Large near resonance third order nonlinearity in GaN

Chi Kuang Sun*, Yong Liang Huang, Jian Chin Liang, Jiun Cheng Wang, Kian Giap Gan, Fu Jen Kao, Stacia Keller, Michael P. Mack, Umesh Mishra, Steven P. Denbaars

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

16 Scopus citations


We have studied third order nonlinearities, including two-photon absorption coefficient β and nonlinear refractive index n2, of GaN in below bandgap ultraviolet (UV) wavelength regime by using UV femtosecond pulses. Two-photon absorption was investigated by demonstrating femtosecond UV pulse-width autocorrelation in a GaN thin film while femtosecond Z-scan measurements revealed information for both n2 and β. The distribution of n2 versus wavelength was found to be consistent with a model described by the quadratic Stark effect, which is the dominant factor contributed to the nonlinear refractive index near the bandgap. Large β on the order of 10 cm/GW and large negative n2 with a magnitude on the order of several 10-12 cm2/W were obtained. The β at near mid-gap infrared (IR) wavelength was also found to be on the order of several cm/GW by using two-photon-type autocorrelations in a GaN thin film. Taking advantage of the large two-photon absorption at mid-gap wavelengths, we have demonstrated excellent image quality on two-photon confocal microscopy, including two-photon-scanning-photoluminescence imaging and two-photon optical-beam-induced current microscopy, on a GaN Hall measurement sample and an InGaN green light emitting diode.

Original languageEnglish
Pages (from-to)619-640
Number of pages22
JournalOptical and Quantum Electronics
Issue number4-5
StatePublished - 2000
Event1998 International Photonics Conference (IPC '98) - Taipei, Taiwan, China
Duration: 15 Dec 199818 Dec 1998


  • GaN
  • Nonlinear refractive index
  • Third-order nonlinearity
  • Two-photon absorption
  • Two-photon confocal microscopy


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