Tunable and Passively Mode-Locking Nd0.01:Gd0.89La0.1Nbo4 Picosecond Laser

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Article Tunable and Passively Mode-Locking Nd0.01:Gd0.89La0.1NbO4 Picosecond Laser

Shande Liu 1, Yuqing Zhao 1, Ke Zhang 1, Bo Chen 1, Ning Zhang 1, Dehua Li 1,*, Huiyun Zhang 1, Yuping Zhang 1, Lihua Wang 1,*, Shoujun Ding 2,3,4,* and Qingli Zhang 4

1 College of Electronic and Information Engineering, Shandong University of Science and Technology, Qingdao 266590, China; [email protected] (S.L.); [email protected] (Y.Z.); [email protected] (K.Z.); [email protected] (B.C.); [email protected] (N.Z.); [email protected] (H.Z.); [email protected] (Y.Z.) 2 School of Science and Engineering of Mathematics and Physics, Anhui University of Technology, Maanshan 243002, China 3 Key Laboratory of Optoelectronic Materials Chemistry and Physics, Chinese Academy of Sciences, Fuzhou 350002, China 4 The Key Laboratory of Photonic Devices and Materials, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China; [email protected] * Correspondence: [email protected] (D.L.); [email protected] (L.W.); [email protected] (S.D.)

Abstract: A high-quality Nd0.01:Gd0.89La0.1NbO4 (Nd:GLNO) crystal is grown by the Czochralski method, demonstrating wide absorption and ﬂuorescence spectra and advantage for producing ultrafast laser pulses. In this paper, the tunable and passively mode-locking Nd:GLNO lasers are

characterized for the ﬁrst time. The tuning coverage is 34.87 nm ranging from 1058.05 to 1092.92 nm with a maximum output power of 4.6 W at 1065.29 nm. A stable continuous-wave (CW) passively mode-locking Nd:GLNO laser is achieved at 1065.26 nm, delivering a pulse width of 9.1 ps and a Citation: Liu, S.; Zhao, Y.; Zhang, K.; Chen, B.; Zhang, N.; Li, D.; Zhang, H.; maximum CW mode-locking output power of 0.27 W. Zhang, Y.; Wang, L.; Ding, S.; et al. Tunable and Passively Mode-Locking Keywords: Nd:GLNO crystal; tunable laser; mode-locking

Nd0.01:Gd0.89La0.1NbO4 Picosecond Laser. Molecules 2021, 26, 3179. https://doi.org/10.3390/molecules 26113179 1. Introduction Ultrafast lasers have been applied in various fields, such as high-precision micro Academic Editor: Kejian Yang machining, aerospace, and medical diagnostics [1,2]. Benefiting from their low quantum defects, wide gain bandwidth, and simple three-level electronic structure, Yb3+-doped Received: 7 May 2021 laser mediums attract widespread attention in the 1 µm band [3–5]. However, the overlap Accepted: 24 May 2021 of absorption and emission bands can bring re-absorption loss, resulting in high laser Published: 26 May 2021 threshold. Compared with Yb3+-doped gain mediums, Nd3+-doped crystals have no re- absorption loss and are used in low-threshold and high-efficiency ultrafast laser. As is Publisher’s Note: MDPI stays neutral known, the typical gain bandwidth of the Nd3+-doped laser materials is narrow, e.g., the with regard to jurisdictional claims in gain bandwidth of the Nd:YVO and Nd:YAG crystals were measured to be only 0.96 and published maps and institutional affil- 4 iations. 0.80 nm, respectively [6,7]. For this reason, considerable efforts have been made to explore novel Nd3+-doped laser materials with a broad gain bandwidth. The pulse duration of 19.2 ps at 1064 nm was achieved in a passively mode-locked Nd:YVO4 laser in 2008 [8]. Mohammad et al. [9]. reported pulse duration of 16 ps generation in a Nd:GdVO4 crystal in 2017. He et al. [10]. obtained 3.8 ps pulse duration at a repetition rate of 112 MHz in a Copyright: © 2021 by the authors. Nd:GdYVO4 crystal. Previously, theoretical and experimental results have demonstrated Licensee MDPI, Basel, Switzerland. that Nd3+-doped disordered crystals possess broad emission spectra and are suitable for This article is an open access article generating ultrashort lasers [11–13]. distributed under the terms and conditions of the Creative Commons In the last decade, researchers have invested tremendous enthusiasm into extending 3+ Attribution (CC BY) license (https:// Nd -doped disordered crystals family and exploring their excellent properties. In 2017, creativecommons.org/licenses/by/ a novel disordered crystal Nd0.01:Gd0.89La0.1NbO4 (Nd:GLNO) was successfully grown 4.0/). by Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences [14].

