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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 16, Iss. 5 — Mar. 3, 2008
  • pp: 3320–3325
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Growth and passively self-Q-switched laser output of new Nd3+,Cr5+:GdVO4 crystal

Haohai Yu, Huaijin Zhang, Zhengping Wang, Jiyang Wang, Yonggui Yu, Wenlan Gao, Xutang Tao, and Minhua Jiang  »View Author Affiliations


Optics Express, Vol. 16, Issue 5, pp. 3320-3325 (2008)
http://dx.doi.org/10.1364/OE.16.003320


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Abstract

A new passively self-Q-switched Nd, Cr:GdVO4 laser crystal was grown by Czochralski method for the first time to our knowledge. Polarized absorption spectra were measured at room temperature. The absorption bands display polarization character and an absorption band of Cr5+ ions at 1110 nm enables the crystal to be a self-Q-switched laser material at 1.06 µm. In the passive self-Q-switching operation, the maximum output power, shortest pulse width, and largest pulse energy were obtained to be 265 mW, 230 ns, and 1.12 µJ, respectively.

© 2008 Optical Society of America

1. Introduction

2. Experiments

By the Czochralski method, the Nd, Cr:GdVO4 crystal was grown from the melts of mixed polycrystalline material NdVO4, GdVO4 and GdCrO4 under a nitrogen atmosphere containing 2% oxygen (v/v) in an iridium crucible. The growing process was the same as that of Nd:GdVO4. Figure 1 shows the as-grown Nd, Cr:GdVO4 crystal boule with dimensions of about Φ30 mm×20 mm. Observed under He-Ne laser, no light scattering is obtained, which means that the as-grown crystal has excellent quality and is suitable for the application in the laser experiment. Both of the Nd and Cr concentrations in Nd, Cr:GdVO4 crystal were measured to be 1 at.% by the X-ray fluorescence method. The crystal was cut along its a-axis with dimensions of 3×3×4 mm3, and its two 3×3 mm2 end-faces were polished.

The polarized absorption spectra of Nd, Cr:GdVO4 were measured with Hitachi U-3500 spectrophotometer in the wavelength of 400 nm-1500 nm at room temperature. The incident light was perpendicular to the face of the crystal during the absorption spectra measurement. The ground absorption cross-section σGSA of Nd, Cr:GdVO4 at 1.06 µm was estimated by using the mode-locked Nd:YAG laser with a repetition rate of 10 Hz and a pulse duration of 40 ps, which is very short compared to the Cr5+ excited-state lifetime (about 3.5 ns) [7

7. S. A. Zolotovskaya, K. V. Yumashev, N. V. Kuleshov, V. N. Matrosov, T. A. Matrosova, and M. I. Kupchenko, “Absorption saturation properties and laser Q-switch performance of Cr5+-doped YVO4 crystal,” Appl. Phys. B 86, 667–671 (2007). [CrossRef]

].

The pulsed laser experimental setup is based on a plano-concave resonator with the length of about 30 mm. The pump source employed in the experiment was a fiber-coupled laser-diode with the central wavelength around 808 nm. Through the focusing optics (N. A.= 0.22), the output of the source was focused into the crystal with a spot radius of 0.256 mm. The pump mirror M1 was a concave mirror with a curvature radius of 500 mm, AR coated at 808 nm on the flat face, high-reflection coated at 1.06 µm and high-transmission coated at 808 nm on the concave face. The flat mirrors M2 were output couplers with different transmissions of OC=40% and 30% at 1.06 µm. The average output powers were measured by the power meter (EPM 2000. Melectron Inc.). To remove the heat generated from Nd, Cr:GdVO4 under high pump power levels, the crystal was wrapped with indium foil and mounted in a water-cooled copper block with cooling water controlled to be 18 °C.

Fig. 1. As-grown crystal Nd, Cr:GdVO4 boule.
Fig. 2. Polarized absorption spectra of Nd:Cr:GdVO4 at room temperature.

3. Results and discussions

The polarized absorption spectra are shown in Fig. 2. With respect to the spectra of Cr:GdVO4 [8

8. H. H. Yu, H. J. Zhang, Z.P. Wang, J. Y. Wang, Y. G. Yu, W. L Gao, X. T. Tao, J. H. Liu, X. Y. Zhang, and M. H. Jiang, “Cr5+:GdVO4 as a saturable absorber for a diode-pumped Nd:Lu0.5Gd0.5VO4 laser,” Opt. Express 15, 11679–11684 (2007). [CrossRef] [PubMed]

] and Nd:GdVO4 [10

10. T. Jensen, V. G. Ostroumov, J-P. Meyn, G. Huber, A. I. Zagumennyi, and I. A. Scherbakov, “Spectroscopic characterization and laser performance of diode-laser-pumped Nd: GdVO4,” Appl. Phys. B 58, 373–379 (1994). [CrossRef]

