Mode-locked Ytterbium-doped Fiber Research Articles

21 kW, 166 fs pulses from passive mode-locked ytterbium-doped fiber laser employing Bi2O2Te nanosheets as saturable absorber in 1 μm

21 kW, 166 fs pulses from passive mode-locked ytterbium-doped fiber laser employing Bi2O2Te nanosheets as saturable absorber in 1 μm

Switchable mode-locked ytterbium-doped fiber laser based on macrobending loss tuning of figure-eight knot fiber structure

Switchable mode-locked ytterbium-doped fiber laser based on macrobending loss tuning of figure-eight knot fiber structure

Sensitivity Improvements for Picosecond Ultrasonic Thickness Measurements in Gold and Tungsten Nanoscale Films

Picosecond ultrasonics, as a nondestructive and noncontact method, can be employed for nanoscale metallic film thickness measurements. The sensitivity of the system, which determines the measurement precision and practicability of this technique, is often limited by the weak intensity of the ultrasonic signal. To solve this problem, we investigate the distinct mechanisms involved in picosecond ultrasonic thickness measurement for two types of metals, namely tungsten (W) and gold (Au). For thickness measurement in W films, theory and simulation show that optimizing the pump and probe laser wavelengths, which determine the intensity and shape of the ultrasonic signal, is critical to improving measurement sensitivity, while for Au film measurements, where acoustic-induced beam distortion is dominant, the signal intensity can be optimized by selecting an appropriate aperture size and sample position. The above approaches are validated in experiments. A dual-wavelength pump–probe system is constructed based on a passively mode-locked ytterbium-doped fiber laser. The smoothing method and multipeak Gaussian fitting are employed for the extraction of ultrasonic time-of-flight. Subnanometer measurement precision is achieved in a series of W and Au films with thicknesses of 43–750 nm. This work can be applied to various high-precision, noncontact measurements of metal film thickness in the semiconductor industry.

Synchronously pumped mode-locked ultrafast ytterbium-doped fiber laser

Synchronously pumped mode-locking, which avoids the usage of saturable absorbers or intracavity modulators, is a promising technique to generate ultrashort pulses for industrial applications. However, because of the lack of all-fiber single-mode ultrafast pump sources, it is difficult to apply this technique in ytterbium-doped fiber lasers (YDFLs). To the best of our knowledge, this study has demonstrated a synchronously pumped mode-locked ultrafast YDFL for the first time. Based on a home-built 976-nm pulsed fiber laser as the pump, it generates dissipative solitons with a pulse duration of 31.3 ps and a repetition frequency of ∼ 27.95 MHz. The laser is developed with an all-polarization-maintaining architecture; therefore, it exhibits excellent environmental stability and self-starting capacity. Furthermore, we have also conducted experimental work for investigating the mechanism of this mode-locking technique. The results indicate that instead of the gain modulation effect, the pulsed pump-induced cross-phase modulation effect plays a dominant role in pulse shaping. This study demonstrates a potential strategy for realizing high-performance ultrafast fiber sources in the spectral regions without efficient modulators or saturable absorbers.

Narrow bandwidth spatiotemporal mode-locked Yb-doped fiber laser.

We report a narrow bandwidth spatiotemporal mode-locked (STML) ytterbium-doped fiber laser, based on a homemade carbon nanotube/polyvinyl alcohol composite film and the multimode interference filtering effect. The wavelength-tunable narrow bandwidth STML operations combined with different pulse states are achieved, including single pulse, multiple pulses, and harmonics. The 3-dB bandwidth at the single-pulse state is 103 pm, while at the harmonic state, it is as narrow as 26 pm. To give an insight into the generation of the narrow bandwidth STML pulses, numerical simulations are performed. Such a laser has a wide range of potential applications in fields of optical communication and optical measurement, as well as provides a favorable platform for studying the evolution dynamics of multimode solitons.

Mode-locked ytterbium-doped fiber laser with zinc phthalocyanine thin film saturable absorber

A stable mode-locked laser was demonstrated using a newly developed zinc phthalocyanine (ZnPc) thin film as passive saturable absorber (SA) in ytterbium-doped fiber laser (YDFL). The ZnPc thin film was obtained using a casting method and then inserted between the two fiber ferrules of a YDFL ring cavity to generate mode-locked pulses. The resulting pulsed laser operated at a wavelength of 1034.5 nm having a repetition rate of 3.3 MHz. At pump power of 277 mW, the maximum output power and pulse energy are achieved at 4.92 mW and 1.36 nJ, respectively. ZnPc has a high chemical and photochemical stability, and its significance for use as a potential SA in a mode-locked laser is reported in this work.Graphical

