Q-switched Laser Pulses Research Articles

Dual Eu3+ and Er3+ doping in ZnO nanoporous 2D frameworks for tuning photocatalytic activity, linear and non-linear optical response

Recent days, the greater attention of research materials are focusing on the porous nano frame structure due to their distinctive properties and high photocatalytic activity. The porous defective materials revealed a significant role in numerous research fields like sensors, catalysts, energy production, magnetic memory storage, bio medical etc. In our work, pure ZnO and 4f shell shielded rare earth metals doped ZnO metal oxide nanomaterials attributed in the photocatalytic dye degradation, non-linear optical and magnetic properties. We were synthesized pure ZnO and ZnO0.1–2xEuxErxHMT0.1–2x (2x = 0.025,0.05,0.075, 0.010 wt%) nanoparticles using a straightforward hydrothermal route. The hexagonal wurtzite structure of ZnO and Eu:Er-doped ZnO (Eu:Er@ZnO) exhibited by PXRD, and the optical bandgap (Eg) range from 3.14 eV to 3.18 eV was determined by Tauc relation (αhγ)2 = 0. The porous nanoplate morphology of as-synthesized materials revealed by HR-SEM and HR-TEM techniques. All synthesized materials exposed weak ferromagnetic property nature by VSM studies. Among all the synthesized materials, the 0.0025 wt% Eu:Er@ZnO nanoparticles exhibited porous nanoplate structures capable of catalyzing the breakdown of reactive black 5 (RB5) dye, achieving a photocatalytic activity of 93.2 % after 65 min of UV light exposure. The dopant concentration significantly influenced this photocatalytic activity, with lower concentrations showing enhanced performance, particularly in acidic conditions. Moreover, all synthesized porous nano-plate materials followed pseudo-first-order kinetics. Additionally, the Z-scan technique was employed to assess the nonlinear optical properties of the synthesized materials using Q-switched nanosecond Nd laser pulses at 532 nm wavelength. The open-aperture Z-scan revealed reverse saturable absorption (RSA) in all samples. The Eu:Er@ZnO porous nano-plates exhibited promising nonlinear absorption characteristics, with a higher nonlinear absorption coefficient ranging from 5.21 to 7.84 × 10−11 m/W and a lower optical limiting threshold between 0.87 and 0.95 × 1012 W/m2.

Nanostructured LNTO saturable absorber for generating multi-wavelength laser in Q-switched EDFL

In this paper, we propose a new and efficient ferroelectric nanostructure metal oxide lithium niobate [(Li1.075Nb0.625Ti0.45O3), (LNTO)] solid film as a saturable absorber (SA) for modulating passive Q-switched erbium-doped fiber laser (EDFL). The SA is fabricated as a nanocomposite solid film by the drop-casting process in which the LNTO is planted within polyvinylidene fluoride-trifluoroethylene [P(VDF-TrFE)] as host copolymer. The optical and physical characteristics of the solid film are experimentally established. The SA is incorporated within the cavity of EDFL to examine its capability for producing multi-wavelength laser. The experimental results proved that a multi-wavelength laser is produced, where stable four lines with central wavelengths at 1529.5, 1530.5, 1531.5, and 1532 nm are observed on the laser spectrum at 157 mW pumped power. Furthermore, at maximum available pumped power (157 mW), laser pulses are running with a rate of 178 kHz and pulse width of 2.64 μs. The output power of 3.7 mW is attained at pumped power of 157 mW. The result proved that the LNTO-SA could be a potential candidate for generating multi-wavelength passive Q-switched fiber laser pulses.

Fast fabrication of superhydrophobic Ti-6Al-4V surface using Q-switched nanosecond pulsed laser at 1064 nm and cyclohexane

Superhydrophobic and superhydrophilic surfaces are attracting significant attention in fundamental and applied research. This study fabricated the micro/nanostructure with a Q-switched nanosecond pulsed laser on the Ti-6Al-4V surface. Three laser-generated surface topographies on titanium were produced based on three different pitch sizes (51 μm, 34 μm, and 29 μm). The laser textured surfaces (LTS) were studied in terms of both structure evolution and chemical composition using Field Emission Scanning Electron Microscopy (FE-SEM), Optical Microscopy (OM), Confocal Laser Scanning Microscopy (CLSM), Raman Spectroscopy, and X-ray Diffractometer (XRD). 29 μm pitch displayed the lowest water contact angle of 18.5° and surface roughness of 0.5 μm. This structure was further treated with cyclohexane at different temperatures. The best sample reached superhydrophobicity with a maximum water contact angle of 155.1° immediately after being treated with cyclohexane at the low temperature of 70 °C for 2 h, while the raw surface, for comparison, showed no change in hydrophobicity after being treated with cyclohexane under the same condition. Thus showing clear evidence of a combined effect between LTS and post-treatment. The surface features were assessed to explain the underlying process.

