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Harmonic violet light generation in periodically poled bulk near-stoichiometric MgO-doped LiNbO3
Optics Communications 224 (2003) 149–153 www.elsevier.com/locate/optcom
Harmonic violet light generation in periodically poled bulk near-stoichiometric MgO-doped LiNbO3 Ya-Hui Chen, Jiang-Hong Yao *, Bo-Xia Yan, Hao-Liang Deng, Yong-Fa Kong, Shao-Lin Chen, Jing-Jun Xu, Guang-Yin Zhang Physical Science Department, Photonics Research Center, College of Physical Science, Nankai University, Weijing Road 94, Tianjin 300071, PeopleÕs Republic of China TEDA Applied Physics College, Nankai University, Tianjin 300060, PeopleÕs Republic of China National Laboratory for Infrared Physics, Chinese Academy of Science, Shanghai 200083, PeopleÕs Republic of China Received 20 January 2003; received in revised form 26 May 2003; accepted 14 July 2003
Abstract By the method of vapor transport equilibration, high optical quality 1.8 mol% MgO-doped near-stoichiometric LiNbO3 (Mg:SLN) crystals were grown. A uniformly periodic domain structure in a 1.0 mm thick slab of Mg:SLN was fabricated by applying external pulsed field. Using a Ti:sapphire laser with a pulse width of 60 fs and a repetition rate of 82 MHz, third-order quasi-phase-matched second harmonic violet light generation was demonstrated by free propagation of 800 nm fundamental beam in a 12 mm long Mg:SLN slab at room temperature, with an energy conversion efficiency of 20.5%. Ó 2003 Elsevier B.V. All rights reserved. PACS: 42.65.Ky; 61.50.Nw Keywords: MgO-doped near-stoichiometric LiNbO3 ; Second harmonic generation; Reversal electric field
1. Introduction In recent years, quasi-phase-matched (QPM) non-linear crystals have been demonstrated to give efficient second harmonic generation (SHG) and optical parametric oscillation in both the cw and the Q-switched regiments. There are significant advantages of QPM over birefringent phase *
Corresponding author. Tel.: +862223508398; fax: +86222 3508411. E-mail address: [email protected] (J.-H. Yao).
matching, such as high conversion efficiency, a wide phase-matching spectral window, and engineered non-linearity [1]. In particular, the periodically poled LiNbO3 (PPLN) crystal has been extensively studied [2–5], because of its large nonlinear optical coefficient, d33 . However, PPLN has been found to have several limitations when used to obtain high power output light, such as a high electric field of 21 kV/mm for ferroelectric domain reversal and very weak photorefractive damage resistance. It has been reported that addition of 5 mol% MgO to congruent LiNbO3
0030-4018/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0030-4018(03)01757-7
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crystals results in a remarkable increase in the photorefractive damage threshold [6]. However, a large amount of MgO doping subsequently causes difficulty in growing high optical-quality crystals. Recently, it has been reported that photorefraction damage in LiNbO3 was completely eliminated by the doping of small amounts of MgO in crystals with near-stoichiometric composition [7,8]. These notable changes in material properties are strongly related to the elimination of Nb antisite defects (NbLi ) by the substitution of Mg on Li sites. At the same time, we reported that near-stoichiometric LiNbO3 crystals show almost a 1-order-of magnitude lower switching field for 180° ferroelectric domain reversal than does congruent LiNbO3 [9], which showed that stoichiometric LiNbO3 crystals have potential as better materials for PPLN. In this paper, high optical-quality MgO-doped near-stoichiometric LiNbO3 (Mg:SLN) crystals were grown by the method of vapor transport equilibration and a periodically domain-inverted structure for a third-order QPM SHG was fabricated in a 1.0 mm thick Mg:SLN crystal. Using a Ti:sapphire laser with a pulse width of 60 fs and a repetition rate of 82 MHz, femtosecond harmonic violet of average 43 mW (k ¼ 400 nm) was generated with 210 mW of near infrared light in a single pass through a 12 mm interaction length at room temperature, with an energy conversion efficiency of 20.5%. The other aim of this research was to examine the resistance to photorefractive damage in Mg:SLN, and, in our experiment, we found no photorefractive damage even at very high peak power.
