Compact Fiber Laser Research Articles

Generation of high-energy self-mode-locked pulses in a Tm-doped fiber laser

The incorporation of a material-based or artificial saturable absorber into a fiber laser cavity imposes a limitation on energy enhancement owing to its low damage threshold and high environmental sensitivity. To address this issue, one promising alternative approach is the utilization of the self-mode-locking technique. Here, we present a robust self-mode-locked Tm-doped fiber laser with high pulse energy emission. A simple and compact fiber laser structure is realized by utilizing a section of a Tm-doped fiber, serving both as a gain medium and a saturable absorber. Thus, the operational stability is enhanced, especially under high-energy conditions. Furthermore, the realization of high-energy pulses is accomplished through the integration of dispersion management technique. Experimental results reveal that the maximum single-pulse energy increases from 34.8 pJ to 120.2 nJ as the round-trip group delay dispersion decreases from −0.43 to −12.40 ps2. The proposed self-mode-locked Tm-doped fiber laser under high-energy operation exhibits remarkable performance. Our results provide a simple approach to obtaining a mid-infrared laser source with high pulse energy and hold significant potential for advancing high-energy laser systems.

Tunable and switchable multi-wavelength mode-locked fiber lasers induced by an optimized hybrid mode-locked composite filtering effect

A multi-wavelength mode-locked fiber laser can generate different wavelengths from a single laser cavity, offering potential as a dual-frequency comb and serving as an ideal light source for terahertz wave generation. We present an optimized hybrid mode-locked Er-doped fiber laser with flexible outputs: switchable and tunable dual-wavelength mode-locking, along with stable tri-wavelength mode-locking, which is achieved by introducing 0.69 m polarization-maintaining fiber and bent 200 m single-mode fiber to enhance intra-cavity birefringence and nonlinear effect to optimize the hybrid mode-locking effect, that is, build the composite filter effect. The dual-wavelength mode-locking not only covers a tunable wavelength range of 5 nm but also provides tunable wavelength intervals of 4-26 nm due to the composite filter effect. The formation dynamics of the tri-wavelength mode-locking can be switched either pair-by-pair or one-by-one. This approach enables the realization of wavelength interval tunable dual-wavelength mode-locking in mode-locked fiber lasers simply by introducing fiber without additional actions. Such a simple, compact fiber laser with tunable wavelength capabilities holds significant potential for diverse applications.

Tunable mode-locked holmium-doped fiber laser based on GIMF-SIMF-GIMF structure at 2.09 µm

In this study, a structure of graded-index multimode fiber-step index multimode fiber-graded index multimode fiber (GIMF-SIMF-GIMF) was used as a saturable absorber (SA) to generate mode-locking in a holmium-doped fiber laser (HDFL). The HDFL was pumped with a compact in-house thulium-doped fiber laser (TDFL) operating at 1943 nm with a maximum output power of 2.1 W. Mode-locked pulses with a pulse duration of 1.61 ps were successfully generated at the center wavelength of 2091.1 nm. The pulse had a repetition rate of 12.79 MHz with a bit of fluctuation of 2.09 %, indicating stable pulses. The mode-locked pulses were also tunable with a range from 2086.5 nm to 2091.1 nm by stretching the GIMF part of the SA. This first report demonstrated mode-locking using nonlinear multimode interference (NL-MMI) using GIMF-SIMF-GIMF structure as a saturable absorber in HDFL operating near 2.1 µm wavelength.

GHz-rate 57-fs acousto-optic mode-locking fiber laser based on cascaded all-fiber pulse compression.

We demonstrate a compact ultrafast fiber laser system that can deliver 1.87 GHz pulse train at 1550 nm with a pulse energy of 52 pJ and an ultrashort pulse duration of 57 fs. While an acousto-optic mode-locking fiber laser was used as the seed light source at GHz rate, a stage of Er-doped fiber amplifier boosted the laser power to ∼320 mW, giving a pulse energy of ∼170 pJ. Then, a pulse compression setup was constructed, providing a high compression ratio of ∼10 with a total efficiency of ∼32%. In the cascaded compression configuration, multiple fiber samples with alternately normal and anomalous dispersion were fused together, providing efficient nonlinear spectral broadening while suppressing excessive pulse broadening over propagation. This GHz-rate ultrafast fiber laser, with compact configuration, broad optical spectrum, and high time-resolving ability could be used as the seed light source for constructing high-rate, high-power ultrafast laser systems and may find a few applications in optical measurements and microwave photonics.

