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CN-122018218-A - Non-reciprocal light field regulation and control device and method based on nonlinear spatial filtering

CN122018218ACN 122018218 ACN122018218 ACN 122018218ACN-122018218-A

Abstract

The invention discloses a nonlinear spatial filtering-based nonreciprocal light field regulating device and a nonlinear spatial filtering-based nonreciprocal light field regulating method, wherein the device adopts a sandwich type integrated structure, a core comprises a nonlinear medium and a first linear modulation module and a second linear modulation module which are directly written on two sides of the nonlinear medium through femtosecond lasers, and strict collinearly phase matching conditions in a nonlinear frequency conversion process are used as a natural spatial filter. When light is transmitted forward, high-frequency space phase information introduced by the first module is physically filtered out in nonlinear conversion due to non-collinear phase mismatch, and the output end only presents modulation information of the second module, and when the light is transmitted backward, the information is opposite. The invention overcomes the dependence of the traditional nonreciprocal device on magneto-optical materials through anisotropic selective transfer of the spatial frequency spectrum, realizes high-fidelity unidirectional controlled transmission of complex spatial wave fronts, and has important application value in the fields of integrated photonics, optical information encryption and the like.

Inventors

  • SUN JIAHAO
  • ZHOU CHAO
  • Fan Weiwen
  • XU XIAOYI
  • ZHANG YONG

Assignees

  • 南京大学

Dates

Publication Date
20260512
Application Date
20260327

Claims (10)

  1. 1. The non-reciprocal optical field regulation and control device based on nonlinear spatial filtering is characterized by comprising a first linear modulation module, a nonlinear medium and a second linear modulation module which are sequentially arranged along the propagation direction of an optical path, wherein the first linear modulation module and the second linear modulation module are integrated on the surfaces or near-surface layers of two sides of the nonlinear medium in a femtosecond laser direct writing mode, and the nonlinear medium is configured to meet the collinear phase matching condition of fundamental frequency light and frequency doubling light.
  2. 2. The apparatus of claim 1, wherein the first linear modulation module, the second linear modulation module, and the nonlinear medium are near field tight coupled to enhance a nonreciprocal controlled extinction ratio by eliminating diffraction and diffusion of spatial information prior to entering the nonlinear region of action.
  3. 3. The apparatus of claim 1, wherein the linear modulation module is a refractive index modulation structure, a phase grating, an amplitude grating, or a complex amplitude modulation structure.
  4. 4. The apparatus of claim 1, wherein the nonlinear medium is a crystalline material having a second order nonlinear effect.
  5. 5. The device of claim 4, wherein the crystalline material comprises lithium niobate, periodically poled lithium niobate, potassium titanyl phosphate, or beta-barium borate crystals.
  6. 6. The apparatus of claim 1, wherein the first linear modulation module and the second linear modulation module are loaded with different spatial phase and/or amplitude encoded information.
  7. 7. A non-reciprocal optical field regulating method adopting the device of claim 1 is characterized by comprising the steps of forming integrated linear modulation modules on two sides of a nonlinear medium through femtosecond laser direct writing, enabling the nonlinear medium to be in a collinear phase matching state through environment parameter tuning, carrying out first linear spatial modulation on incident light, filtering high-frequency spatial frequency components generated by modulation by utilizing the narrow-band characteristic of nonlinear collinear phase matching bandwidth, carrying out nonlinear interaction in the nonlinear medium meeting the collinear phase matching condition, and carrying out second linear spatial modulation to enable forward and reverse propagation optical fields to carry different spatial modulation information.
  8. 8. The method of claim 7, wherein the co-linear phase matching condition is adjusted by crystal orientation, temperature tuning, or periodic polarization structure such that only co-linear non-linear processes occur efficiently, while non-co-linear non-linear processes carrying spatial frequency modulation produce significant phase mismatch.
  9. 9. The method of claim 7, wherein the environmental parameters include laser wavelength, crystal temperature, polarization direction of incident light, and numerical aperture, the parameters being set such that the nonlinear medium satisfies a collinear phase matching condition and such that the non-collinear spatial frequency components produced by the first linear modulation module are in a phase mismatch state.
  10. 10. An application of the non-reciprocal optical field regulating device based on nonlinear spatial filtering in the fields of optical information encryption, unidirectional holographic and AR display, integrated photonics and precise optical anti-counterfeiting according to claim 1.

