## Phonon dynamics in γ-ray irradiated sapphire crystals studied by fs-CARS technique |

Optics Express, Vol. 18, Issue 22, pp. 22937-22943 (2010)

http://dx.doi.org/10.1364/OE.18.022937

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### Abstract

We have studied the ultrafast dynamics of coherent phonons in sapphire crystals irradiated with ^{60}Co γ-rays for three different doses by femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) technique at room temperature. The obtained fs-CARS signals exhibit well-defined quantum beats, which are ascribed to the interference of the 645 and 750 cm^{−1} phonon modes. The dephasing times of the two modes both decrease with increasing irradiation dose, which is due to the scattering of coherent phonons by the defects introduced by γ-ray irradiation.

© 2010 OSA

## 1. Introduction

1. A. G. Lanin, E. L. Muravin, V. P. Popov, and V. N. Turchin, “Thermal shock resistance and thermal-mechanical processing of sapphire,” J. Eur. Ceram. Soc. **23**(3), 455–468 (2003). [CrossRef]

3. G. G. Wang, M. F. Zhang, J. C. Han, X. D. He, H. B. Zuo, and X. H. Yang, “High-temperature infrared and dielectric properties of large sapphire crystal for seeker dome application,” Cryst. Res. Technol. **43**(5), 531–536 (2008). [CrossRef]

4. M. Hase, K. Ishioka, M. Kitajima, K. Ushida, and S. Hishita, “Dephasing of coherent phonons by lattice defects in bismuth films,” Appl. Phys. Lett. **76**(10), 1258–1260 (2000). [CrossRef]

5. K. Ishioka, M. Hase, M. Kitajima, and K. Ushida, “Ultrafast carrier and phonon dynamics in ion-irradiated graphite,” Appl. Phys. Lett. **78**(25), 3965–3967 (2001). [CrossRef]

6. M. Hase, K. Ishioka, M. Kitajima, and K. Ushida, “Ultrafast carrier and plasmon-phonon dynamics in ion-irradiated n-GaAs,” Appl. Phys. Lett. **82**(21), 3668–3670 (2003). [CrossRef]

7. R. Leonhardt, W. Holzapfel, W. Zinth, and W. Kaiser, “Terahertz beats of vibrational modes studied by femtosecond coherent Raman spectroscopy,” Rev. Phys. Appl. (Paris) **22**(12), 1735–1741 (1987). [CrossRef]

14. M. Karavitis, R. Zadoyan, and V. Ara Apkarian, “Time resolved coherent anti-Stokes Raman scattering of I_{2} isolated in matrix argon: Vibrational dynamics on the ground electronic state,” J. Chem. Phys. **114**(9), 4131–4140 (2001). [CrossRef]

^{60}Co γ-rays for different doses, we observed well-defined quantum beat signals, which are ascribed to the interference of the 645 and 750 cm

^{−1}phonon modes. By fitting the experimental data, we are able to simultaneously give the dephasing times of the two modes, both of them decrease with increasing irradiation dose, which is due to the scattering of coherent phonons by the defects introduced by γ-ray irradiation. This work offers the possibility of developing a new non-destructive detection approach to predict the damage degree of crystals.

*τ*between the probe pulse and the simultaneous pump and Stokes pulses. Obviously, the fs-CARS technique is perfectly suitable for the selective excitation of phonon modes by adjusting the frequency difference between the pump and Stokes pulses. In this work, we use a white-light continuum (WLC) for the Stokes pulse. Due to the chirp characteristics of the ultrabroadband WLC, no complicated laser system is required for the wavelength tuning of the Stokes pulse.

## 2. Experiment

3. G. G. Wang, M. F. Zhang, J. C. Han, X. D. He, H. B. Zuo, and X. H. Yang, “High-temperature infrared and dielectric properties of large sapphire crystal for seeker dome application,” Cryst. Res. Technol. **43**(5), 531–536 (2008). [CrossRef]

^{60}Co γ-rays at doses of 1 × 10

^{7}, 1 × 10

^{8}and 5 × 10

^{8}rad, respectively.

