Poster template by ResearchPosters.co.za Mode-cleaning in Non-Hermitian Fibers and Waveguides M. N. Akhter1, R. Herrero1, M. Botey1 and K. Staliunas1, 2 1Departament de Fisica, Universitat Politecnica de Catalunya (UPC), Rambla Sant Nebridi 22, 08222, Terrassa, • Barcelona, Catalonia, Spain 2Institucio Catalana de Recerca i Estudis Avancats (ICREA), Passeig Llus Companys 23, E-08010, Barcelona, Spain Abstract Motivation Non-Hermitian GRIN MMF GRIN MMF 𝜙index modulation gain/loss modulation core radius Unidirectionality (2+1)D Linear Schrödinger Equation [5] 𝜕𝐴 𝜕𝑧= 𝑖1 2 𝛻2𝐴−𝑖∆ 𝑟𝑐 2 (𝑥2+𝑦2)𝐴+ 𝑖𝒎𝒓𝒆𝒄𝒐𝒔𝒒𝒛+ 𝒊𝒎𝒊𝒎𝒄𝒐𝒔𝒒𝒛+ 𝝓𝑽(𝒙, 𝒚)𝐴 𝜙 index modulation gain/loss modulation index modulation • Non-Hermitian potential: index and gain /loss modulation • Unidirectional, asymmetric, mode coupling • 𝑽(𝒛) ∝𝒄𝒐𝒔𝒒𝒛−𝒊𝒔𝒊𝒏(𝒒𝒛) = 𝒆𝒙𝒑−𝒊𝒒𝒛 • Couples any mode 𝑘𝑧with 𝑘𝑧−𝑞only • Hermitian potential [4]: only index modulation • Bidirectional, symmetric, mode coupling 𝑽𝒛𝒄𝒐𝒔𝒒𝒛= 𝟏 𝟐{𝒆𝒙𝒑𝒊𝒒𝒛+ 𝒆𝒙𝒑−𝒊𝒒𝒛} • Couples any mode 𝑘𝑧with 𝑘𝑧+ 𝑞and 𝑘𝑧−𝑞 Results: Antisymmetrically modulated non-Hermitian potential Conclusions Non-Hermitian potential controls the mode dynamics in parabolic multimode waveguides. Depending on the spatial delay between the real and imaginary part, higher or lower order modes are favored. Mode cascading towards lower order modes leads to effective all-optical spatial mode-cleaning. Different geometries of the potential leads to different mode coupling in 2D case. 1. J. Medina Pardell, et al. Opt. Exp. 29, 23997-24009 (2021). 2. S. Benadouda Ivars, et al. Phys. Rev. A 105, 033510 (2022). 3. K. Krupa, et al. Nature Photon 11, 237–241 (2017). 4. C. Mas Arabí, et al. Phys. Rev. A 97, 023803 ( 2018). 5. M. N. Akhter et al. Phys. Rev. Lett. 131, 043604 (2023). References This Project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 861152. https://mefista.astonphotonics.uk/ [3]. 𝜕𝐴 𝜕𝑧= 𝑖𝑑𝛻2𝐴−𝑖𝑐𝑥2𝐴+ 𝑖𝒎𝒓𝒆𝒄𝒐𝒔𝒒𝒛+ 𝒊𝒎𝒊𝒎𝒄𝒐𝒔𝒒𝒛+ 𝝓 𝒙 𝒙𝟎 𝒆 −𝒙𝟐 𝒙𝟎 𝟐 𝐴 𝐴𝑥, 𝑧= ෍ 𝑛 𝑎𝑛𝐻𝑛𝑥𝑒−𝑖𝑛𝑞𝑧 ∂𝑎𝑚 ∂𝑧= 𝑎𝑚𝑖𝛽𝑚+ 𝑖𝑚𝑞+ 𝑖𝑚+𝐶𝑚+1,𝑚𝑎𝑚+1 + 𝑖𝑚−𝐶𝑚−1,𝑚𝑎𝑚−1 𝑖Δ𝑞1 𝑖𝑚+𝐶21 0 ⋯ 0 𝑖𝑚−𝐶12 𝑖Δ𝑞2 𝑖𝑚+𝐶32 ⋯ 0 0 𝑖𝑚−𝐶23 ⋱ ⋮ ⋮ ⋮ ⋮ ⋮ ⋱ 𝑖𝑚+𝐶𝑛,𝑛−1 0 0 ⋯ 𝑖𝑚−𝐶𝑛−1,𝑛 𝑖Δ𝑞𝑛 One dimensional waveguide Two dimensional fiber 𝐈 𝑽𝒙, 𝒚, 𝒛= 𝑽𝒛𝑽𝒙, 𝒚= 𝑽(𝒛) 𝒙 𝒓𝟎 𝒆 −𝒙𝟐+𝒚𝟐 𝒓𝟎 𝟐 𝐈𝐈 𝑽(𝒙, 𝒚, 𝒛) = 𝑽(𝒛) 𝒙+ 𝒚 𝒓𝟎 𝒆 −𝒙𝟐+𝒚𝟐 𝒓𝟎 𝟐 (1+1)D Linear Schrödinger Equation index modulation gain/loss modulation index modulation gain/loss modulation We propose an all-optical control of the mode dynamics in multimode waveguides, by simultaneous modulation of the refractive index and of the gain/loss coefficient. The induced unidirectional mode-coupling, yields to the enhancement or reduction of the excitation of higher order transverse modes, depending on the modulation parameters [1, 2]. In the latter case, the all-optical mode-cleaning is observed. We analytically predict the effect on a coupled mode theory for 1D waveguides, which is numerically proven solving the wave propagation equation. The proposal is generalized to the more involved case of 2D waveguides for different geometrics. Analytics Eigenmodes as a function of the spatial delay (𝝓) Numerical Maps in Parameter space One dimensional mode-cleaning Different geometries of the potential Δ𝑞𝑚= 𝛽𝑚+𝑚𝑞 𝑂𝐼𝑛= ׭ 𝐴× 𝐻𝑛𝑑𝑥 2 ׭ 𝐴2 𝑑𝑥× ׭ 𝐻𝑛2 𝑑𝑥 𝑚𝑟𝑒= 𝑚𝑖𝑚= 1.5 × 10−4, 𝜙= 𝜋, 𝑞= 0.9 Δ𝑘𝑧 𝐶𝑛𝑚= ׬ 𝐻𝑛𝐻𝑚 𝑥 𝑥0 𝑒 −𝑥2 𝑥02 𝑑𝑥.