Showing papers on "Pulse duration published in 2018"
TL;DR: The experimental results demonstrated that the parasitic lasing as well as the transverse amplified spontaneous emission of the homemade 235-mm-diameter Ti:sapphire final amplifier were suppressed successfully via the temporal dual-pulse pumped scheme and the index-matching liquid cladding technique.
Abstract: We report on the laser pulse output of 339 J centered at 800 nm from a chirped-pulse amplification (CPA) Ti:sapphire laser system at the Shanghai Superintense Ultrafast Laser Facility. The experimental results demonstrated that the parasitic lasing as well as the transverse amplified spontaneous emission of the homemade 235-mm-diameter Ti:sapphire final amplifier were suppressed successfully via the temporal dual-pulse pumped scheme and the index-matching liquid cladding technique. The maximum pump-to-signal conversion efficiency of 32.1% was measured for the final amplifier. With a compressor transmission efficiency of 64% and a compressed pulse duration of 21 fs obtained for the sample light at a lower energy level, this laser system could potentially generate a compressed laser pulse with a peak power of 10.3 PW. The experimental results represent significant progress with respect to the CPA laser.
125 citations
TL;DR: In this article, the inverse spin hall effect in Fe/Pt bilayers on MgO and sapphire substrates was used for terahertz radiation generation.
Abstract: We report on generation of pulsed broadband terahertz radiation utilizing the inverse spin hall effect in Fe/Pt bilayers on MgO and sapphire substrates. The emitter was optimized with respect to layer thickness, growth parameters, substrates and geometrical arrangement. The experimentally determined optimum layer thicknesses were in qualitative agreement with simulations of the spin current induced in the ferromagnetic layer. Our model takes into account generation of spin polarization, spin diffusion and accumulation in Fe and Pt and electrical as well as optical properties of the bilayer samples. Using the device in a counterintuitive orientation a Si lens was attached to increase the collection efficiency of the emitter. The optimized emitter provided a bandwidth of up to 8 THz which was mainly limited by the low-temperature-grown GaAs (LT-GaAS) photoconductive antenna used as detector and the pulse length of the pump laser. The THz pulse length was as short as 220 fs for a sub 100 fs pulse length of the 800 nm pump laser. Average pump powers as low as 25 mW (at a repetition rate of 75 MHz) have been used for terahertz generation. This and the general performance make the spintronic terahertz emitter compatible with established emitters based on optical rectification in nonlinear crystals.
122 citations
TL;DR: In this paper, a type of microfiber-based MoTe2 SA fabricated by the magnetron-sputtering deposition (MSD) method was used for high-energy wave-breaking free soliton pulses.
Abstract: The pulse energy in the ultrafast soliton fiber laser oscillators is usually limited by the well-known wave-breaking phenomenon owing to the absence of a desirable real saturable absorber (SA) with high power tolerance and large modulation depth. Here, we report a type of microfiber-based MoTe2 SA fabricated by the magnetron-sputtering deposition (MSD) method. High-energy wave-breaking free soliton pulses were generated with pulse duration/pulse energy/average output power of 229 fs/2.14 nJ/57 mW in the 1.5 μm regime and 1.3 ps/13.8 nJ/212 mW in the 2 μm regime, respectively. To our knowledge, the generated soliton pulses at 1.5 μm had the shortest pulse duration and the highest output power among the reported erbium-doped fiber lasers mode locked by transition metal dichalcogenides. Moreover, this was the first demonstration of a MoTe2-based SA in fiber lasers in the 2 μm regime, and the pulse energy/output power are the highest in the reported thulium-doped fiber lasers mode locked by two-dimensional materials. Our results suggest that a microfiber-based MoTe2 SA could be used as an excellent photonic device for ultrafast pulse generation, and the MSD technique opens a promising route to produce a high-performance SA with high power tolerance and large modulation depth, which are beneficial for high-energy wave-breaking free pulse generation.
118 citations
TL;DR: This work demonstrates the great potential for black phosphorus as an excellent candidate for long-term stable ultrashort pulse generation and delivers self-starting, 102 fs stable pulses centered at 1555 nm with 40 nm spectral bandwidth.