Gold Metasurfaces as Saturable Absorbers for All-Normal-Dispersion Ytterbium-Doped Mode-Locked Fiber Laser

Optical metasurfaces, i.e., thin planar structures with subwavelength metal or dielectric unit cells, have attracted great interest due to their intriguing capabilities of shaping light in both linear and nonlinear regimes. However, their saturable absorption properties and corresponding applications have so far been rarely exploited. Here we report on passively mode-locked ytterbium-doped fiber lasers utilizing saturable metasurfaces made of periodically arranged gold nanorods. Three 400-nm-period metasurfaces with gold nanorods of different lengths (from 210 to 240 nm) and plasmonic resonances (from 968 to 1044 nm) are fabricated and found to exhibit nonlinear absorption with decent modulation depths, facilitating the formation of mode-locking states at 1060 nm. The corresponding lasers generate typically mode-locked pulses with the duration of ∼ 62.3 ps, repetition rate of 10.33 MHz, and signal-to-noise ratio of ∼74 dB. Our experimental results demonstrate that the gold nanorod-based metasurfaces can be used as relatively broadband mode-lockers in the 1-μm-wavelength range.

Mode-Locked YDFL Using Topological Insulator Bismuth Selenide Nanosheets as the Saturable Absorber

Fiber lasers have long remained relevant for various applications worldwide in many industries. This paper presents a mode-locked ytterbium-doped fiber laser (YDFL) using our home-made topological insulator Bi2Se3 nanosheets (TI Bi2Se3) as the saturable absorber. The fabricated TI Bi2Se3 is transported to the end of the fiber ferrule using an optical deposition process, which is a key ingredient for initiating a pulsed fiber laser. With a pump power of 211.1 mW, the captured repetition rate and pulse width are 8.3 MHz and 6.2 ns, respectively. The length of the setup configuration is approximately 20 m, which corresponds to an output power measurement of 12.4 mW with a calculated pulse energy of 1.5 nJ. There are no significant Kelly sidebands, but the strong stability of the pulsed laser is defined by a high signal-to-noise ratio (SNR) of around 60.35 dB.

Generation of rectangular pulses in ytterbium-doped fiber laser based on a SnSe2 saturable absorber

Based on an as-prepared high-quality tin diselenide-polyvinyl alcohol (SnSe2-PVA) saturable absorber (SA), the stable rectangular pulses operating at the dissipative soliton resonance (DSR) region were observed in a passively mode-locked ytterbium-doped fiber (YDF) laser at the center wavelength of 1062.3 nm. The laser characteristics versus the pump power were investigated experimentally. As the pump power increased, the wave-breaking-free DSR pulse width varied from 20.5 ns to 44.7 ns. At the pump power of 365 mW, the maximum pulse energy of the DSR pulse is 0.928 nJ, corresponding to a signal to noise ratio (SNR) up to 74 dB. The results demonstrate the excellent saturable absorption performance of SnSe2 in generating the DSR pulses in fiber lasers.

All Polarization-maintaining Passively Mode-locked Ytterbium-doped Fiber Lasers, Behavior under Two Different Cavity Configurations

ABSTRACT In this work, we review our recent investigations on the behavior of a polarization-maintaining passively mode-locked ytterbium-doped laser in two different cavity configurations, namely: fiber-ring (FR) and Fabry-Perot (FP). Opposed to standard configurations that rely on the use of strong filtering within the cavity by including an ad hoc component with this purpose, here the filtering action is solely performed by the spectral overlapping of the different components within the fiber lasers. We found that the lack of a specific filter within the cavity does not deteriorate the performance as compared with previous works. We also report the changes in the output light pulses when the net dispersion of the cavity was varied. Additionally, different lengths of an ad hoc anomalous polarization-maintaining (PM) photonic crystal fiber (PCF) were used as intracavity dispersion compensator, to shift the operation of the laser from net-normal to the net-anomalous regime. The shortest output light pulses [6 ps (FR) and 8 ps (FP)] were obtained when the net-cavity dispersion approached zero. Since the obtained light pulses were far to be transform-limited, we also discuss the possibility of out-of-cavity recompression by using the same PM-PCF mentioned above. After recompression, pulse widths of 3 ps were obtained, limited by the available length of PM PCF.

All-fiber mode-locked ytterbium-doped fiber laser with a saturable absorber based on the nonlinear Kerr beam cleanup effect.

