Peculiarities of the Resonant Response of a Subwavelength Double Grating with Optical PT-Symmetry

Abstract

In this paper, we study the features of the resonant response of a system consisting of two subwavelength one-dimensional periodic structures, considering the dispersion of the refractive index in the presence of optical PT-symmetry for TM polarization. For the considered structure in the green wavelength range, two possible resonance lines were identified at 514.86 nm and 518.5 nm. Ultra-narrow resonances (FWHM of 0.00015 nm) have been obtained for transmitted and reflected waves, and a significant enhancement of the resonant response has been achieved (up to 105 times). The dependence of the system’s optical response on the relative position of its two sub-wavelength gratings and the magnitude of the amplification coefficient of the active part was investigated. This can be used to tune the spectral characteristics of filters, modulate the optical radiation, and create optomechanical sensors such as strain gauges.

Application of PT-symmetry in metasurfaces for measuring the inclination angle

“…Consider the proposed idea on the example of a previously developed metastructure with PT-symmetry properties [17,18]. The metastructure is formed by two optically coupled subwavelength diffraction gratings with a rectangular stroke profile, one of which (passive) is characterized by losses, and the other (active) by gain (see Fig.…”

“…Therefore, for greater simplicity and clarity, for the active lattice 3 (in order not to be distracted by the development and description of the pumping mechanism), some abstract material was used in most of its properties identical to silicon, but it is possible to control the imaginary part of its refractive index (for example, by changing the level of optical pumping).Further in the article, the value of the imaginary part of the refractive index of item 3 n3Im will be expressed in terms of fractions of the imaginary part of the refractive index of the item 4 (active) n4Im: n3Im = -An4Im, where A is the corresponding dimensionless coefficient. The geometric parameters of the matastructure were set the same as in previous studies [17,18]: the height of the gratings is 60 nm, the period of the lattice strokes is 320 nm, the filling coefficient of the gratings is 0.6, the layer height between the structured layers is 630 nm. As it was demonstrated earlier, at these parameter values, α = 0 and A = 1 (n3Im = -n4Im), the system probably is located near a singular point (the point of phase transition from state with PT-symmetry to a state with destroyed PT-symmetry).…”

Modeling of Subwavelength Gratings: Near-Field Behavior

“…They can also enhance the performance of InGaAs infrared polarization imaging [8]. The incorporation of double SWGs has demonstrated promise in creating ultranarrow resonances in the optical response of systems, leading to gain factors of up to 10 5 [9]. In hybrid multiplexing technology, subwavelength gratings (SWGs) play a crucial role in enhancing optical communication capacity by combining multiple wavelengths, modes, and dual polarizations [10].…”