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Carboxyl graphene oxide solution saturable absorber for femtosecond mode-locked erbium-doped fiber laser
摘要： The carboxyl-functionalized graphene oxide (GO-COOH) is a kind of unique two-dimensional (2D) material and possesses excellent nonlinear saturable absorption property and high water-solubility. In this paper, we prepare saturable absorber (SA) device by depositing GO-COOH nanosheets aqueous solution on a D-shaped ?ber. The modulation depth (MD) and saturable intensity of the SA are measured to be 9.6% and 19 MW/cm2, respectively. By inserting the SA into the erbium-doped ?ber (EDF) laser, a passively mode-locked EDF laser has been achieved with the spectrum center wavelength of 1562.76 nm. The pulse duration, repetition rate, and the signal-to-noise ratio (SNR) are 500 fs, 14.79 MHz, and 80 dB, respectively. The maximum average output power is measured to be 3.85 mW. These results indicate that the GO-COOH nanosheets SA can be used as a promising mode locker for the generation of ultrashort pulses.
关键词： nonlinear optical materials,mode-locked pulse,?ber lasers,carboxyl graphene oxide
更新于2025-11-28 14:24:03
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BaHgGeSe4 and SrHgGeSe4: Two New Hg-based Infrared Nonlinear Optical Materials
摘要： New practically usable IR nonlinear optical (NLO) crystals, especially those suitable for high-efficient pumping of the commercial 1 μm laser, are in urgent demand. However, only a few new IR NLO materials have been grown into bulk crystals and realized IR laser output during the past twenty years due to the extreme difficulty in achieving the coexistence of various strongly-correlated properties. In the manuscript, based on the bonding characteristics of the Hg element and an efficient screening strategy for high-performance new crystals, we identified two new Hg-based IR nonlinear (NLO) materials, BaHgGeSe4 and SrHgGeSe4. They crystallize in the polar space group Ama2 with the distorted HgSe4 and GeSe4 tetrahedra aligned parallelly. They exhibit exceptional balance among all the preferred properties for practical applications, especially for high-efficient pumping of the commercial 1 μm laser: Their large band gap (~2.5 eV) can avoid the two-photon absorption of 1 μm laser and increase the laser damage threshold; They are phase matchable with very strong NLO response (5×AgGaS2); They can cover both the 3-5 μm and 8-12 μm atmospheric windows. Moreover, they melt congruently, which indicate that bulk crystals can be obtained by the Bridgman method. Their overall properties outperform the traditional materials AgGaQ2 (Q = S, Se) in a large degree. Detailed structural analysis and calculations elucidate the crucial role of cations in regulating the packing of the anionic groups and that of the highly-polarizable HgSe4 in balancing optical properties.
关键词： phase matchability,second harmonic generation,BaHgGeSe4,IR nonlinear optical materials,SrHgGeSe4,congruent-melting,Hg-based chalcogenides
更新于2025-11-19 16:56:35
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Polycrystal Synthesis, Crystal Growth, Structure, and Optical Properties of AgGaGe <sub/><i> <i>n</i> </i> </sub> S <sub/> 2( <i> <i>n</i> </i> +1) </sub> ( <i>n</i> = 2, 3, 4, and 5) Single Crystals for Mid-IR Laser Applications
摘要： AgGaGenS2(n+1) crystal is a series of quaternary for mid-IR laser applications of nonlinear optical materials converting a 1.064 μm pump signal (Nd:YAG laser) to 4?11 μm laser output, but only AgGaGeS4 has attracted the most attention, remaining the other promising AgGaGenS2(n+1) crystal whose physicochemical properties can be modulated by n value. In this work, AgGaGenS2(n+1) (n = 2, 3, 4, and 5) polycrystals are synthesized by vapor transport and mechanical oscillation method with di?erent cooling processes. High-resolution X-ray di?raction analysis and re?nement have revealed that all the four compounds are crystallized in the noncentrosymmetric orthorhombic space group Fdd2, resulting in the excellent nonlinear optical property, and the distortion of tetrahedron with the variation of n value causes the discrepancy of physicochemical property. Besides, using the modi?ed Bridgman method, AgGaGenS2(n+1) single crystals with 15 mm diameter and 20?40 mm length have been grown. We have discussed the structure and composition of AgGaGenS2(n+1) by XPS spectra and analyzed the three kinds of vibration modes of tetrahedral clusters by the Raman spectra. The Hall measurement indicates that the AgGaGenS2(n+1) single crystals are p-type semiconductor, and the carrier concentration decreases with the increasing n value. All the transmittances of as-grown AgGaGenS2(n+1) samples exceeds 60% in the transparent range, especially the transmittance of AgGaGe2S6, is up to 70% at 1064 nm, and the band gap of as-grown crystal increases from 2.85 eV for AgGaGe2S6 to 2.92 eV for AgGaGe5S12. After a thermal annealing treatment, the absorptions at 2.9, 4, and 10 μm have been eliminated, and the band gap changed into the range of 2.89?2.96 eV.
