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US-20260126700-A1 - WAVEGUIDE ARRANGEMENT AND METHOD FOR DEFLECTING AT LEAST ONE LIGHT BEAM OR LIGHT BEAM PAIR

US20260126700A1US 20260126700 A1US20260126700 A1US 20260126700A1US-20260126700-A1

Abstract

A waveguide assembly for exciting/deflecting the partial light beams of at least one light beam pair, comprises a layer stack made of a plurality of layers stacked in a stacking direction, the layer stack comprising: two transparent dielectric cover layers, each including at least one transparent cover layer; a resonator stack having a predetermined number of layers between the two cover layer stacks, wherein at least one layer group including some successive layers in the stacking direction of all the layers of the resonator stack forms a resonator that includes at least one light-deflecting structure; at least one switching assembly, by way of which a phase change of at least one of two partial light beams of a light beam pair which can be guided between the outer boundaries of the cover layer stacks can be locally caused at least intermittently, which can be propagated without self-interference in the two cover layer stacks and with self-interference in the at least one resonator.

Inventors

  • Patrick GOERRN

Assignees

  • BERGISCHE UNIVERSITAET WUPPERTAL

Dates

Publication Date
20260507
Application Date
20220923
Priority Date
20211025

Claims (20)

  1. 1 . A waveguide assembly for exciting or deflecting partial light beams of at least one light beam pair, comprising a layer stack made of a plurality of layers stacked in a stacking direction, the layer stack comprising: a. two transparent dielectric cover layer stacks, wherein each cover layer stack comprises one transparent cover layer, partial light beams being guidable between outer boundaries of the cover layer stack by total reflection; b. a resonator stack having a predetermined number of layers, and which is disposed between the two cover layer stacks, all said layers being stacked in a stacking direction, wherein at least one layer group of the resonator stack including some layers of the resonator stack which follow one another consecutively in the stacking direction form at least one resonator, and this at least one resonator includes at least one light-deflecting structure formed by a light-deflecting structured layer; c. at least one switching assembly along a direction perpendicular to the stacking direction of a plurality of switching assemblies disposed next to one another wherein, by way of a respective switching assembly a phase change of at least one of two partial light beams of a light beam pair which can be guided between the outer boundaries of the cover layer stack can be at least intermittently effectuated locally, the partial light beams of the at least one light beam pair being propagatable without self-interference in the two cover layer stacks and with self-interference in the at least one resonator stack.
  2. 2 . The waveguide assembly according to claim 1 , wherein the at least one resonator in the resonator stack is disposed with respect to the stacking direction so that at least 90% of the surface of the light-deflecting structure of the at least one resonator which is transilluminated by one of the partial light beams is simultaneously also transilluminatable or transilluminated by the other partial light beam when the partial light beams intersect in an intersecting region thereof, for which purpose the resonator is disposed in the center, or at least close to the center, or around the center, of the intersecting region, and the resonator is situated less than 20% of an extension of the intersecting region in the stacking direction away from the center thereof with respect to the stacking direction.
  3. 3 . The waveguide assembly according to claim 1 , wherein the self-interference in the two cover layer stacks is avoided by selecting a respective minimum thickness t D,k,i , of the respective at least one cover layer within the two cover layer stacks as a function of at least one light beam parameter of the partial light beam of the light beam pair to be guided, which propagates in the respective cover layer, a refractive index difference of neighboring cover layers within the cover layer stack, if more than one cover layer is present in a cover layer stack, being smaller than 10 −2 , by a. selecting a thickness t D,k,i of the respective cover layers as a function of a maximum beam cross-section Ø D,k,i,max of a partial light beam and a minimum angle θ D,k,i,min within the cover layer i of the cover layer stack k according to the condition max ⁢ ( ∅ D , k , i , max cos ⁡ ( θ D , k , i , min ) ) ≤ 2 ⁢ ∑ i = 1 P k t D , k , i ⁢ tan ⁢ θ D , k , i , min , for avoiding spatial overlap of the partial light beams in the cover layer stacks, or b. selecting the thickness t D,k,i of the respective cover layers according to the condition c ⁢ Δτ p ≤ 2 ⁢ ∑ i = 1 P k ⁢ t D , k , i ⁢ n D , k , i cos ⁢ θ D , k , i , min for a temporally pulsed light beam pair at a smallest angle of θ D,k,i,min of a partial light beam that occurs within the cover layer i and a pulse duration of Δτ P , or c. selecting the thickness t D,k,i of the respective cover layers according to the condition c ⁢ Δτ ≤ 2 ⁢ ∑ i = 1 P k ⁢ t D , k , i ⁢ n D , k , i cos ⁢ θ D , k , i , min for a minimum angle θ D,k,i,min of a partial light beam that occurs within the cover layer i, having a coherence length of cΔτ and a coherence time of Δτ.
  4. 4 . The waveguide assembly according to claim 3 , wherein the respective thicknesses t R,k,i of the partial layers of the layer group k forming at least one resonator, with the partial layers l≥1 to m≤N, within the resonator including the partial layers 1 to N in the stacking direction are selected a. as a function of a maximum occurring angle of θ R,k,i,max of a partial light beam within the partial layer i having a present minimum beam cross-section of θ R,k,i,min according to the condition min ⁢ ( ∅ R , k , i , min cos ⁢ θ R , k , i , max ) > 2 ⁢ ∑ i = l m tan ⁢ θ R , k , i , max ⁢ t R , k , i , with partial light beams that are continuous over time, or b. as a function of a maximum occurring angle θ R,k,I,max of a partial light beam within the partial layer i according to the condition c ⁢ Δ ⁢ τ p > 2 ⁢ ∑ i = l m t R , k , i ⁢ n R , k , i cos ⁢ θ R , k , i , max , with partial light beams that are temporally pulsed with a pulse duration Δτ P , or c. as a function of a maximum occurring angle of θ R,K,i,max of a partial light beam within the partial layer i according to the condition c ⁢ Δτ > 2 ⁢ ∑ i = l m t R , k , i ⁢ n R , k , i cos ⁢ θ R , k , i , max , with partial light beams (S 1 , S 2 ) having a coherence length of cΔτ and a coherence time Δτ.
