Yb-doped Fiber Laser Operating Research Articles

Implementation or Suppression of the Collective Lasing of the Laser Channels at the Intracavity Spectral Beam Combining

The spectral and spatial output parameters of a two-channel, Yb-doped fiber laser operating in the intracavity spectral beam combining mode were investigated. We showed that by using active media with slightly different gain spectra, it is possible to implement either the spectral combining mode of the independent laser channels or the mode of collective lasing of the channels. The difference in the gain spectra of the active media was realized due to the difference in the threshold inverse population in the Yb-doped fibers.

Demonstration of kilowatt monolithic Yb-doped fiber laser operation near 980 nm.

In this Letter, to the best of our knowledge, the first kilowatt monolithic Yb-doped fiber laser operating near 980 nm is demonstrated. The fiber laser is achieved with the help of an all-fiber amplifier fabricated with a 105/250-µm core/cladding-diameter double-cladding Yb-doped fiber. With 11-W seed light, about 1.11-kW output power was obtained with 65.3% slope efficiency. The center wavelength was around 978 nm with a 10-dB bandwidth of about 0.6 nm. About 34-dB suppression of 1030-nm amplified spontaneous emission was realized, and the output beam quality (M2 factor) was about 16.2 at maximum output power. Better beam quality can be expected by optimizing the seed light and active fiber. This work can provide significant guidance for the study and designation of high-power fiber lasers operating near 980 nm and other three-level fiber sources.

Investigation into the impact of the recovery time of a saturable absorber for stable dissipative soliton generation in Yb-doped fiber lasers.

In this study, we conduct a numerical evaluation of the impact of the recovery time of a saturable absorber (SA) on the output performance of an Yb-doped fiber laser operating in the dissipative soliton regime. Particularly, we evaluate the output pulse characteristics, such as the pulse width, spectral bandwidth, pulse peak power, and pulse energy depending on the change in recovery time. Applying a too-slow SA recovery time above a certain critical value is shown to make the output pulse unstable and broken. Furthermore, we demonstrate that there is an optimum recovery time range for stable dissipative soliton pulse generation, depending on the cavity dispersion and modulation depth of the SA. Further, we perform an additional numerical simulation of the pulse compression to demonstrate the relationship between the output dechirped pulse width and SA recovery time. The optimum approach for the generation of the shortest dechirped pulses in the dissipative soliton regime will be to construct a fiber laser cavity with a small normal cavity group velocity dispersion and use an SA with an appropriate recovery time.

Generation of dissipative soliton resonance in a fiber laser based on a nonlinear optical loop mirror

We experimentally demonstrate generation of mode-locked pulses in dissipative soliton resonance (DSR) regime. The DSR pulses are obtained from a passively mode-locked figure-8 Er:Yb doped fiber laser operating in large net anomalous dispersion regime. The modelocked laser emission is based on a polarization-imbalanced nonlinear optical loop mirror (NOLM), acting as artificial saturable absorber. Stable square DSR pulses, obtained by carefully adjusting the NOLM properties, increase their duration from 2.47 ns to 46.52 ns as the pump power is increased from 0.68 to 6.31 W. With the maximum pump power launched, average output power of 73.95 mW with pulse energy of 53.39 nJ is achieved.

Harmonic dissipative soliton resonance in an Yb doped fiber laser with 110 W all fiber polarization-maintaining amplifier

The formation of harmonic dissipative soliton resonance (DSR) is experimentally investigated in an Yb-doped fiber laser operating in large normal dispersion regime. The DSR is observed at a fundamental frequency of 221 KHz, which delivered square-shaped with of 18.7–98.5 ns and single pulse energy of 0.25 μJ at 1056 nm. By adjusting the PCs, the DSR square pulses could be split into their harmonic mode-locked (HML) counterparts. These experimental results provide a new viewpoint for the further understanding of the mechanism and characteristics of HML square pulses. Based on a two-stage all-fiber PM master oscillator power amplifier (MOPA) system seeded by this oscillator, the pulses are amplified up to 110 W output power with the polarization extinction ratio (PER) of 18.7 dB at different frequencies ranging from 221KHz to 663 KHz and a record pulse energy of 0.51 mJ at the frequency of 221 KHz is achieved.

