We report on the first observation of the nonlinear cascading chi((3))  chi((3)) effects in UV spectral range and second harmonic generation stipulated by the "defect" nonlinearity under one-micron pumping in crystalline ceramics based on cubic oxides Sc2O3 and Lu2O3. Broadband their multi-wavelength Stokes and anti-Stokes combs with the extension of 10475 cm(-1) (for Sc2O3) and 8232 cm(-1) (for Lu2O3) were recorded as well

Dong, J.

Eichler, H. J.

Kaminskii, A. A.

Rhee, H.

Shirakawa, A.

Takaichi, K.

Tokurakawa, M.

Ueda, K.

Yagi, H.

Yanagitani, T.

董俊

Laser Physics Letters

Xiamen University Institutional Repository

Laser Phys. Lett. 5, No. 2, 109–113 (2008) / DOI 10.1002/lapl.200710093 109Abstract: We report on the first observation of the nonlinearcascading χ(3) ↔ χ(3) effects in UV spectral range and sec-ond harmonic generation stipulated by the “defect” nonlinearityunder one-micron pumping in crystalline ceramics based on cu-bic oxides Sc2O3 and Lu2O3. Broadband their multi-wavelengthStokes and anti-Stokes combs with the extension of 10475 cm−1(for Sc2O3) and 8232 cm−1 (for Lu2O3) were recorded as well.Photosensitivity, arb. units0.51.002.00.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8InGaAs-CCDSi-CCDSiSpectral sensitivity of Si- and InGaAs-CCD linear image sensorsS3923-1024Q and G9204-512D, respectivelyc© 2008 by Astro Ltd.Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaANew nonlinear-laser effects in crystalline fine-grainedceramics based on cubic Sc2O3 and Lu2O3 oxides:second and third harmonic generation, and cascadedself-sum-frequency mixing in UV spectral regionA.A. Kaminskii, 1,∗ H. Rhee, 2 H.J. Eichler, 2 K. Ueda, 3 K. Takaichi, 3 A. Shirakawa, 3 M. Tokurakawa, 3 J. Dong, 3H. Yagi, 4 and T. Yanagitani 41 Institute of Crystallography, Russian Academy of Sciences, Moscow 119333, Russia2 Institute of Optics and Atomic Physics, Technical University of Berlin, Berlin 10623, Germany3 Institute for Laser Science, University of Electro-Communications, Tokyo 182-8585, Japan4 Takuma Works, Konoshima Chemical Co. Ltd, Kagawa 769-1103, JapanReceived: 24 September 2007, Accepted: 27 September 2007Published online: 15 October 2007Key words: nonlinear-laser effect; laser cascading; stimulated Raman scattering; SHG; THG; Stokes and anti-Stokes comb; Sc2O3and Lu2O3 ceramicsPACS: 78.30.-j, 42.65.Dr, 42.65.Ky, 42.55.Rz1. IntroductionIn last decade modern crystalline gain materials dopedwith lanthanide (Ln3+) lasants are increasingly employedin the ceramic forms. A number of revolutionary fabrica-tion methods have been developed (see, e.g. [1]) to addand replace commonly used crystal growth techniques sothat laser ceramics can be obtained a lower cost and largersize. The constitution of grains and grain boundaries arefundamental difference between the crystalline ceramicsand single crystals.In spate the fact that with these ceramics allowed to getalready very impressive advances, e.g. the achievement ofabout 100 KW output CW power (4F3/2 → 4I11/2 chan-nel of Nd3+:Y3Al5O12 ceramic laser [2]) and efficientsub-100 fs ytterbium generation (2F5/2 → 2F7/2 lasing∗ Corresponding author: e-mail: kaminalex@mail.ruc© 2008 by Astro Ltd.Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA110 A.A. Kaminskii, H. Rhee, et al.: New nonlinear-laser effectsCeramics Space group a) Ln3+ lasant Nonlinear effect gSt1ssR,b) cm/GWSc2O3 T 7h Yb3+ SRS, SHG, THG,self-SFM(SRS) c) ≈ 0.72 [8]Y2O3 T 7h Nd3+, Yb3+ SRS ≈ 0.4 [9]Y3Al5O12 O10h Nd3+, Er3+, Yb3+ SRS ≈ 0.1 [9–11]Ba(Sn,Zr,Mg,Ta)O3 (E-type) d) O5h – SRS ≈ 0.15 [12]Ba(Sn,Zr,Mg,Ta)O3 (Z-type) d) O5h – SRS ≈ 0.15 [12]Lu2O3 T 7h Nd3+, Yb3+ SRS, SHG, THG, self-SFM(SRS) c) ≈ 0.3 [13]a) Grains of the ceramics are randomly oriented nano- or micro-size single crystals.b) gSt1ssR is the steady-state Raman gain coefficient for first Stokes lasing component measured under one-micron pumping radiation from picosecondNd3+:Y3Al5O12 laser.c) Self-SFM(SRS), i.e. self-sum frequency mixing of the arising SRS lasing components and pumping generation.d) In microcrystalline grains of the Ba(Sn,Zr,Mg,Ta)O3 ceramics the B’ and B” octahedral sites statistically occupy by four unlike valency cations Mg2+, Sn4+,Zr4+, and Ta5+, i.e. in this materials is realized the second low of crystal-field disorder [14].Table 1 Nonlinear-laser effects in highly-transparent “cubic” ceramicsin Y2O3 and Sc2O3 ceramics [3,4]), many their physicalproperties need more comprehensive investigation.In the first place this concerns the grain boundaryproperties which play a key role in the determination ofmain characteristics of crystalline laser ceramics and dif-ferent types of laser on their basis. Recently, it was foundthat the grain boundaries in these laser-host ceramics im-proved mechanical toughness and micro-hardness to thesame name laser-host crystals [5]. Comparative experi-ments with the same names of laser single crystals andceramics have shown that grain boundaries in the latterdo not contribute to reducing the optical damage limit[6]. Review paper on the influence of the grain bound-aries on the heat transfer in laser ceramics on the baseof cubic oxides is given in [7]. The walls of micro-sizegrains in ceramics on the base of oxide, in particularSc2O3 and Lu2O3, are surface defects where the cen-trosymmetric cubic crystallographic nature (their spacegroup is T 7h−Ia3) is broken. Therefore, in these bulk crys-talline ceramics with high concentration of grain-boundarywalls should be manifested both cubic χ(3)- and quadraticχ(2)- nonlinearities under high peak-power of laser excita-tion, as stimulated Raman scattering (SRS), low-intensitynon-phase-matched third and second harmonic generation(THG and SHG)), as well as multi-wave parametric mix-ing processes. The main goal of this work was the discov-ery of all these possible nonlinear-laser effects under one-micron picosecond pumping in highly-transparent Sc2O3and Lu2O3 ceramics which were fabricated in KonoshimaChemical Co. Ltd. Incidentally, in this experiments wasthe task to significant widen of Stokes and anti-Stokeswings in their SRS spectra. The Table 1 summarized ofobserved nonlinear-laser interactions in crystalline ceram-ics on the base of cubic oxides.2. Multi-wavelength nonlinear lasing fromUV till mid-IR regionFor more detail investigation of single-pass Raman in-duced nonlinear lasing processes in crystalline host-Photosensitivity, arb. units0.51.002.00.