Maximum Single Pulse Energy Research Articles

Demonstration of passively Q-switched and mode-locked operations through dispersion control in Er-doped fiber lasers with a cylindrite-based saturable absorber

Two-dimensional (2D) materials have been extensively investigated in the fields of electronics, biology, and chemistry. Especially in the field of optoelectronics, profiting from 2D layered materials-based photonic devices, such as optical switchers, optical modulators, and optical polarizers, new research areas of ultrashort pulse lasers have been opened up. Cylindrite is a kind of sulfosalt mineral with highly anisotropic optical responses. Two isotropic layers, a SnS2-like layer and a PbS-like layer, are stacked together to form a natural van der Waals heterostructure. Thin cylindrite flakes can be obtained through both mechanical exfoliation (ME) and liquid-phase exfoliation (LPE) methods. In this work, cylindrite nanosheets are prepared successfully by the LPE method. Nonlinear optical absorption properties are studied firstly in advance of exploring the potential of cylindrite as optical modulators. Dispersion management is realized by increasing the length of single-mode fiber. And with the intracavity net dispersion (IND) changing from −0.24 ps2 to −4.47 ps2, both Q-switched and mode-locked operations could be observed in a cylindrite-based Er-doped fiber laser (EDFL) in turn. Q-switched pulses outputs are obtained when the IND are about −0.24 ps2 and -0.68 ps2. The maximum average output power is 1.71 mW. The obtainable maximum single pulse energy is 53.89 nJ. Mode-locked operations are demonstrated when the IND are about −0.91 ps2, -2.01 ps2, -3.44 ps2, and -4.47 ps2. Besides, a double-ended pumped mode-locked EDFL with a signal-to-noise ratio of about 51 dB can also be obtained. This work reveals the nice nonlinear optical properties of the cylindrite-based saturable absorber and indicates that the cylindrite-based optical modulator holds tremendous potential and feasibility in the field of ultrashort pulse fiber lasers.

Dual-loss-modulated Q-switched YVO4/Nd:YVO4 laser based on both Bi2Se3 and Cr4+:YAG

A dual-loss-modulated Q-switched laser at 1.06 µm is investigated. Bi2Se3 and Cr4+:YAG saturable absorber were simultaneously inserted into a laser cavity and used to study output characteristics of Q-switched laser at 1.06 µm. The obtained shortest pulse width, repetition rate and maximum single pulse energy were 240 ns, 140 kHz, and 2.57 μJ, respectively. Compared with those obtained in Q-switched laser with single Bi2Se3 SA, the pulse width is compressed by 70% and peak power increases 3.3 times. The results show that Bi2Se3 is a promising material for all-solid-state Q-switched laser and dual-loss-modulated technique is an effective method to optimize the output characteristics of Q-switched laser with two-dimensional materials.

Third-order harmonic mode-locked and Q-switched Er-doped fiber laser based on a Cr2Ge2Te6 saturable absorber.

This paper reports the generation of fundamental solitons and third-order solitons in an erbium-doped fiber laser (EDFL) by a Cr2Ge2Te6-polyvinyl alcohol (CGT-PVA) saturable absorber (SA). Stable fundamental solitons at 1559.09 nm at a repetition frequency of 5.1 MHz were detected, and third-order solitons with a maximum output power of 6.807 mW and narrowest monopulse duration of 615.2 fs were obtained under a repetition frequency of 15.3 MHz by changing pump power. To the best of our knowledge, it is the first time to achieve a Q-switched pulse with a minimum pulse duration of 2.2 µs and maximum single pulse energy of 12.11 nJ in EDFL based on CGT-PVA SA after reducing the cavity length. Its repetition rate monotonically increased from 18.8 kHz to 61.8 kHz with a tuning range of about 43 kHz. The experimental results sufficiently demonstrate that CGT has enormous potential as an ultrafast photonics device.