Ultraviolet-enhanced supercontinuum generation with a mode-locked Yb-doped fiber laser operating in dissipative-soliton-resonance region.

We experimentally demonstrate an all-fiber, ultraviolet-enhanced, supercontinuum generation in a specifically designed seven-core photonic crystal fiber pumped by a picosecond Yb-doped master oscillator power amplifier (MOPA). The MOPA source is seeded by a giant-chirped Yb-doped mode-locked fiber laser operating in the dissipative-soliton-resonance (DSR) region. The DSR is achieved by using a nonlinear optical loop mirror (NOLM) with a fundamental repetition rate of 4.5 MHz and a central wavelength of 1035 nm. An extremely wide optical spectrum spanning from 350 nm to 2400 nm is obtained with a total output power of 6.86 W.

Passively Q-Switched Yb-Doped Fiber Laser Operating at 1.06 μm with Two-Dimensional Silver Nanoplate as Saturable Absorber**Supported by the Foundation of Shandong Province under Grant No J13LN28, and the National Natural Science Foundation of China under Grant No 11304184.

A two-dimensional silver nanoplate is prepared with the seed-mediated growth method and is used for achieving pulse fiber laser operation. By controlling the dimension parameters of the silver nanoplate, the surface plasmon resonance absorption peak of the material is successfully adjusted to 1068 nm. Based on the silver nanoplate as a saturable absorber, a passively Q-switched Yb-doped fiber laser operating at 1062 nm is demonstrated. The maximum average output power of 3.49 mW is obtained with a minimum pulse width of 1.84 μs at a pulse repetition rate of 65.7 kHz, and the corresponding pulse energy and peak power are 53.1 nJ and 28.8 mW, respectively.

Diode-Pumped 1178-nm High-Power Yb-Doped Fiber Laser Operating at 125 C

We demonstrate a high-power Yb-doped fiber laser operating at 1178 nm based on commercial silica double-cladding fiber and laser diode (LD) pumping regime at 976 nm. It is experimentally proved that heating the active fiber is an efficient way to suppress amplified spontaneous emission (ASE) and to increase the parasitic lasing threshold in long-wavelength Yb-doped fiber lasers. By adopting output coupling fiber Bragg grating (OC FBG) with high reflectivity and heating the Yb-doped fiber to 125 $^{\circ}\text{C}$ , a record output power of 31 W is obtained, and the corresponding slope efficiency is $\sim$ 44% with respect to the pump power. To the best of our knowledge, it is the highest output power of Yb-doped fiber lasers, which adopt commercial double-cladding active fiber and operate in the range beyond 1160 nm. Furthermore, it is first experimentally proved that the parasitic lasing threshold is related to the power of the backward ASE and the length of the active fiber.

High-Energy Square Pulses in a Mode-Locked Yb-Doped Fiber Laser Operating in DSR Region

We report the experimental observation of high-energy square pulses in all-normal-dispersion passively mode-locked Yb-doped fiber laser under dissipative soliton resonance (DSR) condition using a nonlinear polarization rotation technique. The generated square pulses are mode locked with fundamental cavity repetition rate of 1.86 MHz. The maximum output average power and the corresponding pulse energy are 62.1 mW and 34 nJ, respectively. The output square pulses are wave-breaking-free and can be tuned in pulsewidth from hundreds of picoseconds to several nanoseconds by changing the pump power. The multistability of DSR in all-normal-dispersion cavity has been first demonstrated in experiment, which is in agreement with theoretical prediction. The observed experimental results will enhance the understanding of fundamental physics of DSR phenomenon.

