pattern Formation in All-Normal All-PM Yb-Doped Fiber Laser Using a Nonlinear Optical Loop Mirror

We report the evolution of single-pulse and multi-pulse in a mode-locked all polarization-maintaining fiber laser based on a nonlinear optical loop mirror (NOLM). The main parameters of the laser were determined by numerically simulating the relationship between the number of pulses and the basic parameters of each element. Experiments demonstrate generation of 1 to 6 pulses per cavity round trip. There is an unstable regime between the stable N and N + 1 pulses states when gradually increasing the pump power, while the intervals of the unstable regime shrink or even disappear when the direction of pump power variation is reversed. Our experimental results are different from those previously reported where the intervals of the unstable pulse regime are almost unchanged regardless of the pump power adjustment direction. We also describe how to obtain fundamental mode-locking from the multi-pulse state. The laser operated in the single-pulse regime shows excellent stability.

694 W sub-GHz polarization-maintained tapered fiber amplifier based on spectral and pump wavelength optimization.

The comprehensive suppression of the stimulated Brillouin scattering (SBS) and transverse mode instability (TMI) is a critical issue for the power scaling of fiber laser with sub-GHz spectral linewidth. In this manuscript, a narrow linewidth and polarization-maintained (PM) fiber amplifier based on tapered Yb-doped fiber (T-YDF) is established, and the effects of spectral linewidth, spectral shape and pump wavelength on the SBS and/or TMI thresholds are investigated. Up to 694 W polarization-maintained fiber laser with just ∼790 MHz linewidth is obtained by combining the advantages of tapered Yb-doped fiber, near-rectangular spectral injection and 915 nm pump manner. This work could provide a well reference solution for the realization of high-power ultra-narrow linewidth fiber lasers.

10-Hz, 636-ps, 1064-nm, all polarization-maintaining fiber front-end based on ultrafast optical fiber pulse chopping

We demonstrate a robust 10-Hz, 1064-nm, all polarization-maintaining (PM) fiber laser front-end for a joule-level solid-state amplification system applying ultrafast optical pulse chopping. A 1064-nm single frequency continuous wave (CW) laser is chopped by an in-line acousto-optic modulator (AOM) to generate ∼7 ns duration pulses at 500-kHz repetition rate, followed by a Sagnac loop (SL) consisting of a 50:50 PM fiber coupler and an electro–optical (EO) phase modulator, which further shortens the pulse duration from 7 ns to 636 ps via a passively fixed optical chopping gate. Finally, the pulse energy is amplified to the sub-µJ level and its repetition rate is further reduced to 10-Hz by another in-line AOM stage. This 10-Hz, 636-ps, sub-µJ level fiber laser realized in an all-PM-fiber configuration can be used as a robust front-end for joule-level solid-state amplification and follow-on nonlinear frequency conversion experiments.

Linearly polarized polarization-maintaining Er3+-doped fluoride fiber laser in the mid-infrared

We demonstrated the ∼2.8-μm and ∼3.5-μm linearly polarized continuous wave (CW) laser outputs from a polarization-maintaining (PM) Er3+-doped fluoride fiber laser. By introducing a film polarizer into the cavity to select the laser polarization orientation, the ∼2.8-μm linearly polarized CW laser with a high polarization extinction ratio (PER) of ∼23 ​dB and maximum output power of 2.37 ​W was achieved under double-end pumping at 976 ​nm. By adding another 1981-nm pump source simultaneously, the ∼3.5-μm linearly polarized CW laser was also obtained, giving higher PER of ∼27 ​dB and maximum output power of 307 ​mW which is only limited by the available power of 1981-nm pump. To the best of our knowledge, this is the first report on a mid-infrared linearly polarized CW PM fiber laser in the >2.5-μm mid-infrared region. This work not only opens up opportunities for some new mid-infrared applications, but also provides a promising platform for developing high-stability and versatile mid-infrared laser sources.