Fabrication of Sb2O3 by an improved chemical reaction assisted vertical micro sublimation method and its saturable absorber performance

Two-dimensional molecular crystals (2DMCs) are emerging ideal materials for future high-performance optoelectronic devices. People are constantly exploring new methods to solve the problem of difficult growth. Here, we design an improved chemical reaction-assisted vertical micro sublimation method based on vertical micro sublimation for the growth of two-dimensional Sb2O3 inorganic molecular crystals for the first time. The saturation absorption characteristics of the self-made Sb2O3 2DMCs were systematically tested, and the Q-switched laser output characteristics of Sb2O3 2DMCs at 1 µm were verified by using Nd: GYAP mixed crystal. The maximum average output power of 231 mW was achieved at 1080.6 nm, corresponding shortest pulse with a duration of 472 ns and maximum pulse repetition rate of 376 kHz. The maximum single pulse energy and the maximum peak power of the laser output were 0.614 µJ and 1.3 W, respectively. The growth of other 2DMCs would be motivated and its potential applications in the field of ultrafast photonics would be expanded with our findings.

Liquid-Phase Exfoliation of Ta2NiS5 and Its Application in Near-Infrared Mode-Locked Fiber Lasers with Evanescent Field Interactions and Passively Q-Switched Bulk Laser.

We report on the application of a 1 μm solid-state passively Q-switched (PQS) laser and 1, 1.5 μm mode-locked (ML) fiber lasers based on ternary chalcogenide Ta2NiS5 saturable absorber (SA), which were successfully fabricated by liquid-phase exfoliation method (LPE). The nonlinear absorption of the Ta2NiS5-SA was characterized by 0.32 GW/cm2 and 0.25 GW/cm2 saturation intensities with 7.3% and 5.1% modulations depths at 1 μm and 1.5 μm, respectively. A PQS solid-state laser operating at 1.0 μm has been realized with the Ta2NiS5-SA. The maximum average output power, shortest pulse width, pulse energy, and pulse peak power from the PQS laser are 0.257 W, 180 ns, 1.265 μJ, and 7 W. Moreover, highly stable femtosecond laser centered at 1.5 μm, and picosecond centered at 1 μm, ML fiber lasers were obtained using the Ta2NiS5-SA. A 70 dB signal-to-noise ML laser with a pulse duration of 781 fs was observed in the telecommunication window, which is better than the duration of the previously reported lasers based on Ta2NiS5. The corresponding maximum single pulse energy and peak power are 0.977 nJ and 1251 W, respectively. The Ta2NiS5-SA fabricated by the LPE method was applied in near-infrared (NIR) ML fiber lasers (evanescent field interactions) and PQS bulk lasers. The results indicate that Ta2NiS5-SA prepared by the LPE method can be applied in a 1 μm bulk PQS laser and improved by the new combination mode (evanescent field interactions) for better output performance of the fiber laser.

A 1625 nm Q‐Switched All‐Fiber Laser

A Q‐switched all‐fiber Er‐doped laser operated at a wavelength up to 1625 nm is proposed and demonstrated. A self‐developed, element hybridization (Al, Ge, La, P, and Er in the core, Si and P in the cladding region) glass fiber with gain extended to U‐band is employed as gain medium. The compact laser cavity contains a fiber Bragg grating which was manufactured by means of point‐by‐point femtosecond laser inscription technique. Stable Q‐switched laser pulse train is successfully achieved using a semiconductor saturable absorber mirror at a low pump threshold of 29 mW. The laser has a maximum single pulse energy of 746 nJ and a minimum pulse duration of 26.8 μs. The pulse repetition rate can be gradually tuned from 6.47 to 11.87 kHz by increasing the pump power. In particular, the laser wavelength of the Q‐switched all‐fiber laser can be as long as 1625 nm. This is, to the best of our knowledge, the longest wavelength for the Q‐switched Er‐doped fiber lasers at this waveband.

Passively Mode-Locked Er-Doped Fiber Laser Based on Sb2S3-PVA Saturable Absorber.