Abstract: We demonstrate a long-term stable, all-fiber, erbium-doped femtosecond laser mode-locked by a black phosphorus saturable absorber. The saturable absorber, fabricated by scalable and highly controllable inkjet printing technology, exhibits strong nonlinear optical response and is stable for long-term operation against intense irradiation, overcoming a key drawback of this material. The oscillator delivers self-starting, 102 fs stable pulses centered at 1555 nm with 40 nm spectral bandwidth. This represents the shortest pulse duration achieved from black phosphorus in a fiber laser to date. Our results demonstrate the great potential for black phosphorus as an excellent candidate for long-term stable ultrashort pulse generation.
98 citations
TL;DR: The high efficiency and approximately four-optical-cycle pulse duration mark an important milestone towards the realization of a compact, high power oscillator-based driver for XUV frequency combs and other nonlinear processes.
Abstract: In this work, we present a nonlinear spectral broadening and compression scheme based on self-phase modulation in bulk media inside a Herriott-type multipass cell. With this reliable approach, we achieved a spectral broadening factor of 22 while maintaining an efficiency of over 60% at an average input power of 100 W, and an excellent output beam quality with M2=1.2. The output pulses were compressed to 18 fs, with the broadest spectrum supporting a Fourier-transform limit of 10 fs. The high efficiency and approximately four-optical-cycle pulse duration mark an important milestone towards the realization of a compact, high power oscillator-based driver for XUV frequency combs and other nonlinear processes.
93 citations
TL;DR: Results indicate that WSe2 is a powerful competitor in the application of ultrashort pulse lasers, based on transition-metal dichalcogenides SAs.
Abstract: In this paper, a WSe2 film prepared by chemical vapor deposition (CVD) is transferred onto a tapered fiber, and a WSe2 saturable absorber (SA) is fabricated. In order to measure the third-order optical nonlinearity of the WSe2, the Z-scan technique is applied. The modulation depth of the WSe2 SA is measured as being 21.89%. Taking advantage of the remarkable nonlinear absorption characteristic of the WSe2 SA, a mode-locked erbium-doped fiber laser is demonstrated at 1557.4 nm with a bandwidth of 25.8 nm and signal to noise ratio of 96 dB. To the best of our knowledge, the pulse duration of 163.5 fs is confirmed to be the shortest compared with previous mode-locked fiber lasers based on transition-metal dichalcogenides SAs. These results indicate that WSe2 is a powerful competitor in the application of ultrashort pulse lasers.
90 citations
TL;DR: The multifarious performance comparisons indicate that the CVD-based MoSe2 saturable absorber with the tapered fiber structure has unique advantages not only in the generation of ultrashort pulses, but also in the optimization of laser stability.
Abstract: Two-dimensional materials have been widely used as optical modulator materials in mode-locked fiber lasers. In terms of the performance of the fiber laser, one with an ultrashort pulse and high stability has great commercial value. Herein, the MoSe2 grown by the chemical vapor deposition (CVD) method with high modulation depth, quality lattice structure and uniformity is successfully applied in a mode-locked erbium-doped fiber laser. The pulse duration and signal-to-noise ratio of the laser are 207 fs and 85 dB, respectively. The multifarious performance comparisons indicate that the CVD-based MoSe2 saturable absorber with the tapered fiber structure has unique advantages not only in the generation of ultrashort pulses, but also in the optimization of laser stability.
88 citations
TL;DR: This system represents a new average power record for thulium-doped fiber lasers (1150 W uncompressed) and ultrashort pulse fiber lasers with diffraction-limited beam quality, in general, even considering single-channel ytterbium- doped fiber amplifiers.
Abstract: In this Letter, we report on the generation of 1060 W average power from an ultrafast thulium-doped fiber chirped pulse amplification system. After compression, the pulse energy of 13.2 μJ with a pulse duration of 265 fs at an 80 MHz pulse repetition rate results in a peak power of 50 MW spectrally centered at 1960 nm. Even though the average heat-load in the fiber core is as high as 98 W/m, we confirm the diffraction-limited beam quality of the compressed output. Furthermore, the evolution of the relative intensity noise with increasing average output power has been measured to verify the absence of transversal mode instabilities. This system represents a new average power record for thulium-doped fiber lasers (1150 W uncompressed) and ultrashort pulse fiber lasers with diffraction-limited beam quality, in general, even considering single-channel ytterbium-doped fiber amplifiers.
88 citations
TL;DR: In this article, the authors presented an experimental study on the laser cutting of CFRP plate, 1 1/5mm in thickness by means of 150 W Nd:YAG pulsed laser.