homogeneity. The reacted powders were heated at the temperature of 1050 °C for 6 h to obtain the mixture of LiNbO3 and Li3 NbO4 . And then the congruent Mg:LiNbO3 crystals were supported parallel to and slightly above the powers surface contained in the platinum crucible. The reaction crucible and the independently suspended crystal were heated to the temperature of 1100 °C for 120 h. The VTE processed LiNbO3 crystals were polished before characterizing its crystal composition. The Raman scattering technique has been used to measure the composition, xc ([Li]/[Nb + Li]), of the prepared crystals [10]. The composition xc of our samples was determined from the linewidth C of the lowest frequency EðTO1 Þ mode at 152 cm1 vibration which is very intense and well separated from the other lines. The linewidth C was measured along the depth of the crystal. The results are shown in Fig. 1, which was approximately 6.56 cm1 . The corresponding composition xc was found to be 49.92 mol%. From Fig. 1 we can see the VTE processed LiNbO3 has a quite homogeneous composition along the depth of the crystal. The concentration of MgO was 1.8 mol%, which was analyzed using inductively coupled plasma atomic emission spectrometry (ICP-ASES) [11]. The prepared crystals were found to be crack, void, and inclusion-free and exhibited single structure. The position of the fundamental absorption edge is very sensitive to the composition of lithium niobate. We found a blue shift from 320 to 306 nm for Mg:SLN crystals, which was shown in Fig. 2. (Data for congruent LiNbO3 crystal doped 1.8 mol% MgO (Mg:CLN) were also shown for comparison.) The position of the band edge was
2. Experimental results and discussion Mg:SLN crystals were fabricated by vapor transport equilibration. Starting crystals for VTE processing were congruent Mg:LiNbO3 with a thickness of 1.0 mm, which was grown by Czochralski method. Li-rich powder charges were prepared using Li2 CO3 and Nb2 O5 mixture, and powder ratios were chosen to establish a net composition of 68 mol% LiO2 . The 99.99% purity raw Li2 CO3 , Nb2 O5 powders were mixed, reacted, milled, and then re-reacted to ensure compositional
Fig. 1. The linewidth C of the EðTO1 Þ vibration mode along the depth of the crystal.
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Fig. 2. The absorption spectra for Mg:SLN (solid curve) and Mg:CLN (dashed curve).
Fig. 3. The reversal electric field as a function of the composition in Mg:SLN.
defined as the wavelength where the absorption coefficient is 15 cm1 . It should be noted that the absorption edge in Mg:SLN shifts toward shorter wavelength, which was very helpful for the harmonic violet and ultraviolet light generation. Although the relationship is non-linear, the measurement of the UV absorption edge would be a very convenient way for characterizing the crystal composition. The blue shift of absorption edge demonstrated that the Mg:SLN crystals had a near-stoichiometric composition. In our experiment, the set up used for ferroelectric domain reversal was similar to that originally designed by Myers et al. [1], in which the transient current flown through the LiNbO3 substrate was measured as the voltage drop across a series resister. In order to stabilize the domain reversal process, a fast turn-on rectifying diode was put in series with the poling apparatus such that relaxation of the inverted domain can be inhibited at the termination of the pulsed field. Mg:SLN exhibited a very low electric field of 2.5 kV/mm for ferroelectric domain reversal, which was desired for the fabrication of the samples more than 0.5 mm thick. For periodic poling of the substrate, the sample was subjected to 5 pulses of 2.5 kV with a duration of 20 ms each. Fig. 3 shows the reversal electric field as the function of [Li]/ [Li + Nb]. It could be found that the reversal electric field Ed decreased as the [Li]/[Li + Nb] increased and Ed for SLN is approximately one tenth of that for CLN, which seems to be consistent with the observation reported by Gopalan et al. [12]. After the poling process, the substrate was etched
in a 1:2 HF + HNO3 solution at 80 °C for several minutes to reveal the domain patterns on both surfaces of the crystal. The etched patterns were observed using an optical microscope, and Fig. 4 shows the +z surface domain structure pattern. The period of the periodically domain-inverted grating is 7.8 lm. Evidently, there is a nearly homogeneous periodic structure, and the duty cycle is close to 50%. The observed gratings are suitable for SHG of the 800 nm Ti:sapphire laser at room temperature. In order to examine the quality of the inverted domains in the sample, we demonstrated femtosecond harmonic violet light generation in the sample by free propagation of fundamental Gaussian beam. For the SHG experiment, we used a-diode-pumped mode-locked Ti:sapphire laser as a pump source with a pulse width of 60 fs, a
Fig. 4. The domain patterns on the +z surface in the periodically poled Mg:SLN.