Compact and efficient high-power mid-infrared supercontinuum fiber laser source based on a noise-like pulse and germania fiber

Here, we demonstrate a compact and efficient high-power mid-infrared supercontinuum (MIR-SC) laser source based on a tunable noise-like pulse (NLP) fiber laser system and a short section of single-mode germania-core fiber (GCF). The NLP all-polarization-maintaining fiber laser system can deliver the maximum output power of ∼30.6 W and a broadband spectrum (∼1.8-2.7 µm) with a compact single-stage fiber amplifier. By directly pumping only ∼6.5 cm-long GCF with a core diameter of ∼3.5 µm, a MIR-SC (spectral coverage of ∼1.5-3.3 µm) with a maximum power of ∼25.2 W and a power conversion efficiency ∼81.2% is obtained, which represent the highest power and efficiency in any single-mode GCF-based MIR-SCs, to the best of our knowledge. Our study contributes to the high-power MIR-SC laser source with compact all-fiber configuration, and will prompt its practical applications.

Efficient single-pixel imaging based on a compact fiber laser array and untrained neural network

This paper presents an efficient scheme for single-pixel imaging (SPI) utilizing a phase-controlled fiber laser array and an untrained deep neural network. The fiber lasers are arranged in a compact hexagonal structure and coherently combined to generate illuminating light fields. Through the utilization of high-speed electro-optic modulators in each individual fiber laser module, the randomly modulated fiber laser array enables rapid speckle projection onto the object of interest. Furthermore, the untrained deep neural network is incorporated into the image reconstructing process to enhance the quality of the reconstructed images. Through simulations and experiments, we validate the feasibility of the proposed method and successfully achieve high-quality SPI utilizing the coherent fiber laser array at a sampling ratio of 1.6%. Given its potential for high emitting power and rapid modulation, the SPI scheme based on the fiber laser array holds promise for broad applications in remote sensing and other applicable fields.Graphical

Enhancing frequency stability and mode control in a Brillouin random fiber laser with a strongly scattering disordered grating

Random fiber lasers (RFLs) with disordered scattering feedback media provide a range of functionalities and properties. The primary drawback with weak Rayleigh scattering (RS)-based RFLs is their large frequency drift and mode hopping, which are caused by the random walk of photons at different round trips. Here, we present a technique to control the mode propagation of RFLs by using a narrow gain bandwidth from stimulated Brillouin scattering and photon localization from a strongly scattering disordered grating. Multiple scattering of light within the disordered grating leads to photon localization and narrow reflection peaks, which suppresses frequency drift and reduces the number of modes. The compact Brillouin random fiber laser (BRFL) with a 200 m strongly scattering disordered grating enables single-mode lasing with an ultra-narrow linewidth of ∼650 Hz. The results of the real-time spectral evolution obtained by the heterodyne method demonstrate long-term stability of the lasing frequency, confirming the capability of the strongly scattering disordered grating to control mode propagation of the BRFL. The BRFL exhibits an ultra-high frequency stability of 0.48 MHz and mode-hop-free operation up to 120 s. This work provides a perspective on the development of RFLs with high coherence and stability.

Low repetition rate 915 nm figure-9 ultrafast laser with all-fiber structure.

The advent of optical metrology applications has necessitated the development of compact, reliable, and cost-effective picosecond lasers operating around 900 nm, specifically catering to the requirements of precise ranging. In response to this demand, our work introduces an innovative solution-an all-fiber, all-polarization-maintaining (PM) figure-9 mode-locked laser operating at 915 nm. The proposed figure-9 Nd-doped fiber laser has a 69.2 m long cavity length, strategically designed and optimized to yield pulses with a combination of high pulse energy and low repetition rate. The laser can generate 915 nm laser pulses with a pulse energy of 4.65 nJ, a pulse duration of 15.2 ps under the repetition rate of 3.05 MHz. The 1064 nm amplified spontaneous emission (ASE) is deliberately filtered out, in order to prevent parasitic lasing and increase the spectral proportion of the 915 nm laser. The all-PM fiber configuration of this laser imparts exceptional mode-locking performance and environmental robustness, which is confirmed by long-term output power and spectral stability test. This compact and long-term reliable fiber laser could be a promising light source for applications like inter-satellite ranging.

