Laser Conversion Efficiency Research Articles

High-pulse-energy ultrafast 3 µm laser generation through OPG/DFG in PPMgLN

Abstract We report high-pulse-energy ultrafast 3 µm laser generation through optical parametric generation/difference frequency generation (OPG/DFG) in periodically poled magnesium-oxide-doped lithium niobate (PPMgLN). A commercial 1030 nm femtosecond laser is applied as the pump light and a homemade broadband nanosecond pulse laser around 1580 nm is used as the signal light in DFG. The broadband 1580 nm laser has a master oscillator power amplifier (MOPA) structure with a directly modulated superluminescent light-emitting diode (SLED) as the pulse seed and three stages of Er/Yb fiber amplifiers to lift its average power. A portion of the 1030 nm output pulse is converted to an electronic pulse via a pin detector, which is used as the trigger signal of the SLED driving circuit to ensure synchronization between the signal and the 1030 nm pump pulse. When injecting 2.12 W pump light into the PPMgLN, a broadband mid-infrared (MIR) output of 280 mW can be achieved directly through OPG with a center wavelength around 2.94 μm, a pulse width of 1.38 ps and a pulse repetition frequency of 500 kHz. The corresponding MIR pulse energy is 0.56 µJ. When injecting 2.62 W signal light simultaneously, a MIR output of 300 mW is achieved through the DFG process at the same pulse repetition frequency, corresponding to a pulse energy of 0.6 µJ. The conversion efficiency of the ultrafast pump laser to MIR reaches 14.1%. This high-pulse-energy 3 μm ultrafast laser has great prospects for applications in biological tissue ablation.

Design of a 1900nm thulium-doped laser emitter

In recent years, laser emitters have developed rapidly, been used in many fields, and have also brought great development to many industries such as communications and medical treatment. Thulium as a rare earth ion has a long service life and laser conversion efficiency, so the study of thulium-doped fiber lasers is of great significance for the development of the laser industry, but there is still a gap in the research in the field of 1900nm thulium-doped fiber lasers, Therefore, this experiment uses the physical model and quantum electric model to study 1900nm thulium-doped fiber lasers. The conclusion that the pump optical power decreases with the increase of distance and the pump optical power increases with the increase of laser power is processed, and the relationship between the pump optical power and the laser power, the relationship between the distance length and the pump optical power and the lasing optical power is shown with images.

Lowest threshold solar-pumped Ce:Nd:YAG laser with 2.06% solar-to-TEM00 mode laser conversion efficiency

A solar-pumped laser with bulk active medium generally requires a considerable amount of concentrated solar power for initiating laser emission. In previous work, 54.9 W threshold incoming solar power was found for a Ce:Nd:YAG solar laser by a 0.075 m2 effective area parabolic mirror. In the present work, a 0.0615 m2 area Fresnel lens was used to concentrate incoming solar power to a 2 mm diameter, 30 mm length Ce:Nd:YAG rod. 1.81 W continuous-wave 1064 nm solar laser output power was measured, corresponding to 3.15% solar-to-laser conversion efficiency, 4.4% laser slope efficiency, and 29.4 W/m2 collection efficiency. More importantly, threshold incoming solar power as low as 16.5 W was achieved, representing a 3.33 times reduction in threshold solar power, as compared to previous record by the parabolic mirror. By using a 0.0855 m2 area Fresnel lens, 2.83 W solar laser power was also measured, leading to 3.56% solar-to-laser conversion efficiency, 4.9% laser slope efficiency, and 33.1 W/m2 collection efficiency. Low threshold incoming solar power of 22.7W was also obtained, representing a 2.42 times reduction in threshold solar power in relation to the previous record. Notably, 1.41 W TEM00 mode solar laser power was also measured by adopting an asymmetric laser resonant cavity, resulting in 2.06% solar-to-TEM00 mode laser conversion efficiency, which, to the best of our knowledge, is 2.61 times larger than the previous record by Nd:YAG medium.