Abstract: Laser cutting is a promising alternative to the traditional methods in CFRP cutting. However, laser cutting is based on thermal interaction that results in thermal damages of both matrix and fibres. The heat affected zone (HAZ) extension is strictly dependent on the adopted laser source and the working parameters. The paper presents an experimental study on the laser cutting of CFRP plate, 1 mm in thickness by means of 150 W Nd:YAG pulsed laser. The cutting region and the influence of process parameters, pulse energy, pulse duration and overlapping, on the kerf geometry and the HAZ were analyzed. Experimental results showed that the adopted laser is able to cut the CFRP plate, up to 10.8 mm/s. However, an accurate selection of the process parameters is necessary in order to obtain the maximum cutting speed and a narrow HAZ. Moreover, a relation between the HAZ extension and the process parameters (average power, cutting speed, pulse frequency and pulse duration) was found.
74 citations
TL;DR: This work demonstrates generation of 0.2 mJ terahertz pulses in lithium niobate driven by Ti:sapphire laser pulses at room temperature using tilted pulse front technique and paves the way for mJ-level THz generation via optical rectification using existing Ti: sapphire Laser systems which can deliver Joule-level pulse energy with sub-50 fs pulse duration.
Abstract: We demonstrate generation of 0.2 mJ terahertz (THz) pulses in lithium niobate driven by Ti:sapphire laser pulses at room temperature. Employing tilted pulse front technique, the 800 nm-to-THz energy conversion efficiency has been optimized to 0.3% through chirping the sub-50 fs pump laser pulses to overcome multi-photon absorption and to extend effective interaction length for phase matching. Our approach paves the way for mJ-level THz generation via optical rectification using existing Ti:sapphire laser systems which can deliver Joule-level pulse energy with sub-50 fs pulse duration.
72 citations
TL;DR: In this article, a long-term stable two-dimensional saturable absorption material under ambient conditions was demonstrated for the first time to the best of our knowledge, and the results indicated that multi-layer antimonene is a promising longterm stable SA material that can be applied in the mid-infrared spectral region.
Abstract: We experimentally demonstrate a long-term stable two-dimensional saturable absorption material under ambient conditions—multi-layer antimonene feasible for the mid-infrared spectral region—for the first time to our knowledge. The multi-layer antimonene material prepared using a liquid-phase exfoliation method was coated on a quartz/CaF2 for characterizations and an Au mirror as a reflection-type saturable absorber (SA) device. It has a modulation depth of 10.5%, a saturation peak intensity of 0.26 GW/cm2, and a non-saturation loss of 19.1% measured at 2868.0 nm using the typical power-dependent method. By introducing the SA device into a linear-cavity Ho3+/Pr3+-codoped fluoride fiber laser at 2865.0 nm, stable Q-switched pulses were obtained. It generated a maximum output power of 112.3 mW and pulse energy of 0.72 μJ, while the shortest pulse duration and largest repetition rate were 1.74 μs and 156.2 kHz, respectively. The long-term stability of the SA device was also checked using the same laser setup within 28 days. The results indicate that multi-layer antimonene is a type of promising long-term stable SA material under ambient conditions that can be applied in the mid-infrared spectral region.
20 Apr 2018
TL;DR: In this article, a picosecond-pumped optical parametric chirped pulse amplification (OPCPA) system was used to generate high harmonics from solid surfaces with photon energies exceeding 55 eV.
Abstract: For experiments in plasma, nuclear, and high-energy physics, there is a strong demand for laser pulses exhibiting relativistic intensity, few-cycle pulse duration, and a very high contrast. Here we present a picosecond-pumped optical parametric chirped pulse amplification (OPCPA) system delivering pulses at 10 Hz repetition rate with the following key parameters: a compressed pulse duration of less than 7 fs (close to the Fourier limit), a contrast of better than 1011 starting from 1 ps before the main pulse, and a peak intensity of 6.9×1019 W/cm2 achieved with an off-axis parabolic mirror (f/1.6). In a proof-of-principle experiment, these pulses were used to generate high harmonics from solid surfaces with photon energies exceeding 55 eV. These results underline the promising perspectives of the reported system for relativistic light–matter interaction experiments and attosecond science.
TL;DR: In this paper, the polarization reversal of an 8 nm-thick HZO film deposited by the atomic layer deposition with voltage pulses varying in amplitude (0.8-2 V) and duration (200 ns-7.6 ms).
