Ph.D. Defense: Gongwen Zhu

    Monday, August 3, 2015 - 10:00am
    Meinel 547

    "Q-Switched and Mode-Locked Mid-Infrared Fiber Lasers"


    Mid-infrared lasers (2-12 micrometers) have found tremendous applications in medical surgeries, spectroscopy, remote sensing, etc. Nowadays, mid-infrared emissions are usually generated from semiconductor lasers, gas lasers and solid-state lasers based on nonlinear wavelength conversion. However, they usually have disadvantages including poor beam quality, low efficiency and complicated configurations. Mid-infrared fiber lasers have the advantages of excellent beam quality, high efficiency, inherent simplicity, compactness and outstanding heat-dissipating capability and have attracted significant interest in recent years. In this dissertation, Zhu has studied and investigated Q-switched and mode-locked fiber lasers in the mid-infrared wavelength region.

    This dissertation includes six chapters: In Chapter 1, Zhu reviews the background of mid-infrared lasers and addresses motivation for the research of mid-infrared fiber lasers. In Chapter 2, he presents the experimental results of microsecond and nanosecond Er3+-doped and Ho3+-doped fiber lasers in the 3-micrometer wavelength region Q-switched by Fe2+:ZnSe and graphene saturable absorbers. In Chapter 3, Q-switched 3-micrometer laser fiber amplifiers are investigated experimentally and theoretically and their power scaling is discussed. In Chapter 4, a graphene mode-locked Er3+-doped fiber laser at 2.8 micrometers with a pulse width less than 50 ps is presented. In Chapter 5, extending the spectral range of mid-infrared fiber lasers by use of nonlinear wavelength conversion is addressed and discussed. Zhu's research group have proposed 10-watt-level 3-5 micrometer Raman lasers using tellurite fibers as the nonlinear gain medium, pumped by their Er3+-doped fiber lasers at 2.8 micrometers. In the last chapter, the prospect of mid-infrared fiber laser is addressed and further research work is discussed.

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