Cerium oxide for L-band Q-switched pulse laser generation

Cerium oxide (CeO2), a rare earth metal oxide belonging to the lanthanide group is a mature engineered nanoparticle that has been developed for various industry applications. The nanoparticle features defects in its lattice structure, which is highly advantageous for bandgap tuning, and is acclaimed for its least cytotoxicity among other metal oxides. In this work, CeO2 is employed as a saturable absorber (CeO2-SA) in the generation of an L-band Q-switched erbium-doped fiber laser. Q-switching was attained at 33.33 mW pump power threshold with a central wavelength of 1600.512 nm. Within 33.33 mW to 153.20 mW pump power range, the Q-switched laser obtained pulse repetition rates between 11.00 to 34.48 kHz, and pulse widths between 39.0 to 12.0 µs, with a high maximum pulse energy of 410 nJ. The Q-switched fiber laser remained stable over a 45-minute observation time at 153.20 mW pump power. The room temperature and direct mechanical deposition fabrication technique of the CeO2-SA in this work demonstrates the extreme simplicity and low cost of the device, which would reduce the overall cost and facilitate a wider technology adoption of pulse laser systems.

Production of Cu/Zn Nanoparticles by Pulsed Laser Ablation in Liquids and Sintered Cu/Zn Alloy

As a preliminary step to establish technology for fabricating High-Entropy Alloys (HEAs) that can make a large-scale HEA using a pulse laser with high peak intensity and high-repetition in the future, we fabricated alloys in which two types of metal atom are mixed close together in the order of nanometers. For the method to produce the alloy, metal alloy nanoparticles were prepared by irradiating the material in liquid with focused high-repetition Q-switched laser pulses using an in-liquid laser ablation method. When brass powder was used as an original material, analysis results by TEM showed that numerous nanoparticles mixed with copper and zinc atoms could be produced. Furthermore, it was clarified by SEM EDS that copper and zinc atoms in the nanoalloy were maintained at a ratio of 3:1 in sintered alloy, and that the atoms were spatially uniformly distributed over a wide range in sintered metal.

Q-switched giant pulsed erbium-doped all-fiber laser with V2ZnC MAX phase saturable absorber

Q-switched giant pulsed erbium-doped all-fiber laser with V2ZnC MAX phase saturable absorber

Single-Shot Intensity- and Phase-Sensitive Compressive Sensing-Based Coherent Modulation Ultrafast Imaging.

Ultrafast imaging can capture the dynamic scenes with a nanosecond and even femtosecond temporal resolution. Complementarily, phase imaging can provide the morphology, refractive index, or thickness information that intensity imaging cannot represent. Therefore, it is important to realize the simultaneous ultrafast intensity and phase imaging for achieving as much information as possible in the detection of ultrafast dynamic scenes. Here, we report a single-shot intensity- and phase-sensitive compressive sensing-based coherent modulation ultrafast imaging technique, shortened as CS-CMUI, which integrates coherent modulation imaging, compressive imaging, and streak imaging. We theoretically demonstrate through numerical simulations that CS-CMUI can obtain both the intensity and phase information of the dynamic scenes with ultrahigh fidelity. Furthermore, we experimentally build a CS-CMUI system and successfully measure the intensity and phase evolution of a multimode Q-switched laser pulse and the dynamical behavior of laser ablation on an indium tin oxide thin film. It is anticipated that CS-CMUI enables a profound comprehension of ultrafast phenomena and promotes the advancement of various practical applications, which will have substantial impact on fundamental and applied sciences.

Porous nano-grained cuprous selenide (Cu2Se) for mid-infrared photonics

Recently, mid-infrared photonics has attracted tremendous attention for various applications. To address the dilemma of the limited variety of materials for mid-infrared photonics, the mid-infrared optical modulation characteristics of the porous nano-grained cuprous selenide (Cu2Se) were investigated for the first time. The large effective nonlinear absorption coefficient, large modulation depth, and low saturation absorption intensity at 2.3 μm indicate that the porous nano-grained Cu2Se were promising saturable absorbers for the generation of Q-switched pulsed laser in the mid-infrared regime. As an application, the Tm:GdVO4 passively Q-switched laser operating on the 3H4 → 3H5 Tm3+ transition was achieved for the first time by using the prepared porous nano-grained Cu2Se as the saturable absorber. The minimum pulse duration and the maximum repetition rate of the stable Q-switched pulse train were 440 ns and 76.9 kHz, respectively. Our results demonstrated that the porous nano-grained Cu2Se was a promising candidate for the mid-infrared photonic applications.

