High-quality, ultrafast fiber lasers have long been favored by both research and industry for many desirable properties. Here, we present an Yb-doped fiber laser system by utilizing a directly spliced photonic crystal fiber to amplify a seed source, and sub-100 fs ultrashort pulses are obtained with an average power of 6.55 W and at a repetition rate of 100.15 MHz. The M2 factors are measured to be about M_x^2=1.13 an M_y^2=1.12, respectively. The standard deviation of output power over a 2.5-hour period is determined to be 0.72 % and no significant wavelength drifts or intensity fluctuations are observed. These results demonstrate the promising potential of this compact fiber laser system for both research and industrial applications.
Passively mode-locked fiber laser based on two-dimensional material MnPSxSey saturable absorber is studyed. By changing the doping ratio of S and Se, three magnetic materials, MnPS2.9Se0.1, MnPS2.8Se0.2 and MnPS2.7Se0.3, are obtained. The three materials were fabricated into sandwich absorbers, and stable mode-locked pulse was obtained in ytterbium-doped fiber lasers. The total length of the fiber laser is 88 m, and the corresponding repetition rate is 2.27 MHz. The signal-to-noise ratio of the three materials is all above 60 dB, indicating the stability of the mode-locking pulse. The experimental results show that MnPSxSey has good nonlinear optical modulation characteristics and optical switching ability, which has potential application value.
We experimentally demonstrate wavelength-tunable Self-Mode-Locking (SML) operation generated in an Optically Pumped Semiconductor Disk Laser (OP-SDL) with a straight cavity. The operation is achieved by insetting an etalon into the cavity, and wavelength tuning range of 11 nm can be achieved by adjusting the angle of etalon. After aligning the cavity carefully, stable self-mode-locking is obtained when the pump power was beyond 5 W, and the pulse period of 0.99 ns agrees well with the round-trip time determined by the optical cavity length of 148 mm. Meanwhile, the RF spectrum reveals a clean peak at the fundamental repetition rate of 1.01 GHz and the signal-to-noise ratio of the RF spectrum reaches 60 dB during the whole tuning process, indicating the stability of the pulse was quite excellent. Finally, we obtained a wavelength tunable SML optically pumped semiconductor disk laser. The experimental results prove that under the condition of adding an etalon in the cavity, the OP-SDL could remain a stable operation in a wider wavelength tuning range. This research is helpful to the development of wavelength tunable self-mode-locking optically pumped semiconductor disk lasers and hopes to obtain practical applications in related fields.
Ultrashort pulse lasers are widely used in laser spectroscopy, microwave measurements, high-speed sampling, medical diagnostics, communication systems, and many other fields. This work presents a tunable self-mode-locked semiconductor disk laser, which is based on the combination of the Kerr effect in the gain chip and the soft aperture formed by the overlap of pumping and laser spot. A linear resonator with a length of 93 mm is formed by the high reflectivity distributed Bragg reflector at the bottom of the gain chip and the external output coupler with 100 mm curvature radium. The mode-locking can be started by fine-tuning the size of the pump spot and the length of the resonator, and a stable self-mode-locked output can be achieved at 980 nm wavelength. Then, a thickness of 2 mm birefringent filter is inserted into the resonator at Brewster angle, and a continuous tuning of 37 nm wavelength was obtained by rotating the filter. The repetition rate of achieved stable mode-locked pulse train at 980 nm is 1.6 GHz, the pulse width is 4.3 ps, the maximum output power is 467 mW, and the corresponding peak power is 68 W.
Taking advantage of the technology of dispersive Fourier transform (DFT), we experimentally observed the evolutionary dynamics of convention solitons(CSs) in a simplified Erbium-doped fiber laser. The periodic beating behavior that occurs during the build-up and disappearance of conventional solitons was discovered in a nonlinear polarization rotation (NPR) fiber lasers. We suggest the reasonable assumption that the periodic beating during the dynamic evolution may be a close connection with the modulation depth of the intracavity saturable absorber The results of this study can deepen researchers' understanding of the evolution of CSs and provide additional judgment dimensions for optimizing the laser parameters.