Efficient 10 ns-scale 2-μm optical parametric oscillator based on 1064 nm pump source

Lasers operating around 2-µm have been extensively researched for various applications, such as LiDAR, remote sensing, optical communication, and medicine. One of the approaches to generate 2-µm emission is to employ an optical parametric oscillator pumped by 1-µm laser; however, improving the 2-µm laser conversion efficiency of optical parametric oscillators is still a challenge. In this study, we exploit the high nonlinear coefficient of the KTP crystal at the 2-µm band to realize a high-efficiency optical parametric oscillator. The OPO is driven by a laser diode (LD) side-pumped, electro-optic Q-modulated Nd:YAG laser. The cavity was designed and optimized based on mode matching to increase the peak power density of the pump laser. Different powers were obtained for different pump laser focusing conditions, and the maximum power was obtained when the KTP crystal was placed in front of the pump laser focus. The output characteristics of the KTP at different phase-matching angles were also investigated. An output power of 2.44 W and an output pulse width of 9.04 ns were obtained at 2154.4 nm with an optical-to-optical conversion efficiency of 23.39% and a slope efficiency of 36.09%.

Intracavity frequency-doubled external-cavity surface-emitting blue laser with high conversion efficiency

Blue laser with high power and high beam quality has many applications such as in laser display, underwater communication and imaging, and non-ferrous metal processing. Optically pumped external-cavity surface-emitting laser combines the advantages of both surface-emitting semiconductor lasers and solid-state disk lasers, and can produce high output power and good beam quality simultaneously. Its high intracavity circulating power is more conducive to intracavity frequency doubling, achieving high-power and high beam quality blue light through fundamental laser in the near-infrared waveband. This paper reports an efficient intracavity frequency doubled 490 nm high power blue light by using a 980 nm fundamental laser in an external-cavity surface-emitting laser. The V-type resonant cavity is formed by the high reflectivity distributed Bragg reflector (DBR) at the bottom of gain chip, a folded flat concave mirror (high reflectivity coated for 980 nm and anti-reflectivity coated for 490 nm), and a flat concave end mirror (high reflectivity coated for 980 nm and 490 nm). By inserting a nonlinear crystal LBO into the cavity at the beam waist formed by the folded mirror and end mirror, and employing a birefringent filter (BRF) to polarize the fundamental laser and narrow the linewidth of the laser, a high power and high beam quality blue laser with high conversion efficiency is obtained. The effects of different factors including the length of nonlinear crystal, the linewidth of fundamental laser, and the compensation of walk off angle on the output power of the blue laser are studied experimentally. The length of the nonlinear crystal is optimized based on the size of the fundamental laser beam waist at the position of the crystal in the resonant cavity. Under the type-I phase matching condition of LBO, over 6 W output power at 491 nm wavelength is obtained when the crystal length is 5 mm and the BRF thickness is 1 mm. The beam quality <i>M</i><sup>2</sup> factor in the <i>x</i> direction and the <i>y</i> direction are both 1.08, and the conversion efficiency of frequency doubling is 63%. The experimental results also show that symmetrically placed nonlinear crystals can compensate for the walk-off angle during frequency doubling to a certain extent, thereby clearly improving the conversion efficiency of the frequency doubled blue laser.

382 mW External-Cavity Frequency Doubling 461 nm Laser Based on Quasi-Phase Matching

To rapidly improve strontium optical clocks, a high-power, high-efficiency, and high-beam-quality 461 nm laser is required. In blue lasers based on periodically poled KTiOPO4 crystals, the optical absorption in the crystals can induce thermal effects, which must be considered in the design of high-efficiency external-cavity frequency doubling lasers. The interdependence between the absorption and the thermally induced quasi-phase mismatch was taken into account for the solution to the coupled wave equations. By incorporating multilayer crystal approximation, a theoretical model was developed to accurately determine the absorption of the frequency doubling laser. Based on experimental parameters, the temperature gradient in the crystal, the influence of the boundary temperature on the conversion efficiency, and the focal length of the thermal lens were simulated. Theoretical calculations were employed to optimize the parameters of the external-cavity frequency doubling experiment. In the experiment, in a bow-tie external cavity was demonstrated by pumping a 10 mm long periodically poled KTiOPO4 crystal with a 922 nm laser, a 461 nm laser with a maximum output power of 382 mW. The conversion efficiency of the incident fundamental laser was 66.2%. The M2 factor of the frequency doubling beam was approximately 1.4.

