Maximum Pump Power Research Articles

Tunable Dual-Wavelength with Twin-Pulse Dissipative Solitons in All-Normal Dispersion Yb-Doped Fiber Laser.

A tunable dual-wavelength with two separated twin-pulse dissipative solitons (DSs) of Yb-doped mode-locked fiber laser in the all-normal-dispersion (ANDi) regime is firstly reported and demonstrated in this paper. A Sagnac loop is used as an all-fiber format spectral filter in the laser cavity, and stable twin-pulse DSs with different wavelength mode-locked lasers are achieved by the nonlinear polarization evolution (NPE) effect. By adjusting the polarization state of the Sagnac loop, the spectral ranges of the dual-wavelength can be tuned from 1031.3 nm to 1041.5 nm and from 1067.1 nm to 1080.9 nm, respectively. However, the pulse space between the two separated twin-pulse DSs is maintained, i.e., 41.63 ns. Furthermore, the twin-pulse can regress to the single-pulse when the pump power keeps dropping. It has been observed that the highest energy of the two twin-pulse DSs output is 23.36 nJ at a repetition rate of 2.282 MHz with a maximum pump power of 560 mW.

Optical net gain measurement on Al0.07Ga0.93N/GaN multi-quantum wells.

We report net gain measurements at room temperature in Al0.07Ga0.93N/GaN 10-period multi-quantum well layers emitting at 367 nm, using the variable stripe length method. The separate confinement heterostructure was designed targeting electron-beam pumped lasing at 10 kV. The highest net gain value was 131 cm-1, obtained at the maximum pumping power density of the experimental setup (743 kW/cm2). The net gain threshold was attained at 218 kW/cm2 using 193 nm optical pumping. From these experiments, we predict an electron-beam-pumped lasing threshold of 370 kW/cm2 at room temperature, which is compatible with the use of compact cathodes (e.g. carbon nanotubes). In some areas of the sample, we observed an anomalous amplification of the photoluminescence intensity that occurs for long stripe lengths (superior to 400 µm) and high pumping power (superior to 550 kW/cm2), leading to an overestimation of the net gain value. We attribute such a phenomenon to the optical feedback provided by the reflection from cracks, which were created during the epitaxial growth due to the strong lattice mismatch between different layers.

A novel technique for the fabrication of a saturable absorber for fiber lasers: pulsed laser deposition

In the present work, for the first time, it is demonstrated that a zinc oxide (ZnO) thin film deposited directly on a fiber ferrule using a pulsed laser deposition (PLD) is a novel technique to prepare a saturable absorber (SA) for doped fiber lasers. The erbium-doped fiber laser based on this SA and erbium-doped fiber as a gain medium yields optical pulses with emission wavelength 1567.86 nm at a 3 dB spectral bandwidth of 1.24 nm at 42 mW. As the pump power is increased, the pulse duration decreases from 23.58 µs to 5.6 µs, and the pulse repetition rates increase from 10.79 kHz to 70.78 kHz. A maximum peak power, pulse energy and average output power of about 9.4 mW, 65.8 nJ, and 4.6 mW, respectively, have been achieved at a maximum pump power of 368 mW. The long-term stability and the damage threshold of the SA are also discussed. These findings suggest that the PLD technique is a promising technique to fabricate a cost-effective and stable SA for the fabrication of passively Q-switched fiber lasers.

Nano-tungsten trioxide saturable absorber for L-band noise-like pulse mode-locked fiber laser

We demonstrate the generation of noise-like pulse (NLP) in L-band erbium-doped fiber laser incorporating nano-tungsten trioxide and polydimethylsiloxane (WO3/PDMS) decorated onto a tapered fiber structure. A Raman pump unit with 3.5 W pump power was employed for a core-pumping scheme of 7 m long highly doped erbium-doped fiber. At the maximum pump power, the NLP lasing wavelength was at 1602 nm with a broad spectral bandwidth of 19.05 nm. The generated pulse was characterized to have 10.38 nJ energy and 19.66 mJ/cm2 output fluence. The measured NLP spike pulse width was 178.87 fs within 56.56 ps pedestal range. This work paves way for future development of generating NLP from nano-tungsten trioxide under extreme pump powers.

2 × 2 kW near-single-mode bidirectional high-power output from a single-cavity monolithic fiber laser.