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repetition rate of 82 MHz and output wavelength in the range of 750–850 nm. A Faraday isolator was placed in the beam to eliminate the effect of the reflected beam on the laser. The output beams, which included both the fundamental and the second harmonic light, were then separated using a dichroic beamsplitter. The violet power level varied slightly with position across the sample, indicating that there were regions where the domains were insufficiently regular. Fig. 5 shows the SHG intensity from a good position across the sample when tuning the fundamental wavelength between 780 and 820 nm. In our sample, conversion efficiency peaks at 800 nm. The spectral bandwidth [full width at half maximum (FWHM)] obtained in the sample is 2.0 nm. The bandwidth expected for an ideal 12 mm long Mg:SLN structure is 1.6 nm [13]. This broadening is due to the inhomogeneous domain size in our crystal. Fig. 6 shows the SHG power dependence on fundamental input power at peak wavelength with consideration of the violet loss of the dichroic beamsplitter. The pump power was varied with all other experimental parameters unchanged. Following the coupled wave equations and the conditions for phase matching [14], we obtained the second harmonic power P2 x in the high conversion limit for a Gaussian beam. It is as follows: !1=2 2 2 n2x 8pd33 L Px ð0Þ 2 P2x ¼ Px ð0Þ tanh ; ð1Þ nx n22x nx ck2x e0 x20 where Px ð0Þ is the pumped power, L is the interaction length, nx , n2x are the refractive indices at
Fig. 6. Third-order QPM SHG power against fundamental power in bulk Mg:SLN.
the fundamental and second harmonic wavelength, respectively, e0 is the permittivity of free space, c is the speed of light, x0 is the 1=e2 radius of the fundamental beam in the crystal, and d33 is the non-linear coefficient. Following Eq. (1), the theoretical second harmonic power was calculated, which is also shown in Fig. 6. In our experiments, up to 43 mW of violet output was obtained for a total power of 210 mW. This represents an overall efficiency of 20.5%, which is nearly 81% of the corresponding theoretical value. Because we used femtosecond laser pulses, the peak laser power and intensity are much higher. Therefore, we have obtained the higher conversion efficiency with the lower average input power. However, when the fundamental power is lower than 20 mW, the output power of violet is too small to be evidently distinguished from the noise, so there are no experimental data in this region. All experiments were demonstrated at room temperature, and the fluctuation of the output violet beam caused by the photorefractive damage was not observed under these conditions, which confirmed that the nearstoichiometric LiNbO3 doped 1.8 mol% MgO had a very high photorefractive damage resistance.
3. Conclusion
Fig. 5. The phase matching spectrum for SHG in Mg:SLN.
In conclusion, the Mg:SLN was grown by the method of vapor transport equilibration. The sample has been found to have high optical quality, shorter absorption edge, and lower reversal electric
Y.-H. Chen et al. / Optics Communications 224 (2003) 149–153
field. Third-order QPM second harmonic violet light generation in the 1.0 mm thick and 12 mm long sample was demonstrated at room temperature with an energy conversion efficiency of 20.5%. No photorefractive damage was found, which confirmed that the SLN doped 1.8 mol% MgO had a high photorefractive damage resistance. Acknowledgements This work is financially supported by the National Natural Science Foundation of China (90101022, 60178024, 10174040) and the National Education Ministry of China (G1999033004). References [1] L.E. Myers, R.C. Echardt, M.M. Fejer, J. Opt. Soc. Am. B 12 (1995) 2102. [2] L.E. Myers, G.D. Miller, R.C. Echardt, Opt. Lett. 20 (1995) 52.