, 11

11. H. Zhang, J. Liu, J. Wang, C. Wang, L. Zhu, Z. Shao, X. Meng, X. Hu, M. Jiang, and Y. T. Chow, “4Characterization of the laser crystal Nd:GdVO4,” J. Opt. Soc. Am. B 19, 18–27 (2002). [CrossRef]

], it can be noted that the spectra of Nd, Cr:GdVO4 are the combination of those of Cr:GdVO4 and Nd:GdVO4. Due to the strong absorption of Nd3+ ions at about 680 nm (transmission of 4I9/2 to 4F9/2) for π polarization, that of Cr5+ ions at 642 nm (2A1 to 2E), which is only allowed for σ polarization (E⊥c), is not evident. The inset of Fig. 2 shows the absorption spectra in the wavelength from 780 nm to 900 nm. The full width at half-maximum (FWHM) at 808 nm (4I9/2 to 4F5/2+2H9/2) is 10 nm, which is much larger than that of Nd:GdVO4 (4 nm [11

11. H. Zhang, J. Liu, J. Wang, C. Wang, L. Zhu, Z. Shao, X. Meng, X. Hu, M. Jiang, and Y. T. Chow, “4Characterization of the laser crystal Nd:GdVO4,” J. Opt. Soc. Am. B 19, 18–27 (2002). [CrossRef]

] or 1.6 nm [10

10. T. Jensen, V. G. Ostroumov, J-P. Meyn, G. Huber, A. I. Zagumennyi, and I. A. Scherbakov, “Spectroscopic characterization and laser performance of diode-laser-pumped Nd: GdVO4,” Appl. Phys. B 58, 373–379 (1994). [CrossRef]

, 12

12. C. Maunier, J. L. Doualan, and R. Moncorgé, “Growth, spectroscopic characterization, and laser performance of Nd:LuVO4, a new infrared laser materials that is suitable for diode pumping,”J. Opt. Soc. Am. B 19, 1794–1800 (2002). [CrossRef]

]). It can be believed that the wider absorption line of Nd3+ ions is ascribed to the inhomogeneous broadening which is caused by the variation in the crystal field experienced by the Nd ions due to the random distribution of Cr and V ions at the V-ion sites (with respect to the pure Nd:GdVO4) neighboring the Nd ions. The absorption band of Cr5+ ions at 1110 nm, with FWHM of about 250 nm, is generated by the transmission of 2A1 to 2B2 [8

8. H. H. Yu, H. J. Zhang, Z.P. Wang, J. Y. Wang, Y. G. Yu, W. L Gao, X. T. Tao, J. H. Liu, X. Y. Zhang, and M. H. Jiang, “Cr5+:GdVO4 as a saturable absorber for a diode-pumped Nd:Lu0.5Gd0.5VO4 laser,” Opt. Express 15, 11679–11684 (2007). [CrossRef] [PubMed]

] which is electric dipole allowed only for p polarization, and is not overlapped with that of Nd3+ ions at 808 nm. From the spectra, it can be proposed that Nd, Cr:GdVO4 should be a potential highly-efficient self-Q-switched laser material at 1.06 µm. Using the same measuring method as the ground absorption cross-section of Cr:GdVO4, the σGSA of Nd, Cr:GdVO4 was estimated, which is almost the same as that of Cr:GdVO4 (about 1.5×10-18 cm2) [8

8. H. H. Yu, H. J. Zhang, Z.P. Wang, J. Y. Wang, Y. G. Yu, W. L Gao, X. T. Tao, J. H. Liu, X. Y. Zhang, and M. H. Jiang, “Cr5+:GdVO4 as a saturable absorber for a diode-pumped Nd:Lu0.5Gd0.5VO4 laser,” Opt. Express 15, 11679–11684 (2007). [CrossRef] [PubMed]

].

Fig. 3. Variation of the output power versus incident pump power.
Fig. 4. Variations of PRF and pulse width versus incident pump power.
Fig. 5. Variation of pulse energy versus incident power.
Fig. 6. Pulse train with the repetition rate of 60.2 kHz

Figure 3 presents the variation of the average output power (Pav) with the increase of incident pump power. The maximum output powers of 243 and 265 mW were obtained with OC=40% and 30%, respectively, at the incident pump power of 3.2 W, with the respective corresponding optical conversions of 7.6% and 8.3%. The thresholds were achieved to be 1.87 and 1.43 W, and the slope efficiencies were 18.3% and 15.3%, with OC=40% and 30%, respectively.