Traditional monolithic fiber lasers can only achieve unidirectional high-power laser output. In this Letter, a novel high-power linear cavity fiber laser that can achieve bidirectional high-power output is proposed and demonstrated. In an ordinary laser resonant cavity, we replace the high-reflectivity fiber Bragg grating with a low-reflectivity fiber Bragg grating to realize bidirectional laser output. In our experiment, the laser cavity was composed of two fiber Bragg gratings with a reflectivity of about 10%. The pump power provided by the 976 nm laser diodes was injected into a double-clad Yb-doped fiber with core/cladding diameters of 20/400 µm. At the maximum pump power, the bidirectional output powers were 2025 W and 1948 W, respectively, and the output laser beam quality (M2 factor) at both ends was about 1.5. For the first time, to the best of our knowledge, the feasibility of a bidirectional output fiber laser that can achieve double high (2-kW-level) power was verified. Compared with a traditional unidirectional output laser, this type of bidirectional output laser can achieve a double high-power laser by employing a laser resonant cavity. Thus, the average cost and structure size can be further reduced in mass production.

Thermal release tape assisted mechanical exfoliation of pristine TMD and the performance of the exfoliated TMD saturable absorbers for Q-switched laser generation

This research applied an enhanced material exfoliation and transfer mechanism to process various pristine transition metal dichalcogenide (TMD) materials into a few-layer structure. The mechanical exfoliation of the TMD materials was done using a thermal release tape (TRT) with a different adhesion property compared to the scotch tape (ST) commonly used in the conventional scotch tape assisted mechanical exfoliation (ST-ME) technique. The thermal release tape assisted mechanical exfoliation (TRT-ME) performs better than the ST-ME. Four pristine TMD saturable absorbers, including molybdenum disulfide (MoS2), tungsten disulfide (WS2), molybdenum diselenide (MoSe2), and tungsten diselenide (WSe2), have been fabricated using the TRT-ME technique. Subsequently, the performances of these materials were investigated using the same experimental systems and settings. These TMD materials were tested as saturable absorbers (SAs) to induce pulsed lasing in an Erbium-doped fiber laser (EDFL) cavity. The TRT-exfoliated TMD saturable absorbers were incorporated into the laser cavity by sandwiching in between two fiber ferrules using a fiber connector. Incorporating these saturable absorbers into the laser cavity has successfully induced promising Q-switching operations at the C-band region. Besides the pump power-dependent output performance, the stability and wavelength tunability of the Q-switched lasers were also studied at the maximum pump power. The findings from the studies show that the Q-switched lasers induced by the TRT-exfoliated pristine TMD saturable absorbers were stable and wavelength-tunable. In the context of Q-switched laser, the TRT-exfoliated WS2 has the best performance among other pristine saturable absorbers due to its ability to generate the highest pulse energy.

Generation of Kelly and dip type sidebands soliton employing Topological insulator (Bi2Te3) as saturable absorber

Conventional Kelly sidebands soliton and dip-type sidebands soliton were observed with the employment of Bi2Te3 as saturable absorber (SA) in Erbium-Doped Fiber Laser (EDFL). The fabricated Bi2Te3 possessed the following characteristics: Isat 102 MW/cm2, modulation depth 41.4%, and non-saturable absorption at 10%. The Bi2Te3 solution was transferred to the end of the fiber ferrule by the optical deposition method. Conventional Kelly sidebands soliton was obtained with a fundamental repetition rate and pulse width of 24 MHz and 0.78 ps, respectively. The existing cavity length was extended and with the appropriate tuning of light polarization, dip-peak intensity soliton sidebands with bunched pulses were observed. The oscillation trace revealed the repetition rate of dip-peak intensity sidebands soliton was ascertained at 13.5 MHz, which was in accordance with the cavity length. There was a total of 144 pulses in a single bunch envelope under the maximum available pump power. With the appropriate tuning of light polarization, constructive and destructive interference between soliton and dispersive waves took place in EDFL resulting in the formation of peak intensity (Kelly sidebands) and dip-peak intensity on the soliton spectrum. To the best of the author’s knowledge, this is the first demonstration of dip-peak intensity sidebands soliton using Bi2Te3.

Tunable and switchable multi-wavelength actively Q-switched fiber laser based on electro-optic modulator and an improved Sagnac filter

A switchable and tunable multi-wavelength actively Q-switched erbium-doped ring fiber laser based on electro-optic modulator (EOM) and an improved Sagnac filter is proposed and demonstrated. The number of maximum wavelengths obtained is seven in the laser. The maximum wavelength tuning ranges of single and dual-wavelength outputs are about 11 nm and 7 nm respectively. The triple, quadruple and quintuple-wavelength outputs with different kinds of wavelength intervals are obtained. By continuing to adjust the polarization controllers (PCs), the six and seven-wavelength outputs with same intervals are also obtained in this laser. Under the condition of maximum pump power, the maximum output power is 58 μW and the minimum pulse width is less than 2 μs. For the laser output characteristics, the maximum wavelength drift and power fluctuation are 0.17 nm and 0.56 dB respectively.