We demonstrated a wavelength tunable mode-locked optically pumped semiconductor disk laser (OP-SDL) based on a SESAM. The wavelength tuning is achieved by incorporating an uncoated, 100 μm thick, fused silica etalon into the cavity of the laser, and the central wavelength of the pulse train varied from 972 nm to 977 nm. The average power of the mode-locked states measured at different wavelengths was about 80mW, meanwhile, the repetition rate was 1.2 GHz in the tuning process, and the signal-to-noise ratio of the radio frequency spectrum signal exceeds 50 dB, which illustrates that the laser can maintain a stable mode-locked state even the central wavelength varies greatly. In addition, we calculated the influence of etalon's related parameters on its transmittance. This research contributes to the development of wavelength-tunable mode-locked OP-SDLs and to gain practical applications in related fields.
The synchronization of ultrashort pulses is an important research content in laser technology and has important applications in the fields of pump probe, optical frequency metrology, optical coherent synthesis, and nonlinear optics, etc. In this paper, the mode locking of two Yb-doped fiber lasers is realized by nonlinear polarization rotation, and then two circulators are used to make both two laser beams propagate in a piece of fiber. By matching the cavity length of one laser to the other, and with the cross phase modulation of two laser beams in the shared single-mode fiber, two lasers are passively synchronized. Two lasers deliver picosecond pulses near 1.04 μm and 1.05 μm, respectively, and the repetition rate is locked around 38.1100 MHz.
Generation of noise-like pulses in a nonlinear Yb-doped fiber amplification system is investigated in three pump configurations: forward pump, backward pump, and bidirectional pump, respectively. Noise like pulse with a pedestal width as short as 2.99 ps is obtained. The average powers, pulse spectra and auto-correlation traces are measured. The characteristics of noise-like pulses generated in different pump powers and pump configurations are discussed.
A stable Yb doped pulsed fiber nonlinear amplifier are demonstrated. A noise like pulse with the pulse width of 84 fs is generated after compressing by the grating pair. The peak power is 12 kW and the signal-to-noise ratio of RF spectrum is over 80 dB. This experiment is expected to be applied in nonlinear imaging and other fields.
Q-switched Yb-doped fiber lasers based on 2H-MoTe2 was demonstrated in this paper. The saturable absorber (SA) was a film mixed by 2H-MoTe2 and polyvinyl alcohol (PVA). The modulation depth of the SA was 21.4% and the saturable optical intensity was 10.3 GW/cm-2. When the 2H-MoTe2 film was inserted into the cavity, the Q-switched pulses were obtained. To the best of our knowledge, this is the first time to realize the generation of Q-switching in a Yb-doped fiber laser based on 2H-MoTe2-PVA film.
Dark soliton is a promising tool in communication systems for its ability to preserve its good shape. This paper demonstrates the generation of dark soliton in an Yb-doped fiber laser with a compact figure-9 resonator based on the principle of nonlinear amplifying loop mirror. In this laser, when the polarization controller is located in the gain fiber or single-mode fiber, the generation of dark soliton, bright soliton and bright-dark soliton pair, as well as the transformation between them, can be realized. This experiment provides the evidence on the generation of dark soliton at 1 μm, and the results show that the figure-9 fiber laser may obtain dark soliton, bright soliton or bright-dark soliton pair by simply adjusting the PC, which is helpful to obtain dark-soliton pulses in fiber lasers.
The rectangular noise-like pulse (NLP) and dissipative soliton resonance (DSR) were generated in a thulium-doped fiber laser based on a nonlinear optical loop mirror (NOLM). The NLP and DSR pulses could be switched in the fiber laser by properly manipulating the intracavitary polarization controller (PC). The two different states are investigated by using the optical spectrum and radio frequency spectrum. The center wavelength of NLP is 1930.11 nm with the 3-dB bandwidth of 12.19 nm, and aforesaid parameters of DSR is 1944.04 nm, 10.36 nm, respectively. The radio frequency spectrum of the NLP pulse has two sub-peaks obviously, corresponding to the unstable long pulse train in the time domain. These findings may contribute to distinguish two rectangular pulses and lucubrate the dynamics of the rectangular pulses.