Generation of terahertz waves based on nonlinear frequency conversion with double rapid adiabatic passage technique

In this paper, a nonlinear optical cascaded difference frequency generation model based on double rapid adiabatic passage technique is established, and a theoretical scheme for generating THz waves based on the above model is proposed. In this model, when the incident signal laser interacts with a pump laser, the signal laser can be completely converted into the output laser by special processing of the coupling wave equation and making reasonable assumptions. Numerical simulation results show that THz waves with a centre frequency of 260 GHz can be obtained. The maximum quantum conversion efficiency of the signal laser to THz waves is about 43.4%. Under the premise of keeping the wavelength of the pump laser unchanged, the tunable THz waves of 0.26–2.94 THz can be obtained when tuning the wavelength of the signal laser to change in the range of 1.054–1.064 μm. Compared with the scheme using stimulated Raman adiabatic passage technique, the scheme can still generate terahertz waves during the application of a pump laser to two simultaneous difference frequency generation processes, and the intensity of the pump laser can be reduced from Gigawatt level to Megawatt level. This scheme is robust to the temperature variation and provides a new method for generating terahertz wave band for high-speed wireless transmission.

Broadband ultrafast ultraviolet laser output by using β-BaB2O4 crystal

In this paper, a broadband ultrafast ultraviolet (UV) laser was generated through sum-frequency method with β-BaB2O4 (BBO) crystal by using a femtosecond (fs) Ti:sapphire laser as the fundamental laser source. We studied the influence of the power ratio between the fundamental frequency and second harmonic laser beams on output power and conversion efficiency of UV laser. The time delay method was used to change the optical path difference in the sum-frequency generation (SFG). At the same time, the cutting angle of the crystal was optimized and the effect of different focal lengths of lenses on the experimental results was studied. Finally, we obtained a tunable UV laser beam with a tuning range from 226.7 nm to 360 nm generated by the BBO crystal. The laser had high conversion efficiency, and the maximum output power was 540 mW at 270 nm.

Lowest-threshold solar laser operation under cloudy sky condition

Classical solar-pumped lasers often demand a significant amount of concentrated solar power for laser emission, which is only attainable under clear sky condition, limiting their applicability. In this research, we report the first solar laser emission at very low threshold solar power under cloudy sky condition by end-side-pumping a 2.5 mm diameter, 25 mm length Ce:Nd:YAG rod at the focus of a parabolic mirror concentrator. The Ce:Nd:YAG solar laser performance was also evaluated under clear sky condition for comparison. Low threshold pump power of 32.4 W for continuous-wave solar-pumped laser was obtained under clear sky condition, being two times lower than the previous record. However, the cloud-filtered infrared sunlight enabled notable improvements in the solar laser performance by lessening the thermal lensing effects in the laser medium. The threshold pump power was further reduced to 29.2 W and maximum solar laser output of 14 W was successfully measured. This nearly doubled the focal slope efficiency from 4.03% during clear weather to 7.71% under a cloudy sky. The solar-to-laser conversion efficiency of 6.32% was nearly tripled compared to the 2.32% on a clear sky, while the solar laser conversion efficiency of 21.47 W/m2 was nearly twice the value of 12.62 W/m2 obtained on a clear day. This demonstrates that a cloudy environment could be an asset for solar laser research.

High beam quality yellow laser at 588 nm by an intracavity frequency-doubled composite Nd:YVO4 Raman laser.

