Passive Q-switching Performance Research Articles

Study on Saturable Absorption Characteristics of Bi2Se3 Topological Insulators with Film Thickness Dependence and Its Laser Application

In our work, a multi-layer topological insulator (TI) Bi2Se3 thin film was prepared by the chemical vapor deposition method (CVD), and its saturable absorption and damage characteristics were experimentally studied. The results show that when the wavelength is 1064 nm, the saturable absorption parameters of TI: Bi2Se3 film, including modulation depth αs, non-saturable loss αns, and saturation power intensity Isat, increase with the increase in film thickness, and the damage threshold is inversely proportional to the film thickness. The thicker the film layer, the lower the damage threshold. Among them, modulation depth αs is up to 51.2%, minimum non-saturable loss αns is 1.8%, maximum saturation power intensity Isat is 560.8 kW/cm2, and the damage threshold is up to 909 MW/cm2. The influence of the controllable thickness of TI: Bi2Se3 film on passive Q-switching and mode-locking performance of laser is discussed and analyzed when TI: Bi2Se3 film is prepared by the CVD method as a saturable absorber (SA). Finally, the performance of TI: Bi2Se3 thin film applied to nanosecond laser isolation at the 1064 nm band is simulated and analyzed. It has the natural advantage of polarization independence, and the maximum isolation can reach 16.4 dB.

Efficient continuous-wave and passively Q-switched operation of an Yb:YPO4 microchip laser

We report on the performance of an Yb:YPO4 microchip laser that could be efficiently operated in both continuous-wave (CW) and passive Q-switching mode, with a 2D WS2 acting as the saturable absorber. With 6.30 W of pump power absorbed, a CW output power of 3.81 W was generated, leading to an optical conversion efficiency of 60.5%, while the slope efficiency amounting to 71%. In passively Q-switched operation, a pulsed output power of 1.67 W was produced at 660 kHz of repetition frequency, with a slope efficiency of 52%; the largest pulse energy, minimum pulse width, and highest peak power, which were achievable with different output mirrors, were respectively 2.52 μJ, 67 ns, and 31.7 W. The results demonstrated in this work represent a significant improvement in CW and passive Q-switching performance of Yb:YPO4 microchip lasers.

Passive Q-switched Dy:ZBLAN fibre laser at 3.1 µm

The passive Q-switching performance of an in-band pumped Dy-doped fluorozirconate fibre laser emitting around 3.1 µm is investigated. Passively Q-switched laser operation is demonstrated employing semi-conductor saturable absorber mirrors. Stable operation is achieved, with a minimum pulse duration of 464 ns, a highest repetition frequency of 210 kHz and peak pulse powers up to 3 W.

Mid-IR tunable CW and passively Q-switched laser operation of Dy-doped fluoride fiber

We report a comprehensive characterization of tunable continuous-wave (CW) and passive Q-switching laser performance of Dy-doped zirconium fluoride fiber emitting around 3 µm. The in-band pumped CW laser operation is investigated for pump wavelengths varying from 2.7 µm to 2.825 µm, for fiber lengths ranging from 0.4 m to 2 m, and for output coupling efficiency from 10% to 50%, leading to a maximum laser slope efficiency of 44% and a tuning range larger than 300 nm. With Findlay-Clay analysis and Rigrod analyses, optimal cavity parameters are retrieved, paving the way for further optimizations in performance. The passively Q-switched laser operation of Dy-doped fluoride fiber is achieved employing a semiconductor saturable absorber mirror for the first time, demonstrating a stable operation with a minimum pulse duration of 580 ns, a highest repetition frequency of 103 kHz and a pulse energy up to 300 nJ.

Passively Q-switched laser action of Yb:LaCa4O(BO3)3 crystal

We report on the passive Q-switching laser performance of Yb:LaCa4O(BO3)3 crystal with Cr4+:YAG or two-dimensional (2D) MoS2 acting as a saturable absorber. With Cr4+:YAG, a pulsed output power of 3.8 W was produced at 71 kHz with a slope efficiency of 49%, whereas at a lower repetition rate, the average pulse energy achieved could reach 250 µJ; the shortest duration and peak power were respectively 17 ns and 14.7 kW. For passive Q-switching with 2D MoS2, 1.61 W of pulsed output power was achieved at 395 kHz; the resulting pulse energy, duration, and peak power were 4.1 µJ, 220 ns, and 18.6 W, respectively.