Synthesis of Nano Silicon Using Lasers

Two lasers of the same wavelength (1.06 μm) and various specifications were employed to synthesize silicon nanoparticles. The experimental data reveal the formation of stable silicon nanoparticles with different features such as UV-vis absorption, photoluminescence spectrum, Raman spectrum, Zeta potential, and SEM morphology. Theoretical simulations using COMSOL software were adopted to estimate the surface temperature distribution at the silicon surface and underneath. It is found that maximum temperatures of about (5700 K) and (4600 K) were generated when a Q-switched laser pulse of (10 ns) and fiber laser pulse of (127 ns) were used, respectively. While the recoil pressure at the silicon surface was (6.5*105 N/m2) and (1*103 N/m2) when Nd:YAG and fiber laser were used respectively. It found that increasing the laser energy for Nd:YAG laser and fiber laser power leads to a blue shift of the absorption spectra while the absorption intensity increases with the number of laser pulses and irradiation time. Raman spectroscopy for the prepared silicon nanoparticles was carried out. The Raman peaks for silicon nanoparticles reveal the formation of amorphous silicon. These peaks were observed at (482) and (475 cm-1) when Nd:YAG and fiber lasers were used to produce those nanoparticles. While the photoluminescence of the prepared silicon nanoparticles exhibits peaks at (457 nm) and (495 nm) for Nd:YAG and fiber lasers. The zeta potential reveals that silicon nanoparticle stability is greater for nanoparticles produced by fiber lasers (27 mv) than those produced by Nd:YAG lasers (17 mv) for three months. The corresponding silicon nanoparticle sizes refer to (3.8 nm) and (6 nm). Potential applications of silicon nanoparticles in optoelectronics and biological imaging can be conducted due to the controllable laser micro/nano machining process.

Experimental study of injection seeded single-longitudinal-mode Q-switched fiber laser

--The role of injection seeding power on the operation and output characteristics of a single-longitudinal-mode (SLM) injection seeded Q-switched fiber laser is investigated. The mode coupling between seeding laser and the potential longitudinal-modes of the oscillator changes as the injection seeding power increase. So the Q-switched laser may operate at different regimes which can be distinguished by the pulse features. Only with a proper range of injection seeding power that is not too larger or too small, the operation of injection seeded Q-switched fiber laser with narrow-linewidth, high peak power and narrow pulsewidth laser pulses is possible. The Q-switched fiber laser linewidth is narrowed through inserting a dual-OCs oscillator into the laser cavity. 200-ns, 1-W peak power SLM Q-switched laser pulse with nearly transform-limited linewidth is obtained when the pump power is 300 mW.

Q-switched Erbium Doped Fiber Laser Generation Using the Kerr Effect of Multimode Interference

This work demonstrates a single mode fibre-step index multimode fibre-single mode fibre (SMS) structure as saturable absorber (SA) to generate Q-switched laser based on the Kerr-effect of multimode interference (MMI) in an Erbium-doped fibre laser (EDFL) cavity. A 156 mm length of step index multimode fibre (SIMF) was spliced directly into a ring cavity to modulate the cavity loss. By bending and applying proper pressure on the SIMF, steady Q-switched pulse was generated without strict length restriction of the SIMF. The Q-switched laser had a high repetition rate from 87 to 158 kHz, while the corresponding pulse width was low, ranging from 4.2 μs to 2.5 μs as the pump power increased from 115 to 342 mW. The signal-to-noise ratio (SNR) of the fundamental mode for the pulsed laser was about 67 dB at a central wavelength of 1530 nm. The experiment demonstrated that SMS structure can be used as stable SA to generate Q-switched laser for high power applications. It also indicated that even with large core diameter step index multimode fiber, SMS structure can be utilized to generate stable Q-switched pulsed laser with very simple cavity settings.