*ω*

_{p},

*k*_{p}) and probe (

*ω*

_{pr}=

*ω*

_{p},

*k*_{pr}) pulses, and the third one is focused into a 4 mm thick Al

_{2}O

_{3}crystal to produce a WLC used for the Stokes pulse (

*ω*

_{s},

*k*_{s}). Two delay lines are employed. The Stokes pulse defines an arbitrary temporal zero point. The delay time between the pump and Stokes pulse and that between the probe and Stokes pulse can be varied. Figure 1(b) displays the energy diagram. A folded BOXCARS configuration [see Fig. 1(c)] with properly chosen angles (less than 2 degrees) between the beams, determined by the phase matching condition, is used. The CARS signal is collected by a silica fibre, dispersed in a spectrometer (Bruker Optics 500 IS/SM) and detected by a CCD detector (Andor DU440-BU2).

## 3. Results and discussion

^{60}Co γ-rays at doses of 1 × 10

^{7}, 1 × 10

^{8}and 5 × 10

^{8}rad is set at 758 nm, corresponding to an excitation wavenumber of 693 cm

^{−1}. This is approximately the mean wavenumber value of the 645 and 750 cm

^{−1}modes. The time-integrated CARS signal intensity can be written as [17

17. A. Volkmer, L. D. Book, and X. S. Xie, “Time-resolved coherent anti-Stokes Raman scattering microscopy: Imaging based on Raman free induction decay,” Appl. Phys. Lett. **80**(9), 1505–1507 (2002). [CrossRef]

18. M. Cui, M. Joffre, J. Skodack, and J. P. Ogilvie, “Interferometric Fourier transform coherent antistokes Raman scattering,” Opt. Express **14**(18), 8448–8458 (2006). [CrossRef] [PubMed]

*P*_{c}

^{(3)}consists of two contributions: the fast nonresonant part due to the response of the electronic system and the slow resonant part due to the response of the coherent phonons [7

7. R. Leonhardt, W. Holzapfel, W. Zinth, and W. Kaiser, “Terahertz beats of vibrational modes studied by femtosecond coherent Raman spectroscopy,” Rev. Phys. Appl. (Paris) **22**(12), 1735–1741 (1987). [CrossRef]

18. M. Cui, M. Joffre, J. Skodack, and J. P. Ogilvie, “Interferometric Fourier transform coherent antistokes Raman scattering,” Opt. Express **14**(18), 8448–8458 (2006). [CrossRef] [PubMed]

19. D. S. Choi, S. C. Jeoung, and B. H. Chon, “Thickness dependent CARS measurement of polymeric thin films without depth-profiling,” Opt. Express **16**(4), 2604–2613 (2008). [CrossRef] [PubMed]

7. R. Leonhardt, W. Holzapfel, W. Zinth, and W. Kaiser, “Terahertz beats of vibrational modes studied by femtosecond coherent Raman spectroscopy,” Rev. Phys. Appl. (Paris) **22**(12), 1735–1741 (1987). [CrossRef]

9. M. Heid, S. Schlücker, U. Schmitt, T. Chen, R. Schweitzer-Stenner, V. Engel, and W. Kiefer, “Two-dimensional probing of ground-state vibrational dynamics in porphyrin molecules by fs-CARS,” J. Raman Spectrosc. **32**(9), 771–784 (2001). [CrossRef]

11. H. Kano and H. Hamaguchi, “Femtosecond coherent anti-Stokes Raman scattering spectroscopy using supercontinuum generated from a photonic crystal fiber,” Appl. Phys. Lett. **85**(19), 4298–4300 (2004). [CrossRef]

^{−1}) of the 645 and 750 cm

^{−1}modes.