153
[3] K. Mizuuchi, K. Yamamote, M. Kato, Electron. Lett. 25 (1997) 731. [4] V. Prunevi, J. Webjorn, P.St.J. Russell, Opt. Commun. 116 (1995) 159. [5] P. Schlup, S.D. Butterworth, I.T. Mchiuuie, Opt. Commun. 154 (1998) 191. [6] D.A. Bryan, R. Gerson, H.E. Tomaschke, Appl. Phys. Lett. 44 (1984) 847. [7] Y. Furukawa, K. Kitamura, S. Takekawa, Opt. Lett. 23 (1998) 1892. [8] Y. Furukawa, K. Kitamura, S. Takekawa, Appl. Phys. Lett. 77 (2000) 2494. [9] J.H. Yao, J.J. Xu, G.Y. Zhang, Chin. Phys. Lett. 17 (2000) 515. [10] G.I. Malovichiko, V.G. Grachev, E.P. Kokanya, O.F. Schirmer, K. Betzler, F. Jermann, S. Klauer, U. Schlarb, M. Wohlecke, Appl. Phys. A 56 (1993) 103. [11] Y. Furnkawa, K. Kitamura, S. Takekawa, K. Niwa, Y. Yajima, N. Iyi, I. Mnushkina, P. Guggenheim, J. Cryst. Growth 211 (2000) 230. [12] V. Gopalan, T. Mitchell, Y. Fukukawa, Appl. Phys. Lett. 72 (1998) 1981. [13] M.M. Fejer, G.A. Magel, D.H. Jundt, R.L. Byer, IEEE J. Quantum Electron. 28 (1992) 2631. [14] R. Eckardt, J. Reinijes, IEEE J. Quantum Electron. 20 (1984) 1178.
Harmonic violet light generation in periodically poled bulk near-stoichiometric MgO-doped LiNbO3 Ya-Hui Chen, Jiang-Hong Yao *, Bo-Xia Yan, Hao-Liang Deng, Yong-Fa Kong, Shao-Lin Chen, Jing-Jun Xu, Guang-Yin Zhang Physical Science Department, Photonics Research Center, College of Physical Science, Nankai University, Weijing Road 94, Tianjin 300071, PeopleÕs Republic of China TEDA Applied Physics College, Nankai University, Tianjin 300060, PeopleÕs Republic of China National Laboratory for Infrared Physics, Chinese Academy of Science, Shanghai 200083, PeopleÕs Republic of China Received 20 January 2003; received in revised form 26 May 2003; accepted 14 July 2003
Abstract By the method of vapor transport equilibration, high optical quality 1.8 mol% MgO-doped near-stoichiometric LiNbO3 (Mg:SLN) crystals were grown. A uniformly periodic domain structure in a 1.0 mm thick slab of Mg:SLN was fabricated by applying external pulsed field. Using a Ti:sapphire laser with a pulse width of 60 fs and a repetition rate of 82 MHz, third-order quasi-phase-matched second harmonic violet light generation was demonstrated by free propagation of 800 nm fundamental beam in a 12 mm long Mg:SLN slab at room temperature, with an energy conversion efficiency of 20.5%. Ó 2003 Elsevier B.V. All rights reserved. PACS: 42.65.Ky; 61.50.Nw Keywords: MgO-doped near-stoichiometric LiNbO3 ; Second harmonic generation; Reversal electric field
1. Introduction In recent years, quasi-phase-matched (QPM) non-linear crystals have been demonstrated to give efficient second harmonic generation (SHG) and optical parametric oscillation in both the cw and the Q-switched regiments. There are significant advantages of QPM over birefringent phase *
Corresponding author. Tel.: +862223508398; fax: +86222 3508411. E-mail address: [email protected] (J.-H. Yao).