Performance of an Yb:LaCa4O(BO3)3 crystal laser at 1.03–1.04 μm passively Q-switched with 2D MoTe2 saturable absorber

The passive Q-switching performance of an Yb:LaCa4O(BO3)3 crystal laser was investigated for the first time to our knowledge. Stable repetitively pulsed laser action was demonstrated with a 2D MoTe2 saturable absorber under high output couplings ranging from 70% up to 95%. A maximum pulsed output power of 2.11 W was produced at a repetition rate of 357 kHz, with a slope efficiency of 32% in terms of incident pump power. The largest pulse energy, minimum pulse duration, and highest peak power achievable were, respectively, 6.6 μJ, 103 ns, and 52.4 W. Our work suggests that this relatively new monoclinic oxyborate crystal may be more advantageous over most of other Yb-ion materials in making high-energy pulsed lasers passively Q-switched with 2D saturable absorbers.

Anomalous passive Q-switching induced by Cr4+:YAG: with pulse repetition rate approaching up to 1 MHz

Anomalous passive Q-switching behavior was demonstrated in an Yb:KLu(WO4)2 laser, with a Cr4+:YAG crystal plate acting as saturable absorber whose initial transmission amounted to 99.3%. In stable Q-switched operation realized under high output coupling of 80%, 1.83 W of average output power was produced at a pulse repetition rate of 0.97 MHz, far beyond the upper limit imposed by the recovery time of the saturable absorber. The largest pulse energy, shortest pulse duration, and highest peak power were, respectively, 1.89 µJ, 39 ns, and 48.5 W. The high-repetition-rate passive Q-switching performance shows a close similarity to some Yb-ion lasers passively Q-switched by 2D saturable absorbers.

High-power passive Q-switching performance of a Yb:YCa4O(BO3)3 laser with a few-layer Bi2Te3 topological insulator as a saturable absorber

We demonstrate multi-watt passively Q-switched operation induced by a few-layer Bi2Te3 topological insulator saturable absorber, in an Yb:YCa4O(BO3)3 laser under high output couplings. An average output power of 3.85 W at pulse repletion rate of 400 kHz is produced at an incident pump power of 16.7 W with a slope efficiency of 28%; the resulting pulse energy, duration, and peak power are respectively 9.63 μJ, 96 ns, and 100.3 W. Our work shows the great potential of Yb:YCa4O(BO3)3 and other Yb-doped rare-earth calcium oxyborates crystals in the development of high-power, high-repetition-rate, short-duration, passively Q-switched solid-state lasers in the 1-μm region with 2D topological insulators acting as saturable absorbers.

Size effect of WSe2 on red passively Q-switched fiber laser output performance.

Transition metal dichalcogenides (TMDs) possess a direct bandgap in the visible frequency range and can be applied as attractive visible saturable absorbers (SAs). In this paper, a new TMDs tungsten selenide (WSe2)-based red Q-switcher is fabricated and successfully used for Q-switched pulse generation in a red Pr3+-doped ZBLAN fiber laser. The passive Q-switching fiber laser at 635.2nm generates a stable pulse with pulse duration of 504ns and average output power of 4.91mW as well as a tunable pulse repetition rate of 131.9-260.4kHz. Furthermore, the size effect of WSe2 on the 635nm passive Q-switching output performance is also investigated. Our work will provide certain significance for the optimization of passive Q-switching red fiber lasers based on TMDs.

High-power continuous-wave and high-energy Q-switched miniature Yb:Y3Ga5O12 crystal lasers

We report on the continuous-wave (CW) and passive Q-switching performance of a miniature Yb:Y3Ga5O12 crystal laser end pumped by a 935-nm diode laser. A maximum CW output power of 12.03 W is produced with an optical-to-optical efficiency of 54.4%, while the slope efficiency is 63%. In the passively Q-switched operation achieved with a Cr4+:YAG saturable absorber, an average output power of 2.12 W at 1025.2 nm is generated with a slope efficiency of 46% at a pulse repetition rate of 5.0 kHz. The pulse’s energy, duration, and peak power are 424 μJ, 2.3 ns, and 184.3 kW, respectively.