**22**(12), 1735–1741 (1987). [CrossRef]

9. M. Heid, S. Schlücker, U. Schmitt, T. Chen, R. Schweitzer-Stenner, V. Engel, and W. Kiefer, “Two-dimensional probing of ground-state vibrational dynamics in porphyrin molecules by fs-CARS,” J. Raman Spectrosc. **32**(9), 771–784 (2001). [CrossRef]

^{−1}, which are consistent with the difference between the 645 and 750 cm

^{−1}modes. We confirm that the 645 and 750 cm

^{−1}modes are coherently excited at the same time, and the beat signals are ascribed to the interference of the two modes. It should be noted that the dephasing times

20. A. Laubereau and W. Kaiser, “Vibrational dynamics of liquids and solids investigated by picosecond light pulses,” Rev. Mod. Phys. **50**(3), 607–665 (1978). [CrossRef]

9. M. Heid, S. Schlücker, U. Schmitt, T. Chen, R. Schweitzer-Stenner, V. Engel, and W. Kiefer, “Two-dimensional probing of ground-state vibrational dynamics in porphyrin molecules by fs-CARS,” J. Raman Spectrosc. **32**(9), 771–784 (2001). [CrossRef]

^{−1}mode and the shorter one

^{−1}mode.

4. M. Hase, K. Ishioka, M. Kitajima, K. Ushida, and S. Hishita, “Dephasing of coherent phonons by lattice defects in bismuth films,” Appl. Phys. Lett. **76**(10), 1258–1260 (2000). [CrossRef]

20. A. Laubereau and W. Kaiser, “Vibrational dynamics of liquids and solids investigated by picosecond light pulses,” Rev. Mod. Phys. **50**(3), 607–665 (1978). [CrossRef]

21. V. Chernyak, A. Piryatinski, and S. Mukamel, “Complete Determination of Relaxation Parameters from Two-Dimensional Raman Spectroscopy,” Laser Chem. **19**(1–4), 109–116 (1999). [CrossRef]

23. G. A. Garrett, T. F. Albrecht, J. F. Whitaker, and R. Merlin, “Coherent THz Phonons Driven by Light Pulses and the Sb Problem: What is the Mechanism?” Phys. Rev. Lett. **77**(17), 3661–3664 (1996). [CrossRef] [PubMed]

24. M. Hase, K. Mizoguchi, H. Harima, S. Nakashima, and K. Sakai, “Dynamics of coherent phonons in bismuth generated by ultrashort laser pulses,” Phys. Rev. B **58**(9), 5448–5452 (1998). [CrossRef]

## 4. Conclusion

^{60}Co γ-ray irradiated sapphire crystals by fs-CARS technique at room temperature, in spite of the difficulties in experimental operation. We use the ultrabroadband WLC for the Stokes pulse. Due to the chirp characteristics of the WLC, we have achieved the selective excitation of the phonon modes without requiring complicated laser system for the wavelength tuning of the Stokes pulse. The observed well-defined quantum beat signals are ascribed to the interference of the 645 cm

^{−1}

^{−1}

## Acknowledgments

## References and links

1. | A. G. Lanin, E. L. Muravin, V. P. Popov, and V. N. Turchin, “Thermal shock resistance and thermal-mechanical processing of sapphire,” J. Eur. Ceram. Soc. |

2. | T. Vodenitcharova, L. C. Zhang, I. Zarudi, Y. Yin, H. Domyo, T. Ho, and M. Sato, “The effect of anisotropy on the deformation and fracture of sapphire wafers subjected to thermal shocks,” J. Mater. Process. Technol. |

3. | G. G. Wang, M. F. Zhang, J. C. Han, X. D. He, H. B. Zuo, and X. H. Yang, “High-temperature infrared and dielectric properties of large sapphire crystal for seeker dome application,” Cryst. Res. Technol. |

4. | M. Hase, K. Ishioka, M. Kitajima, K. Ushida, and S. Hishita, “Dephasing of coherent phonons by lattice defects in bismuth films,” Appl. Phys. Lett. |