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novel disordered crystal Nd0.01:Gd0.89La0.1NbO4 (Nd:GLNO) was successfully grown by Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences [14]. Owing 3+ 3+ to La3+ having Owinga relatively to La largehaving ionic aradi relativelyus in the large lanthanide ionic radius system, in the the La lanthanide3+-doped dis- system, the La - doped disordered crystals exhibit a wider fluorescence bandwidth [15]. Moreover, the ordered crystals exhibit a wider fluorescence bandwidth3+ [15].3+ Moreover, the difference in ionic radii betweendifference La3+ and in ionic Gd3+ radiiions is between small, denoting La and the Gd Nd:GLNOions is small, crystal denoting possesses the Nd:GLNO excellent latticecrystal matching possesses and thermal excellent property lattice matching [16,17]. The and fluorescence thermal property lifetime [16 and,17]. the The fluorescence lifetime and the radiative lifetime of Nd:GLNO crystal was obtained to be 176.1 µs and radiative lifetime of Nd:GLNO crystal was obtained to be 176.1 μs and 184.5 4μs, respec- 184.5 µs, respectively. The luminescent quantum efficiency of the F3/2 level was estimated tively. The luminescent quantum efficiency of the 4F3/2 level was estimated to be 95.4% to be 95.4% [18]. Ma et al. presented the CW and passively Q-switched Nd:GLNO lasers [18]. Ma et al. presented4+ the CW and passively Q-switched Nd:GLNO lasers with with Cr :YAG crystal and PdSe2 as saturable absorbers (SAs), respectively, in 2018 and Cr4+:YAG crystal and PdSe2 as saturable absorbers (SAs), respectively, in 2018 and 2020 2020 [15,19]. Unfortunately, the tunable and CW mode-locking Nd:GLNO crystal lasers [15,19]. Unfortunately, the tunable and CW mode-locking Nd:GLNO crystal lasers have have not been studied to date. not been studied to date. In this paper, the absorption and florescence spectra of the Nd:GLNO crystal were In this paper, the absorption and florescence spectra of the Nd:GLNO crystal were sys- systematically investigated demonstrating a wide absorption and emission band. A tunable tematically investigated demonstrating a wide absorption and emission band. A tunable operation Nd:GLNO crystal laser was realized with a tuning range of 34.87 nm from 1058.05 operation Nd:GLNO crystal laser was realized with a tuning range of 34.87 nm from 1058.05 to 1092.92 nm. By employing a semiconductor saturable absorber mirror (SESAM) as SA, to 1092.92 nm.a By stable employing CW mode-locking a semiconductor Nd:GLNO saturable crystal absorber laser mirror was achieved, (SESAM) generating as SA, a the shortest stable CW mode-lockingpulse duration Nd:GLNO of 9.1 ps crystal and the lase maximumr was achieved, mode-locking generating output the power shortest of 0.27 W. pulse duration of 9.1 ps and the maximum mode-locking output power of 0.27 W. 2. Experimental Setup 2. Experimental Setup Figure1 demonstrates schematic setups of the Nd:GLNO lasers. The 808 nm laser Figure 1 demonstratesdiode was chosen schematic as a setups pump of source the Nd:GLNO with a