Abstract

We demonstrate what is to our knowledge the first example of four-photon luminescence microscopy in GaN and apply it to quality mapping of bulk GaN. The simultaneously acquired second- and third-harmonic generation can be used to map the distribution of the piezoelectric field and the band-tail state density, respectively. Through spectrum- and power-dependent studies, the fourth power dependence of the band edge luminescence is confirmed. The superb spatial resolution of the four-photon luminescence modality is also demonstrated. This technique provides a high-resolution, noninvasive monitoring and tool for examining the physical properties of semiconductors.

© 2005 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. S. Nakamura and G. Fasol, The Blue Laser Diode, GaN Based Light Emitters and Lasers (Springer-Verlag, 1997).
  2. B. J. Skromme, H. Zhao, D. Wang, H. S. Kong, M. T. Leonard, G. E. Bulman, and B. J. Molnar, Appl. Phys. Lett. 71, 829 (1997).
    [CrossRef]
  3. T. J. Schmidt, Y. H. Cho, G. H. Gainer, J. J. Song, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 73, 1892 (1998).
    [CrossRef]
  4. T. Takeuchi, C. Wetzel, S. Yamaguchi, H. Sakai, H. Amano, and I. Akasaki, Appl. Phys. Lett. 73, 1691 (1997).
    [CrossRef]
  5. S. Chichibu, T. Azuhata, T. Sota, and S. Nakamura, Appl. Phys. Lett. 70, 2822 (1997).
    [CrossRef]
  6. C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 77, 2331 (2000).
    [CrossRef]
  7. C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, A. Abare, U. K. Mishra, and S. P. DenBaars, Scanning 23, 182 (2001).
    [CrossRef] [PubMed]
  8. C.-K. Sun, J.-C. Liang, J.-C. Wang, F.-J. Kao, S. Keller, M. P. Mack, U. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 76, 439 (2000).
    [CrossRef]
  9. C.-K. Sun, S.-W. Chu, S.-Y. Chen, T.-H. Tsai, T.-M. Liu, C.-Y. Lin, and H.-J. Tsai, J. Struct. Biol. 147, 19 (2004).
    [CrossRef] [PubMed]
  10. T. Kawashima, H. Yoshikawa, S. Adachi, S. Fuke, and K. Ohtsuka, J. Appl. Phys. 82, 3528 (1997).
    [CrossRef]
  11. J. H. Edgar, S. Strite, I. Akasaki, H. Amano, and C. Wetzel, Properties, Processing and Applications of Gallium Nitride and Related Semiconductors (Institution of Electrical Engineers, 1999).
  12. D. Kim, I. H. Libon, C. Voelkmann, Y. R. Shen, and V. Petrova-Koch, Phys. Rev. B 55, R4907 (1997).
    [CrossRef]
  13. L. Moreaux, O. Sandre, and J. Mertz, J. Opt. Soc. Am. B 17, 1685 (2000).
    [CrossRef]
  14. J. X. Cheng and X. S. Xie, J. Opt. Soc. Am. B 19, 1604 (2002).
    [CrossRef]
  15. J. M. Schins, T. Schrama, J. Squier, G. J. Brakenhoff, and M. Müller, J. Opt. Soc. Am. B 19, 1627 (2002).
    [CrossRef]

2004

C.-K. Sun, S.-W. Chu, S.-Y. Chen, T.-H. Tsai, T.-M. Liu, C.-Y. Lin, and H.-J. Tsai, J. Struct. Biol. 147, 19 (2004).
[CrossRef] [PubMed]

2002

2001

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, A. Abare, U. K. Mishra, and S. P. DenBaars, Scanning 23, 182 (2001).
[CrossRef] [PubMed]

2000

C.-K. Sun, J.-C. Liang, J.-C. Wang, F.-J. Kao, S. Keller, M. P. Mack, U. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 76, 439 (2000).
[CrossRef]

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 77, 2331 (2000).
[CrossRef]

L. Moreaux, O. Sandre, and J. Mertz, J. Opt. Soc. Am. B 17, 1685 (2000).
[CrossRef]

1998

T. J. Schmidt, Y. H. Cho, G. H. Gainer, J. J. Song, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 73, 1892 (1998).
[CrossRef]