The pulse repetition frequency (PRF), pulse width (t), and pulse energy (E) versus incident pump power are shown in Figs. 4 and 5, respectively. The PRF increased from 60.2 kHz to 250 kHz and 59 to 366 kHz with the increase of incident pump power by using OC=40% and 30%, respectively. When the incident pump power was increased to be larger than 3.2 W, the laser output became almost continuous-wave (cw), which is due to the small modulation depth of the Nd, Cr:GdVO4 crystal at 1.06 µm and can be overcome by increasing the Cr5+ concentrations in the crystal. We believe that, for a low Cr-doped crystal which has the small modulation depth, it is easy to be bleached by the intracavity power. Thus the saturable absorber acts as a linear absorption and the laser operates in cw rather than Q-switching mode, when the intracavity power becomes high. The minimum pulse widths of 230 and 362 ns were obtained with OC=40% and 30%, respectively, under the incident pump power of 2.92 W. The maximum pulse energies were gotten to be 1.12 µJ and 0.9 µJ with the two output couplers, respectively, under the respective corresponding incident pump powers of 2.6 W and 2.33 W. By the pulse energy and width, the peak power can be calculated. The highest peak power of 3.82 W was achieved with OC=40%. The pulse train with 60.2 kHz is shown in Fig. 6. The inset of this figure presents the pulse profile with a pulse width of 230 ns.

4. Conclusion

Acknowledgment

This work is supported by the National Basic Research Program of China under Grand 2004CB619002.

References and links

1.

A. A. Danilov, V. L. Evstigneev, N. N. Il’ichev, A. A. Malyutin, M. Yu, Nikol’skiĭ, A. F. Umyskov, and I. A. Shcherbakov, “Compact GSGG:Cr3+:Nd3+ laser with passive Q switching,” Sov. J. Quantum Electron. 17, 573–574 (1987). [CrossRef]

2.

B. X. Jiang, Z. W. Zhao, X. D. Xu, P. X. Song, and J. Xu, “Study of the effects of Cr ions on Nd in self-Q-switched laser crystal Cr4+,Nd3+:Gd3Ga5O12,” Proc. SPIE. 5627, 167–171 (2005). [CrossRef]

3.

J. Dong and K. Ueda, “Observation of repetitively nanosecond pulse-width transverse patterns in microchip self-Q-switched laser,” Phys. Rev. A , 73, 053824 (2006). [CrossRef]

4.

J. Dong, P. Deng, Y. Lu, Y. Zhang, Y. Liu, J. Xu, and W. Chen, “Laser-diode-pumped Cr4+,Nd3+:YAG with self-Q-switched laser output of 1.4 W,” Opt. Lett. 25, 1101–1103 (2000). [CrossRef]

5.

S. Zhou, K. K. Lee, Y. C. Chen, and S. Li, “Monolithic self-Q-switched Cr,Nd:YAG laser,” Opt. Lett. 18, 511–512 (1993). [CrossRef] [PubMed]

6.

J. Dong and K. Ueda, “Longitudinal-mode competition induced instabilities of Cr4+,Nd3+:Y3Al5O12 self-Q-switched two-mode laser,” Appl. Phys. Lett. 87, 151102 (2005). [CrossRef]

7.

S. A. Zolotovskaya, K. V. Yumashev, N. V. Kuleshov, V. N. Matrosov, T. A. Matrosova, and M. I. Kupchenko, “Absorption saturation properties and laser Q-switch performance of Cr5+-doped YVO4 crystal,” Appl. Phys. B 86, 667–671 (2007). [CrossRef]

8.

H. H. Yu, H. J. Zhang, Z.P. Wang, J. Y. Wang, Y. G. Yu, W. L Gao, X. T. Tao, J. H. Liu, X. Y. Zhang, and M. H. Jiang, “Cr5+:GdVO4 as a saturable absorber for a diode-pumped Nd:Lu0.5Gd0.5VO4 laser,” Opt. Express 15, 11679–11684 (2007). [CrossRef] [PubMed]

9.

R. A. Fields, M. Birnbaum, and C. L. Fincher, “Highly efficient Nd:YVO4 diode-laser end-pumped laser,” Appl. Phys. Lett. 51, 1885–1886 (1987). [CrossRef]

10.

T. Jensen, V. G. Ostroumov, J-P. Meyn, G. Huber, A. I. Zagumennyi, and I. A. Scherbakov, “Spectroscopic characterization and laser performance of diode-laser-pumped Nd: GdVO4,” Appl. Phys. B 58, 373–379 (1994). [CrossRef]

11.

H. Zhang, J. Liu, J. Wang, C. Wang, L. Zhu, Z. Shao, X. Meng, X. Hu, M. Jiang, and Y. T. Chow, “4Characterization of the laser crystal Nd:GdVO4,” J. Opt. Soc. Am. B 19, 18–27 (2002). [CrossRef]

12.