关键词： Hall measurement,nonlinear optical materials,thermal annealing treatment,vapor transport,AgGaGenS2(n+1),Bridgman method,Raman spectra,mid-IR laser applications,XPS spectra,mechanical oscillation method
更新于2025-11-14 15:27:09
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Growth, optical, mechanical and thermal behavior of unidirectionally grown L-Glutaminium p-Toluenesulfonate crystal
摘要： Organic crystal of L-Glutaminium p-Toluenesulfonate (LGPT) was grown unidirectional by Sankaranarayanan and Ramasamy (SR) method. The grown crystal belongs to monoclinic crystal system with noncentrosymmetric space group P21. High resolution XRD confirms crystalline perfection of the grown crystal. Optical transmission shows that unidirectional grown crystal has higher transmittance and the lower cut-off wavelength is 290 nm. The emission wavelength of grown crystal is 410 nm and emission region is confirmed by luminescence spectra. The laser damage threshold value of unidirectional crystal has increased by 0.3 GW/cm2. The grown LGPT crystals belong to hard material category and it confirms the normal indentation size effect. The grown LGPT crystal is thermally stable upto 165 oC and decomposition of the molecules were elucidated by using TGA and DSC. Powder second harmonic generation measurement confirms the efficiency of the grown LGPT crystal is 0.8 times that of KDP.
关键词： Nonlinear optical materials,Crystal growth,Recrystallization,Optical properties
更新于2025-09-23 15:23:52
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Pb <sub/>2</sub> GaF <sub/>2</sub> (SeO <sub/>3</sub> ) <sub/>2</sub> Cl: Band Engineering Strategy by Aliovalent Substitution for Enlarging Bandgap while Keeping Strong Second Harmonic Generation Response
摘要： Wide bandgap and strong second-order generation (SHG) effect are two crucial but contradictory conditions for practical nonlinear optical (NLO) materials. Herein, a new NLO crystal Pb2GaF2(SeO3)2Cl (I) containing novel functional (GaO3F3)6? octahedra is designed and synthesized by a rational band engineering strategy with aliovalent substitution. Benefiting from the removal of transition metal cations and the introduction of bridged F anions, I exhibits the widest bandgap among all reported phase-matchable NLO selenites. Meanwhile, a strong SHG response more than 4.5 times of KH2PO4 (KDP) is maintained. The dominate role of the (GaO3F3)6? groups to the enlarged bandgap in I are elucidated by first-principles studies.
关键词： aliovalent substitution,second harmonic generation,nonlinear optical materials,selenites,band engineering
更新于2025-09-23 15:21:21
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Light control through a nonlinear lensing effect in a colloid of biosynthesized gold nanoparticles
摘要： Biosynthesis of four samples of colloidal suspensions of gold nanoparticles is achieved using hydroalcoholic extract and three different separated compounds of the plant Bacopa procumbens. The nonlinear optical properties of each sample are characterized with the Z-scan technique. In all cases, the Z-scan curves indicate a negative or self-defocusing response, which is mainly attributed to thermal effects. Among the four samples, the hydroalcoholic extract was noted to have the highest nonlinear optical response and was selected to demonstrate the formation of self-collimated beams (SCBs). This kind of beams are obtained when a convergent CW laser, with only few tens of milliwatts of optical power, is introduced into the sample and induces a negative-lens effect that shifts the focal spot forward. As a result, the otherwise highly focused beam propagate with little divergence over lengths of up to 10 mm. Moreover, an SCB is capable of controlling and steering a weak probe beam of a different wavelength, since the probe experiences the lensing induced by the pump. Noteworthy, the response time of the material was found to be less than 0.07 s, which makes it a plausible candidate for photonic applications.