1997

T. Takeuchi, C. Wetzel, S. Yamaguchi, H. Sakai, H. Amano, and I. Akasaki, Appl. Phys. Lett. 73, 1691 (1997).
[CrossRef]

S. Chichibu, T. Azuhata, T. Sota, and S. Nakamura, Appl. Phys. Lett. 70, 2822 (1997).
[CrossRef]

B. J. Skromme, H. Zhao, D. Wang, H. S. Kong, M. T. Leonard, G. E. Bulman, and B. J. Molnar, Appl. Phys. Lett. 71, 829 (1997).
[CrossRef]

T. Kawashima, H. Yoshikawa, S. Adachi, S. Fuke, and K. Ohtsuka, J. Appl. Phys. 82, 3528 (1997).
[CrossRef]

D. Kim, I. H. Libon, C. Voelkmann, Y. R. Shen, and V. Petrova-Koch, Phys. Rev. B 55, R4907 (1997).
[CrossRef]

Abare, A.

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, A. Abare, U. K. Mishra, and S. P. DenBaars, Scanning 23, 182 (2001).
[CrossRef] [PubMed]

Adachi, S.

T. Kawashima, H. Yoshikawa, S. Adachi, S. Fuke, and K. Ohtsuka, J. Appl. Phys. 82, 3528 (1997).
[CrossRef]

Akasaki, I.

T. Takeuchi, C. Wetzel, S. Yamaguchi, H. Sakai, H. Amano, and I. Akasaki, Appl. Phys. Lett. 73, 1691 (1997).
[CrossRef]

J. H. Edgar, S. Strite, I. Akasaki, H. Amano, and C. Wetzel, Properties, Processing and Applications of Gallium Nitride and Related Semiconductors (Institution of Electrical Engineers, 1999).

Amano, H.

T. Takeuchi, C. Wetzel, S. Yamaguchi, H. Sakai, H. Amano, and I. Akasaki, Appl. Phys. Lett. 73, 1691 (1997).
[CrossRef]

J. H. Edgar, S. Strite, I. Akasaki, H. Amano, and C. Wetzel, Properties, Processing and Applications of Gallium Nitride and Related Semiconductors (Institution of Electrical Engineers, 1999).

Azuhata, T.

S. Chichibu, T. Azuhata, T. Sota, and S. Nakamura, Appl. Phys. Lett. 70, 2822 (1997).
[CrossRef]

Brakenhoff, G. J.

Bulman, G. E.

B. J. Skromme, H. Zhao, D. Wang, H. S. Kong, M. T. Leonard, G. E. Bulman, and B. J. Molnar, Appl. Phys. Lett. 71, 829 (1997).
[CrossRef]

Chen, S.-Y.

C.-K. Sun, S.-W. Chu, S.-Y. Chen, T.-H. Tsai, T.-M. Liu, C.-Y. Lin, and H.-J. Tsai, J. Struct. Biol. 147, 19 (2004).
[CrossRef] [PubMed]

Cheng, J. X.

Chichibu, S.

S. Chichibu, T. Azuhata, T. Sota, and S. Nakamura, Appl. Phys. Lett. 70, 2822 (1997).
[CrossRef]

Cho, Y. H.

T. J. Schmidt, Y. H. Cho, G. H. Gainer, J. J. Song, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 73, 1892 (1998).
[CrossRef]

Chu, S.-W.

C.-K. Sun, S.-W. Chu, S.-Y. Chen, T.-H. Tsai, T.-M. Liu, C.-Y. Lin, and H.-J. Tsai, J. Struct. Biol. 147, 19 (2004).
[CrossRef] [PubMed]

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, A. Abare, U. K. Mishra, and S. P. DenBaars, Scanning 23, 182 (2001).
[CrossRef] [PubMed]

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 77, 2331 (2000).
[CrossRef]

DenBaars, S. P.

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, A. Abare, U. K. Mishra, and S. P. DenBaars, Scanning 23, 182 (2001).
[CrossRef] [PubMed]

C.-K. Sun, J.-C. Liang, J.-C. Wang, F.-J. Kao, S. Keller, M. P. Mack, U. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 76, 439 (2000).
[CrossRef]

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 77, 2331 (2000).
[CrossRef]

T. J. Schmidt, Y. H. Cho, G. H. Gainer, J. J. Song, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 73, 1892 (1998).
[CrossRef]

Edgar, J. H.

J. H. Edgar, S. Strite, I. Akasaki, H. Amano, and C. Wetzel, Properties, Processing and Applications of Gallium Nitride and Related Semiconductors (Institution of Electrical Engineers, 1999).

Fasol, G.

S. Nakamura and G. Fasol, The Blue Laser Diode, GaN Based Light Emitters and Lasers (Springer-Verlag, 1997).

Fuke, S.