5. | K. Ishioka, M. Hase, M. Kitajima, and K. Ushida, “Ultrafast carrier and phonon dynamics in ion-irradiated graphite,” Appl. Phys. Lett. |

6. | M. Hase, K. Ishioka, M. Kitajima, and K. Ushida, “Ultrafast carrier and plasmon-phonon dynamics in ion-irradiated n-GaAs,” Appl. Phys. Lett. |

7. | R. Leonhardt, W. Holzapfel, W. Zinth, and W. Kaiser, “Terahertz beats of vibrational modes studied by femtosecond coherent Raman spectroscopy,” Rev. Phys. Appl. (Paris) |

8. | R. Leonhardt, W. Holzapfel, W. Zinth, and W. Kaiser, “Terahertz quantum beats in molecular liquids,” Chem. Phys. Lett. |

9. | M. Heid, S. Schlücker, U. Schmitt, T. Chen, R. Schweitzer-Stenner, V. Engel, and W. Kiefer, “Two-dimensional probing of ground-state vibrational dynamics in porphyrin molecules by fs-CARS,” J. Raman Spectrosc. |

10. | M. Heid, T. Chen, U. Schmitt, and W. Kiefer, “Spectrally resolved fs-CARS as a probe of the vibrational dynamics of a large polyatomic molecule: magnesium octaethylporphyrin,” Chem. Phys. Lett. |

11. | H. Kano and H. Hamaguchi, “Femtosecond coherent anti-Stokes Raman scattering spectroscopy using supercontinuum generated from a photonic crystal fiber,” Appl. Phys. Lett. |

12. | D. Pestov, M. C. Zhi, Z. E. Sariyanni, N. G. Kalugin, A. Kolomenskii, R. Murawski, Y. V. Rostovtsev, V. A. Sautenkov, A. V. Sokolov, and M. O. Scully, “Femtosecond CARS of methanol–water mixtures,” J. Raman Spectrosc. |

13. | S. Meyer, M. Schmitt, A. Materny, W. Kiefer, and V. Engel, “A theoretical analysis of the time-resolved femtosecond CARS spectrum of I |

14. | M. Karavitis, R. Zadoyan, and V. Ara Apkarian, “Time resolved coherent anti-Stokes Raman scattering of I |

15. | Y. J. Lee, S. H. Parekh, Y. H. Kim, and M. T. Cicerone, “Optimized continuum from a photonic crystal fiber for broadband time-resolved coherent anti-Stokes Raman scattering,” Opt. Express |

16. | M. Kadleíková, J. Breza, and M. Veselý, “Raman spectra of synthetic sapphire,” Microelectron. J. |

17. | A. Volkmer, L. D. Book, and X. S. Xie, “Time-resolved coherent anti-Stokes Raman scattering microscopy: Imaging based on Raman free induction decay,” Appl. Phys. Lett. |

18. | M. Cui, M. Joffre, J. Skodack, and J. P. Ogilvie, “Interferometric Fourier transform coherent antistokes Raman scattering,” Opt. Express |

19. | D. S. Choi, S. C. Jeoung, and B. H. Chon, “Thickness dependent CARS measurement of polymeric thin films without depth-profiling,” Opt. Express |

20. | A. Laubereau and W. Kaiser, “Vibrational dynamics of liquids and solids investigated by picosecond light pulses,” Rev. Mod. Phys. |

21. | V. Chernyak, A. Piryatinski, and S. Mukamel, “Complete Determination of Relaxation Parameters from Two-Dimensional Raman Spectroscopy,” Laser Chem. |

22. | G. Q. Zhou, Y. J. Dong, J. Xu, H. J. Li, J. L. Si, X. B. Qian, and X. Q. Li, “Φ140 mm sapphire crystal growth by temperature gradient techniques and its color centers,” Mater. Lett. |