Sub-10-fs pulse generation from 10 nJ Yb-fiber laser with cascaded nonlinear pulse compression.

We demonstrate cascaded nonlinear pulse compression of a Yb-doped fiber laser. The system is based on two pulse compression stages with bare single-mode fiber (SMF) and ultra-high NA (UHNA) fibers combined with two pairs of chirped mirrors. The 10 nJ, 110 fs input pulses are compressed down to 9.1 fs at 90 MHz, revealing a broadband spectrum from 800 nm to 1350 nm. This technique provides a simple approach to sub-10-fs compact Yb-doped fiber lasers for a variety of applications.

Compact, ultrastable, high repetition-rate 2 μm and 3 μm fiber laser for seeding mid-IR OPCPA.

We report a compact and reliable ultrafast fiber laser system optimized for seeding a high energy, 2 μm pumped, 3 μm wavelength optical parametric chirped pulse amplification to drive soft X-ray high harmonics. The system delivers 100 MHz narrowband 2 μm pulses with >1 nJ energy, synchronized with ultra-broadband optical pulses with a ∼1 μm FWHM spectrum centered at 3 μm with 39 pJ pulse energy. The 2 μm and 3 μm pulses are derived from a single 1.5 μm fiber oscillator, fully fiber integrated with free-space downconversion for the 3 μm. The system operates hands-off with power instabilities <0.2% over extended periods of time.

MOFs-derived hierarchical NiO-Co3O4 for versatile pulses generation

Polyhedral NiO-Co3O4 materials, as a novel type of metal organic frameworks (MOFs), are considered to be attractive emerging materials in the fields of optoelectronics, energy storage systems, sensing and catalysis because of their high specific surface area, rich variable metal sites and unique morphology. Ultrafast pulse has become an important research tool in basic research and industrial application fields, including supercontinuum generation, laser material processing, laser surgery, lidar and terahertz generation. The saturable absorber (SA) is a key component that affects the laser parameters and generates ultrafast pulses, so it has caused an upsurge in the research of SA. Although MOFs and their derivatives have attracted the attention of researchers in many fields, few works have been carried out in ultrafast photonics. Here, we use the cobalt-based zeolite imidazole framework (ZIF-67-Co) as a precursor to synthesize NiO-Co3O4 polyhedron by calcination, and utilize it as an effective SA in a compact erbium-doped fiber laser (EDFL). The NiO-Co3O4 SA was measured based on home-made double-arm measurement system, which showed that its modulation depth was 5.6%. It shows that high-quality Q-switched mode-locking (QML) with a repetition rate of 5.2 MHz and a pulse width of 1.41 ps can be obtained when the pump power reaches 251.1 mW. After further improvement of the EDFL, we obtained a stable continuous wave mode-locked (CWML) pulse with a pulse duration of 1.35 ps. This is the first demonstration of a versatile pulse fiber laser based on a NiO-Co3O4 polyhedral SA. This work shows that the novel NiO-Co3O4 polyhedron is expected to serve as a highly potential nonlinear optical element in the fields of ultrafast photonics, light modulators and photodetectors.

Low-noise compact fiber laser based on nonlinear polarization evolution in an all-polarization-maintaining figure-8 cavity

Low-noise compact fiber laser based on nonlinear polarization evolution in an all-polarization-maintaining figure-8 cavity

GaAs-chip-based mid-infrared supercontinuum generation

The mid-infrared spectral region opens up new possibilities for applications such as molecular spectroscopy with high spatial and frequency resolution. For example, the mid-infrared light provided by synchrotron sources has helped for early diagnosis of several pathologies. However, alternative light sources at the table-top scale would enable better access to these state-of-the-art characterizations, eventually speeding up research in biology and medicine. Mid-infrared supercontinuum generation in highly nonlinear waveguides pumped by compact fiber lasers represents an appealing alternative to synchrotrons. Here, we introduce orientation-patterned gallium arsenide waveguides as a new versatile platform for mid-infrared supercontinuum generation. Waveguides and fiber-based pump lasers are optimized in tandem to allow for the group velocities of the signal and the idler waves to match near the degeneracy point. This configuration exacerbates supercontinuum generation from 4 to 9 µm when waveguides are pumped at 2750 nm with few-nanojoule energy pulses. The brightness of the novel mid-infrared source exceeds that of the third-generation synchrotron source by a factor of 20. We also show that the nonlinear dynamics is strongly influenced by the choice of waveguide and laser parameters, thus offering an additional degree of freedom in tailoring the spectral profile of the generated light. Such an approach then opens new paths for high-brightness mid-infrared laser sources development for high-resolution spectroscopy and imaging. Furthermore, thanks to the excellent mechanical and thermal properties of the waveguide material, further power scaling seems feasible, allowing for the generation of watt-level ultra-broad frequency combs in the mid-infrared.