C. Maunier, J. L. Doualan, and R. Moncorgé, “Growth, spectroscopic characterization, and laser performance of Nd:LuVO4, a new infrared laser materials that is suitable for diode pumping,”J. Opt. Soc. Am. B 19, 1794–1800 (2002). [CrossRef]

OCIS Codes
(140.3380) Lasers and laser optics : Laser materials
(140.3540) Lasers and laser optics : Lasers, Q-switched

ToC Category:
Lasers and Laser Optics

History
Original Manuscript: November 26, 2007
Revised Manuscript: February 11, 2008
Manuscript Accepted: February 22, 2008
Published: February 27, 2008

Citation
Haohai Yu, Huaijin Zhang, Zhengping Wang, Jiyang Wang, Yonggui Yu, Wenlan Gao, Xutang Tao, and Minhua Jiang, "Growth and passively self-Q-switched laser output of new Nd3+,Cr5+:GdVO4 crystal," Opt. Express 16, 3320-3325 (2008)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-5-3320


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References

  1. A. A. Danilov, V. L. Evstigneev, N. N. Il'ichev, A. A. Malyutin, M. Yu, Nikol'ski?, A. F. Umyskov, and I. A. Shcherbakov, "Compact GSGG:Cr3+:Nd3+ laser with passive Q switching," Sov. J. Quantum Electron. 17, 573-574 (1987). [CrossRef]
  2. B. X. Jiang, Z. W. Zhao, X. D. Xu, P. X. Song, and J. Xu, "Study of the effects of Cr ions on Nd in self-Q-switched laser crystal Cr4+,Nd3+:Gd3Ga5O12," Proc. SPIE. 5627, 167-171 (2005). [CrossRef]
  3. J. Dong and K. Ueda, "Observation of repetitively nanosecond pulse-width transverse patterns in microchip self-Q-switched laser," Phys. Rev. A  73, 053824 (2006). [CrossRef]
  4. J. Dong, P. Deng, Y. Lu, Y. Zhang, Y. Liu, J. Xu, and W. Chen, "Laser-diode-pumped Cr4+,Nd3+:YAG with self-Q-switched laser output of 1.4 W," Opt. Lett. 25, 1101-1103 (2000). [CrossRef]
  5. S. Zhou, K. K. Lee, Y. C. Chen, and S. Li, "Monolithic self-Q-switched Cr,Nd:YAG laser," Opt. Lett. 18, 511-512 (1993). [CrossRef] [PubMed]
  6. J. Dong and K. Ueda, "Longitudinal-mode competition induced instabilities of Cr4+,Nd3+:Y3Al5O12 self-Q-switched two-mode laser," Appl. Phys. Lett. 87, 151102 (2005). [CrossRef]
  7. S. A. Zolotovskaya, K. V. Yumashev, N. V. Kuleshov, V. N. Matrosov, T. A. Matrosova, and M. I. Kupchenko, "Absorption saturation properties and laser Q-switch performance of Cr5+-doped YVO4 crystal," Appl. Phys. B 86, 667-671 (2007). [CrossRef]
  8. H. H. Yu, H. J. Zhang, Z.P. Wang, J. Y. Wang, Y. G. Yu, W. L Gao, X. T. Tao, J. H. Liu, X. Y. Zhang, and M. H. Jiang, "Cr5+:GdVO4 as a saturable absorber for a diode-pumped Nd:Lu0.5Gd0.5VO4 laser," Opt. Express 15, 11679-11684 (2007). [CrossRef] [PubMed]
  9. R. A. Fields, M. Birnbaum, and C. L. Fincher, "Highly efficient Nd:YVO4 diode-laser end-pumped laser," Appl. Phys. Lett. 51, 1885-1886 (1987). [CrossRef]
  10. T. Jensen, V. G. Ostroumov, J-P. Meyn, G. Huber, A. I. Zagumennyi, and I. A. Scherbakov, "Spectroscopic characterization and laser performance of diode-laser-pumped Nd: GdVO4," Appl. Phys. B 58, 373-379 (1994). [CrossRef]
  11. H. Zhang, J. Liu, J. Wang, C. Wang, L. Zhu, Z. Shao, X. Meng, X. Hu, M, Jiang, and Y. T. Chow, "Characterization of the laser crystal Nd:GdVO4," J. Opt. Soc. Am. B 19, 18-27 (2002). [CrossRef]
  12. C. Maunier, J. L. Doualan, and R. Moncorgé, "Growth, spectroscopic characterization, and laser performance of Nd:LuVO4, a new infrared laser materials that is suitable for diode pumping," J. Opt. Soc. Am. B 19, 1794-1800 (2002). [CrossRef]

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