Continuous-Wave and Passive Q-Switching Laser Performance of Yb:YCa<inline-formula><tex-math>$_{\bf 4}$ </tex-math></inline-formula>O(BO<inline-formula><tex-math>$_{\bf 3}$</tex-math></inline-formula>)<inline-formula> <tex-math>$_{\bf 3}$</tex-math></inline-formula> Crystal

We have conducted an investigation into the continuous-wave (CW) and passive Q-switching laser performance of the Yb:YCa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> O(BO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (Yb:YCOB) crystal, aiming to evaluate its capability of power or energy scaling in compact end-pumped lasers. Efficient CW laser operation was realized with output coupling changed over a wide range from 0.4% to 60%. Operating in CW mode in the long-wavelength sideband around 1085 nm, the Z-cut Yb:YCOB laser produced an output power of 10.7 W with an optical-to-optical efficiency of 56%; in CW operation of the Y-cut Yb:YCOB laser oscillating in the main emission band, an output power of 17.0 W was reached, with optical-to-optical and slope efficiencies being respectively 62% and 78% (with respect to incident pump power). In passive Q-switching regime, the X-cut crystal proved to be the most advantageous in generating high average power and high pulse energy. With a Cr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4+</sup> :YAG crystal plate serving as saturable absorber whose initial transmission was T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 97.5%, and with an output coupling of T = 20%, an average output of 10.72 W was generated at a pulse repetition rate of 26.3 kHz, the resulting pulse duration was 22.3 ns. While under Q-switching operational conditions of T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 90.0% and T = 40%, a maximum average output power of 4.13 W could be reached at a rather low repetition rate of 3.23 kHz, yielding a pulse energy that was as high as 1.28 mJ, the resulting pulse duration and peak power being 5.0 ns and 256 kW, respectively.

Continuous-wave and passive Q-switching laser performance of Yb:YSGG crystal.

We report, for the first time, on the passive Q-switching laser performance of Yb:YSGG disordered garnet crystal. An average output power of 2.6 W at 1025.8 nm was produced at a pulse repetition rate of 11 kHz with a slope efficiency of 47%; the resulting pulse energy, duration, and peak power were respectively 236 μJ, 3.6 ns and 65.6 kW. The laser performance in continuous-wave mode under 935-nm diode pumping was also investigated, with output coupling changed over a wide range from 0.5% to 60%.

Passive Q-Switching Laser Performance of Yb:YVO4 Crystal

We report on the passive Q-switching laser performance of Yb:YVO4 crystal. Utilizing a Cr4+:YAG crystal plate as the saturable absorber, which is of an initial transmission as high as 99.3%, we demonstrate a stable passively Q-switched laser operation at 1017.2 nm, producing an average output power of 0.87 W at a pulse repetition rate of 71.4 kHz, with a slope efficiency of 30%. The resulting pulse energy, duration, and peak power are 12.2 μJ, 87 ns, and 0.14 kW, respectively.

All-fiberized, passively Q-switched 1.06 μm laser using a bulk-structured Bi2Te3 topological insulator

We experimentally demonstrate the use of a bulk-structured Bi2Te3 topological insulator (TI) deposited on a side-polished fiber as an effective saturable absorber for the implementation of an all-fiberized passively Q-switched 1.06 μm fiber laser. Unlike previous Q-switched laser demonstrations based on nanosheet-based TIs, which require complicated and sophisticated fabrication procedures, a ∼9.1 μm-thick bulk-structured Bi2Te3 TI film that was prepared using a mechanical exfoliation method was chosen to be used in this experimental demonstration due to ease of fabrication. The modulation depth of our prepared bulk-structured Bi2Te3 TI-deposited side-polished fiber was measured to be ∼2.5% at 1.06 μm. By incorporating such an absorber in an all-fiberized ytterbium-doped fiber ring cavity, stable Q-switched pulses were obtained through evanescent field interaction between the oscillated beam and the Bi2Te3 TI film. The temporal width and repetition rate of the output pulses were tunable from ∼1 to ∼1.3 μs and from ∼77 to ∼35 kHz, respectively, depending on the pump power. Through a performance comparison of our laser with recently demonstrated Q-switched 1 μm fiber lasers using carbon nanotubes, graphene, and nano-structured TIs, our bulk-structured Bi2Te3 TI-based saturable absorber is shown to have passive Q-switching performance comparable to saturable absorbers based on carbon nanotubes or nano-structured TIs.