We theoretically and experimentally demonstrate a novel, to the best of our knowledge, mode-locked ytterbium-doped fiber laser with a saturable absorber based on the nonlinear Kerr beam cleanup effect. The saturable absorber was formed by a 2-m graded-index multimode fiber, and a single-mode fiber segment served as a diaphragm. With an all-normal-dispersion-fiber configuration, the laser generated dissipative soliton pulses with pulse duration of 26.38 ps and pulse energy more than 0.25 nJ; output pulses could be compressed externally to 615.7 fs. Moreover, the self-starting mode-locking operation of this laser exhibited a high stability with a measured signal-to-noise ratio of 73.4 dB in the RF spectrum.

Dual-wavelength rectangular pulses in a mode-locked ytterbium-doped fiber laser

We demonstrate dual wavelength rectangular pulses in an ytterbium-doped fiber laser in a simple, all-fiber standing wave cavity configuration. The laser cavity consists of a nonlinear optical loop mirror as a saturable absorber at one end and two fiber Bragg gratings at the other end at wavelengths of 1025 and 1055 nm. There are three distinct regimes of operation in the cavity with an increase in the pump power, one where only 1025 nm wavelength pulses appear, then both 1025 and 1055 nm pulses are supported in the cavity after that, only 1055 nm wavelength pulses are present in the cavity. In the intermediate pumping regime, two sets of pulses are supported in the cavity. These pulses move in the cavity at different speeds and on the cross-over there is no interaction in the pulses. The mode-locked pulses at the 1025 nm wavelength are polarized, whereas pulses corresponding to 1055 nm are nearly unpolarized. Pulses corresponding to both the wavelength bands exhibit a dissipative soliton resonance signature. The laser generates 60 mW total average output power at the maximum pump power of 260 mW at a ∼1.8 MHz repetition rate. The presented cavity mechanism can be utilized to generate various dual- or multi-wavelength mode-locked pulses.

Passively Q-switched mode-locked ytterbium-doped fiber laser based on an Fe3O4-nanoparticle saturable absorber

A passively Q-switched mode-locked ytterbium-doped fiber laser (QMYDFL) at 1084.4 nm using ferroferric-oxide (Fe3O4) nanoparticles (FONPs) as the saturable absorber (SA) is reported. The FONPs SA exhibits a large nonlinear saturable absorption property with the modulation depth of 6.6% at the laser wavelength of 1µm band. Stable passively Q-switched pulse train with the repetition rate increasing from 5.43 kHz to 59 kHz, the corresponding pulse duration reducing from 18 µs to 2.68 µs are achieved when the input pump power increases from 100 mW to 330 mW. The maximum single pulse energy can reach 181.6 nJ. Q-switched mode-locked (QM) phenomenon is also observed by adjusting the state of the polarization controller (PC). When the input pump power is 150 mW, stable QM pulse train occurs. By continuous increasing the pump power to 320 mW, the QM pulse trains with the repetition rate increasing from 17.1 kHz to 34.3 kHz, mode-locked pulse repetition rate of 11.1 MHz and pulse duration of 880 ps are achieved. The observed phenomenon is interpreted as a mutual interaction of dispersion, non-linear effect and insertion loss. This work provides a new mechanism for fabricating cheap QMYDFL with FONPs SA.

长腔被动锁模掺镱光纤激光器的方波脉冲产生

长腔被动锁模掺镱光纤激光器的方波脉冲产生

NOLM-based mode-locked Yb-doped fiber laser with wide-spectrum

In this paper, a mode-locked Ytterbium-doped fiber laser based on nonlinear optical loop mirror (NOLM) is proposed. The laser generates a wide-spectrum dissipative soliton resonance mode-locked pulse with strong stimulated Raman scattering. The fiber laser is pumped forward, and the fiber ring cavity contains double-cladding Yb-doped fiber, output coupler, polarization controller, polarization independent isolator and other elements. NOLM is connected with the ring cavity by through a 3dB beam splitter and 25m single-mode fiber. The total length of the eight-shape cavity laser is about 60meters. By adjusting the intra-cavity polarization controller, a stable dissipative soliton resonance mode-locked spike pulse can be achieved. The repetition frequency of the pulse train is 3.44MHz, which is consistent with the cavity length. The 3dB bandwidth of the spectrum reaches 70.6nm, and the 10dB bandwidth is close to 147.11nm. In this experiment, dissipative soliton resonance mode-locked pulses with wide spectrum and high pulse energy are realized by a traditional mode-locking method, which has wide application in many fields such as laser spectral detection and terahertz wave generation.

