CN-121995577-A - Waveguide mode converter based on manual standard field and loss joint regulation and control

CN121995577ACN 121995577 ACN121995577 ACN 121995577ACN-121995577-A

Abstract

The invention provides a waveguide mode converter based on artificial standard field and loss joint regulation and control, which relates to the technical field of integrated photonics and optical communication, the device introduces a geometric phase e ±2iθ (wherein theta is a mode rotation angle induced by grooving) through a grooving engineered orbital angular momentum waveguide structure, constructs an equivalent artificial normative field, and generates a resultant magnetic flux of phi=2θ. The artificial standard field induced non-hermitian chiral symmetry protection is utilized to realize stable third-order EP (namely three-state degeneracy), and controllable conversion between second-order and third-order EP is realized by adjusting waveguide coupling strength. The method can induce and stabilize polymorphic degeneracy by using an artificial standardization field, reduces the realization difficulty of high-order degeneracy points, and meets the requirement of non-hermitian degeneracy state control in practical application.

Inventors

YANG JUNFU
ZHAO MIAOMIAO
ZHAO DONG
Ke Shaolin

Assignees

湖北科技学院

Dates

Publication Date: 20260508
Application Date: 20260327

Claims (3)

1. A waveguide mode converter based on joint regulation and control of an artificial standard field and loss is characterized in that the waveguide mode converter is a photonic device of an asymmetric double waveguide coupling structure and comprises a few-mode waveguide with notch grooves and a single-mode waveguide with controllable optical loss, the few-mode waveguide with notch grooves is used as a first optical waveguide, the notch grooves can break the rotational symmetry of the waveguide, TE 10 and TE 01 transverse electric modes are induced to rotate in azimuth, an equivalent local coordinate system with the rotation angle of theta is formed, the rotation enables the coupling coefficient between TE 10 and TE 01 modes to carry a phase factor e ±2iθ in a direction of relying on, the phase factor is equivalent to the artificial standard field with the synthetic magnetic flux phi=2θ introduced into the system, the single-mode waveguide is used as a second optical waveguide, a loss regulation layer is arranged, the loss coefficient g of the waveguide is controlled through adjusting the thickness or material characteristics of the loss layer, the first optical waveguide and the second optical waveguide are arranged in parallel, controllable evanescent field coupling exists between the first optical waveguide and the second optical waveguide along the light propagation direction, the coupling strength c can be changed through adjusting the distance d between the waveguide, and the angle of the coupling strength c can be adjusted, and the asymmetric EP three-order system can be realized.
2. The waveguide mode converter based on the combined regulation and control of artificial normative field and loss according to claim 1, wherein the high-dimensional degeneracy is realized by a mechanism that when the rotation angle θ=pi/4, the corresponding artificial normative field is quantized to Φ=pi/2, and the system hamiltonian satisfies the non-hermitian chiral symmetry. The coefficient of the symmetry forcing system characteristic polynomial is a real number, the implementation condition of the third-order degeneracy point is reduced from 4 real constraints to 2 real constraints, so that the third-order EP forms a stable one-dimensional manifold in a three-dimensional parameter space (gamma, c, c 1 ), wherein c 1 is 1/2 of the propagation constant difference of a rotation TE mode and is uniquely determined by a grooving geometric structure, and when the coupling strength deviates from the condition, the third-order degeneracy point is split into two second-order degeneracy points, so that controllable switching among degeneracy points of different orders is realized.
3. The waveguide mode converter based on artificial standard field and loss combined regulation and control according to claim 1, wherein the photonic device is prepared based on a silicon-on-insulator platform, the main width of the first optical waveguide is 0.95 μm, the height is 0.85 μm, the groove depth is 0.03 μm, the width is 0.66 μm, the geometrical parameter corresponds to a mode rotation angle θ=pi/4, the width of the second optical waveguide is about 0.46 μm, the height is 0.85 μm, the distance d between the two waveguides can be regulated within the range of 0.11-0.14 μm, the corresponding coupling strength c is changed within the range of 0.034-0.048 μm -1 , when c is about 0.034 μm -1 and the loss coefficient γ is about 0.064 μm -1 , the system is in a third-order degenerate point, when c deviates from the value (e.g. c is about 0.048 μm -1 ), the third-order degenerate point is split into two second-order degenerate points, the controllable refractive index between different-order refractive cores is realized, the refractive index of the silicon-dioxide layer material is 1550.47, and the refractive index of the cladding material is 3.46.