Passive Q-switching laser performance of Yb:Gd3Ga5O12 garnet crystal

We report on the passive Q-switching laser performance of the Yb:Gd3Ga5O12 garnet crystal. With a Cr4+:YAG crystal used as saturable absorber for passive Q-switching, an average output power of 5.31 W was produced at a pulse repetition rate of 62.5 kHz, the optical-to-optical and slope efficiencies being, respectively, 45% and 61%. Laser pulses of 140 μJ in energy and 5.8 ns in duration were also obtained at 22.2 kHz, with a corresponding peak power amounting to 24.1 kW.

The potential of Yb:YCa_4O(BO_3)_3 crystal in generating high-energy laser pulses

The passive Q-switching laser performance of Yb:YCa(4)O(BO(3))(3) is studied with crystals cut along the principal optical axes. Using a Cr(4+):YAG saturable absorber with initial transmission of 93.7% and an output coupler of transmission of 40%, efficient Q-switched laser operation is achieved with a X-cut crystal, generating an output power of 2.14 W at a pulse repetition rate of 4.5 kHz. The resulting laser pulse is 9.3 ns in duration, with the energy being as high as 476 μJ and the peak power amounting to 51.2 kW. The results demonstrated in this work reveal the great potential of this crystal in developing high-energy compact pulsed lasers.

Nd:YGG crystal laser at 1110 nm: a potential source for detecting carbon monoxide poisoning

We demonstrated a laser-diode pumped Nd-doped yttrium gallium garnet crystal laser at 1110 nm for the first time to our knowledge. By suppressing the oscillation at about 1.06 μm, continuous-wave output power of 2.1 W at 1110 nm was achieved. With a Cr:YAG as the saturable absorber, the passive Q-switching performance at this wavelength was obtained. The shortest pulse width and largest pulse energy were 31.5 ns and 22.7 μJ, respectively. Laser radiation at this wavelength is an important source for detecting carbon monoxide poisoning by simple frequency doubling with a nonlinear crystal.

Passive Q-switching performance of intracavity frequency-doubled red laser with mixed Nd:GdxY1−xVO4 crystals

Passive Q-switching laser operation of Nd:GdxY1−xVO4 mixed crystals at 671nm has been compared in the same V-shape folded cavity. Based on our comparative analysis, the best laser characteristics – the highest pulse energy and peak power and the shortest pulse width – were demonstrated by Nd:Gd0.63Y0.37VO4 crystal. At the same time, this crystal possesses the lowest thermal conductivity in comparison with the other Nd:GdxY1−xVO4 crystals, which could result in decreasing the average laser output power. To verify this assumption we also measured the focal lengths of thermal lens induced in the crystals during the laser operation.

Efficient triwavelength laser with a Nd:YGG garnet crystal

We demonstrate a laser-diode pumped efficient triwavelength laser at about 1.06microm with a Nd-doped yttrium gallium garnet crystal for the first time, to our knowledge. Continuous wave output power of 7.15W was achieved under an absorbed pump power of 14.1W, corresponding to the slope efficiency of 52.7%. With Cr:YAG as the saturable absorber, passive Q-switching performance was obtained. The shortest pulse width, largest pulse energy, and highest peak power were obtained at 3.1ns, 153.8microJ, and 46.6kW, respectively. The laser spectrum was found to be a triwavelength, with respective wavelengths of 1062.1, 1060.3, and 1058.9nm, and three laser transitions were assigned.

Passive Q-switching performance with Co:LMA crystal in a diode-pumped Nd:LuVO4 laser

A diode-pumped passively Q-switched Nd:LuVO4 1.34 μm laser using Co:LMA saturable absorber was successfully demonstrated. The average output power, pulse width, repetition rate of a-cut and c-cut Nd:LuVO4 lasers were studied with different output couplers. The maximum average output power of 164 mW was obtained at the pump power of 10.3 W and the narrowest pulse width of 168 ns was achieved at repetition rate of 457 kHz under pump power of 8.59 W in a-cut Nd:LuVO4 laser with T = 8%.