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8InGaAs-CCDSi-CCDSiFigure 1 (online color at www.lphys.org) Spectral sensitivity ofSi- and InGaAs-CCD linear image sensors S3923-1024Q andG9204-512D, respectively (data from Hamamatsu catalog)ceramics Sc2O3 and Lu2O3 for Ln3+ lasants we used ahome-made Xe-flashlamp-pumped picosecond (≈ 100 ps)Nd3+:Y3Al5O12 laser emitted at a fundamental wave-length λf = 1.06415 µm (4F3/2 → 4I11/2 generation chan-nel of Nd3+ activator ions). The nearly Gaussian profileof its beam was focused into about 15-mm long ceramicsamples with a lens (f = 25 cm), resulting in beam-waistdiameter of about 160 µm. The spectral composition of theSRS and Raman-induced multi-wave mixing was analyzedwith a grating monochromator (McPherson Model 270 inCherny-Turned arrangement) combined with spectromet-ric system (CSMA) equipped with two Hamamatsu linearimage sensors Si-CCD (3923-1024Q) and CCD-InGaAs(G9204-512D) offering good enough spectral sensitivityfrom UV till ≈ 1.7 µm (see Fig. 1). In consequence ofmore careful matching of an excitation scheme and new IRdetector compared to our earlier SRS-measurements [8,13]we significant widened Stokes and anti-Stokes wings forc© 2008 by Astro Ltd.Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA www.lphys.orgLaser Phys. Lett. 5, No. 2 (2008) 111Nonlinear generationWavelength, µm a) Line b) Lasing componentattributionSc2O3, ωSRS ≈ 419 cm−1 (see Fig. 2)0.3344 ASt2λTHG 3ωf + 2ωSRS0.3495 ASt1λTHG 3ωf + ωSRS0.3547 λTHG 3ωf0.3600 St1λTHG 3ωf − ωSRSc)0.3656 St2λTHG 3ωf − 2ωSRSc)0.3712 St3λTHG 3ωf − 3ωSRSc)0.3771 St4λTHG 3ωf − 4ωSRSc)0.3832 St5λTHG 3ωf − 5ωSRSc)0.3894 St6λTHG 3ωf − 6ωSRSc)0.53207 λSHG 2ωf0.5761 ASt19 ωf − 2ωSRS0.5903 ASt18 ωf − 3ωSRS0.6053 ASt17 ωf − 4ωSRS0.6211 ASt16 ωf − 5ωSRS0.6377 ASt15 ωf + 15ωSRS0.6552 ASt14 ωf + 14ωSRS0.6737 ASt13 ωf + 13ωSRS0.6932 ASt12 ωf + 12ωSRS0.7140 ASt11 ωf + 11ωSRS0.7360 ASt10 ωf + 10ωSRS0.7594 ASt9 ωf + 9ωSRS0.7844 ASt8 ωf + 8ωSRS0.8110 ASt7 ωf + 7ωSRS0.8396 ASt6 ωf + 6ωSRS0.8702 ASt5 ωf + 5ωSRS0.9031 ASt4 ωf + 4ωSRS0.9386 ASt3 ωf + 3ωSRS0.9770 ASt2 ωf + 2ωSRS1.0187 ASt1 ωf + ωSRS1.06415 λf ωf1.1138 St1 ωf − ωSRS1.1684 St2 ωf − 2ωSRS1.2285 St3 ωf − 3ωSRS1.2952 St4 ωf − 4ωSRS1.3695 St5 ωf − 5ωSRS1.4528 St6 ωf − 6ωSRSLu2O3, ωSRS ≈ 392 cm−1 (see Fig. 3)0.3498 ASt1λTHG 3ωf + ωSRS0.3547 λTHG 3ωf0.3597 St1λTHG 3ωf − ωSRSc)0.3648 St2λTHG 3ωf − 2ωSRSc)0.3701 St3λTHG 3ωf − 3ωSRSc)0.3756 St4λTHG 3ωf − 4ωSRSc)0.53207 λSHG 2ωf0.6382 ASt16 ωf + 16ωSRS0.6546 ASt15 ωf + 15ωSRSNonlinear generationWavelength, µm a) Line b) Lasing componentattribution0.6718 ASt14 ωf + 14ωSRS0.6900 ASt13 ωf + 13ωSRS0.7092 ASt12 ωf + 12ωSRS0.7294 ASt11 ωf + 11ωSRS0.7509 ASt10 ωf + 10ωSRS0.7737 ASt9 ωf + 9ωSRS0.7979 ASt8 ωf + 8ωSRS0.8236 ASt7 ωf + 7ωSRS0.8511 ASt6 ωf + 6ωSRS0.8805 ASt5 ωf + 5ωSRS0.9120 ASt4 ωf + 4ωSRS0.9458 ASt3 ωf + 3ωSRS0.9822 ASt2 ωf + 2ωSRS1.0215 ASt1 ωf + ωSRS1.06415 λf ωf1.1105 St1 ωf − ωSRS1.1610 St2 ωf − 2ωSRS1.2114 St3 ωf − 3ωSRS1.2773 St4 ωf − 4ωSRS1.3446 St5 ωf − 5ωSRSa) Measurement accuracy is 0.0003 µm.b) For example, the condition notation of cascaded generation ASt1λT HGis defined as the first anti-Stokes component connected with THG of fun-damental pump emission.c) One of possible five-wave parametric interaction involving pump andStokes lasing emission.Table 2 Room-temperature spectral composition of nonlinear-laser generation in crystalline ceramics based on cubic oxidesSc2O3 and Lu2O3 under picosecond Nd3+:Y3Al5O12-laser ex-citation at its fundamental wavelength λf = 1.06415 µmboth studied ceramics, from 0.5761 µm to 1.4528 µm forSc2O3 and from 0.6382 µm to 1.3446 µm wavelengthsfor Lu2O3. These results are shown in Figs. 2a,b andFigs. 