Passively mode-locked Yb-doped all-fiber oscillator operating at 979 nm and 1032 nm with the single wall carbon nanotubes as SA

We report on an all-fiber passively mode-locked ytterbium-doped (Yb-doped) fiber laser with single polymer composite saturable absorber (SA) based on the single wall carbon nanotubes (SWCNTs) with diameters of 0.8 nm. The SWCNTs are mixed with sodium carboxymethylcellulose (NaCMC) to form SWCNTs SA film. The non-saturable absorption coefficient, modulation depth and saturable intensity of the SWCNTs SA are measured to be 29%, 12% and 0.12 MW/cm2, respectively. By using the SWCNTs as SA, a passively mode-locked Yb-doped fiber laser has been achieved at 979 nm with pulse duration of 228 ps and repetition rate of 15.47 MHz. To our knowledge, this is the first time ever reported in an all-fiber Yb-doped mode-locked fiber laser using SWCNTs as SA at 980 nm, which overcome the difficulties of low gain and serious re-absorption effects in the quasi-three-level system. In order to verify the saturation absorption performance of the SWCNTs, mode-locking experiment in quasi-four-level system is also carried out around 1030 nm and the stable and uniform mode-locked pulses are obtained. A mode-locked fiber laser at 1032 nm is realized with a pulse width of 485 ps and repetition rate of 8.78 MHz. It is sufficiently manifested that SWCNTs with diameters of 0.8 nm have excellent saturable absorption performance as optical mode-locking elements in ultrafast photonic applications.

Investigation of stimulated Raman scattering in a mode-locked ytterbium-doped fiber amplifier setup

Studies on stimulated Raman scattering (SRS) in an ytterbium (Yb)-doped all-fiber amplifier setup seeded by a mode-locked all-normal dispersion Yb-doped fiber oscillator have been carried out. Oscillator pulses at 40 MHz repetition rate, centered at about 1060 nm having a spectral width of ~10 nm, were amplified in an all-fiber multi-stage amplifier setup in chirped pulse amplification configuration. We observed that the length of the fiber used as a stretcher plays a crucial role in SRS generation. Experimentally, 8.4 W power in the first SRS band at ~1120 nm was obtained from total amplifier output power of 10.8 W with a 30 m length of stretcher fiber, leading to as high as ~77% conversion efficiency. This is the highest average output power and conversion efficiency achieved without any external seed source at Stokes wavelength or with a synchronous pumping mechanism. Numerical simulations have also been carried out to show that there is an optimum stretcher fiber length for which maximum conversion of the amplifier power into the first SRS band takes place.

Mode-locked ytterbium-doped fiber laser based on offset-spliced graded index multimode fibers

We developed a passively mode-locked ytterbium-doped fiber laser based on offset-spliced graded index multimode fibers (OS-GIMFs), where OS-GIMFs play the role of saturable absorbers. The modulation depth of the saturable absorber is 15.28%, which significantly improves the performance of saturable absorber by adopting offset-spliced method. A stable mode-locked pulse train at 1040 nm with a 27.32 MHz repetition rate is generated when pump power reaches the threshold. The output pulse-width is a ∼11 ps and can be compressed to 980 fs by using a pair of gratings. The fiber laser is superior in terms of low cost, high damage threshold, and easy fabrication; thus, it has potential for application in ultrafast photonics and industrial processing.

Q-switched mode-locked ytterbium-doped fiber laser with radial polarization

A Q-switched mode-locked, radially polarized ytterbium-doped fiber laser was demonstrated. In the study, the combination of a c-cut YVO4 birefringent crystal and a single-lens was utilized as the intracavity polarization discriminator, and a semiconductor saturable absorber mirror was used as passive mode-locked element. A narrow band-pass filter was inserted into the cavity to stabilize the mode-locked pulses and lasing wavelength. At the absorbed pump power of 1.56 W, the output power was 202 mW, corresponding to slope efficiency of 22.8%. The repetition rate and width for Q-switched envelope were 60.5 kHz and 315 ns, respectively. The mode-locked pulses inside the Q-switched envelope had a repetition rate of 66.67 MHz, the pulse width of 163 ps and the largest single-pulse peak power of 975 W.

Yb-doped fiber laser mode-locked with Au nanocages/SiO2 saturable absorber

Au nanocages/SiO2 (Au-NCs/SiO2) are prepared through a seed-mediated growth method, and the performance is investigated in an all-fiber passively mode-locked ytterbium-doped fiber laser, for the first time. Its saturating intensity and modulation depth are measured to be about 0.461 MW/cm2 and 5.3%, respectively. With the Au-NCs/SiO2 saturable absorbers (SA) film, the pulse with the pulse duration of 1.116 ns and repetition rate of 32.02 MHz was generated at 1063.14 nm, under the pump power of 342 mW. And the corresponding average output power of 4.82 mW was obtained. These results indicate that Au-NCs/SiO2 has excellent saturable absorption properties with the potential for important applications in the field of ultra-short pulse lasers.