  5. 5 . The waveguide assembly according to claim 1 , wherein the at least one layer group forming a resonator within the resonator stack a) includes at least one light-deflecting structure, which is surrounded by two layer arrangements, each including one transparent dielectric layer; or b) comprises a layer arrangement, each including one transparent dielectric layer, in which the transparent dielectric layer, is surrounded by two light-deflecting structures ( 4 ); or c) comprises a layer arrangement in which a plurality of light-deflecting structures and a plurality of dielectric transparent layers are stacked.
  6. 6 . The waveguide assembly according to claim 1 , wherein a progression of the complex-valued refractive index of the layer stack, viewed in the stacking direction, is configured mirror-symmetrically around a center plane in at least one of at least two switch states, whereby a guidable partial light beam of a light beam pair forms a mirror copy of the other guidable partial light beam of the same light beam pair at a center plane, and the resonator stack is disposed in an intersecting region of the two partial light beams, non-linearity being provided, which is asymmetric around the center plane so that an effect of a switching process by way of a switching assembly on the refractive index is asymmetric so that, in a switch state, a mirror-symmetric progression, viewed in the stacking direction, of a complex-valued refractive index of the layer stack is present, and, in another switch state, a deviation from this mirror symmetry can be set.
  7. 7 . The waveguide assembly according to claim 1 , wherein the layer group forming the at least one optical resonator a. comprises one transparent dielectric layer on both sides next to the light-deflecting structure, a refractive index of which is smaller than a refractive index of an adjoining cover layer of the cover layer stack or an adjoining layer of the resonator stack which does not belong to the layer group; or b. comprises a plurality of transparent dielectric layers, a refractive index of which increases from the light-deflecting structure toward the respective cover layer stack; or c. comprises one transparent dielectric layer on both sides next to the light-deflecting structure, the refractive index of which is greater than the refractive index of an adjoining cover layer of the cover layer stack or an adjoining layer of the resonator stack which does not belong to the layer group; or d. comprises a plurality of transparent dielectric layers, the refractive index of which decreases from the light-deflecting structure to the outside, toward the respective cover layer stack, whereby, in cases a and b, a respective reflectivity smaller than 80% and greater than 5% results at the outer boundaries of the layer group with an adjoining layer, and a respective reflectivity of 100% results in cases c and d.
  8. 8 . The waveguide assembly according to claim 1 , wherein a. each of the at least one light-deflecting structure is a diffractive structure, diffraction coefficients, based on the entire resonator stack, for partial light beams incident on the resonator stack on both sides thereof having the same amplitude, the diffraction coefficients being in-phase or out-of-phase; or b. each of the at least one light-deflecting structure is a scattering structure, the scattering coefficients, based on the entire resonator stack, for partial light beams incident on the resonator stack on both sides thereof having the same amplitude, the scattering coefficients being in-phase or out-of-phase.
  9. 9 . The waveguide assembly according to claim 1 , a. comprising a laser beam source by way of which at least one light beam having a beam cross-section that avoids self-interference in the cover layer stacks and a beam cross-section that, at the same time, ensures self-interference in the at least one resonator can be generated; and b. comprising at least one coupling device by way of which the at least one generated light beam can be coupled into at least one of the cover layer stacks so that an internal angle results which ensures that self-interference in the cover layer stacks is avoided and self-interference is established in the at least one resonator.
  10. 10 . The waveguide assembly according to claim 1 , wherein the at least one switching assembly is formed by at least two electrodes, a. one electrode being held by a transparent spacer layer spaced apart from the outer boundary of one of the cover layer stacks, and the other electrode being held by a transparent spacer layer spaced apart from the outer boundary of the other cover layer stack; or b. both electrodes being held, situated next to one another, by a transparent spacer layer spaced apart from the same outer boundary of one of the two cover layer stacks, the respective spacer layer having a lower refractive index than the boundary of the cover layer stack at which the spacer layer is disposed, and an electrical field being at least intermittently generatable between the electrodes, the generated electrical field permeating an optically non-linearly acting transparent material, the transparent material having a Kerr and/or Pockels effect, at least one of the transparent dielectric layers of the cover layer stack being formed of an optically non-linearly acting material across the entire layer extension thereof.
  11. 11 . The waveguide assembly according to claim 10 , wherein in alternative a), two layers which are located on both sides of the resonator stack, are disposed between the two electrodes of the switching assembly ( 5 , 6 ), the two layers being two cover layers of the two cover layer stacks or two layers within the at least one resonator within the resonator stack, it being possible, under the action of a same electrical field, to generate in the two layers an opposite, or at least a different change of the refractive indices or of the geometrical thickness of the two layers by selecting the two layers so as to be made of same crystalline material having different crystal directions relative to the stacking direction.