In this paper, antimony trisulfide (Sb2S3) was successfully prepared with the liquid phase exfoliation method and embedded into polyvinyl alcohol (PVA) as a saturable absorber (SA) in a passively mode-locked Er-doped fiber laser for the first time. Based on Sb2S3-PVA SA with a modulation depth of 4.0% and a saturable intensity of 1.545 GW/cm2, a maximum average output power of 3.04 mW and maximum peak power of 325.6 W for the stable mode-locked pulses was achieved with slope a efficiency of 0.87% and maximum single pulse energy of 0.81 nJ at a repetition rate of 3.47 MHz under a pump power of 369 mW. A minimum pulse width value of 2.4 ps with a variation range less than 0.1 ps, and a maximum signal to noise ratio (SNR) of 54.3 dB indicated reliable stability of mode-locking, revealing promising potentials of Sb2S3 as a saturable absorber in ultrafast all-fiber lasers.

Nonlinear saturable properties of indium selenide film fabricated by molecular beam epitaxy method in near infrared region and Q-switched laser performance for Nd:GdYNbO laser

Two-dimensional layered materials have caught considerable attention for their intrinsic value. Much effort has been made to excavate novel 2D materials with more distinctive characteristics as optical modulators. Single-crystal indium selenide (In2Se3) film with few layers fabricated by molecular beam epitaxy method, for the first time, is employed in this study as a saturable absorber for an Nd3+ doped Gd:GdYNbO infrared laser. Our experimental results demonstrate that the high-quality In2Se3 film achieves a desirable modulation depth of 18.4%, but only 5.9% for the LPE one. The shortest pulse duration and maximum single pulse energy of In2Se3 film are both much better than those of MoS2 and WS2 films in the same laser system. It further confirms the distinguishing properties of the MBE-growth In2Se3 film for optical modulation in infrared region.

Investigation of the common Q-switching voltage choice in dual-wavelength alternating Q-switched infrared laser

A dual-wavelength co-voltage alternating Q-switched infrared laser is demonstrated by combining the voltage-increased and voltage-decreased electro-optic (EO) Q-switched technologies. We experimentally studied the output characteristics of the laser under different common Q-switching voltages. The selection law of the common Q-switching voltage for 1064 nm and 1319 nm dual-wavelength laser is obtained. The results show that the selection of the common Q-switching voltage should be slightly greater than the quarter-wave voltage of 1319 nm laser(1500 V). Otherwise, the threshold of 1319 nm laser will become higher or the difference of maximum single pulse energy between two wavelengths will be greater.

Ultraflat Langmuir–Blodgett assembled graphene oxide saturable-absorber films for pulsed near-infrared laser generation

Large-scale production of ultraflat broadband saturable-absorber films is highly desired for passive mode-locked solid-state lasers. However, the current vapour deposition and spin coating routes for fabricating saturable absorbers (SAs) are suffering from the limited flexibility in substrate choice and complexity of mass production processes. Here, we demonstrate an ultraflat carboxyl-functionalized graphene oxide (GO-COOH) SA film via Langmuir–Blodgett (LB) assembly for solid state laser mode-locking. Hydrophilic carboxyl groups from GO sheets weaken the aggregation effect thus contribute to the uniform and stable dispersion of GO sheets in water. Such GO suspensions are made into an ultrathin large-area graphene-based SA film by a LB assembly process ensuring high surface uniformity. The room-temperature and highly repeated operation for GO LB films avoids the thermal damage of GO sheets and improves the membrane repeatability. Consequently, the ultrathin GO-COOH SA shows the modulation depth (2.3%) and low saturation intensity (24.7 KW cm−2) under 1064 nm laser irradiation. By inserting the GO SA into a Nd:GdVO4 laser, both passive Q-switched (QS) and passive Q-switched mode-locked (QML) operations are also attained. The slope efficiency of QS laser is up to 35.6% and the maximum single pulse energy is 1.48 μJ. In particular, the QML pulses can be achieved stably and repeatedly with an average output power of 1.33 W and a pulse energy of 13.2 nJ. Our strategy provides a new concept for improving the modulation stability of graphene-based SAs and promoting their industrial application in pulsed solid-state lasers.

