Q-switched Pulses Research Articles

Broadband Tunable Passively Q-Switched Erbium-Doped ZBLAN Fiber Laser Using Fe3O4-Nanoparticle Saturable Absorber

We experimentally demonstrate a passively Q-switched wavelength tunable 2.8 μm erbium-doped fiber laser. Fe3O4 nanoparticles deposited on a gold mirror are used as a saturable absorber (SA). Stable Q-switched pulses within the tunable range of 2710–2810 nm are obtained. At the wavelength of 2760 nm, a maximum Q-switched output power of 188 mW is achieved with a repetition rate of 115.8 kHz and a pulse width of 1.3 μs. The corresponding pulse energy is 1.68 μJ. This demonstration shows the ability of Fe3O4 to function as a broadband mid-infrared SA.

Indium Selenide as passive saturable absorber for Q-switching in Erbium-doped fiber lasers

• Demonstrated erbium-doped fiber laser Q-switched using Indium Selenide. • The Q-switched performances were achieved at the maximum pump power of 125.63 mW with a repetition rate of 109.2 kHz and a minimum pulse width of 2.89 µs. • The higher pulse energy obtained is 73.8 nJ, with a maximum average output power of 8.06 mW. Q switching was demonstrated in an Erbium-doped fiber laser by utilizing Indium Selenide (In 2 Se 3 )-PVA as a passive saturable absorber (SA). The In 2 Se 3 PVA thin film was sandwiched between two fibre ferrules using 980 nm laser diode at the operating wavelength of 1550 nm. Stable Q-switched pulse started to generate at the threshold pump power of 24.13 mW with centre wavelength of 1558.7 nm. The Q-switched performances were achieved at the maximum pump power of 125.63 mW with a repetition rate of 109.2 kHz and a minimum pulse width of 2.89 µs. The higher pulse energy obtained is 73.8 nJ, with a maximum average output power of 8.06 mW. Our findings suggest that In 2 Se 3 has merciless performance in acting as passive saturable absorber in mid-infrared regime and will provide useful guidance for future ultra-fast optical devices.

Passively Q-switched mode-locked laser based on a MoS2/MoSe2 heterostructure saturable absorber

We have achieved stable output of Q-switched mode-locked laser at 1.06 μm by using MoS2/MoSe2 heterostructure saturable absorber. The saturable absorption characteristics of MoS2/MoSe2 heterojunction is investigated. At a pump power of 10 W, Q-switched mode-locked pulses with a repetition rate of 26 MHz, a minimum envelope width of 30.9 ns, and a maximum single pulse energy of 23.07 nJ are obtained. Compared with the previous results obtained on Q-switched mode-locked lasers with two-dimensional materials, higher envelope repetition rate and shorter envelope duration can be obtained. The results demonstrate that the MoS2/MoSe2 heterojunction is a competitive saturable absorber for all-solid-state lasers.

Harmonic mode-locked noise-like pulses under a Q-switched envelope in an erbium doped all-fiber ring laser.

We report for the first time, to the best of our knowledge, harmonic mode-locked noise-like pulses under a Q-switched envelope in an all-fiber erbium doped ring laser cavity, mode locked using the nonlinear polarization rotation (NPR) technique. For a cavity with a fundamental repetition rate of 1.33 MHz, stable mode-locked noise-like pulses, with few nanoseconds durations, single pulse energies around 30-40 nJ, and Q-switched repetition rates up to 31 kHz, were produced and characterized from the fundamental to the eighth harmonic. The formation and evolution of Q-switched harmonic mode-locked noise-like pulses were preceded by the formation of Q-switched mode-locked noise-like pulse bunches. This is also the first report on noise-like bunches under a Q-switched envelope, to our knowledge. Our studies also provide further insights into the interplay of different physical mechanisms involved in the production of such ultrashort pulses. Such sources should prove especially useful for efficient supercontinuum generation and laser micromachining.

Antimonene-based saturable absorber for a soliton mode-locked and Q-switched fiber laser in the 2 μm wavelength region

We demonstrate antimonene as a saturable absorber (SA) to generate an ultrafast mode-locked and Q-switched laser in the 2 μm wavelength region. The two antimonene-based SAs were prepared and inserted separately in a thulium–holmium-doped fiber laser to produce the pulsed laser. Antimonene was coated onto a tapered fiber to generate soliton mode-locked pulses and used in thin-film form for the generation of Q-switched pulses. The mode-locking was stable within a pump power of 267 mW–511 mW, and the laser operated at a central wavelength of 1897.4 nm. The mode-locked laser had a pulse width of 1.3 ps and a repetition rate of 12.6 MHz, with a signal-to-noise ratio of 64 dB. Q-switched laser operation was stable at a wavelength of 1890.1 nm within a pump power of 312 mW–381 mW. With the increase in pump power from 312 mW to 381 mW, the repetition rate increased to a maximum of 56.63 kHz and the pulse width decreased to a minimum value of 2.85 μs. Wide-range tunability of the Q-switched laser was also realized within the wavelength range of 1882 nm–1936 nm.