  12. 12 . The waveguide assembly according to claim 1 , wherein the at least one switching assembly is formed by at least one phase-changing and fully reflective assembly which is directly or indirectly provided at one of the outer boundaries of a cover layer stack as a metasurface, a dielectric plasmonic resonator, a liquid crystal array, an array of phase change materials, a transparent electrode on a spacer layer, a photonic crystal or a combination thereof.
  13. 13 . The waveguide assembly according to claim 1 , wherein the waveguide assembly is configured so that an interaction of the partial light beams with the resonator stack in an intersecting region, which is perceptible in the far field of the waveguide assembly, can be suppressed by setting a certain first phase difference between the two partial light beams of the light beam pair which intersect at the resonator stack by the generation of a bound state by destructive interference of the partial light beams deflected by diffraction or scattering.
  14. 14 . The waveguide assembly according to claim 1 , wherein the waveguide assembly is configured so that by setting a certain second phase difference, which deviates 180 degrees from a the first phase difference suppressing an interaction, perceptible in the far field of the waveguide assembly, of the partial light beams with the resonator stack in an the intersection region, between two partial light beams of the light beam pair which intersect at the resonator stack, it is possible to generate an interaction, perceptible in the far field of the waveguide assembly, of the partial light beam portions with the resonator stack in the intersection region, in particular by constructive interference of the portions of the partial light beams which are deflected by diffraction or scattering.
  15. 15 . The waveguide assembly according to claim 1 , wherein the plurality of first switching assemblies are disposed next to one another in a first direction perpendicular to the stacking direction and a plurality of second switching assemblies are assigned to each first switching assembly, the plurality of second switching assemblies being disposed next to one another in a second direction perpendicular to the stacking direction which is perpendicular to the first direction, it being possible to deflect light from the, on average, first direction by way of each first switching assembly by the generation of a predetermined phase difference between two propagating partial light beams which intersect at the resonator stack and, on average, propagate in the first direction, with the light, after the deflection, on average, propagating in the second direction and, with each second switching assembly, by the generation of a predetermined phase difference of the partial light beams of deflected light which intersect at the resonator stack and, on average, propagate in the second direction, it being possible to deflect light out of the, on average, second direction, out of the waveguide assembly.
  16. 16 . A method for deflecting partial light beams of a light beam pair in a waveguide assembly according to claim 1 , comprising the following steps: a. generating at least one light beam pair, partial light beams of which propagate and are guided without self-interference in the two cover layer stacks by total reflection at the outer boundaries of the cover layer stack in the waveguide assembly in a middle propagation direction, and with self-interference in the at least one resonator, the partial light beams of the light beam pair intersecting in intersecting regions which are spaced apart from one another in the middle propagation direction, and in which the resonator stack is disposed; b. locally changing the phase difference between the propagating partial light beams by the at least one switching assembly, c. by changing the phase difference, the intensity of interaction between the partial light beams and the resonator stack being changed between a first state in which the resonator stack causes a change in propagation direction of the partial light beams intersecting the resonator stack, and a second state in which the resonator stack does not effectuate a change in the propagation direction of the partial light beams intersecting the resonator stack or at least only effectuating a change for a negligible part of power guided by the partial light beams compared to the first state.
  17. 17 . The method according to claim 16 , wherein the partial light beams a. are coupled out of the waveguide assembly by deflection in the first state; or b. change the propagation direction thereof in the waveguide assembly and are switched between different propagation regions of a same waveguide assembly, by deflection, in the first state; or c. are switched by deflection between different waveguide assemblies stacked directly on top of one another in the first state; or d. are generated by the diffraction or scattering of a light beam in the waveguide assembly which is incident on the assembly from the outside followed by beam splitting at the at least one resonator including at least one light-deflecting structure within the resonator stack.
  18. 18 . The method according to claim 16 , wherein a light beam to be coupled in, for coupling light into the waveguide assembly, is incident on the waveguide assembly from the outside environment and strikes the resonator stack at a position at which a light beam pair propagating in the waveguide having a required set phase difference can be outcoupled.
  19. 19 . The method according to claim 18 , wherein, after a light beam has been coupled in from the outside environment, a phase change of 180 degrees is effectuated between the propagating incoupled partial light beams, by way of a switching assembly at an intersecting region which, in a middle propagation direction of the incoupled partial light beams, follows a region of the in-coupling.
  20. 20 . The method according to claim 16 , wherein a light-absorbing interaction comprising fluorescence or phosphorescence or simulated emission-exciting interaction with a light-deflecting structure is generated, which leads to spontaneous or stimulated emission of light having a longer wavelength compared to the absorbed light of the light beam pair exciting the absorption as a result of the phase setting of the partial light beams of this light beam pair which propagate in the waveguide assembly.