Wavelength switchable Q-switched fiber laser based on Fe[formula omitted]O[formula omitted] nanoparticles

We experimentally demonstrate an erbium-doped Q-switched fiber laser at 1.5µm by incorporating Fe3O4 nanoparticles as a saturable absorber. A novel approach for SA formation is demonstrated by using the bubble poking method, through which we can fabricate SA films with different thicknesses with ease by changing the number of times of poking the bubbles. The fabricated SA possesses a modulation depth of ∼3.9% and saturable intensity of ∼0.57 MW/cm2. By inserting the SA into the laser cavity, Q-switched laser output is achieved at a pump threshold of 50mW and the central wavelength can be switched when the pump power is above 70mW. This Q-switched all-fiber laser operates stably with a maximum single pulse energy of 126nJ, a maximum repetition rate of 57.5kHz and a minimum pulse width of 5.7µs.

Q-Switched and Mode-Locked Er-doped fiber laser based on MAX phase Ti2AlC saturable absorber

MAX phase materials, exhibiting excellent antioxidation, corrosion resistance and high electrical and optical conductivity, attract much attention. The nonlinear optical properties of the MAX phase Ti2AlC was demonstrated by measuring the saturable absorption of Ti2AlC- polyvinyl (PVA) film. The modulation depth of the Ti2AlC-PVA film is calculated to be 2.21%. Stable Q-switched and mode-locked pulses train were achieved in Erbium-doped fiber ring cavity by using Ti2AlC-PVA film as a saturable absorber. The maximum single pulse energy of the Q-switched laser was 92.8 nJ, and the pulse width of the mode-locked laser was 680 fs. This study shows the great potential of MAX phase materials for ultrashort laser pulses generation and provides some valuable design guidelines for the preparation of SAs based on MAX phase materials.

Diode-pumped SESAM mode-locked low-repetition-rate Tm:CALGO picosecond laser at 1968 nm

A diode-pumped SESAM continuous-wave mode-locked (CWML) Tm:CALGO laser is demonstrated at a new center wavelength of 1968 nm based on a ultra-long Z-shaped folding cavity configuration. A total maximum dual-output power of 328 mW is achieved with a pulse duration of 33.2 ps at a repetition rate of 38.86 MHz, corresponding to a maximum single pulse energy of 4.2 nJ.

3.46 μm Q-switched Er3+:ZBLAN fiber laser based on a semiconductor saturable absorber mirror

By adopting a InAs based semiconductor saturable absorber mirror (SESAM), we have demonstrated a 3.46 μm passively Q-switched Er3+:ZBLAN fiber laser. An amplified spontaneous emission (ASE) seeded 1973 nm pump source is introduced to enhance the temporal stability. Stable 3.46 μm Q-switched pulse trains are obtained with a maximum repetition rate of 58.71 kHz and corresponding pulse width of 2.47 μs. The maximum average output power and single pulse energy are 63 mW and 1.4 μJ, respectively. The pulse characteristics with respect to the two pump powers are also evaluated. The results prove that the commercial SESAMs in stock have the capacity to extend the operation wavelength to the mid-infrared (mid-IR) wavelength region beyond 3.0 μm.

Diode-pumped master oscillator power amplifier system based on cryogenically cooled Tm:Y2O3 transparent ceramics

We demonstrated a master oscillator power amplifier system using cryogenically cooled Tm:Y2O3 transparent ceramics. The electro-optically switched master oscillator acted as a seed source and could be tuned from 1 to 100 Hz. A maximum pulse energy of 1.35 mJ with a pulse duration of 30 ns amounting to a peak power of 45 kW was obtained at 10 Hz. The power amplification via double-pass geometry achieved maximum single pulse energy of 2.94 mJ at 10 Hz with a pulse duration of 32 ns. The results showed the pulsed lasing potential of Tm:Y2O3 transparent ceramics at cryogenic temperatures. This gain material can be considered as an alternative gain medium for high average and peak power laser development around 2 µm in nano-second regime.

Tunable peak power square-wave pulse based on an all-PM thulium-doped mode-locked fiber laser.