Investigating the Impact of SMF on Brillouin Fiber Laser Performance

Using erbium-doped fiber, a steady Q-switched erbium-doped laser (EDFL) was successfully demonstrated. With a 150 m of Single Mode Fiber to generate the Brillouin Fiber Laser and increase the non-linearity inside the cavity. In the absence of a Brillouin pump, a compact Brillouin fiber laser (BFL) is realized by combining an Erbium Doped Fiber (EDF) and a Single Mode Fiber (SMF), which serve as both the Brillouin and linear gain media. It is accomplished by self-Brillouin production in a laser cavity from 4.5 m of EDF and 150 m of SMF with strong nonlinearity. The SMF inside the ring cavity was used to generate self-generating BFL. The BFL in the linear cavity produced more Brillouin stokes at a lower pump threshold. In the experiments, the average of spacing is 0.088 nm was generated at the EDF pump power of 93.468 to 259.493 mW for the 150 m of SMF. This compact BFL has total cavity length (160.34 m). Eventually, this is the most recent gain medium length recorded for Brillouin erbium fiber laser production without the use of a Brillouin pump.

High ytterbium concentration Yb/Al/P/Ce co-doped silica fiber for 1-µm ultra-short cavity fiber laser application.

We demonstrate a high ytterbium concentration Yb/Al/P/Ce co-doped silica fiber by conventional modified chemical vapor deposition (MCVD) technology and solution doping process. The fiber has a Yb concentration of about 2.5 wt%, and the corresponding core absorption coefficient is measured to be ∼1400 dB/m at 976 nm. The gain coefficient was measured to be approximately 1.0 dB/cm. It is found that the Yb/Al/P/Ce co-doped silica shows a lower photodarkening-induced equilibrium loss of 52 dB/m at 633 nm than the Yb/Al/P co-doped silica fiber of 117 dB/m. Using the heavily Yb3+-doped silica fiber, a compact and robust ultrashort cavity single-frequency fiber laser was achieved with a maximum output power of 75 mW and a linewidth of 14 kHz. Furthermore, a compact passively mode-locked fiber laser (MLFL) with a repetition rate of 1.23 GHz was also proposed using our developed Yb-doped fiber. The laser properties of the proposed lasers were systematically investigated, demonstrating the superior performance of this fiber in terms of photodarkening resistance and ultrashort-cavity laser application. Furthermore, utilizing an all-fiber structure based on silica-based fiber offers the significant advantage of high stability and reliability.

Low Threshold and Robust Ultrafast Pulses from Freestanding‐Growth 2D Quaternary BiCuSeO

AbstractSaturable absorber is a key component in ultrafast pulsed laser systems, which are pivotal in ultrafast physics, high‐speed communication, etc. 2D materials appear to be superior candidates as saturable absorbers for compact pulsed fiber lasers in recent years due to their wide band response and ease of integration. However, the integration of mode‐locked devices inevitably involves contamination or polymer in the interface between the layered saturable absorber and the fiber, which contributes to a high start‐up threshold for the ultrafast pulsed lasers. This study develops an on‐fiber femtosecond laser with 2D narrow‐gap semiconducting BiCuSeO as a saturable absorber by a fully dry integration process thanks to the controllable growth of freestanding quaternary BiCuSeO nanoflakes. The corresponding thermodynamic growth mechanism is systemically revealed by electron microscopy and bind‐energy calculation. An electrostatic‐force‐assisted transfer method is developed to avoid damage or chemical contamination. The BiCuSeO‐based femtosecond laser shows decent output performance (pulse width, signal‐noise ratio and repetition rate are 395 fs, 61 dB, 17.1 MHz) with an ultra‐low threshold of 30 mW. The strategy of controllable growth of free‐standing 2D material facilitates a clean interface between the saturable absorber and fibers, which is favorable for high‐performance ultrafast photonic devices.

