Ytterbium-doped Fiber Laser Research Articles

Sub-nanosecond gain-switched Ytterbium-doped fiber laser pumped by 1030 nm dissipative soliton resonance mode-locked fiber laser

In this work we report on a tandem pumped gain-switched Yb-doped fiber laser. We used an amplified dissipative soliton resonance mode-locked fiber laser with the wavelength of 1030 nm as a source of high repetition rate pulsed pump, incorporated with a CW diode laser at the wavelength of 976 nm in hybrid pump scheme. Sub-nanosecond narrow line-width gain-switched pulses with peak power of 10 kW at 1064 nm have been achieved. The line-width of the gain-switched laser is less than 0.06 nm and the repetition rate is 683 kHz.

高功率掺镱光纤振荡器: 研究现状与发展趋势

高功率掺镱光纤振荡器: 研究现状与发展趋势

Tandem-Pumped High-Power Ytterbium-Doped Fiber Lasers: Progress and Opportunities

Tandem-Pumped High-Power Ytterbium-Doped Fiber Lasers: Progress and Opportunities

Generation of Q-switched fiber laser at 1.0-, 1.55- and 2.0-µm employing a spent coffee ground based saturable absorber

Spent coffee ground (SCG) was demonstrated as saturable absorber (SA) for Wideband Q-switched fiber lasers generation. The SCG SA has a broad linear absorption that covers from 1000 nm to 2000 nm wavelength and a modulation depth of 30% at 1.55-µm region. Through purification process, the finer SCG powder is obtained, and be embedded with a polyvinyl alcohol for thin film formation. To realize Q-switching operation lasers, a fabricated SCG film was integrated into three different fiber laser cavities including ytterbium-doped fiber laser, erbium-doped fiber laser, and thulium-doped fiber laser. A peak wavelength has obtainable at 1031 nm, 1563 nm, and 1976 nm for 1-, 1.55-, and 2- µm regions, respectively. The shortest pulse width of 4.80 µs and maximum pulse energy of 0.152 µJ are observed from the YDFL cavity. RF spectrum shows the signal-to-noise ratio for all regions is above 35 dB, indicates a stable pulsing generation. Our technique opens the door for unlimited materials SA from environmentally friendly resources which contribute to sustainable effort.

Passively Q-switched Ytterbium-doped fiber laser using zinc phthalocyanine thin film as saturable absorber

This paper presents a ZnPc: PVA film as saturable absorber (SA) for Q-switched pulse generation at 1-micron region. The SA film was obtained by embedding the ZnPc into polyvinyl alcohol (PVA). It was inserted into an Ytterbium-doped fiber laser (YDFL) cavity to act as a Q-switcher. The Q-switching operation was realized at the center of wavelength of 1036 nm with the minimum pulse width of 2.2 μs. The highest repetition rate and the maximum pulse energy were obtained at 63 kHz and 91 nJ, respectively. A signal to noise ratio (SNR) as high as 49 dB was observed, which indicates a stable operation of Q-switching in the YDFL cavity. This is the first demonstration of the use of ZnPc as Q-switcher in 1-micron wavelength region. A stable and high energy Q-switched pulse was realized with the proposed SA, which was obtained with a low-cost fabrication process.

Self-sweeping ytterbium-doped fiber laser based on a fiber saturable absorber

Generally speaking, the self-sweeping effect relies on the dynamical grating formed in active fiber. Here, the normal self-sweeping was generated in a ytterbium-doped fiber which serves as a fiber saturable absorber and is introduced to the laser cavity by a circulator in this experiment. The sweeping rate and the sweeping range alter as usual, both of which can be controlled by the pump power. Further, a new self-pulse signal is observed and discussed, which shows both the grating feature and saturable absorption of YDFSA. Our work provides a new self-sweeping way and can act as a platform to further deeply study this effect.