High beam quality 588 nm radiation was realized based on a frequency-doubled crystalline Raman laser. The bonding crystal of YVO4/Nd:YVO4/YVO4 was used as the laser gain medium, which can accelerate the thermal diffusion. The intracavity Raman conversion and the second harmonic generation were realized by a YVO4 crystal and an LBO crystal, respectively. Under an incident pump power of 49.2 W and a pulse repetition frequency of 50 kHz, the 588 nm power of 2.85 W was obtained with a pulse duration of 3 ns, corresponding to a diode-to-yellow laser conversion efficiency of 5.75% and a slope efficiency of 7.6%. Meanwhile, a single pulse's pulse energy and peak power were 57 µJ and 19 kW, respectively. The severe thermal effects of the self-Raman structure were overcome in the V-shaped cavity, which has excellent mode matching, and combined with the self-cleaning effect of `Raman scattering, the beam quality factor M2 was effectively improved, which was measured optimally to be Mx 2 = 1.207, and My 2 = 1.200, with the incident pump power being 49.2 W.

Theoretical analysis on improving output power of continuous-wave single-wavelength two-photon pumped Rb-vapor laser with mid-infrared seed laser

We theoretically prove that introducing 5.23-μm mid-infrared (MIR) seed laser can greatly increase output power of two-photon pumped Rb-vapor laser (Rb-TPAL) for the first time. Firstly, MIR laser stimulated radiation is added to the three-dimensional calculation model we reported in Ref. [1]. Then we simulate the Rb-TPAL pumped by a high-power continuous-wave laser diode and analyze the effects of MIR seed power and direction, vapor cell temperature and length, waist radii of pump and MIR seed, and output mirror reflectance on the output characteristics. The results show that by optimizing the above parameters, the MIR seed laser can not only significantly improve the output power and conversion efficiency of blue and MIR laser, but also reduce the pump and temperature thresholds of blue laser. This study can be useful for designing a TPAL system with high-power dual-waveband laser output.

Highly efficient and highly selective CO2 reduction to CO driven by laser

<h2>Summary</h2> Carbon dioxide (CO₂) reduction is a possible way to solve the greenhouse effect. Conventional catalytic CO₂ reduction faces some problems, such as high free energy barriers, limitation of cheap and effective catalysts. Here, we develop a highly efficient and highly selective CO₂ reduction under mild conditions by laser reduction in liquid (LRL). A high CO yield of 12.3 mmol h⁻¹ with near 100% selectivity and 13.3% energy conversion efficiency of laser to CO is achieved. In LRL, abundant active species are created immediately by laser-induced plasma in small bubbles along with transient extremely high temperature. Thermodynamically, CO₂ reduction proceeds quickly with the interaction of active species at high temperature. Kinetically, the rapid quenching process inhibits reverse reaction and keeps products at initial stage. The synergy of thermodynamics and kinetics results in high yield and high selectivity. These findings provide an alternative approach for CO₂ reduction under ambient conditions.

Fluorescence Radiation and Thermal Effect at the Edge of the Disk-Shaped Laser Crystal

The fluorescence radiation property at the edge of the thin disk crystal is very important to the design of thin disk lasers. In order to study this effect, in this paper, we established a theoretical model to describe the edge fluorescence radiation process in thin disk lasers. Subsequently, we used a thin disk crystal with indium absorption cladding to quantitatively test the edge fluorescence intensity. The significant difference between measured and simulated data can be described as P (probability value) &lt; 0.1 at the edge when the measured temperature is lower than the melting point of the metal cladding, and P &lt; 0.05 at the pump area. Finally, we analyze the influence of the edge fluorescence radiation on the thin disk laser operation, and the results show that the edge thermal effect will reduce the conversion efficiency of the disk laser by 20%. To the best of our knowledge, this is the first quantitative study on the edge radiation intensity of disk lasers. The research can provide theoretical guidance for the designing and packaging process of crystal elements in thin disk lasers.