T. Kawashima, H. Yoshikawa, S. Adachi, S. Fuke, and K. Ohtsuka, J. Appl. Phys. 82, 3528 (1997).
[CrossRef]

Gainer, G. H.

T. J. Schmidt, Y. H. Cho, G. H. Gainer, J. J. Song, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 73, 1892 (1998).
[CrossRef]

Kao, F.-J.

C.-K. Sun, J.-C. Liang, J.-C. Wang, F.-J. Kao, S. Keller, M. P. Mack, U. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 76, 439 (2000).
[CrossRef]

Kawashima, T.

T. Kawashima, H. Yoshikawa, S. Adachi, S. Fuke, and K. Ohtsuka, J. Appl. Phys. 82, 3528 (1997).
[CrossRef]

Keller, S.

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, A. Abare, U. K. Mishra, and S. P. DenBaars, Scanning 23, 182 (2001).
[CrossRef] [PubMed]

C.-K. Sun, J.-C. Liang, J.-C. Wang, F.-J. Kao, S. Keller, M. P. Mack, U. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 76, 439 (2000).
[CrossRef]

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 77, 2331 (2000).
[CrossRef]

T. J. Schmidt, Y. H. Cho, G. H. Gainer, J. J. Song, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 73, 1892 (1998).
[CrossRef]

Kim, D.

D. Kim, I. H. Libon, C. Voelkmann, Y. R. Shen, and V. Petrova-Koch, Phys. Rev. B 55, R4907 (1997).
[CrossRef]

Kong, H. S.

B. J. Skromme, H. Zhao, D. Wang, H. S. Kong, M. T. Leonard, G. E. Bulman, and B. J. Molnar, Appl. Phys. Lett. 71, 829 (1997).
[CrossRef]

Leonard, M. T.

B. J. Skromme, H. Zhao, D. Wang, H. S. Kong, M. T. Leonard, G. E. Bulman, and B. J. Molnar, Appl. Phys. Lett. 71, 829 (1997).
[CrossRef]

Liang, J.-C.

C.-K. Sun, J.-C. Liang, J.-C. Wang, F.-J. Kao, S. Keller, M. P. Mack, U. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 76, 439 (2000).
[CrossRef]

Libon, I. H.

D. Kim, I. H. Libon, C. Voelkmann, Y. R. Shen, and V. Petrova-Koch, Phys. Rev. B 55, R4907 (1997).
[CrossRef]

Lin, C.-Y.

C.-K. Sun, S.-W. Chu, S.-Y. Chen, T.-H. Tsai, T.-M. Liu, C.-Y. Lin, and H.-J. Tsai, J. Struct. Biol. 147, 19 (2004).
[CrossRef] [PubMed]

Liu, T.-M.

C.-K. Sun, S.-W. Chu, S.-Y. Chen, T.-H. Tsai, T.-M. Liu, C.-Y. Lin, and H.-J. Tsai, J. Struct. Biol. 147, 19 (2004).
[CrossRef] [PubMed]

Mack, M. P.

C.-K. Sun, J.-C. Liang, J.-C. Wang, F.-J. Kao, S. Keller, M. P. Mack, U. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 76, 439 (2000).
[CrossRef]

Mertz, J.

Mishra, U.

C.-K. Sun, J.-C. Liang, J.-C. Wang, F.-J. Kao, S. Keller, M. P. Mack, U. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 76, 439 (2000).
[CrossRef]

Mishra, U. K.

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, A. Abare, U. K. Mishra, and S. P. DenBaars, Scanning 23, 182 (2001).
[CrossRef] [PubMed]

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 77, 2331 (2000).
[CrossRef]

T. J. Schmidt, Y. H. Cho, G. H. Gainer, J. J. Song, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 73, 1892 (1998).
[CrossRef]

Molnar, B. J.

B. J. Skromme, H. Zhao, D. Wang, H. S. Kong, M. T. Leonard, G. E. Bulman, and B. J. Molnar, Appl. Phys. Lett. 71, 829 (1997).
[CrossRef]

Moreaux, L.

Müller, M.

Nakamura, S.

S. Chichibu, T. Azuhata, T. Sota, and S. Nakamura, Appl. Phys. Lett. 70, 2822 (1997).
[CrossRef]

S. Nakamura and G. Fasol, The Blue Laser Diode, GaN Based Light Emitters and Lasers (Springer-Verlag, 1997).

Ohtsuka, K.

