Dispersion-managed Fiber Research Articles

Transient behaviors in a spectrum-tailored all-PM NALM mode-locked fiber laser.

We demonstrate an all-polarization-maintaining (PM) dispersion-managed mode-locked ytterbium-doped fiber oscillator based on a nonlinear amplifying loop mirror (NALM). Experimentally, three mode-locking regimes with distinct tailored spectra are achieved with carefully designed cavity setup and adjusted pump power. Using the dispersive Fourier transformation (DFT) technique, the real-time transition dynamics among these regimes are observed as the pump power decreases. It is revealed that the intracavity gain does not decrease continuously during the relaxation period of the gain fiber. Instead, it decreases first and then increases, ultimately leading to the overdriving of NALM. This is attributed to the increase in the population inversion rate of gain fiber under the remaining pump. The dynamic evolution of intracavity gain and non-monotonic transmission properties of NALM collectively induce chaotic pulsation during the transformation. This work not only provides a new perspective for the design and development of novel spectrum-tailored laser sources, but also deepens the understanding of the transient dynamics of ultrafast fiber lasers.

High-Power GHz Burst-Mode All-Fiber Laser System with Sub 300 fs Pulse Duration

An all-fiber low-repetition-rate SESAM mode-locked fiber oscillator combined with a dispersion-managed active fiber loop produces a flexible GHz burst-mode laser source. The high-power output is then produced by amplifying the GHz burst-mode laser source using an all-fiber chirped-pulse amplification system. Then, the laser is compressed using a grating pair compressor; a maximum amplified power of 97 W is obtained. This results in a compressed high power of 82.07 W with a power stability RMS of 0.09% and beam quality better than 1.2. Accurate dispersion control allows for the production of a high-quality pulse duration of 265 fs.

206 MHz fully stabilized all-PM dispersion-managed figure-9 fiber laser comb

High-repetition-rate optical frequency combs are useful for precision spectroscopy because of their high power per comb mode, but conventional high-repetition-rate lasers do not have a broad enough spectrum. In this study, a fully stabilized polarization-maintaining figure-9 mode-locked fiber laser with a high repetition rate of 206 MHz and a broad spectrum was demonstrated by employing simultaneous control of cavity dispersion and length. The laser exhibited a 3 dB spectral bandwidth of 88 nm and a compressed pulse width of 66 fs. Additionally, fCEO and frep phase locking were implemented, resulting in low (0.21 rad) in-loop carrier-envelope-offset frequency phase noise. To the best of our knowledge, this is the widest spectrum bandwidth and shortest pulse duration directly obtained from an all-PM figure-9 fiber laser oscillator to date. The combination of high repetition rate and broad spectral range makes this system very useful for a wide range of applications, especially in the field of precision spectroscopy.

Modulational instability in randomly dispersion-managed optical fiber links

Modulational instability in randomly dispersion-managed optical fiber links

Transient behaviors of pulse breaking and recovering in a dispersion-managed mode-locked Yb fiber laser

Various pulse regimes have been discovered in mode-locked fiber lasers with carefully designed cavity setups. However, the transitions between different types of stable pulse solutions are rarely observed in a laser with the same cavity configuration. Here, we report on the experimental observation of the transformation from stretched pulses (SPs) to dissipative solitons (DSs) in an all-polarization-maintaining dispersion-managed mode-locked Yb fiber laser for the first time. By means of the time-stretch dispersive Fourier transform technique, the temporal and spectral dynamics of transient behaviors from pulse breaking to pulse recovering are identified in real time. It is revealed that the overdriven nonlinear effect induced by pump increase triggers the wave breaking of SPs, and the improved net-cavity dispersion originated from wavelength shift helps the self-recovering of DSs. Numerical simulations validate the experimental observations and bring insights to the understanding of transient nonlinear dynamics in ultrafast fiber lasers.

Build-up dynamics of different pulse types in a dispersion-managed Yb-doped fibre laser

We present a dispersion-managed mode-locked ytterbium fibre laser based on the nonlinear polarization evolution technique. Four single-pulse states could be generated by changing group delay dispersion values from anomalous (−0.0038 ps2) to normal (0.051 ps2) with a grating pair. In the normal dispersion regime, the pulse width was gradually decreased with the decrease of the net dispersion. In the anomalous dispersion region, the typical soliton was obtained, which time-bandwidth product could be calculated as 0.526. In addition, the dynamics of four states were also investigated by using the dispersive Fourier transformation technique. Different pulse evolution dynamics were observed from chaotic state to mode-locking.

Estimation of Petermann I, Petermann II spot sizes for kerr-type nonlinear dispersion-shifted along with dispersion-flattened optical fibers in fundamental mode guidance applying a simple but accurate formalism

This paper reports simplified but accurate form of analytical expressions concerning the estimation of Petermann I and II spot sizes. Typical examples of dispersion-managed fibers for fundamental mode guidance with suitable [Formula: see text] numbers have been considered in our investigation. We employ the mathematical formulation in the estimation of Petermann spot sizes for the said fibers under the absence and existence of Kerr-type nonlinearity. Iteration technique is utilized in our investigation. Our predicted outcomes show excellent agreement with the precise numerical results found by complicated finite element method both in the absence and presence of Kerr-kind nonlinearity.