Efficient TEM00-mode solar laser using four Nd:YAG rods/four off-axis parabolic mirrors pumping approach

A four-rod/four-TEM00-mode beam off-axis parabolic mirror solar pumping concept is proposed. Four off-axis parabolic mirrors with 10 m2 total collection area were used as the primary solar concentrators to pump four 3.1-mm diameter, 84-mm length neodymium-doped yttrium aluminum garnet (Nd:YAG) rods within four 2V-shaped pump cavities through four secondary fused-silica aspheric concentrators and four rectangular fused-silica light guides, ensuring a good absorbed pump power distribution within each rod and avoiding the serious thermal lensing and thermal stress issues associated with classical single large rod solar lasers. The laser design parameters were optimized using ZEMAX© and LASer Cavity Analysis and Design (LASCAD©) analysis software to maximize the TEM00-mode laser power. 155.29-W TEM00-mode total laser power was numerically calculated, corresponding to 15.5 W / m2 solar laser collection efficiency and 1.72% solar-to-TEM00-mode laser conversion efficiency, respectively. This result represents an improvement of nearly 2 and 1.24 times, in solar laser collection efficiency and solar-to-TEM00-mode laser conversion efficiency, respectively, as compared with the previous experimental records of the TEM00-mode solar laser pumped through the parabolic mirror primary concentrator. It provides also a 1.14 and 1.19 times improvement, as compared to the previous numerical record of the TEM00-mode solar laser pumped by the Fresnel lens primary solar concentrator.

Effective all-fiber pump recycler for kilowatt fiber lasers.

We report an effective pump recycler for industrial kilowatt fiber lasers. The pump recycler is a (6+1)×1 tapered fiber bundle, with signal ports of Ge-doped fiber (GDF) with core/cladding diameters of 20/400 µm and pump fiber ports (PFPs) with core/cladding diameters of 135/155 µm. By splicing PFPs in pairs, 77.9% of the residual pump light reaching the pump recycler is sent back to the cladding of the GDF. The insertion of a pump recycler increases the power conversion efficiency (PCE) of a fiber laser using an Yb-doped fiber (YDF) from 61.0% to 70.5%, with a maximum output power of 2.78 kW. The laser with a 20 m long YDF and pump recycler compares well to another laser using a 40 m long YDF without pump recycler. In both cases, the PCE is comparable but the laser with a 20 m long YDF and pump recycler benefits from reduced stimulated Raman scattering (SRS), thus enabling an 80% increase in Raman threshold. By giving access to short YDF length, the tapered fiber bundle represents an effective pump recycler since it enables reducing SRS while keeping a large PCE.

Nonlinear frequency conversion of a Ho :YAG laser beam

We report the results of experiments on frequency conversion of a Ho : YAG laser beam (wavelength λ ∼ 2.1 μm) into the near-, mid-, and far-IR regions, aimed at expanding the spectral composition of compact multispectral sources of coherent radiation. The experimentally found laser conversion efficiency into the second harmonic reaches 32 % and 54 % in the cw and repetitively pulsed regimes, respectively. The parametric conversion efficiency into the mid-IR range (λ = 3.5 – 5.0 μm) reaches 55 %, while for the far-IR range (λ = 8 – 8.2 μm) it turns out to be 10.5 %.

Second and cascaded harmonic generation of pulsed laser in a lithium niobate on insulator ridge waveguide.

Nonlinear crystalline ridge waveguides, e.g., lithium niobate-on-insulator ridge waveguides, feature high index contrast and strong optical confinement, thus dramatically enhancing nonlinear interaction and facilitating various nonlinear effects. Here, we experimentally demonstrate efficient second-harmonic generation (SHG) and cascaded fourth-harmonic generation (FHG) in a periodically poled lithium niobate (PPLN) ridge waveguide pumped with pulsed laser at the quasi-phase matching (QPM) wavelength, as well as simultaneous SHG and cascaded third-harmonic generation (THG) waves when pumped at the non-QPM wavelength. Furthermore, the ridge waveguide achieves an efficient single-pass SHG conversion efficiency of picosecond pulsed laser at ∼62%. These results may be beneficial for on-chip nonlinear frequency conversion.