T. Kawashima, H. Yoshikawa, S. Adachi, S. Fuke, and K. Ohtsuka, J. Appl. Phys. 82, 3528 (1997).
[CrossRef]

Petrova-Koch, V.

D. Kim, I. H. Libon, C. Voelkmann, Y. R. Shen, and V. Petrova-Koch, Phys. Rev. B 55, R4907 (1997).
[CrossRef]

Sakai, H.

T. Takeuchi, C. Wetzel, S. Yamaguchi, H. Sakai, H. Amano, and I. Akasaki, Appl. Phys. Lett. 73, 1691 (1997).
[CrossRef]

Sandre, O.

Schins, J. M.

Schmidt, T. J.

T. J. Schmidt, Y. H. Cho, G. H. Gainer, J. J. Song, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 73, 1892 (1998).
[CrossRef]

Schrama, T.

Shen, Y. R.

D. Kim, I. H. Libon, C. Voelkmann, Y. R. Shen, and V. Petrova-Koch, Phys. Rev. B 55, R4907 (1997).
[CrossRef]

Skromme, B. J.

B. J. Skromme, H. Zhao, D. Wang, H. S. Kong, M. T. Leonard, G. E. Bulman, and B. J. Molnar, Appl. Phys. Lett. 71, 829 (1997).
[CrossRef]

Song, J. J.

T. J. Schmidt, Y. H. Cho, G. H. Gainer, J. J. Song, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 73, 1892 (1998).
[CrossRef]

Sota, T.

S. Chichibu, T. Azuhata, T. Sota, and S. Nakamura, Appl. Phys. Lett. 70, 2822 (1997).
[CrossRef]

Squier, J.

Strite, S.

J. H. Edgar, S. Strite, I. Akasaki, H. Amano, and C. Wetzel, Properties, Processing and Applications of Gallium Nitride and Related Semiconductors (Institution of Electrical Engineers, 1999).

Sun, C.-K.

C.-K. Sun, S.-W. Chu, S.-Y. Chen, T.-H. Tsai, T.-M. Liu, C.-Y. Lin, and H.-J. Tsai, J. Struct. Biol. 147, 19 (2004).
[CrossRef] [PubMed]

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, A. Abare, U. K. Mishra, and S. P. DenBaars, Scanning 23, 182 (2001).
[CrossRef] [PubMed]

C.-K. Sun, J.-C. Liang, J.-C. Wang, F.-J. Kao, S. Keller, M. P. Mack, U. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 76, 439 (2000).
[CrossRef]

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 77, 2331 (2000).
[CrossRef]

Tai, S.-P.

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, A. Abare, U. K. Mishra, and S. P. DenBaars, Scanning 23, 182 (2001).
[CrossRef] [PubMed]

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 77, 2331 (2000).
[CrossRef]

Takeuchi, T.

T. Takeuchi, C. Wetzel, S. Yamaguchi, H. Sakai, H. Amano, and I. Akasaki, Appl. Phys. Lett. 73, 1691 (1997).
[CrossRef]

Tsai, H.-J.

C.-K. Sun, S.-W. Chu, S.-Y. Chen, T.-H. Tsai, T.-M. Liu, C.-Y. Lin, and H.-J. Tsai, J. Struct. Biol. 147, 19 (2004).
[CrossRef] [PubMed]

Tsai, T.-H.

C.-K. Sun, S.-W. Chu, S.-Y. Chen, T.-H. Tsai, T.-M. Liu, C.-Y. Lin, and H.-J. Tsai, J. Struct. Biol. 147, 19 (2004).
[CrossRef] [PubMed]

Voelkmann, C.

D. Kim, I. H. Libon, C. Voelkmann, Y. R. Shen, and V. Petrova-Koch, Phys. Rev. B 55, R4907 (1997).
[CrossRef]

Wang, D.

B. J. Skromme, H. Zhao, D. Wang, H. S. Kong, M. T. Leonard, G. E. Bulman, and B. J. Molnar, Appl. Phys. Lett. 71, 829 (1997).
[CrossRef]

Wang, J.-C.

C.-K. Sun, J.-C. Liang, J.-C. Wang, F.-J. Kao, S. Keller, M. P. Mack, U. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 76, 439 (2000).
[CrossRef]

Wetzel, C.