matching, such as high conversion efficiency, a wide phase-matching spectral window, and engineered non-linearity [1]. In particular, the periodically poled LiNbO3 (PPLN) crystal has been extensively studied [2–5], because of its large nonlinear optical coefficient, d33 . However, PPLN has been found to have several limitations when used to obtain high power output light, such as a high electric field of 21 kV/mm for ferroelectric domain reversal and very weak photorefractive damage resistance. It has been reported that addition of 5 mol% MgO to congruent LiNbO3
0030-4018/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0030-4018(03)01757-7
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crystals results in a remarkable increase in the photorefractive damage threshold [6]. However, a large amount of MgO doping subsequently causes difficulty in growing high optical-quality crystals. Recently, it has been reported that photorefraction damage in LiNbO3 was completely eliminated by the doping of small amounts of MgO in crystals with near-stoichiometric composition [7,8]. These notable changes in material properties are strongly related to the elimination of Nb antisite defects (NbLi ) by the substitution of Mg on Li sites. At the same time, we reported that near-stoichiometric LiNbO3 crystals show almost a 1-order-of magnitude lower switching field for 180° ferroelectric domain reversal than does congruent LiNbO3 [9], which showed that stoichiometric LiNbO3 crystals have potential as better materials for PPLN. In this paper, high optical-quality MgO-doped near-stoichiometric LiNbO3 (Mg:SLN) crystals were grown by the method of vapor transport equilibration and a periodically domain-inverted structure for a third-order QPM SHG was fabricated in a 1.0 mm thick Mg:SLN crystal. Using a Ti:sapphire laser with a pulse width of 60 fs and a repetition rate of 82 MHz, femtosecond harmonic violet of average 43 mW (k ¼ 400 nm) was generated with 210 mW of near infrared light in a single pass through a 12 mm interaction length at room temperature, with an energy conversion efficiency of 20.5%. The other aim of this research was to examine the resistance to photorefractive damage in Mg:SLN, and, in our experiment, we found no photorefractive damage even at very high peak power.
homogeneity. The reacted powders were heated at the temperature of 1050 °C for 6 h to obtain the mixture of LiNbO3 and Li3 NbO4 . And then the congruent Mg:LiNbO3 crystals were supported parallel to and slightly above the powers surface contained in the platinum crucible. The reaction crucible and the independently suspended crystal were heated to the temperature of 1100 °C for 120 h. The VTE processed LiNbO3 crystals were polished before characterizing its crystal composition. The Raman scattering technique has been used to measure the composition, xc ([Li]/[Nb + Li]), of the prepared crystals [10]. The composition xc of our samples was determined from the linewidth C of the lowest frequency EðTO1 Þ mode at 152 cm1 vibration which is very intense and well separated from the other lines. The linewidth C was measured along the depth of the crystal. The results are shown in Fig. 1, which was approximately 6.56 cm1 . The corresponding composition xc was found to be 49.92 mol%. From Fig. 1 we can see the VTE processed LiNbO3 has a quite homogeneous composition along the depth of the crystal. The concentration of MgO was 1.8 mol%, which was analyzed using inductively coupled plasma atomic emission spectrometry (ICP-ASES) [11]. The prepared crystals were found to be crack, void, and inclusion-free and exhibited single structure. The position of the fundamental absorption edge is very sensitive to the composition of lithium niobate. We found a blue shift from 320 to 306 nm for Mg:SLN crystals, which was shown in Fig. 2. (Data for congruent LiNbO3 crystal doped 1.8 mol% MgO (Mg:CLN) were also shown for comparison.) The position of the band edge was
2. Experimental results and discussion Mg:SLN crystals were fabricated by vapor transport equilibration. Starting crystals for VTE processing were congruent Mg:LiNbO3 with a thickness of 1.0 mm, which was grown by Czochralski method. Li-rich powder charges were prepared using Li2 CO3 and Nb2 O5 mixture, and powder ratios were chosen to establish a net composition of 68 mol% LiO2 . The 99.99% purity raw Li2 CO3 , Nb2 O5 powders were mixed, reacted, milled, and then re-reacted to ensure compositional
Fig. 1. The linewidth C of the EðTO1 Þ vibration mode along the depth of the crystal.
