Frequency Conversion and Supercontinuum Generation  by Femtosecond Laser Pulses Propagating in Photonic Crystal Fibers

 

Shuguang Li, Wei Zhang, Qiang Du, Zhiyi Wei, Guiyao Zhou, and Lantian Hou

 Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China

Key Laboratory of Metastable Materials Science and Technology, College of Science, Yanshan University, Qinhuangdao, 066004, P.R.China

shuguangli@ysu.edu.cn

Abstract:  The propagation of femtosecond laser pulses in photonic crystal fibers (PCFs) is attracting considerable research interest. Birefringence in PCFs helps to maintain the polarization of guided modes, allowing a highly efficient generation of coherent supercontinuum radiation, and frequency-tunable anti-Stokes line emission, and results in nonlinear-optical spectral transformation of unamplified femtosecond Ti:sapphire laser pulses. Such supercontinuum radiation has already found important applications, e.g., in the fields of optical metrology, sensor technology, optical tomography, and coherent anti-Stokes Raman scattering microscopy. In the experiments, we show that PCFs provide efficient frequency conversion of unamplified femtosecond Ti:sapphire laser pulses. The central wavelength of the input pulses is about 800 nm. The experimental results provide useful information that helps to convert the frequency of pulses to short  or long wavelength efficiently.

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Fig.1. Diagram of the experimental setup.

  

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Fig. 2 (a) A microscope cross-section image of the photonic crystal fiber. (b) Photo picture of  photonic crystal fiber in the experiments.

   

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Fig. 3 The spectra of radiation at the output of the 5-cm PCF measured for different input powers of 10-fs 823-nm pump pulses polarized along (a) the fast and (b) the slow axis of the fiber core. The average power of pump radiation is 80 mW, 140 mW, 200 mW, 260 mW, and 320 mW, respectively.

 

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Fig. 4 (a) A microscope cross-section image of the photonic crystal fiber. (b), (c) and (d) Photo picture of  photonic crystal fiber in the experiments.

   

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Fig. 5 (a) A microscope cross-section image of the photonic crystal fiber. (b), (c), (d), (e) and (f) photo picture of  photonic crystal fiber in the experiments.

    

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Fig. 6  (a) A microscope cross-section image of the photonic crystal fiber. (b)mode field of output, (c), (d), (e) and (f) photo picture of  photonic crystal fiber in the experiments.

 

 

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Fig.7 (a) A microscope cross-section image of the photonic crystal fiber. (b)mode field of output, (c), (d), (e) and (f) photo picture of  photonic crystal fiber in the experiments.