Passively mode-locked optically pumped vertical external cavity surface-emitting lasers (OP-VECSELs) have unique properties, such as excellent beam quality, high-average output power and high repetition rate. Many applications, including frequency comb and supercontinuum, require pulses in the femtosecond regime. A numerical model in the femtosecond regime is essential to understand the pulse formation mechanism. In this paper, we present a numerical model of passively mode-locked VECSELs in the femtosecond regime. We analyze the influence of gain parameters, such as small-signal gain, saturation energy, and the gain bandwidth on the pulse characteristics. The results of the simulation can provide a direction for designing the gain chip.
We demonstrated the noise-like pulse (NLP) generation in an erbium (Er) doped fiber laser at 1560 nm based on 2HMoTe2. The saturable absorber (SA) was a film mixed by 2H-MoTe2 and polyvinyl alcohol (PVA). The moudulation depth of the SA was 21.4% and the saturable optical intensity was 10.3 GW/cm2. When the 2H-MoTe2 film was inserted into the cavity, the stable NLPs with 3-dB spectral bandwidth of 2.44 nm and the repetition rate of 33.7 MHz were obtained. The autocorrelation (AC) trace of NLP has a 1.14 ps spike and a 71 ps pedestal. When the pump power was 600 mW, the maximum output power was 26.09 mW. To the best of our knowledge, this is the first time to realize the generation of NLP mode locking in an Er-doped fiber laser based on 2H-MoTe2-PVA film.
An all-normal-dispersion WS2 mode-locked Yb-doped fiber laser was demonstrated. The saturable absorber (SA) is a piece of WS2-PVA film which is sandwiched between two fiber connectors. The modulation depth and saturation intensity of the WS2-PVA film were 1.78% and 81 MW/cm2 , respectively. When the WS2-PVA film was utilized in the laser cavity, stable mode locking occurred with the pump power of 140 mW. The maximum single pulse energy was estimated to be more than 2.82 nJ. Besides, in order to know more about the influence of the SA on the generation of ultrashort pulses, the dynamic evolution of mode-locked lasers with the parameters of SAs was studied by solving the Ginzburg-Landau equation. Thus the high pulse energy could be reached.
The band structure of InGaAs strained quantum wells are investigated using 8×8 Luttinger-Kohn Hamiltonian including conduction band, heavy hole, light hole, spin-orbit splitting and strain effects. The energy dispersion curves of conduction band and valence band, the material gain spectra of TE and TM mode are given, respectively. The variation of peak gain with carrier density, temperature, well width, and Indium composition of InGaAs are calculated. The calculations show that the higher the In composition of InGaAs and the thicker the well, the longer the emitting wavelength are. The higher carrier density and higher In composition lead to the higher peak gain.
We demonstrated the noise-like pulse (NLP) generation in an ytterbium-doped fiber (YDF) laser with tungsten disulphide (WS2). Stable fundamental mode locking and second-order harmonic mode locking were observed. The saturable absorber (SA) was a WS2-polyvinyl alcohol film. The modulation depth of the WS2 film was 2.4%, and the saturable optical intensity was 155 MW cm−2. Based on this SA, the fundamental NLP with a pulse width of 20 ns and repetition rate of 7 MHz were observed. The autocorrelation trace of output pulses had a coherent spike, which came from NLP. The average pulse width of the spike was 550 fs on the top of a broad pedestal. The second-order harmonic NLP had a spectral bandwidth of 1.3 nm and pulse width of 10 ns. With the pump power of 400 mW, the maximum output power was 22.2 mW. To the best of our knowledge, this is the first time a noise-like mode locking in an YDF laser based on WS2-SA in an all normal dispersion regime was obtained.
