Acta Photonica Sinica, Volume. 52, Issue 6, 0619001(2023)

Transmission and Control of Solitons with Saturable Nonlinear in Linear Defocusing PT-symmetric Waveguide

Qi WU, Juanfen WANG*, Chenrui DU, Lingzhen YANG, Pingping XUE, and Linlin FAN
Author Affiliations
  • College of Optoelectronics, Taiyuan University of Technology, Taiyuan 030600, China
  • show less

    In this paper, based on the normalized saturable nonlinear fractional Schr?dinger equation with linear potential, the transmission and control of solitons in linear defocusing two-channels PT-symmetric waveguide with fractional diffraction and saturable nonlinearity are studied. The equation can be numerically solved by the modified squared-operator iteration method to obtain soliton modes. The Fourier collocation method is used to judge the linear stability of soliton, and the split-step Fourier method is used to simulate the transmission of soliton in the PT (Parity-Time) -symmetric waveguide. According to the requirements of PT-symmetric, the refractive index distribution of two-channels PT-symmetric waveguide is even symmetric and the gain/loss distribution is odd symmetric. In addition, the refractive index of two channels is smaller than that of substrate, so it has the defocusing property. The results show that the PT-symmetric waveguide can support the stable double gray solitons modes in the defocusing saturable nonlinearity. The real part of double gray solitons is even symmetric and the imaginary part is odd symmetric due to the effect of PT-symmetric waveguide. The Lévy index and gain/loss coefficient of PT-symmetric waveguide have little effect on the shape of double gray solitons modes. But the saturable nonlinear coefficient has a great influence on the soliton modes. With the increase of saturable nonlinear coefficient, the background intensity of double gray solitons increases. The Lévy index, gain/loss coefficient, and saturable nonlinear coefficient can affect the transverse energy flow density of solitons. With the increase of Lévy index, gain/loss coefficient, and saturable nonlinear coefficient, the transverse energy flow density of solitons changes more sharply, but it is close to 0 infinitely at the position of waveguide channel. This means that the energies on the left and right of channels reach a balance, thus the double gray solitons are formed. At the same time, the propagation constant also has an effect on the double gray solitons. With the increase of the absolute value of propagation constant, the background intensity of the solitons increases, the gray value decreases and the power increases. Through linear stability analysis, the stable double gray solitons can be obtained at a low gain/loss level. The double gray solitons can transmit stably forward in the waveguide, keeping the width and intensity of original mode unchanged. The width of solitons increases with the increase of saturable nonlinear coefficient and propagation constant.In the focusing saturable nonlinearity, the two-channels PT-symmetric waveguide can control the transmission of bright soliton beams. When it inputs from the center of waveguide, the beam is transmitted as a respirator. With the increase of saturable nonlinear coefficient, the frequency of respirator decreases, the width of beam widens, and the peak intensity decreases. When it doesn't input from the center of waveguide, the beam occurs oscillation with the initial input position as the boundary. This is because the refractive index in the center is the largest, decreasing gradually away from the center between the two-channels PT-symmetric waveguide. This structure is similar to that of gradient index fiber, which has linear focusing effect on beam. When the input is not in the center, under the focusing effect of waveguide, the beams propagate toward the center, through the center to the other, and then reflect back. Thus, the propagation of beam occurs oscillation between two channels. With the increase of saturable nonlinear coefficient, the oscillation frequency of beam increases and the width widens. In addition, the increase of the absolute value of potential good depth in PT-symmetric waveguide will lead to the increase of oscillation frequency and peak intensity of beam. These results can provide some theoretical reference for the application of two-channels PT-symmetric waveguide in all optical control.

    Tools

    Get Citation

    Copy Citation Text

    Qi WU, Juanfen WANG, Chenrui DU, Lingzhen YANG, Pingping XUE, Linlin FAN. Transmission and Control of Solitons with Saturable Nonlinear in Linear Defocusing PT-symmetric Waveguide[J]. Acta Photonica Sinica, 2023, 52(6): 0619001

    Download Citation

    EndNote(RIS)BibTexPlain Text
    Save article for my favorites
    Paper Information

    Category:

    Received: Jan. 12, 2023

    Accepted: Feb. 20, 2023

    Published Online: Jul. 27, 2023

    The Author Email: WANG Juanfen (wangjuanfen@126.com)

    DOI:10.3788/gzxb20235206.0619001

    Topics