Structure design and numerical simulation of chirped periodically polarized lithium niobate crystal for broadband mid-infrared laser generation

Mid-infrared band 3–5 &lt;inline-formula&gt;&lt;tex-math id="M1"&gt;\begin{document}${\text{μm}}$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M1.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M1.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; laser light source has important applications in many fields such as medical treatment, basic science, communication, and industry. Owing to the limitation to available efficient gain media in the mid-infrared band, the traditional methods of generating and amplifying lasers , such as regenerative amplification, are no longer applicable. In order to produce broadband and high-energy mid-infrared laser, in this work we combine quasi-phase matching technology and chirped periodically polarized lithium niobate (CPPLN) crystal for theoretical analysis and numerical design. The second-order nonlinear difference-frequency generation (DFG) process is used to implement the generation of mid-infrared laser via CPPLN. In the differential frequency process, the pump light used is 800 nm in wavelength and the wavelength range of signal light is 0.95–1.6 &lt;inline-formula&gt;&lt;tex-math id="M2"&gt;\begin{document}${\text{μm}}$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M2.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M2.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;. By calculating the dispersion curve of CPPLN crystal, the phase mismatch of difference frequency generation processes with different light signals is obtained. Under the condition of quasi-phase matching, the CPPLN with deliberately poling structures is designed and used to provide phase mismatch compensation in a broad bandwidth. The designed structure can meet the generation of mid infrared laser in a 1.6–5&lt;inline-formula&gt;&lt;tex-math id="M3"&gt;\begin{document}$ {\text{μm}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M3.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M3.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; band according to the numerical simulations. The conversion efficiencies of mid-infrared laser with different wavelengths at different positions in the crystal are obtained by using nonlinear coupled wave equations and fourth-order Runge-Kutta method. The results show that the mid-infrared laser in a wavelength range of 1.6–5 &lt;inline-formula&gt;&lt;tex-math id="M4"&gt;\begin{document}$ {\text{μm}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M4.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220016_M4.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; can be produced efficiently in a single CPPLN crystal, with an average conversion efficiency of about 15%. The theoretical analysis and numerical simulation for the designed CPPLN crystal can provide good schematic reference and theoretical support for further experimental exploration on generation of mid-infrared laser.

Efficiency enhancement of free-electron laser oscillator by kicking the electron beam orbit in a transverse gradient undulator

The conversion efficiency of a conventional free-electron laser (FEL) is on the level of Pierce parameter, which means that only a small portion of electron beam energy is converted into the electric field. Undulator tapering is a common way to enhance the FEL efficiency, however, it has limited effect when applying in the FEL oscillator. Inspired by the fast kicker developed in the high-repetition-rate FELs and storage rings, in this paper we propose to kick the electron beam orbit transversely in a transverse gradient undulator (TGU) after the FEL is saturated in oscillator. The electron beam will experience a different undulator strength after the beam orbit is deflected to the off-axis position. It can be regarded as a dynamic tapering method within the macrobunch while the dynamic detuning on the undulator strength with the normal tapering method is almost impossible in oscillator. Though the TGU will reduce the initial small-signal gain, the FEL efficiency still can be greatly enhanced. Numerical simulations demonstrated that the maximum FEL power can be enhanced to more than 3 times of the normal FEL oscillator.

Direct Generation of 7 W, 360 μJ Multi-Pulse Laser From an Ultra-Compact All-Fiber Gain Switched Tm³+-Doped Double-Clad Fiber Laser

We report on the investigation of multi-pulse Tm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped double clad fiber laser (TDCFL) with an ultra-compact four devices-based all-fiber structure. This multi-pulse is implemented by the long relaxation time of gain-switched process. The number of pulse in a pulse cluster can be tuned from 1 to 8 by changing the pump pulse energy. With laser cavity design (i.e. large laser output coupling ratio and high gain mutual balance), the multi-pulse laser can finally generate an average output power of 7.25 W with corresponding pulse energy of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$362.5~\mu \text{J}$ </tex-math></inline-formula> . The 2017 nm multi-pulse TDCFL has a high laser conversion efficiency of ~30% and the good operation stability with signal to noise ratio (SNR) of 77 dB. The experimental results would be fruitful to the communities interested in all-fiber multi-pulse lasers.