The output characteristics of the mode-locked thulium-doped fiber laser with MoS2 as saturable absorber are simulated based on rate equation and nonlinear Schrodinger equation. With small signal gain efficient as variable, the effect of pump power, length of gain fiber, doping concentration and other parameters on output characteristics are analyzed. The theoretical results show an optimum doping concentration or fiber length exists to obtain maximum gain and average output power for given doped fiber. In experiment a thulium-doped fiber laser is setup and the experimental output characteristics of the laser are compared with theoretical counterpart, as a result, theoretical results are well in consistence with experimental results.
The high energy noise-like pulses (NLPs) were experimentally investigated in a passively mode-locked erbium-doped fiber laser with a long ring cavity by using nonlinear polarization rotation technique. Large net normal group-velocity dispersion of the cavity is estimated as high as 6.46 ps2, which is beneficial to formation of high-energy pulses. With the total pump power of 970 mW (the pump powers of forward pump and backward pump are set at the value of 455 mW and 515 mW, respectively), a stable ultrahigh energy rectangular-shape pulse emission with the pulse duration of 35 ns was observed. The energy of square packet with a fundamental repetition rate of 141.6 kHz is as high as 840 nJ. The signal-to-noise is higher than 60 dB in RF spectrum. The feature of NLPs is confirmed by the coherent spike of autocorrelation trace. When the pump power is beyond 970 mW, the mode locking operation with fundamental repetition rate cannot be achieved despite of the large range variation of polarization controller (PC) settings. However, the forthorder harmonic mode locking can be observed, the square pulse packet duration still remains at ∼ 35 ns. The experimental results demonstrated that the ultrahigh energy NLPs is only realized at the condition of special physical parameters and it is restricted by the number and intensity of ultra short pulses within the envelope to some extent.
We experimentally demonstrated a Q-switched mode-locked (QML) and a continuous-wave mode-locked (CWML) ytterbium-doped fiber lasers with topological insulator: Bi2Se3 as saturable absorber (SA) in all normal dispersion regime. The Bi2Se3-SA is conventionally composited by embedding Bi2Se3 nanoplatelets into polyvinyl alcohol thin film, which provides a modulation depth of 7.6% and a saturation intensity of 38.9 MW/cm2. Based on this SA, with different cavity length, ytterbium-doped fiber laser can be operated at QML and CWML state, respectively. In the QML operation, a Q-switched envelope has the shortest pulse width of 1.12 μs and the tunable repetition rate from 96 to 175 kHz. The largest pulse envelope energy is 39.6 nJ, corresponding to average output power of 6.93 mW. In the CWML operation, an environmentally stable dissipative soliton laser pulse with pulse duration of ∼210 ps is obtained. The single pulse energy is 0.83 nJ with the repetition rate of 11.38 MHz at the wavelength of 1037 nm.
A model of 1.2μm Phosphorus doped Raman fiber laser is discussed. It is pumped by a 1.035μm high power
Yb-doped dual-cladding fiber laser. The coupled equations for forward and backward stokes waves are set up. An
approximate solution for the first –order Stocks laser is obtained by using ‘fsolve’ function in MATLAB which is simply
for writing and calculates fast. The relationships between energy conversion efficiency and the length of P-doped fiber,
the reflectivity of the output FLM are discussed respectively. And the laser system is optimized.
A ring-cavity synchronously-pumped optical parametric oscillator was investigated, which was pumped by a
self-mode-locked Ti:sapphire laser. A periodically poled KTiOPO4 crystal was used in the oscillator, and the parametric
operation was obtained. The wavelength of the signal wave covered from 1000 nm to 1500 nm. The signal wave was
successfully frequency doubled by inserting a nonlinear BBO crystal in the cavity. The wavelength of second harmonic
could be tuned from 550 nm to 650 nm freely by cavity-length tuning. The loss of the cavity and the threshold of the
pump power, a thin glass substrate is inserted into the cavity to couple output the light, then the output power is
measured for varying pump power, based on the measurement the loss in the cavity was discussed. Furthermore, the
characteristic of output pulses is also measured.