Titania-carbon nanocomposite as a saturable absorber for generation passively ytterbium-mode locked pulses

Passively pulse dual-wavelength ytterbium-doped fiber laser (YDFL) around 1 μm utilizing titania–carbon nanocomposite (TiO2–C NC) thin film as the optical modulator is experimentally demonstrated. The TiO2–C NC thin-film reveals great nonlinear saturable absorption characteristics with a transmission difference of 24.06% at the lasing emission around the 1 μm region. Stable self-starting mode-locked emission with a pulse of ~8 ns and a repetition rate of 30.7 MHz was achieved at threshold exciting power of about 115 mW. By adapting the polarization controller (PC) together with the pump power, fundamental, third, and sixth harmonic frequencies can be switched to each other. The corresponding pulse durations to the third and sixth harmonic mode-locked were 6.8 and 1.8 ns, respectively. The corresponding maximum output power was 1.8 mW. This work opens up another way to build cost-effective, greatly stable optical modulators, and presents the option to build novel nanocomposite-based photonic devices with TiO2–C NC.

Ultrafast Yb-Doped Fiber Laser Using Few Layers of PdS2 Saturable Absorber.

Two-dimensional (2D) transition metal dichalcogenide (TMD) materials have exceptional optoelectronic and structural properties, which allow them to be utilized in several significant applications in energy, catalyst, and high-performance optoelectronic devices. Among other properties, the nonlinear optical properties are gaining much attention in the research field. In this work, a unique pentagonal TMD material, palladium disulfide (PdS2), is employed as a saturable absorber (SA) in an ytterbium-doped fiber (YDF) laser cavity and mode-locked laser pulse is generated. At first, liquid phase exfoliation is performed to prepare PdS2 nanoflakes. Afterward, the PdS2-nanoflakes solution was incorporated in the side-polished fiber (SPF) to form SPF-based PdS2-SA. By utilizing this SA, a highly stable mode-locked laser pulse is realized at pump power of 160 mW, which has a center wavelength of 1033 nm and a 3-dB spectral bandwidth of 3.7 nm. Moreover, the pulse duration, maximum power output and corresponding single-pulse energy were determined as 375 ps, 15.7 mW and 0.64 nJ, respectively. During the experiment, the mode-locked pulse remained stable till the pump power reached a value of 400 mW and, for the regulation of power, the slope efficiency is calculated at about 4.99%. These results indicate that PdS2 material is a promising nonlinear optical material for ultrafast optical applications in the near-infrared (NIR) region.

Passively Q-switched ytterbium-doped fiber laser based on a SWCNT@AFI saturable absorber

An all-fiber passively Q-switched ytterbium-doped fiber laser (YDFL) was successfully achieved by using a single-walled carbon nanotube (SWCNT) as a saturable absorber (SA). The SWCNT was fabricated by pyrolyzing tripropylamine in the one-dimensional channel of zeolite single crystal (ZnAPO-5, framework type code: AFI). Zn2+ metal cations were doped to promote the filling density and quality of the SWCNT. Subsequently, by incorporating the SA into an YDFL ring cavity, a stable Q-switched pulse train at 1039.4 nm with a repetition rate of 54.28 kHz was obtained when the pump power elevated to the starting threshold of 245 mW. It proved that this SWCNT@AFI SA can be used as an effective passively Q-switched for operation at 1.0 µm region.

Dark-line laser.

A laser is meant to emit coherent radiation at a particular wavelength. Here, we demonstrate a laser that is prohibited to emit at a particular wavelength, called a dark line in the emission background of its gain spectrum. Specifically, we installed a 150 µm thick etalon mirror on an ytterbium-doped fiber laser. The laser suffers from 100% loss at the resonance of the etalon and generates a dark line in its emission spectrum. The interplay among the etalon resonance, homogenous gain broadening, and gain competition allows wavelength tuning and multiple-color emission from the laser.

Development of a Femtosecond High-Power Ytterbium-doped Fiber Laser System and Study on Spiky Spectral Modulation in Highly Nonlinear Chirped-Pulse Fiber Amplifiers

We have developed and analyzed a femtosecond high-power fiber laser system based on chirped-pulse amplification. The system consists of a homemade femtosecond ytterbium-doped fiber oscillator, a fiber pulse stretcher, a pulse picker, three ytterbium-doped fiber amplifiers and a grating-based pulse compressor. A single-mode photonic crystal fiber with a large mode-field diameter of 30 µm is used in the final amplifier, and the special homemade mode-field adapter based on a graded refractive index fiber has been developed for the photonic crystal fiber. Pedestal-free pulses of 15 µJ are generated after pulse compression at a repetition rate of 500 kHz, and the pulse width is 300 fs. When small-core-size fibers are used at the final amplifier, the generation of spiky modulations in amplified spectra is observed. We analyze the physical origin of the spiky spectral modulation and investigate the effect of the spectral modulation on the pulse shape and contrast after pulse compression by numerical simulations.