core lasers. diameter The 808 of nm 400 laserµm anddi- a numerical ode was chosenaperture as a pump (NA) source of 0.22. with The a core size diameter of the c-cutof 400 Nd:GLNO μm and a numerical crystal was aperture 2 × 2 × 5 mm3. To (NA) of 0.22. Theeffectively size of the reduce c-cut Nd:GLNO the influence crystal of thermalwas 2 × 2 effects, × 5 mm3 the. To laser effectively crystal reduce was covered with the influence ofindium thermal and effects, embedded the laser into cr aystal copper was block. covered The with cooling indium temperature and embedded of the copper block into a copper block.was controlled The cooling at temperature 15.5 ◦C. The of total the lasercopper cavity block length was controlled of the mode-locking at 15.5 °C. and tunable The total laser laserscavity waslength 1.94 of mthe and mode-locking 0.33 m, respectively. and tunable Mirrorslasers was M 11.94,M 2m,M and4,M 0.335 and m, M6 were all respectively. Mirrorsprocessed M1 with, M2, anti-reflectionM4, M5 and M (AR)6 were coating all processed around 808with nm anti-reflection and high-reflection (AR) coating (HR, coating aroundR 808 > 99.9%) nm and at 1030–1100high-reflection nm. Thecoating curvature (HR, R radii > 99.9%) were at R 1030–1100 = ∞, R = 200, nm. R The = ∞ , R = 300 and curvature radiiR were = 150 R mm,= ∞, R respectively. = 200, R = ∞, The R = 300 output andmirror R = 150 M mm,3 was respectively. partial transmittances The output (T) coated at mirror M3 was1030–1100 partial transmittances nm (T = 1, 10, (T) 15%, coated 25% at are1030–1100 available). nm (T A = quartz 1, 10, birefringent15%, 25% are filter (BF) was available). A quartzemployed birefringent in tunable filter laser (BF) cavity was employed to achieve in laser tunable tuning laser operation. cavity to Theachieve parameters of the laser tuning operation.SESAM areThe as parameters follows: saturable of the SESAM fluence are is as 90 follows:µJ/cm2 ,saturable absorptance fluence is 1.5%, is 90 a modulation μJ/cm2, absorptancedepth is is 1.5%, 0.8%, a damage modulation threshold depth isis 300.8%, mJ/cm damage2, and threshold a relaxation is 30 mJ/cm time is2, 1 ps. A laser and a relaxationpower time meteris 1 ps. (Fieldmax-II, A laser power PM10) meter was (Fieldmax-II, used for measuring PM10) was laser used power. for meas- The laser output uring laser power.spectra The and laser pulse output width spectra of mode-locked and pulse width Nd:GLNO of mode-locked laser were measuredNd:GLNO by la- a spectrometer ser were measured(Avantes, by a AcaSpec-3468-NIR256-2.2)spectrometer (Avantes, AcaSpec-3468-NIR256-2.2) and a commercial autocorrelator and a commer- (APE Pulse Check, cial autocorrelator150), (APE respectively. Pulse Check, The 150), typical respectively. pulse profile The andtypical pulse pulse train profile were and recorded pulse by a digital train were recordedoscilloscope by a digital (R&S, oscilloscope RTO 2012) (R&S, together RTO with 2012) a fast together InGaAs with photon a fast detectorInGaAs (New Focus, photon detector1611). (New Focus, 1611).