Q-switched fiber laser generation utilizing metal oxide-based saturable absorber in the region of 1.0 µm and 1.5 µm

In this study, we explored a saturable absorber (SA) using a metal oxide-biopolymer film, resulting in the generation of Q-switched fiber lasers at 1.0 µm and 1.5 µm wavelengths. A straightforward sonochemical technique was employed to synthesize a nickel oxide (NiO) film in cooperation with Chitosan as a host polymer. The fabricated NiO-Chitosan film exhibits nonlinear absorption properties with modulation depth of 32.20%, saturation intensity of 0.43 kW/cm2, and non-saturable loss of 7.80%. Upon integrating the NiO-Chitosan film into the cavities of Erbium-Doped Fiber Laser (EDFL) and Ytterbium-Doped Fiber Laser (YDFL), the emergence of stable self-starting Q-switched pulsed lasers were observed at 1040.86 nm and 1557.60 nm central wavelength, respectively. Notably, the shortest pulse widths of 0.73 µs and 2.44 µs were achieved, along with maximum repetition rates of 111.61 kHz and 61.73 kHz, respectively, at these wavelengths. Our investigation identifies an effective SA material with good nonlinear absorption properties for inducing Q-switching in the 1.0 µm and 1.5 µm regions. Significantly, the Chitosan properties, encompassing biocompatibility, non-toxicity, and high thermal resistance, combined with the uncomplicated NiO fabrication process and cost-effectiveness, hold promise for diverse applications.

Optical Discharge Regimes Sustained by a Continuously Pumped, Q-Switched Pulsed CO2 Laser

Optical Discharge Regimes Sustained by a Continuously Pumped, Q-Switched Pulsed CO2 Laser

Rate Equations Model to Simulate the Dual Generation of Nd+3: YAG Passive Q-Switched Laser Pulses

Rate Equations Model to Simulate the Dual Generation of Nd+3: YAG Passive Q-Switched Laser Pulses

An Unmanned Vehicle-Based Remote Raman System for Real-Time Trace Detection and Identification

Raman spectroscopy is a type of inelastic scattering that provides rich information about a substance based on the coupling of the energy levels of their vibrational and rotational modes with an incident light. It has been applied extensively in many fields. As there is an increasing need for the remote detection of chemicals in planetary exploration and anti-terrorism, it is urgent to develop a compact, easily transportable, and fully automated remote Raman detection system for trace detection and identification of information, with high-level confidence about the target’s composition and conformation in real-time and for real field scenarios. Here, we present an unmanned vehicle-based remote Raman system, which includes a 266 nm air-cooling passive Q-switched nanosecond pulsed laser of high-repetition frequency, a gated ICMOS, and an unmanned vehicle. This system provides good spectral signals from remote distances ranging from 3 m to 10 m for simulating realistic scenarios, such as aluminum plate, woodblock, paperboard, black cloth, and leaves, and even for detected amounts as low as 0.1 mg. Furthermore, a convolutional neural network (CNN)-based algorithm is implemented and packaged into the recognition software to achieve faster and more accurate detection and identification. This prototype offers a proof-of-concept for an unmanned vehicle with accurate remote substance detection in real-time, which can be helpful for remote detection and identification of hazardous gas, explosives, their precursors, and so forth.

Soliton interaction in a MXene-based mode-locked fiber laser.

MXenes are a class of two-dimensional layered structure ternary metal carbide or/and nitride materials. Recently, the MXene V2CTx has demonstrated excellent long-term stability, strong saturable absorption, and fast optical-switching capability, used to generate Q-switched and ultrashort pulsed lasers. However, bound-state fiber lasers based on V2CTx have not been reported yet. In this study, V2CTx is combined with a D-shaped fiber to form a saturable absorber device, whose modulation depth is measured to be 1.6%. By inserting the saturable absorber into an Er-doped fiber laser, bound states with different soliton separation and munbers are successfully obtained. Additionally, bound states with a compound soliton structure, such as the (2 + 2)- and (2 + 1)-type, are also realized. Our findings show that V2CTx can be developed as an efficient ultrafast photonics candidate to further understand the complex nonlinear dynamics of bound-state pulses in fiber lasers.

Transvascular delivery of talaporfin sodium to subcutaneous tumors in mice by nanosecond pulsed laser-induced photomechanical waves

BackgroundWe previously developed a site-specific transvascular drug delivery system (DDS) based on photomechanical waves (PMWs) or laser-induced stress/shock waves (LISWs). In this study, we investigated the validity of this method to deliver a clinical photosensitizer, talaporfin sodium (TS), to subcutaneous tumors in mice and to enhance the efficacy of photodynamic therapy (PDT). MethodsTS solution (2.5 mg/kg) was intravenously injected into mice. Immediately thereafter, PMWs were applied to the tumor by irradiating a laser target with a Q-switched ruby laser pulse (0.8 J/cm2). Five hours after TS administration, some tumors were excised to evaluate the depth distribution of the delivered TS under a fluorescence microscope. Other tumors were subjected to PDT by irradiating the tissues with a 665 nm continuous-wave laser diode (75 mW/cm2, 667 s) at this timepoint. The effects of PDT were evaluated on the basis of the two primary therapeutic mechanisms of TS-mediated PDT: i) damage to tumor cells and ii) damage to endothelial cells of tumor vessels, i.e., the vascular shutdown effect on tumors. ResultsPMW application significantly increased the accumulation of TS in the tumor parenchyma but not in the tumor vessel walls; the endothelial cell junctions of tumor vessels should be the route of TS delivery enhanced by PMWs. Thus, as a result of PMW application followed by PDT, while the vascular shutdown effect on the tumors was not enhanced, direct damage to the tumor cells was increased, resulting in significant tumor growth retardation without body weight loss for 7 days after treatment.