23. | G. A. Garrett, T. F. Albrecht, J. F. Whitaker, and R. Merlin, “Coherent THz Phonons Driven by Light Pulses and the Sb Problem: What is the Mechanism?” Phys. Rev. Lett. |

24. | M. Hase, K. Mizoguchi, H. Harima, S. Nakashima, and K. Sakai, “Dynamics of coherent phonons in bismuth generated by ultrashort laser pulses,” Phys. Rev. B |

**OCIS Codes**

(300.6230) Spectroscopy : Spectroscopy, coherent anti-Stokes Raman scattering

(300.6500) Spectroscopy : Spectroscopy, time-resolved

(300.6530) Spectroscopy : Spectroscopy, ultrafast

**ToC Category:**

Spectroscopy

**History**

Original Manuscript: July 28, 2010

Revised Manuscript: September 24, 2010

Manuscript Accepted: October 7, 2010

Published: October 14, 2010

**Citation**

Xin Du, Mingfu Zhang, Qingkun Meng, Yunfei Song, Xing He, Yanqiang Yang, and Jiecai Han, "Phonon dynamics in γ-ray irradiated sapphire crystals studied by fs-CARS technique," Opt. Express **18**, 22937-22943 (2010)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-22-22937

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### References

- A. G. Lanin, E. L. Muravin, V. P. Popov, and V. N. Turchin, “Thermal shock resistance and thermal-mechanical processing of sapphire,” J. Eur. Ceram. Soc. 23(3), 455–468 (2003). [CrossRef]
- T. Vodenitcharova, L. C. Zhang, I. Zarudi, Y. Yin, H. Domyo, T. Ho, and M. Sato, “The effect of anisotropy on the deformation and fracture of sapphire wafers subjected to thermal shocks,” J. Mater. Process. Technol. 194(1–3), 52–62 (2007). [CrossRef]
- G. G. Wang, M. F. Zhang, J. C. Han, X. D. He, H. B. Zuo, and X. H. Yang, “High-temperature infrared and dielectric properties of large sapphire crystal for seeker dome application,” Cryst. Res. Technol. 43(5), 531–536 (2008). [CrossRef]
- M. Hase, K. Ishioka, M. Kitajima, K. Ushida, and S. Hishita, “Dephasing of coherent phonons by lattice defects in bismuth films,” Appl. Phys. Lett. 76(10), 1258–1260 (2000). [CrossRef]
- K. Ishioka, M. Hase, M. Kitajima, and K. Ushida, “Ultrafast carrier and phonon dynamics in ion-irradiated graphite,” Appl. Phys. Lett. 78(25), 3965–3967 (2001). [CrossRef]
- M. Hase, K. Ishioka, M. Kitajima, and K. Ushida, “Ultrafast carrier and plasmon-phonon dynamics in ion-irradiated n-GaAs,” Appl. Phys. Lett. 82(21), 3668–3670 (2003). [CrossRef]
- R. Leonhardt, W. Holzapfel, W. Zinth, and W. Kaiser, “Terahertz beats of vibrational modes studied by femtosecond coherent Raman spectroscopy,” Rev. Phys. Appl. (Paris) 22(12), 1735–1741 (1987). [CrossRef]
- R. Leonhardt, W. Holzapfel, W. Zinth, and W. Kaiser, “Terahertz quantum beats in molecular liquids,” Chem. Phys. Lett. 133(5), 373–377 (1987). [CrossRef]
- M. Heid, S. Schlücker, U. Schmitt, T. Chen, R. Schweitzer-Stenner, V. Engel, and W. Kiefer, “Two-dimensional probing of ground-state vibrational dynamics in porphyrin molecules by fs-CARS,” J. Raman Spectrosc. 32(9), 771–784 (2001). [CrossRef]