3a,b and listed in Table 2.In an effort to investigate of our second problem inSc2O3 and Lu2O3 ceramics connected with exacting su-pervision their possible SHG, THG, and χ(3)-nonlinearmulti-wave parametric lasing using filters and other stan-dard experimental contrivances. By this we significantdecreased unwanted (saturated) influence of strong one-micron pump radiation and intensive Stokes and anti-Stokes bands emission on the Si-CCD sensor and thus sig-nificantly enhanced its sensitivity in the visible and UVspectral regions. The results of these measurements areshown in Fig. 2c and Fig. 3c. As seen, in both ceramics un-der picoscond one-micron pumping we recorded relativelylow-intensity signals of SHG at λSHG = 0.53207 µm andTHG at λTHG = 0.3547 µm wavelengths, as well as in theneighbourhood of latter several cascaded five-wave mix-www.lphys.orgc© 2008 by Astro Ltd.Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA112 A.A. Kaminskii, H. Rhee, et al.: New nonlinear-laser effects(b) (a)(c)0.57610.59030.60530.62110.6377 0.65520.67370.69320.71400.75940.73600.83960.81100.78440.87020.90311.01870.97700.93861.06415*1.11381.29521.22851.16841.45281.36950.33440.34950.35470.36000.36560.37120.37710.38320.3894THGSHG0.53207Sc2O3ceramicsSRS intensity, arb. units432100.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.3 1.4 1.51.2Wavelength, µm0.35 0.40 0.45 0.50 0.55ωSRS ~ 419 cm-1~Figure 2 Room-temperature spectra of nonlinear self-frequency lasing in fine-grained Sc2O3 ceramics obtained with excitation of one-micron generation of picosecond Nd3+:Y3Al5O12-laser recorded: (a) and (b) with InGaAs-CCD and Si-CCD sensors, respectively; (c)with Si-CCD sensor and under strong attenuation of pump and its intensive Stokes and anti-Stokes signals (see inset). The wavelengthof all lasing lines given in µm (pump line is marked by an asterisk). Stokes and anti-Stokes lines (see spectra (a) and (b)) related toSRS-promoting vibration modes ωSRS ≈ 419 cm−1 are indicated by horizontal scale brackets(b) (a)(c)0.63820.65460.67180.69000.7092 0.75090.72940.85110.82360.77370.79790.88050.91201.02150.98220.94581.06415*1.11051.27731.21141.16101.34460.34980.35470.35970.36480.37010.3756THGSHG0.53207Lu2O3ceramicsSRS intensity, arb. units432100.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.3 1.41.2Wavelength, µm0.35 0.40 0.45 0.50 0.55ωSRS ~ 392 cm-1~Figure 3 Room-temperature spectra of nonlinear self-frequency lasing in fine-grained Lu2O3 ceramics obtained with excitation of one-micron generation of picosecond Nd3+:Y3Al5O12-laser recorded: (a) and (b) with InGaAs-CCD and Si-CCD sensors, respectively; (c)with Si-CCD sensor and under strong attenuation of pump and its intensive Stokes and anti-Stokes signals (see inset). Stokes and anti-Stokes lines (see spectra (a) and (b)) related to SRS-promoting vibration modes ωSRS ≈ 392 cm−1 are indicated by horizontal scalebrackets. Other notation as in Fig. 2c© 2008 by Astro Ltd.Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA www.lphys.orgLaser Phys. Lett. 5, No. 2 (2008) 113ing UV components. Whereas all observed χ(3)-nonlinearcomponents in Sc2O3 and Lu2O3 ceramics are sufficientlyunderstandable and in a great part agrees with the data onmeasurements of nonlinear refractive indices n2 (which di-rectly related to χ(3)-susceptibility) [15], as well as withrecently achieved efficient sub-100 fs Kerr-lens mode-locked lasing in Yb3+:Sc2O3 ceramics [4], while the ex-pected and observed SHG need be investigated with greatcare. The case is that the efficiency of recorded self-frequency doubling was very low in both ceramics stud-ied. It should be noted here, that week SHG could be asso-ciated also with induced χ(2)-nonlinearity (local mechan-ical stress) and with arising plasma in micro-interstices(babbles or pores) in centrosymmetric crystalline materialsunder focusing strong laser excitation. But, these possiblereasons are not likely to take place in our case.3. ConclusionWe have discovered several new nonlinear-laser effects inhighly transparent crystalline host-ceramics (for Ln3+ las-ants) based on cubic oxides Sc2O3 and Lu2O3, namely: thenon-phase-matched THG and nonlinear cascaded χ(3) ↔χ(3) lasing in UV spectral area arising from one-micron pi-cosecond laser excitation and Raman induced Stokes andanti-Stokes lasing fields in near-IR, as well as SHG aris-ing from induced χ(2)-nonlinearity related to fundamen-tal property of fine-grained nature of ceramics studied.It is worth noting that nonlinear laser cascading in crys-talline materials has been observed up to now only of theχ(2) ↔ χ(3) type (see, e.g. [16-18]). Thanks to the im-provement of the excitation and recorded condition wealso significantly widened of SRS and Raman induced fourwave mixing lasing wings. So, we recorded 25 Stokes andanti-Stokes lasing sidebands covered spectral region from0.5761 µm to 1.4528 µm for Sc2O3 and 21 lines within0.6382 µm and 1.3446 µm wavelengths for Lu2O3 ceram-ics.Acknowledgements The research reported here was greatly pro-moted by the cooperation within the “Joint Open Laboratory forLaser Crystals and Precise Laser Systems” and supported in partby the Russian Foundation for Basic Research and the Program“Femtosecond optics and new optical materials” of the RussianAcademy of Sciences, as well as the Technical University ofBerlin and the 21st Century COE program of the Ministry ofEducation, Culture, Sport, Science, and Technology of Japan.References[1] A. Ikesue, Japanese patents JP3463941 and JPS3243278;A. Ikesue, T. Kinoshita, K. Kamata, and K. Yoshida, J. Am.Ceram. Soc. 78, 1033 (1995); A. Ikesue, Opt. Mater. 19, 183(2002); T. Yanagitani, H. Yagi, and M. Ishikawa, Japanesepatent 10-101333 (1998); T. Yanagitani, H. 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New nonlinear-laser effects in crystalline fine-grained ceramics based on cubic Sc2O3 and Lu2O3 oxides: second and third harmonic generation, and cascaded self-sum-frequency mixing in UV spectral region

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New nonlinear-laser effects in crystalline fine-grained ceramics based on cubic Sc2O3 and Lu2O3 oxides: second and third harmonic generation, and cascaded self-sum-frequency mixing in UV spectral region

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