FigureFigure 1. Schematic 1. Schematic setups setups of the of Nd:GLNOthe Nd:GLNO laser, laser, (a) tunable (a) tunable operation; operation; (b) CW (b) CW mode-locking mode-locking operation. operation. 3. Results and Discussion 3. Results and Discussion Figure2 presents the absorption and ﬂuorescence spectra of the c-cut Nd:GLNO Figure 2 presentscrystal at the room absorption temperature. and fluorescence As shown in spectra Figure of2a, the the c-cut absorption Nd:GLNO peak crys- is at 808 nm and tal at room temperature. As shown in Figure 2a, the absorption peak is at 808 nm and FWHM is 13 nm. Based on the equation σ = α(λ)/Nc, where α is the absorption coefﬁcient FWHM is 13 nm. Based−1 on the equation σ = α(λ)/Nc, where 3+α is the absorption coefficient (8.97 cm ) and Nc is the concentration of Nd , the maximum absorption cross-section of the Nd:GLNO crystal was calculated to be 10.49 × 10−20 cm2. Moreover, the stimulated

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Molecules 2021, 26, 3179 3 of 7 (8.97 cm−1) and Nc is the concentration of Nd3+, the maximum absorption cross-section of (8.97the Nd:GLNO cm−1) and N crystalc is the wasconcentration calculated of toNd be3+, the10.49 maximum × 10−20 cm absorption2. Moreover, cross-section the stimulated of −20 2 theemission Nd:GLNO cross-section crystal was (ߪ ୣ୫calculated) can be toestimated be 10.49 ×from 10 thecm fluorescence. Moreover, the spectra stimulated using the emission cross-section (σem) can be estimated fromఒఱ theூሺఒሻ fluorescence spectra using the emission cross-section (ߪୣ୫) can be estimated from5 the fluorescence spectra using the Füchtbauer–Ladenburg equation: ߪୣ୫ሺߣሻ ൌ ఱλమ I(λ) [19,20], where τm, c, n, I(λ) are గ௡ఒ ூሺఒሻ௖ఛౣ׬ఒூሺఒሻୢఒ c n I଼ = ( ) Füchtbauer–Ladenburg equation: σem λ 8πn2cτ R λI(λ)dλ [19,20], where τm, , , (λ) Füchtbauer–Ladenburg equation: ߪୣ୫ሺߣሻ ൌ మ m [19,20], where τm, c, n, I(λ) are arethe the fluorescence fluorescence lifetime, lifetime, velocity velocity of of light, light,଼గ௡ re reflectiveflective௖ఛౣ׬ఒூሺఒሻୢఒ index and fluorescencefluorescence intensity, intensity, the the fluorescence lifetime, velocity of light, reflective index −and20 fluorescence2 intensity, the thecalculated calculated stimulat stimulateded emission emission cross-section cross-section of of 18 18 ×× 1010−cm20cm was2 was relatively relatively large, large, which calculated stimulated emission cross-section of 18 × 10−20cm2 was relatively large, which whichwas suitable was suitable for generating for generating ultrafast ultrafast laser laser pulse. pulse. was suitable for generating ultrafast laser pulse.

FigureFigureFigure 2.2. 2.Absorption Absorption Absorption andand and ﬂuorescencefluorescence fluorescence spectraspectra spectra ofof the theof the Nd:GLNONd:GLNO Nd:GLNO crystal.crystal. crystal. ((aa)) AbsorptionAbsorption (a) Absorption spectra;spectra; spectra; (b) (b) FluorescenceFluorescenceFluorescence spectra.spectra. spectra.