Generation of dual-wavelength Q-switched laser pulses by employing Mo2Ti2AlC3 MAX phase film

In this paper, we experimentally generate dual-wavelength laser pulses from a Q-switched erbium-doped fiber laser (QS-EDFL) by utilizing molybdenum titanium aluminum carbide (Mo2Ti2AlC3) MAX Phase film. The Mo2Ti2AlC3-SA film, which belongs to the MAX phase compound, is prepared using the mechanical exfoliation. The optical and physical properties of Mo2Ti2AlC3-SA are investigated. The fabricated film has a linear absorption of 8 dB and modulation depth of 17 % at 1.55 mm region. A steady dual-wavelength Q-switched laser pulses are achieved with 1531.6 nm and 1557 nm peaks and a free spectral range (FSR) of 25.4 nm. By increasing the input pump power from 131.87 mW to 167 mW, the repetition rate of generated pulses is varied over 104 kHz to 126 kHz. At the highest input power (167 mW), the energy and output power of the obtained pulses are 87.30 nJ and 11 mW, respectively. The results reveal that the exfoliated Mo2Ti2AlC3-SA can be operated inside EDFL to produce stable pulses with dual wavelengths.

Passively Q-switched Erbium-Doped Fibre Laser Based on Graphene-Chitin Saturable Absorber

Graphene is a carbon allotrope composed of densely packed sp2-assembled carbon atoms in a honeycomb-like crystal lattice. It is widely used in various fields of materials science to develop sensors, optoelectronic devices, nanocomposites, and others due to its excellent electronic, mechanical, optical, and thermal properties. Graphene offers several advantages, including ease of fabrication, ultrafast recovery times, low fabrication cost, and low saturation intensities. Its unique zero bandgap property makes it the only material with wavelength-independent absorption, which is advantageous in generating pulsed lasers using saturable absorbers. This study investigates the performance of graphene with a chitin bio-host polymer as a saturable absorber in a 1.5 µm erbium-doped fibre laser. Graphene embedded in chitin was fabricated and utilized in a pulsed laser cavity operating in the wavelength region of 1.5 µm to enable Q-switched pulsed laser operation. The study achieved a pulse energy of approximately 19.83 nJ and a peak power of 10.72 mW. Increasing the pump power from 30.67 mW to 174.28 mW resulted in the highest repetition rate of 63.40 kHz, corresponding to the shortest pulse width of 1.74 µs. These findings have significant implications for applications requiring ultrafast precision and accuracy, such as medical laser equipment and flexible sensors.

Steady Q-switched erbium-doped fiber laser pulse generation by exploiting spider silk as a passive saturable absorber

Spider silk is a biomaterial composed of natural protein that possesses unique strength and biocompatibility. Spider silk was explored for the first time that act as a potential saturable absorber (SA) for steady Q-switched erbium-doped fiber laser pulse generation around 1569 nm. The biocompatibility of spider silk SA will lead to the realization of an environment that is free from hazardous precursors and undesirable byproducts. In this study, spider silk was directly deposited onto the end face of the fiber ferrule to complete the fiberized SA assembly. In optical characteristic context, the modulation depth of spider silk SA used was 26 % and its saturation intensity was 0.02 MW/cm2. Results showed that self-started Q-switched at 30 mW threshold pump power was achieved. It was also interesting to find that the repetition rate of spider silk SA increased from 7 kHz to 29 kHz while the pulse width decreased from 32 µs to 10 µs. The signal-to-noise ratio (SNR) of the fundamental frequency was 54 dB, confirming the good stability of the pulsed laser. The highest output power and pulse energy measured at the pump power of 200 mW were 0.04 mW and 1.4 nJ respectively. In a nutshell, these results indicate that spider silk can be a viable alternative to real SA for producing laser at the 1570 nm region and spider silk-based SA can be equally with or even superior to the commonly employed SAs, which then opens up new possibilities for pulsed laser source applications.