Description

Waveguide mode converter based on manual standard field and loss joint regulation and control Technical Field The invention relates to the technical field of integrated photonics and optical communication, in particular to a waveguide mode converter based on artificial standardization field and loss joint regulation. Background The orbital angular momentum (Orbital Angular Momentum, OAM) beam forms an infinite-dimension orthogonal mode space due to the spiral phase distribution e ilφ, and has great application potential in the fields of mode multiplexing optical communication, optical micro-control and the like. However, achieving stable transmission and flexible regulation of OAM modes on integrated photonic platforms faces the key challenge that when the optical waveguide cross-section has ideal rotational symmetry, the OAM modes of topology charge iota= +1 and iota= -1 are degenerate with each other, sharing the same propagation constant. This degeneracy, which results from the continuous rotational symmetry of the system, is beneficial for mode multiplexing, but limits independent regulation of the relative phase between modes, which is an obstacle to the construction of on-chip non-hermite photonic devices. By introducing geometric grooving engineering into the cross section of the waveguide to break the rotational symmetry, the original degenerate OAM mode can be coupled and energy split, and the guided wave mode is induced to generate equivalent rotation in azimuth direction. This geometric rotation is equivalent to introducing a spatially varying canonical potential in the system, i.e., an artificial canonical field. The standard field changes the effective transmission boundary condition of photons in the waveguide, which is equivalent to applying a designable equivalent magnetic flux in the tight binding model, thereby providing a new physical degree of freedom for regulating and controlling the symmetry of photon behaviors and constructing high-order degeneracy points in a non-hermite system under the condition of not depending on an external magnetic field. In a non-hermitian optical system, an exception point (Exceptional Point, EP) is formed when multiple eigenvalues and their corresponding eigenvectors are degenerate at the same time. The sensor shows rich physical effects, such as nonlinear response to perturbation, mode selectivity enhancement and the like, and has important application value in the aspects of ultra-high sensitivity sensing, mode selectivity regulation and control and the like. However, achieving polymorphic degeneracy typically requires multiple complex parameter matching conditions to be satisfied simultaneously, requiring very high degrees of freedom in the system, resulting in difficulty in stable existence in a practical physical system. The prior art mainly relies on gain loss modulation or specific symmetry to reduce implementation difficulty, but the schemes often need to accurately control a plurality of independent parameters, have high system complexity and poor stability, and lack an effective technical scheme capable of stably realizing high-order degeneracy on an integrated photon platform and supporting controllable switching among different orders. The artificial normative field provides a new physical degree of freedom for regulating photon behaviors by constructing equivalent magnetic flux, and can change the energy spectrum property of the system and induce degeneracy which cannot be realized in the traditional crystal lattice. In photonic systems, artificial normative fields can simulate the vector potential of charged particles through complex coupling coefficients, using spatial or temporal modulation to introduce non-reciprocal phases between optical modes, creating equivalent resultant magnetic fields. The orbital angular momentum mode provides a natural basis for generating a canonical field by controlled interference due to its helical phase wavefront. However, the combination research of the artificial standardization field and the high-order degeneracy point in the prior art is still in a starting stage, and development of a novel photonic device which has a simple structure, controllable parameters and easy integration is urgently needed, and the polymorphism degeneracy can be induced and stabilized by using the artificial standardization field so as to meet the requirement of controlling a non-hermeticity system in practical application. Disclosure of Invention The invention provides a waveguide mode converter based on manual standard field and loss combined regulation and control, which aims to solve the defects in the prior art. In order to achieve the above purpose, the present invention adopts the following technical scheme: The device introduces a geometric phase e ±2iθ (wherein theta is a mode rotation angle induced by grooving) through a grooving engineered orbital angular momentum waveguide structure, constructs an equivalent artificial