AAA V-typeV-type V-type laserlaser laser cavitycavity cavity was was designed designed to to toinvest investigate investigateigate the the theCW CW CW laser laser laser output output output properties properties properties of of ofthethe the Nd:GLNO Nd:GLNO Nd:GLNO crystals. crystals. crystals. Figure Figure Figure 3 displays3 displaysdisplays the thethe relationship relationship relationship between between between output output output power power power and and ab-and ab- absorbed pump power at different transmittances of output couplers. The maximum CW sorbedsorbed pump pump power power at at different different transmittanc transmittances esof outputof output couplers. couplers. The Themaximum maximum CW CW output power of 4.60 W was achieved with the output mirror of T = 15%, corresponding outputoutput power power of of 4.60 4.60 W W was was achieved achieved with with th eth outpute output mirror mirror of T of = T15%, = 15%, corresponding corresponding toto anan optical-to-opticaloptical-to-optical efficiencyefficiency of of 37.90%37.90% andand aa slopeslope efficiencyefficiency ofof 49.67%.49.67%. Furthermore,Furthermore, theto laseran optical-to-optical output wavelength efficiency could be of flexibly37.90% tunedand a byslope carefully efficiency varying of 49.67%. the angle Furthermore, of the thethe laser laser output output wavelength wavelength could could be be flexibly flexibly tuned tuned by carefullyby carefully varying varying the anglethe angle of the of the BF.BF. Table Table1 1records records the the tuning tuning wavelength wavelength and and the the corresponding corresponding output output power power with with the the BF. Table 1 records the tuning wavelength and the corresponding output power with the outputoutput couplerscouplers ofof T=T= 1%,1%, 10%10% andand 15%,15%, respectively.respectively. AsAs thethe transmittancetransmittance increased,increased, the the output couplers of T= 1%, 10% and 15%, respectively. As the transmittance increased, the longitudinallongitudinal modemode oscillationoscillation inin thethe cavitycavity was was suppressed.suppressed. Therefore,Therefore, thethe tuningtuning rangerange longitudinal mode oscillation in the cavity was suppressed. Therefore, the tuning range waswas further further reduced. reduced. The The total total tuning tuning coverage coverage of theof the Nd:GLNO Nd:GLNO crystal crystal laser laser was was 34.87 34.87 nm rangingwas further from 1058.05reduced. to The 1092.92 total nm. tuning Figure covera4 demonstratesge of the theNd:GLNO typical singlecrystal wavelength laser was 34.87 nm ranging from 1058.05 to 1092.92 nm. Figure 4 demonstrates the typical single wave- and multi-wavelength spectra of the Nd:GLNO crystal tunable laser. lengthnm ranging and multi-wavelength from 1058.05 to spectra 1092.92 of nm. the Nd:GLNOFigure 4 demonstrates crystal tunable the laser. typical single wavelength and multi-wavelength spectra of the Nd:GLNO crystal tunable laser.

FigureFigure 3.3.Output Output powerpower versusversus absorbedabsorbed pumppump power.power. Figure 3. Output power versus absorbed pump power.

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FigureFigure 4. 4.Typical Typical output output spectra spectra of the tunableof the tu Nd:GLNOnable Nd:GLNO laser with T laser = 1%. with T= 1%.

