Abstract
In this paper, the modulation of the Fano resonance (FR) of dielectric grating has been demonstrated by controlling the crystallization fraction of phase change material film. We analyze the optical characteristics of the grating structure thoroughly by the energy band structure, Q factor, and the electric field distribution of three TE modes. It is verified that the Q factor and the Fano lineshape are related to the thickness of the Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Sb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> (GST) layer. In addition, by changing the crystallization fraction of the GST layer, non-volatile modulation of the Q factor can be achieved. We also demonstrate that the crystallization fraction of the GST layer affects the Fano lineshape significantly. By changing the crystallization fraction of the GST layer, the non-volatile modulation of Fano lineshape from asymmetric parameter <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> = −1 to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> = 1 can be achieved. These features make this grating structure an excellent optically reconfigurable device in various fields including lasing spaser and biosensing with improved performance.
Highlights
Bound states in the continuum (BICs) can achieve perfect confinement when the Q factor is close to infinity, even if their frequencies are within a continuum of leaky modes
We investigate a grating structure composed of silicon and GST layer to realize the modulation of Q factor and the Fano lineshape with different crystallization fractions of the GST layer
We find that the Q factor and the Fano lineshape can be adjusted by changing the thickness of the GST layer
Summary
Bound states in the continuum (BICs) can achieve perfect confinement when the Q factor is close to infinity, even if their frequencies are within a continuum of leaky modes. It has a very large refractive in the infrared range, and the phase change can be thermally [29], optically [30], or electrically [31] induced potentially with an ultrahigh-speed. We investigate a grating structure composed of silicon and GST layer to realize the modulation of Q factor and the Fano lineshape with different crystallization fractions of the GST layer. The Fano lineshape is demonstrated to be strongly dependent on the crystallization fraction of the GST layer This grating structure with the GST layer provides a new reconfigurable choice for various fields, such as lasing spaser and biosensing
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