Aluminum oxide/polydimethylsiloxane-based Q-switched mode-locked erbium-doped fiber laser

A Q-switched mode-locked (QSML) erbium-doped fiber laser integrating aluminum oxide saturable absorber (Al2O3-SA) is demonstrated. With the help of polydimethylsiloxane polymer, Al2O3 powder was securely transferred on a tapered fiber surface and functioned as SA. A QSML pulse sequence was realized at a central wavelength of 1567.4 nm from 80 to 320 mW pump power with its envelope repetition rate ranging from 30.59 to 77.46 kHz. The short duration of 2.54 µs Q-switched envelope comprised of 8.3 ns ML pulses with 252 nJ pulse energy was realized at the maximum pump power of 320 mW. The high damage threshold of Al2O3-SA of beyond 7 GW/cm2 contributes to the future exploration of bulk metal oxide for high-energy optical pulse generation in near-infrared wavelengths.

Saturable absorption property and laser modulation performance of zeolitic imidazolate framework-67 (ZIF-67) at 2.85 µm

In this paper, we prepared zeolitic imidazolate framework-67 (ZIF-67) nanomaterials through the liquid-phase exfoliation method and investigated its nonlinear saturable absorption property at ∼ 3 µm by Z-scan and I-scan method. As a saturable absorber (SA) in the Er:Lu2O3 laser (2.85 µm), the materials show excellent passively Q-switched performance. Under the maximum pump power of 7.3 W, 256-ns laser pulses were delivered at repetition rate of 140-kHz, which corresponds to an average output power of 0.9 W. The experimental results indicated that the ZIF-67 SA is a potential SA candidate in passively Q-switched laser at ∼ 3 µm.

All-Polarization Maintaining Noise-Like Pulse From Mode-Locked Thulium-Doped Fiber Laser Based on Nonlinear Loop Mirror

In this paper, we present a figure-eight all-polarization maintaining thulium-doped mode-locked fiber laser based on a nonlinear optical loop mirror operating at noise-like pulse regimes. The total cavity length is 34.5 m, and the calculated net group delay dispersion is estimated to be ∼−2.616 ps <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . At the maximum pump power, stable noise-like pulse centered at 1943 nm with a spectral full width at half maximum of 32 nm, a pulse energy of 13.51 nJ, and a coherence spike width of 236 fs is generated at a repetition rate of 5.96 MHz with the signal-to-noise ratio ∼64 dB. The polarization extinction ratio is > 15 dB at any mode-locking operation. The slope efficiency and the output power fluctuation of the laser are 5.16% and 0.039%, respectively. The laser does not require polarization state controllers, and it holds very high stability, which is insensitive to temperature changes or mechanical vibrations. Through further amplification, it will be a good laser source for real-time interrogation of fiber Bragg gratings and supercontinuum generation.

Experimental Study Of The Performance Of The Thermal Energy Water Pump Using Tilled Evaporator

Water is one of the important or basic needs for human life. The availability of water in Indonesia is an advantage that our nation has that has not been optimized. Generally, water pumps are driven by electrical energy, but it is possible to be driven by other energy, namely petroleum energy (with a combustion motor). Alternative energy that can be used is thermal energy. Thermal energy can come from coal, solar energy, geothermal or waste heat from industries that are no longer used. The purpose of this study was to determine the discharge, pump power and maximum efficiency. The working fluid used is diethyl ether. The heat comes from an electric stove which will heat the working fluid, namely diethyl ether. The variables measured were temperature, volume and pumping time. Variables that are varied are variations in the height of the pumping head, (1) 170cm, (2) 244cm and (3) 325cm. Variations in the volume of diethyl ether in the reservoir tube, (1) 653ml, (2) 717ml and (3) 844ml. Variations in the volume of compressed air in the compressed tube, (1) 5.49 liters, (2) 4.71 liters, and (3) 3.14 liters. Variations in the use of compressed air tubes, (1) one compressed air tube and (2) two compressed air tubes. The results showed that the maximum discharge of 0.63 liters/minute was obtained at variations in the height of the pumping head 1.7m, ether volume 653ml, compressed air volume 3.14 liters, and using one compressed air tube. The maximum pump power of 0.185 watt and the maximum pump efficiency of 0.047% were obtained at variations in pumping head height of 3.25m, volume of ether 653ml, compressed air volume of 3.14 liters, and using one compressed air tube.