TableTable 1. 1.Output Output parameters parameters of the of tunable the tunable Nd:GLNO Nd:GLNO crystal laser. crystal laser. T (%) Wavelength (nm) Output Power (W) T (%) Wavelength (nm) Output Power (W) 1058.05 0.83 1065.291058.05 1.11 0.83 1065.611065.29 0.86 1.11 1 1091.98 0.58 1092.291065.61 1.00 0.86 1092.61 0.98 1 1092.921091.98 0.79 0.58 1065.291092.29 4.13 1.00 10 1092.29 3.03 1092.611092.61 2.83 0.98 1065.291092.92 4.60 0.79 15 1092.291065.29 0.43 4.13 1092.61 0.31 10 1092.29 3.03 To realize the CWML Nd:GLNO laser operation,1092.61 a Z-type laser cavity was employed2.83 as shown in Figure1b. Ultrafast laser pulse output1065.29 was achieved using a SESAM. To4.60 reduce the intracavity loss and make the SESAM easily saturated, the CWML laser output 15 1092.29 0.43 characteristics were obtained experimentally at the output mirror of Toc = 1%. As shown in Figure5, the minimum absorbed pump power1092.61 to suppress Q-switched mode-locking0.31 laser was 3.05 W. The maximum CWML laser output power 0.27 W was achieved. The CWMLTo pulse realize train the was CWML measured Nd:GLNO using a detector laser operation, and 1 GHz a bandwidth Z-type laser oscilloscope. cavity was employed Figure6 presents the stable mode-locking pulses recorded at nanosecond and microsecond astime shown scales, in respectively. Figure 1b. The Ultrafast pulse repetition laser pulse rate (PRR) output is 51.6 was MHz achieved corresponding using a to SESAM. the To reduce thecavity intracavity length of 1.94loss m. and Figure make7 demonstrates the SESAM the easily signal-to-noise saturated, ratio the of CWML the ﬁrst laser beat. output charac- teristicsThe radio were frequency obtained spectrum experiment was cleanally and at stable,the output indicating mirror excellent of Toc stability= 1%. As of shown the in Figure 5, themode-locking minimum ultrafast absorbed laser. pump The signal-to-noise power to suppre ratio wasss up Q-switched to 72.3 dB at themode-locking fundamental laser was 3.05 W.frequency The maximum of 51.6 MHz. CWML The FWHM laser output bandwidth power of the 0.27 autocorrelation W was achieved. trace was The about CWML pulse train 14.0 ps, corresponding to a pulse duration of 9.1 ps by a sech2-shape pulse ﬁtting. The wasmode-locking measured pulse using spectrum a detector was shown and in 1 theGHz inset band of Figurewidth8. Theoscilloscope. central wavelength Figure 6 presents the stableof the measured mode-locking pulse was pulses located recorded at 1065.26 at nm nanose with acond FWHM and of 0.9 microsecond nm. time scales, respectively. The pulse repetition rate (PRR) is 51.6 MHz corresponding to the cavity length of 1.94 m. Figure 7 demonstrates the signal-to-noise ratio of the first beat. The radio frequency spectrum was clean and stable, indicating excellent stability of the mode-locking ultrafast laser. The signal-to-noise ratio was up to 72.3 dB at the fundamental frequency of 51.6 MHz. The FWHM bandwidth of the autocorrelation trace was about 14.0 ps, corresponding to a pulse duration of 9.1 ps by a sech2-shape pulse fitting. The mode-locking pulse spectrum was shown in the inset of Figure 8. The central wavelength of the measured pulse was located at 1065.26 nm with a FWHM of 0.9 nm.

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FigureFigureFigure 5. 5.5.The The TheThe CW CW CWCW mode-locking mode-locking mode-lockingmode-locking output output outputoutput power power power versus versus versus the the absorbed absorbed the absorbed pump pump power. pump power. power.

Figure 6. Pulse train of the CW mode-locking Nd:GLNO crystal laser. FigureFigureFigure 6. 6.6.Pulse PulsePulse train traintrain of theofof thethe CW CWCW mode-locking mode-lockingmode-locking Nd:GLNO Nd:GLNO crystal crystal laser. laser.

Figure 7. Recorded RF trace.

FigureFigureFigure 7. 7.7.Recorded RecordedRecorded RF RFRF trace. trace.trace.

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FigureFigure 8. 8.Mode-locking Mode-locking pulse pulse duration duration and the an correspondingd the corresponding spectrum. spectrum.