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.

Raman suppression within the gain fiber of high-power fiber lasers.

We report the effective suppression of Raman emission in a monolithic ytterbium-doped fiber laser by the insertion of a chirped and tilted fiber Bragg grating (CTFBG) directly within the gain fiber of the laser. In comparison with a non-compensated filtered laser cavity for which the Raman threshold occurs at an output power of 1.54 kW, the insertion of a CTFBG within the gain medium leads to an increase in the Raman threshold by 260 W. We also demonstrate that the insertion of a CTFBG in between a laser cavity and a passive beam delivery fiber leads to an increase in the Raman threshold by 100 W with respect to the non-compensated case.

Passively Q-switched pulses from ytterbium-doped fiber laser (YDFL) using copper oxide (CuO) nanoparticles as a saturable absorber

A high pulse energy Q-switched ytterbium-doped fiber laser (YDFL) based on copper oxide (CuO) nanoparticles as a saturable absorber (SA) is demonstrated. The CuO nanoparticles have been fabricated into a thin film using a liquid-phase exfoliation method then it was integrated into a laser cavity to act as Q-switcher. The proposed Q-switched YDFL operates at a central wavelength of 1035.4 nm with a 3-dB bandwidth of 0.26 nm. The Q-switched laser has a repetition rate range from 57 kHz to 104 kHz by varying the pump power from 179 mW to 226.5 mW, while the pulse width was tuned from 4.5 µs to 2.2 µs. Relatively, high pulse energy around 0.192 µJ was achieved at an average output power of 20 mW. This laser with high pulse energy can be seen as a very promising pulsed laser source in many industrial and optical sensing applications. To the best of our knowledge, this is the first demonstration of a Q-switched fiber laser using CuO-SA in YDF.

Low-noise high-order Raman fiber laser pumped by random lasing.

Raman fiber lasers (RFLs) have been widely utilized in long-haul optical transmission systems as pump sources for distributed Raman amplification (DRA) to increase transmission distance and capacity. However, RFLs with relatively large temporal intensity fluctuations would deteriorate signal quality due to the transfer of relative intensity noise (RIN). In this Letter, a low-noise high-order RFL common cavity pumped by an ytterbium-doped random fiber laser (YRFL) is proposed and demonstrated for the first time, to the best of our knowledge. Stable 4th-order random Raman lasing operating at 1365 nm is generated with 8.9 W of output power, without use of a multi-stage master oscillation power amplification system. Thanks to the YRFL common-cavity pumping where a wavelength division multiplexer (WDM)-assisted fiber-loop mirror is used to generate stable 1090 nm ytterbium-doped random lasing and cascaded random Raman lasing simultaneously, the RIN of the 1365 nm RFL is suppressed as low as -120dB/Hz without any peak over a 0-100 MHz span. Furthermore, the output power and lasing wavelength of this RFL can be flexibly tuned by adjusting the laser diode pump power, high-reflectivity fiber Bragg grating center wavelength, and single-mode fiber length. Hence, such a low-noise high-order RFL paves a way for the development of novel tunable RFLs with stable temporal output, leading to potential replacement of conventional RFLs for DRA in long-haul optical transmission systems to achieve better performances.

Dissipative soliton generation from a large anomalous dispersion ytterbium-doped fiber laser.

Dissipative soliton (DS) is demonstrated in a large anomalous dispersion ytterbium-doped fiber laser. A chirped fiber Bragg grating is implemented into a figure-of-9 cavity to provide a large anomalous dispersion. A self-starting and stable DS operation is achieved with 3.5 nJ pulse energy and 12.9 ps pulse duration under a 26.4 MHz repetition rate. Numerical simulations reveal that the DSs presented here experience strong temporal, spectral, and chirp breathing in the cavity. Thanks to the characteristic chirp breathing, the output DS pulses can maintain a narrow spectral bandwidth of 0.17 nm. We believe that the laser design presented here has a lot of potential and could be an outstanding ultrafast seed laser solution for industrial applications including micromachining and hard-brittle material processing.

