We theoretically investigate the coherent control of anisotropic surface plasmon polaritons (SPPs) in an anisotropic medium. The transverse electric and transverse magnetic reflection and transmission coefficients, dispersion relations, wavelengths, and propagation lengths of the SPPs are analyzed under the influence of a coherent field. The perpendicular component of the dielectric tensor incorporates a three-level <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$\Lambda $</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="normal">Λ</mi> </math></EquationSource> </InlineEquation>-type atomic configuration. The dispersion along the x and y axes can be tuned by adjusting the control field, probe-field detuning, and the optical axis orientation <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$\phi $</EquationSource> <EquationSource Format="MATHML"><math> <mi>ϕ</mi> </math></EquationSource> </InlineEquation>. The SPP wavelength along both directions remains in the sub-wavelength regime for almost all control field values and optical orientation angles, except at <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\phi = 40^\circ $</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ϕ</mi> <mo>=</mo> <msup> <mn>40</mn> <mo>∘</mo> </msup> </mrow> </math></EquationSource> </InlineEquation>, where the wavelength along the y direction slightly exceeds the incident wavelength. A maximum propagation length of 270 <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$\mu $</EquationSource> <EquationSource Format="MATHML"><math> <mi>μ</mi> </math></EquationSource> </InlineEquation>m along the x direction is observed for <InlineEquation ID="IEq5"> <EquationSource Format="TEX">$\phi = 30^\circ $</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ϕ</mi> <mo>=</mo> <msup> <mn>30</mn> <mo>∘</mo> </msup> </mrow> </math></EquationSource> </InlineEquation> and a control field <InlineEquation ID="IEq6"> <EquationSource Format="TEX">$\Omega _c = 2\gamma $</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi mathvariant="normal">Ω</mi> <mi>c</mi> </msub> <mo>=</mo> <mn>2</mn> <mi>γ</mi> </mrow> </math></EquationSource> </InlineEquation> (with all other parameters scaled to <InlineEquation ID="IEq7"> <EquationSource Format="TEX">$\gamma $</EquationSource> <EquationSource Format="MATHML"><math> <mi>γ</mi> </math></EquationSource> </InlineEquation>), which is nearly five times longer than the propagation distance along the y direction, indicating lower energy losses along the horizontal direction. These results enable precise spatial manipulation of SPPs and may be leveraged in the development of active plasmonic components such as tunable directional waveguides, reconfigurable optical switches, and anisotropic metasurfaces for polarization-sensitive signal processing.

Coherent Control of Surface Plasmon Polaritons in Anisotropic Medium

期刊论文
发表日期：

2025年8月9日

查看全文

Jabir Khan,
Amjad Sohail,
Muhammad Shafiq,
Rafi Ud Din,
Hazrat Ali,
Asad Ali,
Saif Al-Kuwari,
Saeed Haddadi

摘要

We theoretically investigate the coherent control of anisotropic surface plasmon polaritons (SPPs) in an anisotropic medium. The transverse electric and transverse magnetic reflection and transmission coefficients, dispersion relations, wavelengths, and propagation lengths of the SPPs are analyzed under the influence of a coherent field. The perpendicular component of the dielectric tensor incorporates a three-level $\Lambda $ $Λ$ -type atomic configuration. The dispersion along the x and y axes can be tuned by adjusting the control field, probe-field detuning, and the optical axis orientation $\phi $ $ϕ$ . The SPP wavelength along both directions remains in the sub-wavelength regime for almost all control field values and optical orientation angles, except at $\phi = 40^\circ $ $ϕ = 40^{\circ}$ , where the wavelength along the y direction slightly exceeds the incident wavelength. A maximum propagation length of 270 $\mu $ $μ$ m along the x direction is observed for $\phi = 30^\circ $ $ϕ = 30^{\circ}$ and a control field $\Omega _c = 2\gamma $ $Ω_{c} = 2 γ$ (with all other parameters scaled to $\gamma $ $γ$ ), which is nearly five times longer than the propagation distance along the y direction, indicating lower energy losses along the horizontal direction. These results enable precise spatial manipulation of SPPs and may be leveraged in the development of active plasmonic components such as tunable directional waveguides, reconfigurable optical switches, and anisotropic metasurfaces for polarization-sensitive signal processing.