T. Takeuchi, C. Wetzel, S. Yamaguchi, H. Sakai, H. Amano, and I. Akasaki, Appl. Phys. Lett. 73, 1691 (1997).
[CrossRef]

J. H. Edgar, S. Strite, I. Akasaki, H. Amano, and C. Wetzel, Properties, Processing and Applications of Gallium Nitride and Related Semiconductors (Institution of Electrical Engineers, 1999).

Xie, X. S.

Yamaguchi, S.

T. Takeuchi, C. Wetzel, S. Yamaguchi, H. Sakai, H. Amano, and I. Akasaki, Appl. Phys. Lett. 73, 1691 (1997).
[CrossRef]

Yoshikawa, H.

T. Kawashima, H. Yoshikawa, S. Adachi, S. Fuke, and K. Ohtsuka, J. Appl. Phys. 82, 3528 (1997).
[CrossRef]

Zhao, H.

B. J. Skromme, H. Zhao, D. Wang, H. S. Kong, M. T. Leonard, G. E. Bulman, and B. J. Molnar, Appl. Phys. Lett. 71, 829 (1997).
[CrossRef]

Appl. Phys. Lett.

B. J. Skromme, H. Zhao, D. Wang, H. S. Kong, M. T. Leonard, G. E. Bulman, and B. J. Molnar, Appl. Phys. Lett. 71, 829 (1997).
[CrossRef]

T. J. Schmidt, Y. H. Cho, G. H. Gainer, J. J. Song, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 73, 1892 (1998).
[CrossRef]

T. Takeuchi, C. Wetzel, S. Yamaguchi, H. Sakai, H. Amano, and I. Akasaki, Appl. Phys. Lett. 73, 1691 (1997).
[CrossRef]

S. Chichibu, T. Azuhata, T. Sota, and S. Nakamura, Appl. Phys. Lett. 70, 2822 (1997).
[CrossRef]

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, U. K. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 77, 2331 (2000).
[CrossRef]

C.-K. Sun, J.-C. Liang, J.-C. Wang, F.-J. Kao, S. Keller, M. P. Mack, U. Mishra, and S. P. DenBaars, Appl. Phys. Lett. 76, 439 (2000).
[CrossRef]

J. Appl. Phys.

T. Kawashima, H. Yoshikawa, S. Adachi, S. Fuke, and K. Ohtsuka, J. Appl. Phys. 82, 3528 (1997).
[CrossRef]

J. Opt. Soc. Am. B

J. Struct. Biol.

C.-K. Sun, S.-W. Chu, S.-Y. Chen, T.-H. Tsai, T.-M. Liu, C.-Y. Lin, and H.-J. Tsai, J. Struct. Biol. 147, 19 (2004).
[CrossRef] [PubMed]

Phys. Rev. B

D. Kim, I. H. Libon, C. Voelkmann, Y. R. Shen, and V. Petrova-Koch, Phys. Rev. B 55, R4907 (1997).
[CrossRef]

Scanning

C.-K. Sun, S.-W. Chu, S.-P. Tai, S. Keller, A. Abare, U. K. Mishra, and S. P. DenBaars, Scanning 23, 182 (2001).
[CrossRef] [PubMed]

Other

J. H. Edgar, S. Strite, I. Akasaki, H. Amano, and C. Wetzel, Properties, Processing and Applications of Gallium Nitride and Related Semiconductors (Institution of Electrical Engineers, 1999).

S. Nakamura and G. Fasol, The Blue Laser Diode, GaN Based Light Emitters and Lasers (Springer-Verlag, 1997).

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (4)

Fig. 1
Fig. 1

(A) Nonlinear emission spectrum of a 2.5 - μ m -thick GaN thin film excited by a femtosecond Cr:forsterite laser. Inset, enlarged view of the spectrum between 340 and 400 nm , where the 365 nm BEL and the 370 380 nm bandtail luminescence can both be observed. (B) Excitation power dependence of the BEL (rectangles) and THG (triangles) intensities. The well-fitted slope of 4 and the slope of 3 of the lines for BEL and THG, respectively, indicate that they are four-photon and three-photon processes, respectively.

Fig. 2
Fig. 2

Far-field forward emission profiles of (A) SHG and (B) THG from GaN thin film, collected by an oil-immersion condenser and recorded by a CCD camera.

Fig. 3
Fig. 3

Scanning (A) SHG, (B) THG, and (C) four-photon excited BEL images of GaN thin film. Scale bar, 10 μ m .

Fig. 4
Fig. 4

Normalized axial response of four-photon excited BEL (filled triangles), THG (circles), and SHG (rectangles) in 2.5 μ m thick GaN thin film.

Metrics