Flat visible spectrum by a genetic algorithm optimized photonic crystal fiber in the GHz comb spacing.

Coherent and flat supercontinuum (SC) sources are demanded for applications of metrology, spectroscopy, and bio-imaging. However, the process of SC generation is usually very complicated. We demonstrated a convenient and efficient method based on a genetic algorithm (GA). According to an objective spectrum, this algorithm could reverse-design the geometry of a fiber or waveguide without knowing the specific non-linear processes involved. Using this method, we designed a dispersion-managed photonic crystal fiber (PCF) for SC generation at 1 GHz comb spacing. With an input pulse of ∼150 fs, 450 pJ at 1050 nm, a 3 dB fluctuation spectrum ranging from 510 nm to 850 nm is obtained, which is absolutely fit to the calibration of an astronomical spectrograph.

Dynamic behaviors of special noise-like pulses and rogue waves in an L-band ultrafast fiber laser

We demonstrate a composite regime of the special noise-like pulses (NLPs) and rogue waves (RWs) in an L-band dispersion-managed fiber laser. Apart from stable ultrashort pulses, the fiber laser can easily generate unique NLPs with clear peak on broad spectrum at high pump power and proper polarization state. In this regime, these tiny pulses with irregular intervals experience random fluctuations, making the dynamic evolutions of these pulse envelopes look like the endless undulating mountains along the hundreds of intra-cavity roundtrips. In addition, the real-time observation based on the time-stretch technique shows that there are the unique lacking pieces and changeable pulse durations in this NLPs regime. Besides, the chaotic pulse packets with intensity fluctuations are observed at the proper condition, showing the typical statistical distribution with L shape, which can be called as the typical RWs. It is believed that these results will facilitate the further understanding of the nonlinear characteristics of the NLPs and RWs in ultrafast fiber lasers.

Sideband-free dispersion-managed Yb-doped mode-locked fiber laser with Gires–Tournois interferometer mirrors

High-order dispersion introduced by Gires–Tournois interferometer mirrors usually causes spectral sidebands in the near-zero dispersion region of mode-locked fiber lasers. Here, we demonstrate a sideband-free Yb-doped mode-locked fiber laser with dispersion-compensating Gires–Tournois interferometer mirrors. Both the simulation and the experiment demonstrate that the wavelength and energy of the sidebands can be tuned by changing the transmission coefficient of the output mirror, the pump power, and the ratio of the net cavity dispersion to the net third-order dispersion in the cavity. By optimizing these three parameters, the laser can generate a sideband-free, Gaussian-shaped spectrum with a 13.56-nm bandwidth at -0.0232 ps2 net cavity dispersion, which corresponds to a 153-fs pulse duration.

Dispersion-Managed Tm-Ho Co-Doped Ultrashort Pulse Fiber Laser Using Single-Walled Carbon Nanotube and Spectral Filter

In this paper, we have demonstrated a dispersion-managed, high-power, Tm-Ho co-doped ultrashort pulse fiber laser using a single walled carbon nanotube (SWNT) dispersed in polyimide film. An in-line type spectral filter was developed to control the output pulse spectra. Two SWNT films with different modulation depths were examined as a mode-locker. Normal dispersion fiber was used in the fiber laser oscillator, and dependence on net cavity dispersion was investigated. Passive mode-locking was achieved in a wide dispersion range, from −0.319 to +0.101 ps2. Stable soliton mode-locking operation and dissipative soliton mode-locking operations were observed. The pumping efficiency was ~3 times higher than that in a Tm-doped fiber laser with a similar configuration. The developed fiber laser showed self-start and stable operations, and this laser is useful for practical applications.

Axial dispersion-managed liquid-core fibers: A platform for tailored higher-order mode supercontinuum generation

Soliton-based supercontinuum generation is a powerful approach for generating light with the desired properties, although limited dispersion tuning capabilities remain a key challenge. Here, we introduce liquid-core fibers (LCFs) with longitudinally controlled dispersion of a higher-order mode, achieved by axial modulation of the liquid core diameter. This approach provides a versatile photonic platform with unique dispersion control capabilities that are particularly relevant to ultrafast, non-linear frequency conversion. Our tuning concept uses LCFs with anomalous dispersion at telecommunication wavelengths (TE01-mode) and relies on the strong dependence of dispersion on the core diameter. Non-monotonic, complex dispersion profiles feature multiple dispersive waves formation when launching ultrashort pulses. For example, this effect has been used to fill spectral gaps in fibers with linearly decreasing core diameter in order to spectrally smooth the output spectra. Our results highlight the potential of LCFs for controlling dispersion, particularly along the fiber axis, thus yielding novel dispersion landscapes that can reveal unexplored nonlinear dynamics and generate tailored broadband spectra.