关键词： gold nanoparticles,Nonlinear optics,nonlinear optical materials,self-effects
更新于2025-09-23 15:21:01
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Linear-nonlinear optical, dielectric and surface microscopic investigation of KH2PO4 crystal to uncover the decisive impact of dopant glycine
摘要： Present investigation has been started to perform the comparative study of pure and glycine doped KH2PO4 (KDP) single crystals grown by most commercial slow solvent evaporation technique. The grown crystals were subjected to single crystal X-ray diffraction analysis to determine their structural parameters. The linear optical studies of pure and glycine doped KDP crystal have been undertaken within 200 nm to 1100 nm wavelength range by means of UV-Vis studies. The enhancement in second harmonic generation (SHG) ef?ciency of glycine doped KDP crystal has been determined using a standard Kurtz-Perry powder test. The dielectric measurements have been carried out to explore the impact of glycine dopant on dielectric constant and dielectric loss of KDP crystal. The surface growth habitat and etch pit density of glycine doped KDP crystal have been evaluated using the results of microscopic etching studies. In light of obtained results the suitability of glycine doped KDP crystal for device applications has been discussed.
关键词： optical studies,etching studies,crystal growth,dielectric studies,nonlinear optical materials
更新于2025-09-23 15:19:57
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Q-switched all-fiber laser based on MoSe <sub/>2</sub> films with chemical vapor deposition method
摘要： In this work, MoSe2 ˉlm is synthesized by the chemical vapor deposition method. Saturable absorber (SA) is assembled with the tapered ˉber and MoSe2 ˉlms. Q-switched operation is achieved with the MoSe2-based SA. The experimental result reveals that the MoSe2-based SA has excellent saturable absorption characteristic with 23.41% modulation depth. When the pump power is greater than 289.2 mW, Q-switched all-ˉber lasing action is demonstrated. The repetition rate of the Q-switched pulses varies from 185.6 to 252.8 kHz. The shortest pulse duration is 801.9 ns, and the largest output energy is 69.3 nJ. Results indicate that MoSe2 ˉlms can provide new opportunities for large-modulation-depth optical modulators in ultrafast photonics.
关键词： Q-switched,saturable absorbers,ˉber laser,Nonlinear optical materials
更新于2025-09-23 15:19:57
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Enhancement of nonlinear optical and thermal properties of polyurethanes by modifying the chromophores with fused heterocyclic and pyrimidine rings
摘要： This article describes the synthesis of substituted triazolo[3,4-b]-thiadiazole heterocycles based nonlinear optical (NLO) responsive chromophores. To enhance the NLO properties of the chromophores, the pyrimidine ring was introduced with an appropriate π-bonding. With these chromophores, different series of polyurethanes were prepared by condensation with tolylene-2,4-diisocyanate and 3,30-dimethoxy-4,40-biphenylene diisocyanate. The structure of the resulting chromophores and polyurethanes was confirmed using Fourier transform infrared, proton nuclear magnetic resonance, and Carbon Hydrogen Nitrogen (CHN) analyzer. The inherent viscosities (ηinh) of the polyurethanes measured by Ubbelohde viscometer were in the range of 0.2324–0.2760 dl/g. Thermal behavior of the polyurethanes was investigated using differential scanning calorimetry and thermogravimetric analysis. The molecular orientation in polyurethane films was induced by a corona poling, and this was ascertained using ultraviolet-visible spectrophotometer and atomic force microscope. The thicknesses and refractive indices of thin films were determined by an Ellipsometer. Polyurethanes exhibited excellent solubility in most of the common organic solvents. The second harmonic generation (SHG) coefficients (d33) of the poled polyurethanes ranged from 63.20 and 95.32 pm/V at 532 nm. None of the polyurethanes showed SHG decay below 100°C, and retained 95% of the signal even up to 500 h. The resulting enhanced NLO efficiency and longer temporal stability make these polyurethanes as promising candidates for photonic devices.
关键词： Polyurethanes,Second harmonic generation,Chromophores,Thermal stability,Nonlinear optical materials
更新于2025-09-23 15:19:57
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Photonic and Electronic Properties of Fluoride Materials || Frequency-Doubling Oxide Fluorides, Borate Fluorides, and?Fluorooxoborates
摘要： The frequency-doubling (FD) materials that are able to expand the frequency ranges of lasers by second harmonic generation (SHG) are the core of the solid-state lasers. FD is a nonlinear optical (NLO) process, in which two input laser beams with the same frequency interacting with an FD material “combine” together to generate a new output laser with twice the frequency and half the wavelength of the initial light beams. This phenomenon was first demonstrated by Franken et al. in 1961. They irradiated a quartz sample using a laser beam with a wavelength of 694 nm, and observed the output light at 347.2 nm. FD is only allowed with coherent light and in mediums without inversion symmetry.
关键词： Nonlinear Optical Materials,Borate Fluorides,Second Harmonic Generation,Frequency-doubling,Fluorooxoborates
更新于2025-09-23 15:19:57