Description

Non-reciprocal light field regulation and control device and method based on nonlinear spatial filtering Technical Field The invention relates to nonlinear optics and optical information processing technology, in particular to a nonlinear spatial filtering-based nonreciprocal light field regulating device and method. Background Light field nonreciprocal regulation is an important foundation for realizing optical isolation, unidirectional information transmission and safe optical information processing. The prior art focuses on the use of 3D nonlinear holograms or nonlinear detour phases to synthesize a non-reciprocal wavefront. Such schemes rely on the non-linear polarization ratio @, of) The complex space modification of distribution has great processing difficulty, and the non-reciprocity of the complex space modification is derived from the asymmetric structure of a nonlinear source, so that the compatibility of complex space light fields carrying continuous frequency spectrums is limited. Furthermore, it is generally recognized in the art that phase mismatch (PHASE MISMATCH) in nonlinear processes is a negative factor in suppressing energy conversion efficiency. How to convert the angle sensitivity of phase matching into a positive spatial filtering means and combine the femtosecond laser direct writing technology to realize an integrated nonreciprocal device with high fidelity is a technical problem to be solved in the present. In recent years, non-magnetic non-reciprocal schemes based on time-varying modulation, acousto-optic effects and nonlinear optical effects have received widespread attention. However, the existing non-magnetic non-reciprocal method focuses on the non-reciprocal transmission of light intensity or frequency dimension, and direct and programmable non-reciprocal regulation and control of spatial light fields (such as phase, amplitude and holographic coding information) is still difficult. Meanwhile, part of schemes depend on complex multi-wave coupling or strong pumping conditions, the complexity of the system is high, and the stability is limited. In nonlinear optical processes, the phase matching conditions determine the efficiency of the different nonlinear processes. Particularly with spatial frequency modulation, the collinear and non-collinear nonlinear processes differ significantly in phase matching conditions, potentially introducing selective transfer or suppression of spatial information. However, the prior art has not fully utilized the nonlinear spatial filtering effect to realize the optical field nonreciprocal regulation and control with simple structure and direction correlation. Disclosure of Invention The invention aims to provide a non-reciprocal optical field regulating device and method based on nonlinear spatial filtering, which are highly integrated in structure and overcome the defects of complex structure and low spatial information fidelity of the traditional non-magnetic non-reciprocal device. The nonlinear spatial filtering-based nonreciprocal light field regulating device comprises a first linear modulation module, a nonlinear medium and a second linear modulation module which are sequentially arranged along the light path propagation direction, wherein the first linear modulation module and the second linear modulation module are integrated on the surfaces or near-surface layers of two sides of the nonlinear medium in an integrated manner through a femtosecond laser direct writing mode, and the nonlinear medium is configured to meet the collineation phase matching condition of fundamental frequency light and frequency doubling light. The whole structure is a sandwich structure. Preferably, the first linear modulation module, the second linear modulation module and the nonlinear medium are in near-field tight coupling, and diffraction diffusion of spatial information before entering a nonlinear action area is eliminated, so that the extinction ratio of nonreciprocal regulation is improved. Preferably, the linear modulation module is a refractive index modulation structure, a phase grating, an amplitude grating or a complex amplitude modulation structure. More preferably, the linear modulation module is a refractive index modulation structure, a phase type grating, an amplitude type grating, or a complex amplitude modulation structure formed by femtosecond laser direct writing. Preferably, the nonlinear medium is a crystalline material having a second order nonlinear effect, including but not limited to periodically poled lithium niobate, potassium titanyl phosphate, or beta-barium borate crystals. Preferably, the first linear modulation module and the second linear modulation module are loaded with different spatial phase and/or amplitude encoded information. Preferably, the co-linear phase matching condition is tuned by crystal orientation, temperature tuning, or periodic polarization structure such that only co-linear non-linear processes occur efficie