Large dispersion-managed broadband high-energy fiber femtosecond laser system with sub 300 fs pulses and high beam quality output

We experimentally demonstrate a high-energy sub 300 fs polarization maintaining fiber chirped pulse amplification (CPA) system. The preamplifier is a monolithic fiberized system that uses two cascaded temperature-assisted dispersion-tuning broadband chirped fiber Bragg gratings (CFBGs) with a reflected bandwidth of 20 nm as stretchers. To make full use of the stretcher to lower the system’s nonlinearity accumulation, a homemade mode locked fiber laser with a spectral width of 14.8 nm (full width at half maximum) is selected as the seeder to offer a stretched pulse width of 1.69 ns. The main amplifier is based on a one-stage simple Yb:YAG single crystal fiber amplifier with an amplified output power of 40.6 W at a repetition rate of 200 kHz, and the beam quality is conserved in a single mode beam profile with beam quality of 1.246 and 1.142 in the horizontal direction and vertical direction, respectively. During amplification, the spectral gain narrowing effect is observed. To achieve the high-speed switch of the laser, an acoustical optical modulator (AOM) is inserted before the compressor to achieve high-speed turn-on/off control. The compressor is based on a diffraction grating pair with a groove density of 1600 line/mm to offer a dispersion match with the stretcher of the CFBGs. With the CFBG’s fine-tuned capacity of second-order dispersion and higher-order dispersion, the compressed average power of 29.6 W and pulse duration of 278 fs, corresponding to a pulse energy of 148 µJ and a peak power of 532 MW with ignoring the wings of the pulse, is obtained. The beam quality is well conserved after compression, and the beam quality is 1.250 and 1.196 in the horizontal direction and vertical direction, respectively. A power fluctuation of 0.1% (root mean square) and a beam pointing drift of 8.47 µrad/°C over 8 h are realized. This high peak power and high beam quality femtosecond laser is promising in science and industrial applications.

Symmetrical reversal transmission of Airy pulses in dispersion-managed fiber systems.

Based on the dispersion management technology, the transmission characteristics of Airy pulses in optical fiber systems are studied theoretically and numerically. The results show that the group velocity dispersion and third-order dispersion that change periodically along the transmission direction of the optical fiber can prolong the transmission of pulses. Under the action of periodically varying group velocity dispersion, the symmetrical reversal of the Airy pulse can be realized which the shape of the pulse keeps invariable and the tail converses after the inversion. When the periodic third-order dispersion effect is also considered, the periodically symmetrical reversal of the Airy pulse happens and the pulse can be regenerated periodically at the certain transmission distance. Adjusting the parameters of the third-order dispersion, the inversion position and the period can be manipulated. In addition, it is found that the tight focusing of the Airy pulse is also controllable.

Dispersion-managed Monolithic All Polarization-Maintaining Ultrafast Thulium-doped Fiber Oscillator

We report on our first results of a dispersion-managed monolithic polarization-maintaining ultrafast Thulium-doped fiber oscillator. The design incorporates only commercially available polarization-maintaining components and emits linearly polarized light with a polarization extinction ratio of over 17 dB . The observed optical pulse spectra with up to 10 nm width centered at 1961.5 nm beyond the water absorption lines support sub-1 ps pulse duration. The simple linear configuration and the wide spread availability of the used low cost polarization-maintaining fiber components makes the presented oscillator a valuable concept for an environmental stable seed source.

Large Dispersion-Managed Broadband High-Energy Fiber Femtosecond Laser System with Sub 300 Fs Pulses and High Beam Quality Output

Large Dispersion-Managed Broadband High-Energy Fiber Femtosecond Laser System with Sub 300 Fs Pulses and High Beam Quality Output

Nonlinearity optimization of dispersion-managed mode-locked Yb-doped fiber lasers with near-zero net cavity dispersion

Nonlinearity optimization of dispersion-managed mode-locked Yb-doped fiber lasers with near-zero net cavity dispersion

Design of a 10 W Level Dispersion-Managed High-Power Ultrafast Mid-Infrared Fiber Laser System

Design of a 10 W Level Dispersion-Managed High-Power Ultrafast Mid-Infrared Fiber Laser System

Maximisers for Strichartz inequalities on the torus

We study the existence of maximisers for a one-parameter family of Strichartz inequalities on the torus. In general, maximising sequences can fail to be precompact in , and maximisers can fail to exist. We provide a sufficient condition for precompactness of maximising sequences (after translation in Fourier space), and verify the existence of maximisers for a range of values of the parameter. Maximisers for the Strichartz inequalities correspond to stable, periodic (in space and time) solutions of a model equation for optical pulses in a dispersion-managed fiber.

2-MW peak-power pulses from a dispersion-managed fluoride fiber amplifier at 2.8 µm.

We report on a scheme of pulse amplification and simultaneous self-compression in fluoride fiber for generating a high-peak-power pulse at 2.8-µm wavelength. We find dispersion management plays a key role for the amplification and self-compression process. Through dispersion management with a Ge rod, pulse amplification and simultaneous pulse self-compression were realized in the small anomalous dispersion region. A 2-MW peak-power pulse was achieved through amplification and self-compression in Er:ZBLAN fiber, with pulse energy of 101 nJ and pulse duration of 49 fs. To the best of our knowledge, this is the highest peak power obtained from fluoride fiber at 2.8 µm, and will benefit a series of applications.