Abstract: Ferroelectric Zr-doped HfO2 (HZO) is a promising candidate for steep slope transistors and memory technology. For these applications, it is essential to understand and optimize the switching dynamics of the ferroelectric film. In this letter, we characterize the polarization reversal of an 8 nm-thick HZO film deposited by the atomic layer deposition with voltage pulses varying in amplitude (0.8–2 V) and duration (200 ns–7.6 ms). We show that the measurements are well described by a nucleation limited switching model, which enables extraction of the minimum switching time and the probability distribution of local electric field variations in the polycrystalline film. The close model fit spanning 5 orders of magnitude in pulse duration indicates the applicability of this model to HZO. This characterization framework can be used to quantify, compare, and optimize the switching dynamics of ferroelectric HZO.
TL;DR: In this paper, Bismuth nanosheets (Bi-NSs) were successfully prepared and employed as saturable absorbers to generate a diode-pumped dualwavelength Er3+:SrF2 laser in the mid-infrared region.
Abstract: Bismuth nanosheets (Bi-NSs) were successfully prepared and employed as saturable absorbers to generate a diode-pumped dual-wavelength Er3+:SrF2 laser in the mid-infrared region. Q-switched pulses with a maximum output power of 0.226 W were obtained at an absorbed pump power of 1.97 W. A repetition rate of 56.20 kHz and a minimum pulse duration of 980 ns were achieved. To the best of our knowledge, we present the first application of Bi-NSs in a mid-infrared all-solid-state laser. The results prove that Bi-NSs may be applied as an optical modulator in mid-infrared photonic devices or as a mode-locker and Q-switcher.
TL;DR: This work reports a wavelength and pulse-duration tunable mode-locked Erbium doped fiber laser with single wall carbon nanotube-based saturable absorber that provides a novel light source for various applications requiring variable wavelength or pulse duration.
Abstract: Ultrafast lasers with tunable parameters in wavelength and time domains are the choice of light source for various applications such as spectroscopy and communication. Here, we report a wavelength and pulse-duration tunable mode-locked Erbium doped fiber laser with single wall carbon nanotube-based saturable absorber. An intra-cavity tunable filter is employed to continuously tune the output wavelength for 34 nm (from 1525 nm to 1559 nm) and pulse duration from 545 fs to 6.1 ps, respectively. Our results provide a novel light source for various applications requiring variable wavelength or pulse duration.
TL;DR: Single-shot contrast at 10-10 level has been demonstrated in the SULF-10PW laser at a 24 fs pulse duration, and the measured output energy fluctuation in one hour is <1.8% in rms value.
Abstract: By combining cross-polarized wave generation and femtosecond optical parametric amplification, a high-contrast front end featuring ultrahigh contrast, a broadband spectrum, an excellent beam profile, and good stability is built for a 10-PW-level Ti:sapphire laser in the Shanghai Superintense Ultrafast Laser Facility (SULF-10PW laser). The front end can deliver a cleaned pulse with a 110 μJ energy at 1 kHz, and the bandwidth of the cleaned pulse exceeds 60 nm (FWHM), which can support a 17 fs compressed pulse duration. The measured output energy fluctuation in one hour is <1.8% in rms value. The measurement-limited contrast is 10−10 at 3 ps before the main pulse. Utilizing the high-contrast front end, single-shot contrast at 10−10 level has been demonstrated in the SULF-10PW laser at a 24 fs pulse duration.
TL;DR: In this article, a relativistic Cherenkov oscillator with strong modulation of the e-beam current at the input of two-sectioned slow-wave structure, as well as numerical and experimental results on generation of few gigawatt-level $X$ -band pulses with pulse duration of up to 35 ns.
Abstract: This paper describes a new design of a relativistic Cherenkov oscillator with strong modulation of the e-beam current at the input of two-sectioned slow-wave structure, as well as numerical and experimental results on generation of few gigawatt-level $X$ -band pulses with pulse duration of up to 35 ns. Due to special phase shift between two sections and electrodynamic coupling between $E_{01}$ surface wave and $E_{02}$ volume mode, the first one is locked at the upper boundary of the passband and the second one gains more transparency. An electron beam can interact simultaneously with two waves with higher power conversion efficiencies, which in simulations amount up to 47% and 30% for high (~4 T) and low (~1 T) guiding magnetic fields, correspondingly. The tests of the geometry optimized in simulations were performed on the base of SINUS-7 high-current electron accelerator in the diode voltage range of 400–850 kV and current from 7 to 16 kA. The repeated and full-pulsewidth generation of about 1.5-GW microwave power is achieved only in the low magnetic field. The pulse shortening and the mode competition took place in the strong magnetic field. The results are considered as preliminary for creation of the efficient relativistic millimeter-wave oscillators at magnetic fields below the cyclotron resonance.