4. Conclusions 4. Conclusions In conclusion, the Nd:GLNO crystal was grown by the Czochralski method and the spectralIn characteristicsconclusion, the at room Nd:GLNO temperature crystal were was discussed. grown Theby the maximum Czochralski CW output method and the powerspectral of 4.60characteristics W was obtained at room with thetemperatur output mirrore were of Tdiscussed. = 15%, corresponding The maximum to an CW output optical-to-opticalpower of 4.60 efficiencyW was obtained of 37.90% andwith a slopethe output efficiency mirror of 49.67%. of T The = tuning15%, corresponding coverage to an ofoptical-to-optical the tunable Nd:GLNO efficiency laser was of 34.87 37.90% nm atand T = a 1% slope ranging efficiency from 1058.05 of 49.67%. to 1092.92 The nm. tuning cover- To the best of our knowledge, a picosecond CWML Nd:GLNO laser at 1065.26 nm was age of the tunable Nd:GLNO laser was 34.87 nm at T = 1% ranging from 1058.05 to 1092.92 experimentally demonstrated using a SESAM as saturable absorber for the first time. The maximumnm. To the CWML best laserof our output knowledge, power of a 0.27 picosecond W was achieved. CWML The Nd:GLNO Nd:GLNO laser crystal at 1065.26 nm ultrafastwas experimentally laser produced demonstrated 9.1 ps mode-locked using pulses a SESAM with pulse as saturable repetition rate absorber of 51.6 MHzfor the first time. andThe a maximum signal-to-noise CWML ratio oflaser 72.3 output dB. The power results indicatedof 0.27 W that was the achieved. Nd:GLNO The crystal Nd:GLNO is a crystal promisingultrafast Ndlaser3+-doped produced gain medium9.1 ps mode-locked for generating puls ultrafastes with laser pulse pulses. repetition rate of 51.6 MHz and a signal-to-noise ratio of 72.3 dB. The results indicated that the Nd:GLNO crystal is a Author Contributions: Conceptualization, S.L. and D.L.; methodology, S.L., H.Z. and Y.Z. 3+ (Yupingpromising Zhang); Nd software,-doped N.Z.; gain validation, medium D.L., for L.W. genera andting Q.Z.; ultrafast formal analysis, laser K.Z.;pulses. investigation, B.C.; resources, S.L. and S.D.; data curation, L.W. and Y.Z. (Yuqing Zhao); writing—original draftAuthor preparation, Contributions: S.L. and Y.Z.Conceptualization, (Yuqing Zhao); writing—review S.L. and D.L.; and meth editing,odology, S.L. and S.L., Y.Z. H.Z. (Yuqing and Y.Z. (Yuping Zhao);Zhang); visualization, software, Y.Z.N.Z.; (Yuqing validation, Zhao); supervision,D.L., L.W. and D.L., Q.Z.; L.W. andformal S.D.; analysis, project administration, K.Z.; investigation, B.C.; H.Z.resources, and Y.Z. S.L. (Yuping and S.D.; Zhang). data All curation, authors have L.W. read and and Y.Z. agreed (Yuqing to the Zhao); published writing—original version of the draft prep- manuscript.aration, S.L. and Y.Z. (Yuqing Zhao); writing—review and editing, S.L. and Y.Z. (Yuqing Zhao); Funding:visualization,This research Y.Z. (Yuqing was funded Zhao); by thesupervision, Natural Science D.L., Foundation L.W. and ofS.D.; Shandong project Province administration, (No. H.Z. and ZR2020MF105),Y.Z. (Yuping Zhang). the National All Naturalauthors Science have read Foundation and ag ofreed China to the (Nos. published 61875106 andversion 61775123), of the manuscript. the Key Research and Development Program of Shandong Province (Nos. 2019GGX104039 and 2019GGX104053),Funding: This research the SDUST was Research funded Fund by (No. the 2019TDJH103),Natural Science the NaturalFoundation Science of Foundation Shandong of Province (No. AnhuiZR2020MF105), Province (No. the 2008085QF313) National Natural and the Science University Foundation Natural Science of China Research (Nos. Project 61875106 of Anhui and 61775123), Province,the Key ChinaResearch (No. KJ2019ZD06).and Development Program of Shandong Province (Nos. 2019GGX104039 and Institutional2019GGX104053), Review Boardthe SDUST Statement: ResearchNot applicable. Fund (No. 2019TDJH103), the Natural Science Foundation of Anhui Province (No. 2008085QF313) and the University Natural Science Research Project of An- Informed Consent Statement: Not applicable. hui Province, China (No. KJ2019ZD06). Data Availability Statement: Data are available upon request to the authors. Institutional Review Board Statement: Not applicable. Acknowledgments: Thanks to Yiran Wang and Xiancui Su from the Liaocheng University for their kindInformed discussions. Consent Statement: Not applicable. ConflictsData Availability of Interest: TheStatement: authors declare Data are no conflictavailable of interest. upon request to the authors. SampleAcknowledgments: Availability: Not Thanks applicable. to Yiran Wang and Xiancui Su from the Liaocheng University for their kind discussions. Conflicts of Interest: The authors declare no conflict of interest. Sample Availability: Not applicable.

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