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Fig. 2. The absorption spectra for Mg:SLN (solid curve) and Mg:CLN (dashed curve).
Fig. 3. The reversal electric field as a function of the composition in Mg:SLN.
defined as the wavelength where the absorption coefficient is 15 cm1 . It should be noted that the absorption edge in Mg:SLN shifts toward shorter wavelength, which was very helpful for the harmonic violet and ultraviolet light generation. Although the relationship is non-linear, the measurement of the UV absorption edge would be a very convenient way for characterizing the crystal composition. The blue shift of absorption edge demonstrated that the Mg:SLN crystals had a near-stoichiometric composition. In our experiment, the set up used for ferroelectric domain reversal was similar to that originally designed by Myers et al. [1], in which the transient current flown through the LiNbO3 substrate was measured as the voltage drop across a series resister. In order to stabilize the domain reversal process, a fast turn-on rectifying diode was put in series with the poling apparatus such that relaxation of the inverted domain can be inhibited at the termination of the pulsed field. Mg:SLN exhibited a very low electric field of 2.5 kV/mm for ferroelectric domain reversal, which was desired for the fabrication of the samples more than 0.5 mm thick. For periodic poling of the substrate, the sample was subjected to 5 pulses of 2.5 kV with a duration of 20 ms each. Fig. 3 shows the reversal electric field as the function of [Li]/ [Li + Nb]. It could be found that the reversal electric field Ed decreased as the [Li]/[Li + Nb] increased and Ed for SLN is approximately one tenth of that for CLN, which seems to be consistent with the observation reported by Gopalan et al. [12]. After the poling process, the substrate was etched
in a 1:2 HF + HNO3 solution at 80 °C for several minutes to reveal the domain patterns on both surfaces of the crystal. The etched patterns were observed using an optical microscope, and Fig. 4 shows the +z surface domain structure pattern. The period of the periodically domain-inverted grating is 7.8 lm. Evidently, there is a nearly homogeneous periodic structure, and the duty cycle is close to 50%. The observed gratings are suitable for SHG of the 800 nm Ti:sapphire laser at room temperature. In order to examine the quality of the inverted domains in the sample, we demonstrated femtosecond harmonic violet light generation in the sample by free propagation of fundamental Gaussian beam. For the SHG experiment, we used a-diode-pumped mode-locked Ti:sapphire laser as a pump source with a pulse width of 60 fs, a
Fig. 4. The domain patterns on the +z surface in the periodically poled Mg:SLN.
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repetition rate of 82 MHz and output wavelength in the range of 750–850 nm. A Faraday isolator was placed in the beam to eliminate the effect of the reflected beam on the laser. The output beams, which included both the fundamental and the second harmonic light, were then separated using a dichroic beamsplitter. The violet power level varied slightly with position across the sample, indicating that there were regions where the domains were insufficiently regular. Fig. 5 shows the SHG intensity from a good position across the sample when tuning the fundamental wavelength between 780 and 820 nm. In our sample, conversion efficiency peaks at 800 nm. The spectral bandwidth [full width at half maximum (FWHM)] obtained in the sample is 2.0 nm. The bandwidth expected for an ideal 12 mm long Mg:SLN structure is 1.6 nm [13]. This broadening is due to the inhomogeneous domain size in our crystal. Fig. 6 shows the SHG power dependence on fundamental input power at peak wavelength with consideration of the violet loss of the dichroic beamsplitter. The pump power was varied with all other experimental parameters unchanged. Following the coupled wave equations and the conditions for phase matching [14], we obtained the second harmonic power P2 x in the high conversion limit for a Gaussian beam. It is as follows: !1=2 2 2 n2x 8pd33 L Px ð0Þ 2 P2x ¼ Px ð0Þ tanh ; ð1Þ nx n22x nx ck2x e0 x20 where Px ð0Þ is the pumped power, L is the interaction length, nx , n2x are the refractive indices at
Fig. 6. Third-order QPM SHG power against fundamental power in bulk Mg:SLN.