- M. Heid, T. Chen, U. Schmitt, and W. Kiefer, “Spectrally resolved fs-CARS as a probe of the vibrational dynamics of a large polyatomic molecule: magnesium octaethylporphyrin,” Chem. Phys. Lett. 334(1–3), 119–126 (2001). [CrossRef]
- H. Kano and H. Hamaguchi, “Femtosecond coherent anti-Stokes Raman scattering spectroscopy using supercontinuum generated from a photonic crystal fiber,” Appl. Phys. Lett. 85(19), 4298–4300 (2004). [CrossRef]
- D. Pestov, M. C. Zhi, Z. E. Sariyanni, N. G. Kalugin, A. Kolomenskii, R. Murawski, Y. V. Rostovtsev, V. A. Sautenkov, A. V. Sokolov, and M. O. Scully, “Femtosecond CARS of methanol–water mixtures,” J. Raman Spectrosc. 37(1–3), 392–396 (2006). [CrossRef]
- S. Meyer, M. Schmitt, A. Materny, W. Kiefer, and V. Engel, “A theoretical analysis of the time-resolved femtosecond CARS spectrum of I2,” Chem. Phys. Lett. 281(4–6), 332–336 (1997). [CrossRef]
- M. Karavitis, R. Zadoyan, and V. Ara Apkarian, “Time resolved coherent anti-Stokes Raman scattering of I2 isolated in matrix argon: Vibrational dynamics on the ground electronic state,” J. Chem. Phys. 114(9), 4131–4140 (2001). [CrossRef]
- Y. J. Lee, S. H. Parekh, Y. H. Kim, and M. T. Cicerone, “Optimized continuum from a photonic crystal fiber for broadband time-resolved coherent anti-Stokes Raman scattering,” Opt. Express 18(5), 4371–4379 (2010). [CrossRef] [PubMed]
- M. Kadleı́ková, J. Breza, and M. Veselý, “Raman spectra of synthetic sapphire,” Microelectron. J. 32(12), 955–958 (2001). [CrossRef]
- A. Volkmer, L. D. Book, and X. S. Xie, “Time-resolved coherent anti-Stokes Raman scattering microscopy: Imaging based on Raman free induction decay,” Appl. Phys. Lett. 80(9), 1505–1507 (2002). [CrossRef]
- M. Cui, M. Joffre, J. Skodack, and J. P. Ogilvie, “Interferometric Fourier transform coherent antistokes Raman scattering,” Opt. Express 14(18), 8448–8458 (2006). [CrossRef] [PubMed]
- D. S. Choi, S. C. Jeoung, and B. H. Chon, “Thickness dependent CARS measurement of polymeric thin films without depth-profiling,” Opt. Express 16(4), 2604–2613 (2008). [CrossRef] [PubMed]
- A. Laubereau and W. Kaiser, “Vibrational dynamics of liquids and solids investigated by picosecond light pulses,” Rev. Mod. Phys. 50(3), 607–665 (1978). [CrossRef]
- V. Chernyak, A. Piryatinski, and S. Mukamel, “Complete Determination of Relaxation Parameters from Two-Dimensional Raman Spectroscopy,” Laser Chem. 19(1–4), 109–116 (1999). [CrossRef]
- G. Q. Zhou, Y. J. Dong, J. Xu, H. J. Li, J. L. Si, X. B. Qian, and X. Q. Li, “Φ140 mm sapphire crystal growth by temperature gradient techniques and its color centers,” Mater. Lett. 60(7), 901–904 (2006). [CrossRef]
- G. A. Garrett, T. F. Albrecht, J. F. Whitaker, and R. Merlin, “Coherent THz Phonons Driven by Light Pulses and the Sb Problem: What is the Mechanism?” Phys. Rev. Lett. 77(17), 3661–3664 (1996). [CrossRef] [PubMed]
- M. Hase, K. Mizoguchi, H. Harima, S. Nakashima, and K. Sakai, “Dynamics of coherent phonons in bismuth generated by ultrashort laser pulses,” Phys. Rev. B 58(9), 5448–5452 (1998). [CrossRef]

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