Tunable optical nonlinearity of indium tin oxide for optical switching in epsilon-near-zero region

Abstract The propagation of light in the epsilon-near-zero (ENZ) region of materials exhibits intriguing linear and nonlinear optical phenomenon that have been extensively exploited for a plethora of applications. Here, we show that the optical properties as well as the ENZ wavelength of magnetron-sputtered indium tin oxide (ITO) thin films could be judiciously engineered. The measurement of nonlinear optical properties reveals that the control of deposition conditions allows for the tuning of absorptive optical nonlinearity between saturable absorption and reverse saturable absorption. The ENZ wavelength for the ITO film is deduced as around 1553 nm. We obtain the highest third-order nonlinear absorption coefficient and imaginary part of third-order nonlinear susceptibility for the ITO thin film through Z-scan method as −50.56 cm/GW and ∼38 × 10−14 e.s.u. at 1050 nm, and −64.50 cm/GW and ∼45 × 10−14 e.s.u. at 1550 nm, respectively. We demonstrate further that the strong saturable absorption of the ITO thin film enables Q-switched pulse laser generation in ∼1050 and ∼1550 nm regions with tunable repetition rates and pulse energies. The present results suggest the great application potential of the ITO thin film in the field of nonlinear optical devices.

Graphene-polyvinyl alcohol polymer based saturable absorption at 2000 nm region

A <span>graphene-polyvinyl alcohol (PVA) composite saturable absorption is demonstrated at 2000 nm region. Graphene suspension is produced using low-cost electrochemical exfoliation process. The suspension is mixed with PVA host polymer in 1:1 ratio and left evaporated at room temperature which finally produced graphene-PVA thin film. Thulium doped fiber (TDF) gain medium has been shown to produce a stable Q-switched pulse with a highest repetition rate of 54 kHz, a short pulse duration of 2.89 µs, a maximum peak power of 16 mW, and an estimated maximum pulse energy of 49 nJ. Apparently, at 2000 nm region, superior performances of graphene-PVA composite have been recorded which was largely contributed by meticulous composite preparation and homogenous mixture with PVA host</span>.

Ti3AlC2 coated D-shaped fiber saturable absorber for Q-switched pulse generation

Ti3AlC2 coated D-shaped fiber saturable absorber for Q-switched pulse generation

Few-ns, kW peak power Q-switched pulses from orange and red Pr:YLF lasers

We report on the generation of few-ns pulses with kW peak power in the red and orange spectral range obtained from a passively Q-switched Pr3+:YLF laser. A compact resonator and thorough investigation of the Co:MgAl2O4 saturable absorber’s initial transmission enables peak powers in excess of 1.1 kW at pulse durations of 2.4 ns and 5.3 ns at 640 nm and 607 nm, respectively. These are the shortest pulse durations among any Q-switched Pr3+ laser and make this system a suitable front-end for efficient frequency doubling into the ultraviolet range.

Passively high-power Q-switching in Er- and Er/Yb doped fiber with CdTe

In this work, Cadmium Telluride (CdTe) thin-film was demonstrated as a saturable absorber (SA) to induce Q-switching in the erbium-doped fiber laser (EDFL) and erbium-ytterbium co-doped fiber laser (EYDFL) cavities. CdTe thin film was prepared by the liquid-phase exfoliation method and sandwiched between two fiber ferrules to complete the fiberized SA assembly. Firstly, the CdTe-SA was inserted into the EDFL cavity and stable Q-switched pulses were observed at a threshold pump power of 88mW. The shortest pulse width and the highest repetition rate measured for the EDFL cavity were 6.10 ± 0.02 μs and 42.3 ± 1.3 kHz respectively, at a maximum pump power of 295 mW. At a maximum pump power of 295 mW, the highest average output power produced by the Q-switched pulses in the EDFL cavity was 0.15 mW. Meanwhile, Q-switched pulses in the EYDFL cavity self-start at the threshold pump power of 1.4 W. The maximum repetition rate obtained was 99.5 ± 1.5 kHz and a pulse width of 2 μs at a maximum pump power of 3 W. At this pump power, the highest average output power produced by the Q-switched pulses in the EYDFL cavity was 70.0 ± 0.2 mW. This is the first demonstration of a high average power passively Q-switched fiber laser operating in the C-band employing EDF and EYDF as the gain medium and CdTe thin-film as SA that we are aware of.