High-power few-cycle THz generation at MHz repetition rates in an organic crystal

Ultrafast terahertz (THz) spectroscopy is a potent tool for studying the fundamental properties of matter. Limitations of current THz sources, however, preclude the technique being applied in certain advanced configurations or in the measurement of, e.g., strongly absorbing samples. In response to this problem, here we demonstrate the generation of 1.38 mW broadband THz radiation at 10 MHz repetition rate by combining the highly efficient nonlinear organic crystal HMQ-TMS with ultrafast pump pulses generated using a simple and stable external pulse compression of a high power, near-infrared (NIR) femtosecond ytterbium-doped fiber (Yb:fiber) laser. Utilizing spectral broadening in a large core, polarization maintaining photonic crystal fiber and a pair of SF11 prisms, we achieve a tenfold pulse compression of the Yb:fiber laser, yielding compressed 0.35 µJ pulses with a full-width at half maximum pulse duration of 22 fs, exerting a peak power of 13.8 MW at a repetition rate of 10 MHz. THz generation through optical rectification of the NIR pulses is explored in two distinct thicknesses of the organic crystal, leading to a maximum conversion efficiency of ∼5.5 · 10−4, an order of magnitude higher than that achieved with inorganic nonlinear crystals, e.g., gallium phosphide, for similar pump parameters. The focused THz beam has a peak on-axis field strength greater than 6.4 kV cm−1 in unpurged atmosphere. We believe that our moderately strong-field THz source is well suited to a variety of applications in ultrafast THz spectroscopy, in particular THz-enabled scattering-type near-field, and scanning tunneling spectroscopy, where multi-MHz repetition rate sources are required.

Generation of passively Q‐switched ytterbium laser by using tungsten tri‐oxide film absorber

This study experimentally demonstrates a Q-switched fibre laser using a new tungsten tri-oxide (WO 3 )-based saturable absorber (SA). Using the drop and casting approach, we managed to prepare a thin film that contained WO 3 powders in polyvinyl alcohol. A small bit of the film was used to form an SA which was placed in a ytterbium-doped fibre laser cavity to generate a Q-switched laser. The laser, operating at 1063.78 nm, was realised at the threshold pump power of 85 mW with a repetition rate of 23.87 kHz and a pulse width of 5.56 μs. At the pump power of 147 mW, the laser produced the maximum pulse energy of 625 nJ, signal-to-noise ratio of 59 dB, the repetition rate of 39.79 kHz and pulse width of 2.37 μs. To the best of our knowledge, this is the first demonstration of using WO 3 SA to generate the pulse laser in the 1 μm region.

Thermal lensing effects and nonlinear refractive indices of fluoride crystals induced by high-power ultrafast lasers.

Thermo-optical and nonlinear property characterization of refractive optical components is essential for endoscopic instrumentation that utilizes high-power, high-repetition-rate ultrafast lasers. For example, ytterbium-doped fiber lasers are well suited for ultrafast laser microsurgery applications; however, the thermo-optical responses of many common lens substrates are not well understood at 1035 nm wavelength. Using a z-scan technique, we first measured the nonlinear refractive indices of CaF2, MgF2, and BaF2 at 1035 nm and found values that match well with those from the literature at 1064 nm. To elucidate effects of thermal lensing, we performed z-scans at multiple laser repetition rates and multiple average powers. The results showed negligible thermal effects up to an average power of 1 W and at 10 W material-specific thermal lensing significantly altered z-scan measurements. Using a 2D temperature model, we could determine the source of the observed thermal lensing effects. Linear absorption was determined as the main source of heating in these crystals. On the other hand, inclusion of nonlinear absorption as an additional heat source in the simulations showed that thermal lensing in borosilicate glass was strongly influenced by nonlinear absorption. This method can potentially provide a sensitive method to measure small nonlinear absorption coefficients of transparent optical materials. These results can guide design of miniaturized optical systems for ultrafast laser surgery and deep-tissue imaging probes.