Scientific Reports (Aug 2017)

Deep-ultraviolet second-harmonic generation by combined degenerate four-wave mixing and surface nonlinearity polarization in photonic crystal fiber

  • Jinhui Yuan,
  • Zhe Kang,
  • Feng Li,
  • Guiyao Zhou,
  • Xianting Zhang,
  • Chao Mei,
  • Xinzhu Sang,
  • Qiang Wu,
  • Binbin Yan,
  • Xian Zhou,
  • Kangping Zhong,
  • Kuiru Wang,
  • Chongxiu Yu,
  • Chao Lu,
  • Hwa Yaw Tam,
  • P. K. A. Wai

DOI
https://doi.org/10.1038/s41598-017-10028-3
Journal volume & issue
Vol. 7, no. 1
pp. 1 – 8

Abstract

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Abstract Deep-ultraviolet (UV) second-harmonics (SHs) have important applications in basic physics and applied sciences. However, it still remains challenging to generate deep-UV SHs especially in optical fibers. Here, for the first time, we experimentally demonstrate the deep-UV SH generations (SHGs) by combined degenerate four-wave mixing (FWM) and surface nonlinearity polarization in an in-house designed and fabricated air-silica photonic crystal fiber (PCF). When femtosecond pump pulses with average input power P av of 650 mW and center wavelength λ p of 810, 820, 830, and 840 nm are coupled into the normal dispersion region close to the zero-dispersion wavelength of the fundamental mode of the PCF, the anti-Stokes waves induced by degenerate FWM process are tunable from 669 to 612 nm. Then, they serve as the secondary pump, and deep-UV SHs are generated within the wavelength range of 334.5 to 306 nm as a result of surface nonlinearity polarization at the core-cladding interface of the PCF. The physical mechanism of the SHGs is confirmed by studying the dependences of the output power P SH of the SHs on the PCF length and time. Finally, we also establish a theoretical model to analyze the SHGs.