TL;DR: A Tm-doped mixed sesquioxide ceramic laser is mode-locked near 2 µm using InGaAsSb quantum-well semiconductor saturable absorber and chirped mirrors for dispersion compensation.
Abstract: A Tm-doped mixed sesquioxide ceramic laser is mode-locked near 2 µm using InGaAsSb quantum-well semiconductor saturable absorber and chirped mirrors for dispersion compensation. Maximum average output power of 175 mW is achieved for a pulse duration of 230 fs at a repetition rate of 78.9 MHz with a 3% output coupler. Applying a 0.2% output coupler pulses as short as 63 fs are generated at 2.057 µm.
TL;DR: In this article, the authors applied power modulation in a surfaguide microwave discharge to achieve significant improvement in the energy efficiency of plasma-assisted CO2 conversion, achieving a value of 0.23 and 0.33 for a 0.95 CO2 + 0.05 N2 gas mixture.
Abstract: Significant improvement in the energy efficiency of plasma-assisted CO2 conversion is achieved with applied power modulation in a surfaguide microwave discharge. The obtained values of CO2 conversion and energy efficiency are, respectively, 0.23 and 0.33 for a 0.95 CO2 + 0.05 N2 gas mixture. Analysis of the energy relaxation mechanisms shows that power modulation can potentially affect the vibrational–translational energy exchange in plasma. In our case, however, this mechanism does not play a major role, likely due to the low degree of plasma non-equilibrium in the considered pressure range. Instead, the gas residence time in the discharge active zone together with plasma pulse duration are found to be the main factors affecting the CO2 conversion efficiency at low plasma pulse repetition rates. This effect is confirmed experimentally by the in situ time-resolved two-photon absorption laser-induced fluorescence measurements of CO molecular density produced in the discharge as a result of CO2 decomposition.
TL;DR: In this article, the authors proposed an all-solid microstructured fiber composed only of hexagonal glass elements, which has an ultraflat all-normal dispersion profile, covering a wide wavelength interval of approximately 1.55μm.
Abstract: High flatness, wide bandwidth, and high-coherence properties of supercontinuum (SC) generation in fibers are crucial in many applications. It is challenging to achieve SC spectra in a combination of the properties, since special dispersion profiles are required, especially when pump pulses with duration over 100 fs are employed. We propose an all-solid microstructured fiber composed only of hexagonal glass elements. The optimized fiber possesses an ultraflat all-normal dispersion profile, covering a wide wavelength interval of approximately 1.55 μm. An SC spectrum spanning from approximately 1030 to 2030 nm (corresponding to nearly one octave) with flatness <3 dB is numerically generated in the fiber with 200 fs pump pulses at 1.55 μm. The results indicate that the broadband ultraflat SC sources can be all-fiber and miniaturized due to commercially achievable 200-fs fiber lasers. Moreover, the SC pulses feature high coherence and a single pulse in the time domain, which can be compressed to 13.9-fs pulses with high quality even for simple linear chirp compensation. The Fourier-limited pulse duration of the spectrum is 3.19 fs, corresponding to only 0.62 optical cycles.
TL;DR: This report on the first sub-100 fs mode-locked Ho3+-laser in the 2 μm spectral range employing a disordered co-doped Tm,Ho:CaYAlO4 (Tm, Ho:CALYO) crystal as a gain medium is reported on.
Abstract: We report on, to the best of our knowledge, the first sub-100 fs mode-locked Ho3+-laser in the 2 μm spectral range employing a disordered co-doped Tm,Ho:CaYAlO4 (Tm,Ho:CALYO) crystal as a gain medium Pulses as short as 87 fs are produced with an average output power of 27 mW at 8045 MHz repetition rate An output power of 96 mW is reached for a pulse duration of 98 fs
TL;DR: In this paper, the phase contrast depends on parameters such as excitation frequency, pulse duration, material parameters, crack depth, and inclination angle of the crack, and generalized functions for the dependency of the phase difference on all these parameters were derived.