We describe a synchronously-pumped optical parametric oscillator (OPO) based on periodically poled KTiOPO4(PPKTP). The OPO was pumped by a self-mode-locked Ti:sapphire laser. Its signal wave covers from 1070 nm to 1375
nm, and could be tuned freely by cavity-length tuning, the corresponding idler wave covering from 1.9 μm to 3.2 μm in
the mid-infrared region. Red, green and blue visible light were also generated by intra-cavity sum frequency or
frequency doubling. The threshold was measured to be about 250 mW at 810 nm pump. A thin glass substrate was
inserted to the cavity for output coupling, and the maximal output power was measured to be 26 mW. We adopted ring
cavity and linear cavity experimentally. After optimization, the output characteristics of the ring cavity and linear cavity
were investigated respectively. The approach to improve the output efficiency was also discussed.
An Ytterbium-doped double-cladding fiber laser is demonstrated. The threshold of the pump power is about 1.1W. The
maximum output power is 9.9W at the wavelength of 1045nm when the pump power is 15.3W. The slope efficiency is
around 70%. We discuss an exact numerical model, with a shooting method to solve the power steady-state equations.
Numerical results about the output power as a function of the pump power are in good agreement with measurements.
We present a tunable, high beam quality and narrow linewidth semiconductor disk laser. The maximum output power is 160 mW, and the slope efficiency is 22% using a gain chip without any postprocess under room temperature. When a 40-µm uncoated glass etalon is employed to tune the wavelength, the maximum output power of 110 mW, the tuning range of ~10 nm, the narrow linewidth of 0.07 nm, and the M2 factor of 1.03 are obtained. The tunability of the laser is theoretically analyzed, and the results are in good agreement with experiments.
A 1043nm semiconductor disk laser with a diamond heatspreader is presented. 880mW continuous-wave output power is
produced using a 3% output coupler with the incident pump power of 5900mW. The slope-efficiency is 16.7% and the
optical- to-optical conversion efficiency is 14.9%. The effect of the diamond heatspreader on the laser is also analyzed.
Here we demonstrate a supercontiuum spectrum generated in a tapered fiber pumped by a Ti sapphire laser with 130fs
pulse width at 800nm centre wavelength. The tapered fiber with the diameter of 1.25μm and the length of 16cm was
made by using a tapered machine. The supercontiuum range is from 500nm to 900nm. We simulated the
supercontinuum with the nonlinear Schrodinger Equation and discussed the affecting factors. In some conditions, the
experimental results are agreed very well with the theoretical analyses.
Two independent self-mode-locked Ti:sapphire lasers were synchronized by a thin fused silica slab. The relative
carrier-envelope phase slip was directly detected by beat frequency measurement. A simple optical feedback model was
used to simulate the synchronization process.
A self-starting all-solid-state picosecond (ps) laser was demonstrated. Different with a standard cavity design with
semiconductor saturable-absorber mirror (SESAM), self-starting mode-locking was initiated by stretching the length of
arm to reduce the beam spot, which shows the output beam possess higher beam quality than standard one. With a 10%
output coupler, we achieved 1 W output power and 21 ps pulse duration at pump power of 4.5 W. High efficiency and
high beam quality show the merit of the ps-laser.
We report the experimental research on the measurement and controlling of carrier envelope phase offset (CEO) with a home-made femtosecond Ti:sapphire laser, the beat frequency with a signal to noise ratio of as high as 45 dB is obtained with standard self-referencing technique. Locking the beat signal to the TV-Rb frequency standard by a phase-locked loop electronic circuit, a simple compact frequency comb was established. To further control the CEO with the technology of differenced frequency generation, we develop an ultra-broadened bandwidth femtosecond Ti:sapphire laser by balancing the dispersion with chirped mirrors, spectrum of covering from 600 nm to 1050 nm was observed. It will enable us to measure and control the CEO without photonic crystal fiber.
Two independent femtosecond Ti:sapphire lasers are synchronized by using a new passive synchronization design. By
enhancing the intracavity cross-phase modulation (XPM), stable synchronization operation of remaining for more than 24
hours with a timing jitter of 0.4fs was demonstrated; the tolerance of cavity length mismatch is larger than 10 micrometers.
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