Watt-level high-stability all-solid-state passively Q-switched laser based on germanene nanosheets

Excellent Q-switching operations modulated by new two-dimensional (2D) saturable absorber (SA) materials with stable performance is a hot topic in all-solid-state pulsed laser research. In this work, the watt-level high-stability passive Q-switching operation in a solid-state Nd:YVO4 laser utilizing the 2D germanene nanosheets as SA was first realized. The nonlinear optical properties of the germanene nanosheets (Ge-Ns) were characterized by experimental means. The stable Q-switched pulse sequence was acquired with a 60.6 ns narrowest pulse width and a 528.6 kHz maximal repetition rate. The average output power of 0.965 W and the corresponding pulse peak power of 30.12 W are obtained under the pump power of 7 W. The findings of the experiments demonstrate that germanene material has remarkable nonlinear optical properties and can be used as an excellent saturable absorber in the field of optical pulse modulation.

GaInSn liquid nanospheres as a saturable absorber for Q-switched pulse generation at 639nm.

Liquid metals, which possess the superiority of low cost, shape-reconfigurability, and excellent optoelectronic properties, have been applied in various fields, such as flexible electronics, superconductivity, and coolants. In this paper, high-quality GaInSn liquid nanospheres synthesized by the ultrasonic method are applied for nonlinear optics and laser switches. The saturation absorption property derived from localized surface plasmon resonance at 639 nm is studied based on the open-aperture Z-scan technique, exhibiting a modulation depth of ∼35.5% and a saturation fluence of ∼21.75 mJ/cm2, respectively. The as-prepared GaInSn liquid nanospheres are also successfully utilized as a saturable absorber to achieve a stable Q-switched Pr:YLF laser at 639 nm. The output pulse width can reach ∼280 ns with a pulse repetition rate of ∼174.8 kHz. Our results suggest that GaInSn liquid nanospheres are a candidate material for generating visible laser pulses, which is of great interest for potential applications in visible nonlinear optics.

Continuous-wave and passively Q-switched pulse Er:Yb:Ca3NbGa3Si2O14 microlasers at 1.5–1.6 μm

Compact continuous-wave and passively Q-switched pulse microlasers at 1.5–1.6 μm were developed by using a 5-mm-thick Er:Yb:Ca3NbGa3Si2O14 crystal as a gain medium. End-pumped by a 975.6 nm continuous-wave laser diode, a 1555 nm continuous-wave laser with a maximum output power of 1.05 W and a slope efficiency of 8.8% was obtained at an absorbed pump power of 14.2 W. End-pumped by a 975.6 nm pulsed laser diode with a pulse width of 0.3 ms and a pulse period of 1.0 ms, a stable 1534 nm passively Q-switched pulse laser operating at a repetition frequency of 1.0 kHz was realized by using a Co2+:MgAl2O4 crystal with an initial transmission of 95% as a saturable absorber. At a peak absorbed pump power of 23.6 W, the obtained single-pulse energy, pulse width and peak output power were 8.06 μJ, 7.9 ns, and 1.02 kW, respectively.

Generation of stable Q-switched pulses at 1566 nm by using a segment of erbium-doped fiber as saturable absorber

In this manuscript, the performance of a passively Q-switched fiber laser has been presented, where a segment of un-pumped erbium-doped fiber (EDF) is used as the saturable absorber (SA). We have taken an erbium and ytterbium (Er/Yb) co-doped double cladding fiber as the gain media for efficient pump absorption and checked the potential of the laser by changing the length of the in-house fabricated erbium-doped fiber saturable absorber (EFSA). For a fixed length of EFSA, variation of important system parameters such as output power, repetition rate, pulse width, etc, with the change of the pump power has also been reported. The laser has delivered pulses of a minimum duration of 1.35 µs with maximum energy of 2.8 µJ. The repetition rate varies in the range from 24.8 kHz to 47 kHz with alteration of the length of the SA. The central wavelength of the output spectra is 1566 nm.