Femtosecond all-polarization-maintaining Nd fiber laser at 920 nm mode locked by a biased NALM.

We demonstrate a femtosecond all-polarization-maintaining Nd fiber laser working at 920 nm mode locked by a biased non-linear loop mirror. The broadest spectral width of the pulse is 25.2 nm and the output power is 8 mW with 320 mW pump power. The measured pulse width is 109 fs with extra-cavity compression. The laser configuration of all-polarization-maintaining fiber can directly enhance the environmental stability of generated pulses. The seed pulses of the oscillator were amplified over 400 mW, which served as the light source for a two-photon microscope. To the best of our knowledge, this is the first demonstration of a 920 nm femtosecond Nd polarization-maintaining fiber laser based on a non-linear loop mirror.

Yb-doped polarization-maintaining femtosecond fiber laser using Gires–Tournois interferometers for dispersion management

We demonstrate an ultrashort pulsed Yb-doped polarization-maintaining fiber laser which uses Gires–Tournois interferometers (GTI) for managing dispersion. The GTI placed in the oscillator cavity aims to compress the pulse. Resulting in a pulse with a duration of 78 fs. The fact that the laser does not require additional de-chirp makes it more compact and avoids the insertion loss of additional components. Experiments with different dispersion confirm the excellent dispersion-managed performance of GTI. As far as we know, the duration of 78 fs is the shortest pulse obtained by using intracavity GTI dispersion management in fiber lasers.

10 GHz regeneratively mode-locked thulium fiber laser with a stabilized repetition rate.

GHz pulsed thulium-doped fiber laser with stabilized repetition rate can enable a wide range of applications. By employing regenerative mode-locking and cavity stabilization technique, we have for the first time demonstrated a 10 GHz polarization-maintaining thulium-doped fiber laser, which has a long-term repetition-rate stabilization and picosecond timing-jitter. In our experiment, a RF circuitry is designed to extract the 10 GHz longitudinal clock signal so that stable regenerative mode-locking is achieved. A piezo actuator-based phase-lock-loop is used to lock the regeneratively mode-locked pulses to a local reference synthesizer. The regeneratively mode-locked pulses with picosecond pulse width exhibit a high super-mode suppression ratio of 60 dB. In addition, the repetition rate of the laser shows good long-term stability with a variation of 8 Hz in 8 hours, corresponding to a cavity free spectral range fluctuation of less than 16 mHz. Meanwhile, the Allan deviation of the stabilized 10 GHz regeneratively mode-locked pulses is measured to be as low as 2 × 10-12 over 1000 s average time, which is only limited by the stability of the reference synthesizer. Such an ultra-stable 10 GHz pulsed thulium fiber laser may find potential application in 2 µm optical communication, material processing and spectroscopy.

Wavelength-tunable, linearly polarized Q-switched and gain-switched polarization-maintaining Er[formula omitted]-doped fluoride fiber laser in the range of 2.7[formula omitted]2.83 [formula omitted

We demonstrate the ∼2.8 μm linearly polarized μs-scale pulse generation from a polarization-maintaining (PM) Er3+-doped fluoride fiber laser by Q-switching and gain-switching, for the first time to our knowledge. The achieved pulses have a polarization extinction ratio (PER) of up to ∼23 dB, and a repetition rate of several to tens of kHz with a maximum average power of hundreds of mW. By introducing a ruled reflective diffraction grating into the cavity, the wavelengths are able to be continuously tuned in the spectral range of 2.7∼2.83 μm. This work represents the first report on a linearly polarized short pulse PM fiber laser in the mid-infrared, opening up new opportunities for some specific applications (e.g., frequency doubling, optical parametric oscillation, coherent combining).