Mode-locked fiber laser with coexistence of m ultiple solitons and noise-like pulses

Dissipative solitons (DSs) usually play an important role in understanding the intricate phenomena in various nonlinear systems. As a special regime in the dissipative system, noise-like pulses (NLPs) can have typical characteristics of ultra-broad and smooth spectrum, high pulse energy and low temporal coherence, making them a good candidate for many applications, including supercontinuum generation, industrial micromachining and optical metrology. In this paper, a noteworthy observation concerning the dynamics on coexistence of the multiple solitons and NLPs operation in a net-normal-dispersion passively mode-locked fiber laser based on nonlinear amplifying loop mirror (NALM) is reported. In the experiment, the stable DSs can be easily obtained at a proper pump power. When appropriately increasing the pump power and changing the polarization state, the DS operation can change to the NLP regime. When the fiber laser operates in an NLP state, the single soliton bunch contains multiple pulses with different temporal spacings. And the temporal interval between the adjacent pulses is in a range of several hundred picoseconds, which decreases from left to right with time changing, indicating that there are long-distance interactions among these multiple pulses and they gradually become stronger and stronger. Besides, the pulse number of single soliton bunches on the NLP operation increases almost linearly with pump power increasing. At a maximum pump power, there are eight pulses inside the single soliton bunch. With the increase of pump power, the average output power and pulse energy of these multiple solitons in the NLP state increase. The maximum average output power and pulse energy are 12.3 mW and 1.65 nJ, respectively. In addition, the real-time dynamic evolution of these multiple solitons in the NLP state is investigated by using the time-stretch dispersive Fourier-transform method. The results show that all the pulses in NLP regime actually consist of chaotic noise waves with stochastic intensities. We believe that this paper will be of significance in studying ultrafast fiber lasers and nonlinear optics. Moreover, we hope that these findings will be helpful in understanding the physical mechanism of NLPs and paving the way for exploring other complex soliton dynamics.

Ti2C MXene for multi-wavelength enhancement in S-band Q-switched thulium doped fluoride fiber laser

A titanium carbide (Ti2C)-based saturable absorber was demonstrated in a compact thulium-doped fluoride fiber laser (TDFFL) configured to generate stable microsecond pulses in single- and multiwavelength operations. An in-line Mach-Zehnder interferometer (MZI) based on a two-mode fiber was incorporated into the laser cavity to generate a birefringent effect that has a fixed free spectral range (FSR) and an extinction ratio (ER) of 0.83 nm and 6.17 dB, respectively. At the maximum pump power of 250 mW, the TDFFL generated single-wavelength Q-switched pulses with a maximum frequency of 35.20 kHz, a pulse width of 3.30 µs, and pulse energy of 2.55 nJ, respectively. In the multiwavelength Q-switching operation, the laser-generated pulses have a frequency, pulse width, and pulse energy of 27.02 kHz, 3.17 µs, and 1.79 nJ, respectively. The proposed single- and multiwavelength Q-switched fiber lasers were stable and compact, making them suitable for industrial applications.

Pr:YAlO3 laser performance enhancement by operating the laser close to liquid helium temperatures

Investigation of Pr3+:YAlO3 (Pr:YAP) lasers operating at cryogenic temperatures close to 4 K at fundamental wavelengths covering the visible spectral range is reported. A microchip resonator geometry formed by cavity mirrors directly deposited on the crystal facets was used. This geometry allows to minimize resonator losses and it is also very attractive due to its compact and rugged design. As a pumping sources, blue InGaN laser diode with maximum available pump power of approx. 4 W at 447 nm wavelength was employed. Cooling of the Pr:YAP crystals close to liquid helium temperatures allowed to significantly improve the Pr:YAP laser performances with respect to room temperature, which yielded in Watt-level laser outputs at all studied wavelengths (747 nm, 622 nm, 547 nm, and 493 nm).

Pulse energy enhancement in a Passively Q-switched Yb:Lu[formula omitted]Y[formula omitted]La[formula omitted]VO4 laser with ReS2 saturable absorber

ReS2 is emerging as a promising saturable absorber for solid-state lasers from visible to mid-infrared. In this paper, we report on a new approach of integrating a ReS2 saturable absorber into Yb:Lu0.74Y0.23La0.01VO4 crystal based Q-switched laser. Under maximum pump power, the highest pulse energy at 1.03 μm wavelength was measured as 5.3 μJ, which is one order of magnitude higher compared with the previously reported 1μm solid-state passively Q-switched lasers based on ReS2 saturable absorber.