Description

The invention relates to a waveguide assembly and to a method for deflecting at least one light beam and/or light beam pair. Light shall be understood as an abbreviated term for electromagnetic radiation of any frequency. The described assembly and the described method can thus be utilized in the same manner beyond the visible spectral region that is preferred in the application, for example, for ultraviolet or infrared radiation. The visible spectral region shall preferably be understood to mean a range from 400 nm to 800 nm, the ultraviolet spectral region shall preferably be understood to mean a range smaller than 400 nm, and the infrared spectral region shall preferably be understood to mean a range greater than 800 nm. Waveguides are generally known in the art. These provide the option of transporting light without loss under assumed ideal conditions, in particular to the extent that absorption is negligible. Efforts are being made in the conventional art to also employ waveguides so as to change the propagation direction of light, in particular so as to effectuate a switch in terms of the propagation direction. The problem that exists is that means for switchably effectuating a change in direction usually not only act on the light when the change in the propagation direction is activated, but that an interaction with the light is also present without the change in the propagation direction being activated, which also limits the achievable propagation length in the waveguide in the deactivated state. Waveguides are known from the publications WO 2016/000728 A1 and WO 2018/086727 A1 by the same applicant, which are based on generating a laterally guided mode by self-interference of the light guided in the waveguide by means of total reflection, the transverse intensity profile of which, perpendicularly to the lateral propagation direction, has a node, and thus an intensity minimum, and on disposing a light-deflecting structured layer at the site of the node within the waveguide. When the light of such a mode propagates undisturbed, the interaction between the mode and the structure is decreased compared to the disturbed propagation, since this structure is at the intensity minimum or node of the mode. As a result of a relative displacement between the structure and the node of the mode, which represents disturbed propagation, in contrast, a stronger interaction between the mode and the structure compared to undisturbed propagation can take place, which can effectuate a deflection, in particular considerably increased deflection of the light out of the lateral propagation direction thereof, for example by way of a diffraction effect at the structure. The option thus exists to change the light, with disturbed propagation, in terms of the propagation direction thereof by the described relative displacement in the direction, or to allow the light to propagate with less loss with undisturbed propagation than with disturbed propagation. The problem with this approach is that the intensity minimum at the site of a node in the mode is spatially highly localized, and structures at the site of a node can thus only have a very small thickness so as to achieve an interaction that has considerably reduced losses in the undisturbed case. As a result of this problem, the contrasts C achievable between the switch states (disturbed/undisturbed propagation) with waveguide assemblies of this type that can be technologically implemented are relatively small, typically C<100. It is therefore an object of the invention to provide a waveguide assembly and a method for the operation thereof, and preferably also devices comprising such a waveguide assembly, by way of which greater contrasts, preferably C>100, more preferably C>1000, between switch states are achievable. In particular, a very low-loss deactivated state (=undisturbed propagation), and in particular a lower-loss deactivated state compared to the described state of the art, is to be achieved, which preferably thus corresponds to a large propagation length and makes use of the phenomenon on laterally large length scales, which is to say, large areas, accessible, in particular compared to the described state of the art. At different switch states, preferably the option is to be created to change the direction of light guided in a waveguide in a first switch state (disturbed propagation) at defined lateral positions, for example to outcouple the light from the waveguide in the direction toward the environment, or to incouple light from the environment into the waveguide at defined lateral positions, or to deflect guided light within the waveguide, and to allow the light to propagate in the waveguide in a second switch state (undisturbed propagation), in particular in a lower-loss manner than in the first switch state. According to the invention, this is achieved by way of a waveguide assembly for exciting or deflecting the partial light beams of at least one light bea