Abstract: In the last few years, induction thermography has been established as a non-destructive testing method for localizing surface cracks in metals. The sample to be inspected is heated with a short induced electrical current pulse, and the infrared camera records—during and after the heating pulse—the temperature distribution at the surface. Transforming the temporal temperature development for each pixel to phase information makes not only highly reliable detection of the cracks possible but also allows an estimation of its depth. Finite element simulations were carried out to investigate how the phase contrast depends on parameters such as excitation frequency, pulse duration, material parameters, crack depth, and inclination angle of the crack. From these results, generalized functions for the dependency of the phase difference on all these parameters were derived. These functions can be used as an excellent guideline as to how measurement parameters should be optimized for a given material to be able to detect cracks and estimate their depth. Several experiments on different samples were also carried out, and the results compared with the simulations showed very good agreement.
TL;DR: In this paper, the authors used chemical vapor deposition-grown monolayer WSe2 as a saturable absorber for a mode-locked thulium-doped fiber laser.
Abstract: We report the usage of chemical vapor deposition-grown monolayer WSe2 as a saturable absorber (SA) for a mode-locked thulium-doped fiber laser. The monolayer WSe2 was transferred onto a microfiber and then incorporated into a typical all-fiber-integrated ring cavity configuration. Stable soliton pulses emitting at 1863.96 nm were obtained with pulse duration of 1.16 ps, repetition rate of 11.36 MHz, and an average power of 32.5 mW. This is, to the best of our knowledge, the first demonstration of WSe2-based SA in fiber lasers at 2 μ m regime.
TL;DR: In this paper, the fabrication process and characterization of Bi2Te3 topological insulators (TIs) synthesized by the spin-coating coreduction approach (SCCA) is reported.
Abstract: In this paper, the fabrication process and characterization of Bi2Te3 topological insulators (TIs) synthesized by the spin-coating-coreduction approach (SCCA) is reported. With this approach, high-uniformity nano-crystalline TI saturable absorbers (TISAs) with large-area uniformity and controllable thickness are prepared. By employing these prepared TIs with different thicknesses as SAs in 2-μm solid-state Q-switched lasers, thickness-dependent output powers and pulse durations of the laser pulses are obtained, and the result also exhibits stability and reliability. The shortest pulse duration is as short as 233 ns, and the corresponding clock amplitude jitter is around 2.1%, which is the shortest pulse duration in TISA-based Q-switched 2-μm lasers to the best of our knowledge. Moreover, in comparison with the TISA synthesized by the ultrasound-assisted liquid phase exfoliation (UALPE) method, the experimental results show that lasers with SCCA synthesized TISAs have higher output powers, shorter pulse durations, and higher pulse peak powers. Our work suggests that the SCCA synthesized TISAs could be used as potential SAs in pulsed lasers.
TL;DR: A simply designed gain-switched all-fiber laser emitting a maximum average output power of 11.2 W at 2.826 µm is reported, which significantly surpass previous gain- Switched demonstrations and are close to the state-of-the-art Q-switches laser performances near 2.4 W.
Abstract: We report a simply designed gain-switched all-fiber laser emitting a maximum average output power of 11.2 W at 2.826 µm. The corresponding extracted pulse energy is 80 µJ at a pulse duration of 170 ns. These performances significantly surpass previous gain-switched demonstrations and are close to the state-of-the-art Q-switched laser performances near 2.8 µm, but with a much simpler and robust all-fiber design. The spliceless laser cavity is made of a heavily erbium-doped fluoride glass fiber and is bounded by fiber Bragg gratings written directly in the gain fiber through the protective polymer coating.
TL;DR: The results showed that the MSD-grown α-In2Se3 could be regarded as high efficiency material to be applied in ultrafast photonics.
Abstract: With the magnetron-sputtering deposition method, α phase indium selenide (α-In2Se3) was developed into a saturable absorber (SA) with wideband saturable absorption property at 800, 1560, and 1930 nm. After inserting the α-In2Se3 SA into erbium-doped fiber laser (EDFL) and thulium-doped fiber laser (TDFL) systems, we can easily obtain stable soliton pulse trains. The pulse duration/pulse energy/slope efficiency for EDFL and TDFL were 276 fs/2.03 nJ/15.8% and 1.02 ps/7.1 nJ/23.5%, respectively. These results showed that the MSD-grown α-In2Se3 could be regarded as high efficiency material to be applied in ultrafast photonics.