Nanosecond dissipative soliton resonance pulse is a demonstration of an all polarization-maintaining (PM) thulium-doped fiber laser in a nonlinear amplifying loop mirror (NALM)-based figure-eight configuration. Each loop of the apparatus includes a controllable power amplifier. With increased amplifier power, pulse width broadens linearly from 3.6 to 13.5 ns, and maximum single pulse energy can reach 27.5 nJ. Interestingly, the output peak power presents two completely opposite proportional effects in terms of the variation of settings for two amplifiers, respectively. The experimental results show that the NALM loop plays an important role for tunable pulse duration, and the unidirectional ring part makes a significant contribution for power scaling.

Tunable mode-locked fiber laser to generate ultrashort cylindrical vector beams

In this work, we report a tunable mode-locked fiber laser that can produce ultrashort laser pulses with polarization vortex. Two vortex wave plates (VWPs) are employed in this laser to convert the intracavity beam states between the Gaussian mode and cylindrical vector mode. By adjusting the angle between a diffraction grating and the light beam in the cavity, the center wavelength of the mode-locked pulse can be tuned from 1015 nm to 1030 nm. Mode-locked pulses with full width at half maximum of 1.51 ps with the maximum single pulse energy of 2.2 nJ have been obtained. Through synchronously adjusting the orientations of the two VWPs, the output mode can be switched between radial polarization and azimuthal polarization states. The output vortex pulse from the tunable mode-locked fiber laser may find many applications such as optical manipulation, imaging and laser micro-machining.

Q-Switched and Noise-Like Mode Locked Er-Doped Fiber Laser Based on Nb2AlC Saturable Absorber

Nb 2 AlC is a kind of ternary ceramic material whose special crystal structure makes it both the advantages of metal and ceramics. And it has good electrical conductivity and strong stability at room temperature. In this article, the saturable absorption of Nb 2 AlC based thin film have been investigated, showing that it has saturated light intensity of 0.21 MW/cm 2 and the modulation depth of 2.62%. Noise-like mode locked and Q-switched pulses output based on Nb 2 AlC thin film have been achieved in erbium-doped fiber laser cavity. The narrowest width of noise-like mode-locked pulses' envelope is 13 ns, the maximum single pulse energy is 1.5 nJ, and the full width at half-maximum (FWHM) of the narrowest coherent spike is 2.34 ps. The minimum pulse width of the Q-switched pulse is 8.6 μs and the maximum single pulse energy is 66 nJ. As far as we know, this is the first report of Nb 2 AlC's application in ultrafast optics.

Burst-mode YVO4/Nd:YVO4 laser oscillator with pulse repetition rate up to 500 kHz

A 500 kHz burst-mode YVO4/Nd:YVO41064 nm laser oscillator with a burst duration of 1 ms and a burst energy of 45.0 mJ was presented. The acousto-optically Q-switched frequency could be varied from 10 kHz to 500 kHz, resulting in 10–500 sub-pulses per burst. At the pulse repetition rate of 500 kHz, the maximum single pulse energy reached 90.0 μJ with a pulse width of 37.8 ns, corresponding to a peak power of 2.4 kW. The beam quality factor of burst-mode laser at 500 kHz was measured to be M2=1.6. The burst-mode YVO4/Nd:YVO4laser could be acted as a master oscillator for further power scaling.

Passively mode-locked cascaded Raman fiber laser in a linear cavity

Passively mode-locked cascaded Raman fiber laser is proposed and demonstrated in a linear cavity. The mode-locking is based on nonlinear polarization rotation (NPR) with a polarization beam splitter (PBS) in the proposed laser. The passively mode-locked Raman fiber laser with a spectral range of 220 nm operates in a low pump power level, and up to the three orders Raman frequency shift are observed under our pump power conditions. The maximum output average power and single pulse energy of the proposed laser are 119.3 mW and 63.97 nJ with a slope efficiency of 41.7%. Multi-pulse mode-locked operation can also be generated by precisely adjusting polarization controller (PC) under suitable pump power conditions.