140 kHz, 1.2 ps pulses from an all-PM Yb-doped fiber master oscillator-power amplifier

We report on an environmentally stable mode-locked all polarization maintaining fiber laser with a nonlinear amplifying loop mirror (NALM) at a ultralow repetition rate. Experimentally, using different cavity lengths we have achieved stable mode-locking at different repetition rates. By carefully adjusting the length of the total fiber of NALM, we achieve stable broadband pulse trains with a repetition rate as low as 140 kHz. The pulses can be further amplified up to 27 μJ and compressed down to 1.16 ps. The laser system has potential application for industrial application.

High-precision passive stabilization of repetition rate for a mode-locked fiber laser based on optical pulse injection

We have proposed and implemented a novel scheme to obtain high-precision repetition rate stabilization for a polarization-maintaining mode-locked fiber laser. The essential technique lies in the periodic injection of electronically modulated optical pulses into a nonlinear amplifying loop mirror within the laser resonator. Thanks to the nonlinear cross-phase modulation effect, the injected pulses referenced to an external clock serves as a stable and precise timing trigger for an effective intensity modulator. Consequently, synchronous mode-locking can be initiated to output ultrafast pulses with a passively stabilized repetition rate. The capture range of the locking system reaches to a record of 1 mm, which enables a long-term stable operation over 15 hours without the need of temperature stabilization and vibration isolation. Meanwhile, the achieved standard deviation is as low as 100 μHz with a 1-s sample time, corresponding to a fluctuation instability of 5.0×10-12. Additionally, the repetition rate stabilization performance based on the passive synchronization has been systematically investigated by varying the average power, central wavelength and pulse duration of the optical injection.

321 W high-efficiency continuous-wave green laser produced by single-pass frequency doubling of narrow-linewidth fiber laser.

In this study, a high-power continuous-wave green laser for copper processing is investigated. The laser is produced by single-pass second-harmonic generation (SHG) of a narrow-linewidth fiber laser. Based on Sellmeier equations, the factors (e.g., fundamental wave linewidth, temperature, and angle) that decide LBO noncritical phase matching are theoretically analyzed for optimizing the SHG setup. A narrow-linewidth polarization-maintained fiber laser is used as the fundamental laser with a linewidth of 20 GHz and polarization extinction ratio of greater than 15 dB. Type I noncritical phase-matching LBO is used as the nonlinear crystal in the SHG. A green laser (up to 321 W) is obtained from a 784 W fundamental laser with a conversion efficiency of 40.9%. The green laser is near-diffraction-limited and has a $ M^{2} $ factor of 1.07.

Tunable peak power square-wave pulse based on an all-PM thulium-doped mode-locked fiber laser.

Nanosecond dissipative soliton resonance pulse is a demonstration of an all polarization-maintaining (PM) thulium-doped fiber laser in a nonlinear amplifying loop mirror (NALM)-based figure-eight configuration. Each loop of the apparatus includes a controllable power amplifier. With increased amplifier power, pulse width broadens linearly from 3.6 to 13.5 ns, and maximum single pulse energy can reach 27.5 nJ. Interestingly, the output peak power presents two completely opposite proportional effects in terms of the variation of settings for two amplifiers, respectively. The experimental results show that the NALM loop plays an important role for tunable pulse duration, and the unidirectional ring part makes a significant contribution for power scaling.

Convertible all polarization-maintaining fiber laser in low threshold mode-locked state

报道了一种可实现低阈值自启动的全保偏九字腔光纤激光器。谐振腔结构中使用相移器降低锁模阈值，当泵浦功率达到120 mW时，便可实现自启动的传统孤子锁模，中心波长为1530 nm，脉冲宽度为614.6 fs。随后泵浦功率逐渐增大到470 mW，实现了从孤子脉冲到类噪声脉冲的转换，在该锁模状态下的激光器输出功率为63.2 mW，对应的类噪声脉冲能量为5.69 nJ。所搭建的激光器具有低锁模阈值、自启动的优势，并且仅通过调节泵浦功率就能够实现超快脉冲和高能量脉冲间的转换，具有广泛的应用价值。