Impact of dispersion on pulse dynamics in chirped-pulse fiber lasers

We report on a systematic study of an environmentally stable mode-locked Yb-doped fiber laser operating in the chirped-pulse regime. The linear cavity chirped-pulse fiber laser is constructed with a saturable absorber mirror as nonlinear mode-locking mechanism and a nonlinearity-free transmission-grating-based stretcher/compressor for dispersion management. Mode-locked operation and pulse dynamics from strong normal to strong anomalous total cavity dispersion in the range of +2.5 to −1.6 ps2 is experimentally studied. Strongly positively chirped pulses from 4.3 ps (0.01 ps2) to 39 ps (2.5 ps2) are obtained at normal net-cavity dispersion. In the anomalous dispersion regime, the laser generates average soliton feature negatively chirped pulses with autocorrelation pulse durations from 0.8 ps (−0.07 ps2) to 3.9 ps (−1.6 ps2). The lowered peak power due to the pulse stretching allows one to increase the double pulse threshold. Based on the numerical simulation, different regimes of mode locking are obtained by varying the intra-cavity dispersion, and the characteristics of average soliton, stretched-pulse, wave-breaking-free and chirped-pulse regimes are discussed.

Frequency doubling of Yb-doped fiber laser to 515 nm

Operation of Yb-doped fiber laser (YDFL) at short wavelengths (about 1030 nm) is known to be possible with relatively short active fibers. Frequency doubling of such a laser is studied. It is shown that, in contrast to conventional YDFLs, operating around 1080 nm, the short-wavelength YDFL does not exhibit significant spectral broadening induced by nonlinear effects. Thus, the generated spectrum remains narrower than the FBG reflection profile, which allows an almost twofold intracavity intensity enhancement. Consequently, the second harmonic generation in the KTP crystal placed inside the YDFL cavity appears more effective than the generation in the single-pass scheme by an order of magnitude. An output power of about 0.4 W at a wavelength of 515 nm is demonstrated.

Linearly polarized operation of Yb-doped fiber laser by Brewster's angle-polished fiber end

A new method to obtain linear polarization operation by Brewster's angle-polished fiber end is demonstrated. By using the special polarization operation technique together with introducing a narrow-linewidth fiber grating into the laser cavity, a cladding-pumped linear polarization and single-transverse-mode (M2<1.1) Yb-doped fiber laser with narrow linewidth whose full-width at half-maximm (FWHM) is less than 0.2 nm, is obtained in a simple configuration. The output power is up to 10 W which is continuouswave output at 1085 nm, and the slope eciency is 63% with respect to the coupled pump power and 75% with respect to the absorbed pump power, respectively. The measured 21-dB polarization extinction ratio does not degrade with the output power. The simplicity of such an approach is highly beneficial for a number of applications, including the use of a fiber laser for the nonlinear wavelength conversion (especially for the intracavity frequency doubling) and for the coherent and spectral beam combination.

Multiwavelength $Q$-switched Laser by Incorporating a LiNbO$_{3}$ Phase Modulator in Fabry–PÉrot Cavity

In this letter, we present a simple and compact laser cavity that can be used for Q-switching and multiwavelength oscillation. It is shown that a LiNbO3 phase modulator with relatively low driven voltage inserted into a Fabry-Perot cavity can act simultaneously as an effective component for suppressing the homogeneous line broadening, switching the Q-value of the laser cavity, and a polarizer. Multiwavelength operation of Yb-doped fiber laser is achieved by phase modulation. Q-switching is achieved due to the residual intensity modulation of the phase modulator, and the pulse performance is also impacted by the phase modulation amplitude. Three stable wavelengths with identical wavelength spacing of 3.3 nm and pulsed laser of 0.2 muJ per pulse energy at the repetition rate of 55.8 kHz are demonstrated. The full-width at half-maximum pulse duration is of 2 mus, and the polarization extinction ratio is >23 dB.

High-energy femtosecond Yb-doped fiber laser operating in the anomalous dispersion regime

We report on high-energy ultrashort pulse generation from a passively mode-locked ytterbium-doped large-mode-area photonic crystal fiber oscillator operating in the anomalous dispersion regime. In the single-pulse regime, the laser directly generates 880 mW of average power of sub-500 fs pulses at a repetition rate of 53.33 MHz, corresponding to a pulse energy of 16.5 nJ. Stable and self-starting operation is obtained by adapting the spot size at the saturable absorber mirror to the pulse evolution in the low-nonlinearity fiber. The approach presented demonstrates the scaling potential of fiber based short pulse oscillators towards the microJ-level.