Photo-Excited Switchable Terahertz Metamaterial Polarization Converter/Absorber

In this paper, a photo-excited switchable terahertz metamaterial (MM) polarization converter/absorber has been presented. The switchable structure comprises an orthogonal double split-ring resonator (ODSRR) and a metallic ground, separated by a dielectric spacer. The gaps of ODSRR are filled with semiconductor photoconductive silicon (Si), whose conductivity can be dynamically tuned by the incident pump beam with different power. From the simulated results, it can be observed that the proposed structure implements a wide polarization-conversion band in 2.01–2.56 THz with the conversion ratio of more than 90% and no pump beam power incident illuminating the structure, whereas two absorption peaks operate at 1.98 THz and 3.24 THz with the absorption rates of 70.5% and 94.2%, respectively, in the case of the maximum pump power. Equivalent circuit models are constructed for absorption states to provide physical insight into their operation. Meanwhile, the surface current distributions are also illustrated to explain the working principle. The simulated results show that this design has the advantage of the switchable performance afforded by semiconductor photoconductive Si, creating a path towards THz imaging, active switcher, etc.

Lanthanum hexaboride for Q-switching and mode-locking applications

In this paper, a new saturable absorber (SA) based on Lanthanum Hexaboride (LaB6) is used to produce Q-switched and mode-locked laser pulses. In constructing the SA, the prepared LaB6 powder is dispersed in polyvinyl alcohol (PVA) solution before the mixture is dried to form a thin film. A small piece of the film is placed between two fiber ferrules to form a LaB6 PVA SA and added to a laser cavity of an erbium-doped fiber laser (EDFL) to produce Q-switched and mode-locked pulses. The Q-switched laser operates at 1531 nm. The pulse width of the pulses can be varied between 4.32 to 2.46 μs with a corresponding repetition rate of 62.0 to 89.6 kHz when the pump power is increased from 45.4 to 97.6 mW. At the maximum output power of 4.31 mW, the highest pulse energy of 48.1 nJ was obtained. A passively mode locked EDFL was also successfully realized with LaB6 SA by adding 100 m long single mode fiber inside the cavity. A stable mode-locked laser operating at 1559.1 nm was achieved at the threshold pump power of 102.8 mW with a pulse rate of 1.88 MHz. The pulse energy of 5.6 nJ and output power of 10.54 mW were obtained at a maximum pump power of 144.6 mW. To the best of our knowledge, this is the first demonstration of utilizing LaB6 material as SA to produce pulses in the 1.5 μm region.

Carbon nanohorn modulated nanosecond mid-infrared laser

Carbon nanohorn dahlia aggregates with a lateral size of hundreds of nanometers and a height of a few nanometers were prepared utilizing commercial carbon nanohorn powder. In the mid-infrared spectral region (@ 2845 nm), the saturable absorption property of the carbon nanohorn was experimentally investigated. It was employed as a saturable absorber in a Er:Lu2O3 laser. Laser pulses with a shortest pulse duration of 255 ns were yielded at a repetition rate of 149 kHz under the maximum pump power of 6.5 W. To the best of our knowledge, this is the first time that the saturable absorption property of carbon nanohorn was investigated and pulsed lasers were generated with YAG-based CNH in the mid-infrared. Our investigation indicates that carbon nanohorn exhibits a comparable nonlinear optical performance to carbon nanotube in the mid-infrared region. Further investigation of mid-infrared mode-locking lasers can be realized with carbon nanohorn by decreasing the thickness of the carbon nanohorn.

Theory and experiments of a power-ratio tunable dual-wavelength Nd:YVO4/Nd:GdVO4 laser by varying the pump wavelength

We demonstrate the theory and experiments of a power-ratio tunable dual-wavelength laser with coaxial diode end-pumping configuration by varying the pump wavelength, which is realized by controlling the working temperature of the pump laser diode (LD). Composite laser gain media containing an Nd : YVO4 crystal and an Nd : GdVO4 crystal was used for example. The dynamics of the dual-wavelength laser generation based on practical input operating parameters were simulated, and in the experiment, a total power of 3.72 W was obtained under the maximum LD pump power of 8 W, corresponding to the optical–optical conversion efficiency of 46.5%. The characteristics of the power-ratio tuning and output power agreed well with the theoretical predictions.