the fundamental and second harmonic wavelength, respectively, e0 is the permittivity of free space, c is the speed of light, x0 is the 1=e2 radius of the fundamental beam in the crystal, and d33 is the non-linear coefficient. Following Eq. (1), the theoretical second harmonic power was calculated, which is also shown in Fig. 6. In our experiments, up to 43 mW of violet output was obtained for a total power of 210 mW. This represents an overall efficiency of 20.5%, which is nearly 81% of the corresponding theoretical value. Because we used femtosecond laser pulses, the peak laser power and intensity are much higher. Therefore, we have obtained the higher conversion efficiency with the lower average input power. However, when the fundamental power is lower than 20 mW, the output power of violet is too small to be evidently distinguished from the noise, so there are no experimental data in this region. All experiments were demonstrated at room temperature, and the fluctuation of the output violet beam caused by the photorefractive damage was not observed under these conditions, which confirmed that the nearstoichiometric LiNbO3 doped 1.8 mol% MgO had a very high photorefractive damage resistance.
3. Conclusion
Fig. 5. The phase matching spectrum for SHG in Mg:SLN.
In conclusion, the Mg:SLN was grown by the method of vapor transport equilibration. The sample has been found to have high optical quality, shorter absorption edge, and lower reversal electric
Y.-H. Chen et al. / Optics Communications 224 (2003) 149–153
field. Third-order QPM second harmonic violet light generation in the 1.0 mm thick and 12 mm long sample was demonstrated at room temperature with an energy conversion efficiency of 20.5%. No photorefractive damage was found, which confirmed that the SLN doped 1.8 mol% MgO had a high photorefractive damage resistance. Acknowledgements This work is financially supported by the National Natural Science Foundation of China (90101022, 60178024, 10174040) and the National Education Ministry of China (G1999033004). References [1] L.E. Myers, R.C. Echardt, M.M. Fejer, J. Opt. Soc. Am. B 12 (1995) 2102. [2] L.E. Myers, G.D. Miller, R.C. Echardt, Opt. Lett. 20 (1995) 52.
153
[3] K. Mizuuchi, K. Yamamote, M. Kato, Electron. Lett. 25 (1997) 731. [4] V. Prunevi, J. Webjorn, P.St.J. Russell, Opt. Commun. 116 (1995) 159. [5] P. Schlup, S.D. Butterworth, I.T. Mchiuuie, Opt. Commun. 154 (1998) 191. [6] D.A. Bryan, R. Gerson, H.E. Tomaschke, Appl. Phys. Lett. 44 (1984) 847. [7] Y. Furukawa, K. Kitamura, S. Takekawa, Opt. Lett. 23 (1998) 1892. [8] Y. Furukawa, K. Kitamura, S. Takekawa, Appl. Phys. Lett. 77 (2000) 2494. [9] J.H. Yao, J.J. Xu, G.Y. Zhang, Chin. Phys. Lett. 17 (2000) 515. [10] G.I. Malovichiko, V.G. Grachev, E.P. Kokanya, O.F. Schirmer, K. Betzler, F. Jermann, S. Klauer, U. Schlarb, M. Wohlecke, Appl. Phys. A 56 (1993) 103. [11] Y. Furnkawa, K. Kitamura, S. Takekawa, K. Niwa, Y. Yajima, N. Iyi, I. Mnushkina, P. Guggenheim, J. Cryst. Growth 211 (2000) 230. [12] V. Gopalan, T. Mitchell, Y. Fukukawa, Appl. Phys. Lett. 72 (1998) 1981. [13] M.M. Fejer, G.A. Magel, D.H. Jundt, R.L. Byer, IEEE J. Quantum Electron. 28 (1992) 2631. [14] R. Eckardt, J. Reinijes, IEEE J. Quantum Electron. 20 (1984) 1178.