Browsing by Author "Wang, Zixin"

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    Observation of two PT transitions in an electric circuit with balanced gain and loss
    (Springer, 2020-08) Wang, Tishuo; Fang, Jianxiong; Xie, Zhongyi; Dong, Nenghao; Joglekar, Yogesh N.; Wang, Zixin; Li, Jiaming; Luo, Le; Physics, School of Science
    We investigate 𝓟𝓣-symmetry breaking transitions in a dimer comprising two LC oscillators, one with loss and the second with gain. The electric energy of this four-mode model oscillates between the two LC circuits, and between capacitive and inductive energy within each LC circuit. Its dynamics are described by a non-Hermitian, 𝓟𝓣-symmetric Hamiltonian with three different phases separated by two exceptional points. We systematically measure the eigenfrequencies of energy dynamics across the three regions as a function of gain-loss strength. In addition to observe the well-studied 𝓟𝓣 transition for oscillations across the two LC circuits, at higher gain-loss strength, transition within each LC circuit is also observed. With their extraordinary tuning ability, 𝓟𝓣-symmetric electronics are ideally suited for classical simulations of non-Hermitian systems.
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    Sub-megahertz frequency stabilization of a diode 2 laser by digital laser current modulation
    (2015-05) Li, Jiaming; Liu, Ji; DeMelo, Leonardo; Luo, Le; Lai, Tianshu; Wang, Zixin; Department of Physics, School of Science
    Digital laser current modulation (DLCM) is a convenient laser stabilization scheme whose major advantages are simplicity and inexpensiveness of implementation. However, there is a tradeoff between the SNR of the error signal and the laser linewidth due to the direct laser frequency modulation. In this paper, we demonstrated that DLCM can reduce the FWHM linewidth of a tunable diode laser down to 500 kHz using the modulation transfer spectrum of 𝐷2 line of a Li6 atomic vapor. For this purpose, a theoretical model is provided to analyze the DLCM-based modulation transfer spectrum. From the analysis, we experimentally explored the modulation effect on the DLCM spectrum to minimize the laser linewidth. Our result shows the optimized DLCM can stabilize a diode laser into the sub-megahertz regime without requiring acousto-optic and electro-optic modulators.