All-polarization-maintaining dual-comb fiber laser with mechanically shared cavity configuration and micro-optic component

An all-polarization-maintaining dual-comb fiber laser with a mechanical shared-cavity configuration was demonstrated. The laser cavity configuration was simplified and downsized using the micro-optic component of a saturable absorber mirror and a wavelength-division multiplexer. A high relative frequency stability was achieved with an Allan deviation of 0.02 Hz. Further, the all-polarization-maintained fiber-based configuration facilitated an integrated phase noise of the relative beat note between dual-frequency combs of 378 rad (10 Hz−1 kHz) and 9.0 rad (100 Hz−1 MHz). The simple, compact, and robust dual-comb fiber laser yielded highly mutually coherent dual-optical frequency combs without active servo control, and significantly simplified dual-comb spectroscopy.

One-Point and Multiline Calibration Fiber-Optic Laser-Ablation Spark-Induced Breakdown Spectroscopy for Quantitative Analysis of Elements in Aluminum Alloys

Rapid and accurate analysis of element concentrations in aluminum alloys is crucial due to their widespread use in modern industry. This paper proposes a one-point and multiline calibration fiber-optic laser-ablation spark-induced breakdown spectroscopy (OP-MLC FO-LA-SIBS) for the quantitative analysis of elements in aluminum alloys. The experimental system utilizes a compact fiber laser as the laser-ablation source and spark discharge to enhance the atomic emission. A portable multichannel fiber spectrometer is used to quickly collect spectra in the nongated mode. The concentrations of four elements (Mg, Cr, Cu, and Mn) in four aluminum alloy samples were calculated using the simple and efficient OP-MLC method, which involves taking another sample with a similar matrix as the standard sample. The average relative errors (AREs) for Mg, Cr, Cu, and Mn were 6.38%, 28.09%, 21.92%, and 18.97%, respectively. When the certified concentrations are greater than 0.02 wt.%, the ARE is only 13.04%. The OP-MLC FO-LA-SIBS system is compact, features simple spectra processing, and offers effective measurement, providing a convenient method for rapid and efficient quantitative analysis of elements in aluminum alloys in industrial production.

High-gain fluoro-sulfo-phosphate-based active fiber for compact low-threshold kilohertz-linewidth single-frequency fiber laser

Single-frequency fiber lasers (SFFLs) are of pivotal importance across optical communication, scientific research and national defense due to their excellent beam quality, long coherent length and low noise. However, the development of high-gain rare-earth-doped glass fibers, which are the key medium used in the SFFLs, remains a critical scientific challenge. To address this issue, we design and fabricate a single-mode fluoro-sulfo-phosphate-based Er3+/Yb3+-codoped glass fiber (denoted as FSP-EYDF). The gain properties and laser performance of the FSP-EYDF have been investigated comprehensively. The results show that the small signal gain coefficient of the home-made FSP-EYDF can reach 4.7 dB/cm at 1535 nm, which is three times higher than that of the silica glass fiber. A short piece of FSP-EYDF with a length of only 1.6 cm has been utilized as a gain medium to support an SFFL operating at 1534.4 nm, which has a threshold of ∼18 mW and a linewidth of 3.15 kHz. This study indicates that high-gain FSP fibers are promising candidates for compact low-threshold narrow-linewidth SFFLs.

Optimized segmented cladding fiber for extreme large mode area using latin hypercube sampling

In this paper a new design of octo-wing segmented cladding fiber (SCF) with a uniform core containing a ring and a non-uniform double cladding was proposed and optimized. The Latin hypercube sampling was applied to generate design cases as the input values for estimation of the objective functions as the output variables. Three physical parameters of the core assisted ring: thickness, radius, and refractive index difference were selected as the design variables. Twenty different design cases were numerically simulated by finite element method. To optimize the effective mode area (EMA) as the objective function, response surface methodology was applied. The fiber offers the single mode operation with a confinement loss ratio of over 100 between the fundamental mode (FM) and the higher order mode (HOM). Operating at the wavelength of 1.550μm, the EMA is significantly enlarged to about 884μm2. We have investigated the properties of the proposed optimized ring assisted SCF (RA-SCF) in terms of confinement losses of FM and first HOM considering a perfect matched layer. The proposed RA-SCF provides the potential applications in compact high power fiber lasers.