TL;DR: It is indicated that non-equilibrium electrons can promote a TiS2-based saturable absorber to be an ultrafast switch for a femtosecond pulse output.
Abstract: Non-equilibrium electrons induced by ultrafast laser excitation in a correlated electron material can disturb the Fermi energy as well as optical nonlinearity. Here, non-equilibrium electrons translate a semiconductor TiS2 material into a plasma to generate broad band nonlinear optical saturable absorption with a sub-picosecond recovery time of ∼768 fs (corresponding to modulation frequencies over 1.3 THz) and a modulation response up to ∼145%. Based on this optical nonlinear modulator, a stable femtosecond mode-locked pulse with a pulse duration of ∼402 fs and a pulse train with a period of ∼175.5 ns is observed in the all-optical system. The findings indicate that non-equilibrium electrons can promote a TiS2-based saturable absorber to be an ultrafast switch for a femtosecond pulse output.
TL;DR: A type of 2 μm h-shaped pulse generation in a thulium-holmium-doped fiber laser is reported and its cavity birefringence and pump power dependences are experimentally investigated to demonstrate the related characteristics in detail.
Abstract: We report on a type of 2 μm h-shaped pulse generation in a thulium-holmium-doped fiber laser and experimentally investigate its cavity birefringence and pump power dependences. An asymmetric nonlinear optical loop mirror is employed as an artificial saturable absorber, which incorporates ∼52.7 m dispersion-shifted fiber and ∼3.8 m ultra-high numerical aperture fiber to enhance the nonlinearity. The h-shaped pulse shows both a polarization state (PS) and pump power related evolutions, even when randomly weak birefringence fibers are employed. By further incorporating different lengths of high birefringence polarization-maintaining fiber (PMF), i.e., introducing different amounts of linear cavity birefringence, much larger pulse tuning ranges can be realized. In particular, when the PMF is lengthened to ∼2.3 m through manipulating the PS, the achieved longest pulse duration of ∼318.14 ns can almost cover the whole repetition period of ∼323.96 ns, corresponding to a pulse duty circle of ∼98.2%, the largest ever reported from a fiber laser, to the best of our knowledge. We demonstrate the related characteristics in detail.
TL;DR: The 1 kHz repetition rate, high temporal resolution enabled by the short 11.8 fs driving pulse duration, and bright high-order harmonics generated in helium make this an attractive source for solid-state and molecular-dynamics studies.
Abstract: We present a 0.2 TW sub-two-cycle 1.8 µm carrier-envelope-phase stable source based on two-stage pulse compression by filamentation for driving high-order harmonic generation extending beyond the oxygen K absorption edge. The 1 kHz repetition rate, high temporal resolution enabled by the short 11.8 fs driving pulse duration, and bright high-order harmonics generated in helium make this an attractive source for solid-state and molecular-dynamics studies.
TL;DR: 175 fs dispersion-managed soliton (DMS) mode-locked ytterbium-doped fiber (YDF) laser based on single-walled carbon nanotubes (SWCNTs) saturable absorber (SA) is demonstrated, which is the shortest pulse duration obtained directly from YDF laserbased on broadband SAs.
Abstract: Ultrafast fiber laser light sources attract enormous interest due to the booming applications they are enabling, including long-distance communication, optical metrology, detecting technology of infra-biophotons, and novel material processing. In this paper, we demonstrate 175 fs dispersion-managed soliton (DMS) mode-locked ytterbium-doped fiber (YDF) laser based on single-walled carbon nanotubes (SWCNTs) saturable absorber (SA). The output DMSs have been achieved with repetition rate of 21.2 MHz, center wavelength of 1025.5 nm, and a spectral width of 32.7 nm. The operation directly pulse duration of 300 fs for generated pulse is the reported shortest pulse width for broadband SA based YDF lasers. By using an external grating-based compressor, the pulse duration could be compressed down to 175 fs. To the best of our knowledge, it is the shortest pulse duration obtained directly from YDF laser based on broadband SAs. In this paper, SWCNTs-SA has been utilized as the key optical component (mode locker) and the grating pair providing negative dispersion acts as the dispersion controller.