Te Film as a Saturable Absorber for the Mid-Infrared Er3+-Doped ZBLAN Fiber Laser

We demonstrate a Q-switched Er3+-doped ZBLAN fiber laser at 2.8 µm mid-infrared (mid-IR) region achieved by adopting Te as the saturable absorber mirror (SAM). The modulation depth and saturation intensity of the Te-SAM were measured to be ∼7.2% and 10.81 MW∕cm2, respectively. Stable Q-switched laser pulses with the maximum pulse energy of 3.05 µJ and the minimum pulse width of 0.457 µs at the launched pump power of 4.51 W were obtained. Maximum average output power of 357 mW with repetition rate of 116.98 kHz were achieved. The signal-to-noise ratio (SNR) is 52 dB, which is higher than that of most 2.8 µm mid-infrared Q-switched fiber lasers reported so far. To the best of our knowledge, this is the first demonstration from a Q-switched fiber laser at 2.8 µm based on a Te-SAM.

Highly stable passively Q-switched erbium-doped fiber laser with zeolitic imidazolate framework-67 saturable absorber

In this work, a stable and compact passively Q-switched erbium-doped fiber laser (EDFL) is demonstrated by employing zeolitic imidazolate framework-67 (ZIF-67) membrane as the saturable absorber (SA) for the first time. The passively Q-switched pulse train was realized with a maximum repetition frequency of 32.6 kHz. The shortest pulse width of 2.55 μs and a fundamental signal-to-noise ratio (SNR) of 47 dB were also obtained. The highest average output power was 7.22 mW, corresponding to a maximum single pulse energy of 221.5 nJ. The long term running of the laser was also performed, showing the high stability. Our experiment results support that ZIF-67 nanomaterial has good nonlinear optical properties and superior thermal stability, indicating the great potential in the generation of high energy pulses in the near-infrared region.

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.

Rare-earth Yttrium oxide as Q-switcher in fiber laser system

Yttrium Oxide (Y2O3), a rare-earth material is used as saturable absorber (SA) to induce Q-switching operation in 1.55 µm regime. The Y2O3 was embedded into polyvinyl alcohol (PVA) to form a thin film so that it can be easily integrated into an Erbium-doped fiber laser (EDFL) cavity for modulating the cavity loss. A robust and stable Q-switched pulse centered at 1560.53 nm operating wavelength has been obtained with the integration of Y2O3-PVA SA in the EDFL cavity. The repetition rate of the Q-switched pulse can be varied from 88.03 kHz to 99.22 kHz with the change of pump power from 128.92 mW to 175.87 mW while the corresponding pulse duration reduces from 3.30 μs to 2.97 μs. Also, the analyzed peak power of the pulse increased from 40.92 mW to 52.67 mW within the pump power region.

Nanosecond mid-infrared pulse generation modulated by platinum ditelluride nanosheets

We demonstrated the generation of nanosecond mid-infrared (MIR) pulse from an Er3+-doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber laser modulated by platinum ditelluride nanosheets experimentally. The platinum ditelluride nanosheets exhibit strong nonlinear absorption with the saturation intensity 46.5 GW cm−2 and modulation depth 27.8% at 2.8 μm wavelength, respectively. With the saturable absorber mirror fabricated by depositing the platinum ditelluride nanosheets on a gold mirror, we have obtained the stable Q-switched pulses with repetition rate of 173.4 kHz and pulse duration of 600 ns at 2.8 μm wavelength under the pump power of 5.6 W. In addition, the maximum average output power and pulse energy reach 591 mW and 3.41 μJ, respectively. The experimental results confirm that the platinum ditelluride nanosheets exhibit excellent nonlinear optical behavior towards the MIR spectral range, and may make inroads towards MIR photonics with group-10 transition-metal dichalcogenides.

CuCrO2 nanoparticles-polyimide films as saturable absorber for improving the output characteristics of passively Q-switched in ytterbium doped fiber lasers

CuCrO2 (CCO) Nanoparticles (NPs)-Polyimide (PI) films are successfully used to achieve passively Q-switched pulse output in ytterbium-doped fiber lasers (YDFL). The laser output characteristics can be regulated by using our as-fabricated CCO NPs-PI films at 1.03 μm. The pulse duration and repetition rate are simultaneously compressed by tens of times, at the same time single pulse energy and peak power are increased by one and three orders of magnitude, respectively. In particular, this is the first time that pulse duration and repetition rate are compressing simultaneously in YDFL. In addition, CCO NPs is integrated into YDFL for the first time. The reason for these phenomenons is that reverse saturable absorption reasonably increases the cavity loss, which effectively improves the modulation depth, over threshold degree and the accumulation of inversion particles. All these can prove that CCO NPs can be used as an important SA to construct high-performance Q-switched fiber laser.