Circularly polarized pump tamm plasmon laser with integrated metasurface

Abstract

This invention discloses a circularly polarized pumped Tamm plasmon laser with an integrated metasurface, belonging to the field of micro / nano photonic devices and integrated optics technology. It includes: a substrate; a distributed Bragg mirror disposed on one side of the substrate; a spacer layer disposed on the side of the distributed Bragg mirror away from the substrate; a gain material at the center of the spacer layer; a metal layer disposed on the side of the spacer layer away from the substrate; and a metasurface structure etched on the metal layer, which consists of an array of metal slits arranged in a helical pattern. The metasurface structure achieves chiral selective focusing of the pump light. The pump light, through each metal slit, couples and excites surface plasmons. The gain material radiates photons under the excitation of the surface plasmons, and the Tamm resonant cavity resonates and enhances the radiated photons, thereby emitting laser light. This invention achieves efficient and chiral selective injection of pump light energy, making the polarization state of the pump light a switch to control laser lasing.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano photonic devices and integrated optical technology, specifically relating to a circularly polarized pumped Tamm plasmonic laser with an integrated metasurface. Background Technology

[0002] With the rapid development of photonic integration technology, the market urgently needs miniaturized, low-power, and flexibly switchable on-chip integrated light sources. Among them, schemes that rely on waveguides or surface optical fields to control the pump light and remotely excite the gain medium have shown outstanding potential and have become a research hotspot. However, it remains a core challenge in the industry to simultaneously control the pump input optical path and the beam exit direction using planar devices.

[0003] Tamm plasmons (TPs), confined to the metal-dielectric Bragg mirror interface, offer advantages such as low loss and highly directional emission, making them an excellent solution for fabricating low-threshold microcavity lasers. Surface plasmons (SPPs), on the other hand, possess excellent on-chip optical manipulation capabilities. SPPs can be unidirectionally excited by the chiral nature of circularly polarized pump light, enabling controllable switching of the on-chip optical path. Currently, a mature mechanism is lacking to effectively synergize the flexible on-chip path selection capability of surface plasmons with the radiation enhancement characteristics of Tamm modes. Summary of the Invention

[0004] To address the lack of a mature mechanism in existing technologies to effectively coordinate the flexible on-chip path selection capability of surface plasmons with the radiation enhancement characteristics of Tamm resonators, this invention provides a circularly polarized selectively pumped Tamm plasmon laser based on metasurface modulation. By combining a metasurface structure with chiral selective focusing capability with an optimized Tamm resonator, chiral selective focusing of the pump light and highly directional emission of the radiated light field are achieved, thereby realizing a circularly polarized pumped Tamm plasmon laser with integrated metasurface.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention proposes a circularly polarized pumped Tamm plasmonic laser with an integrated metasurface, the laser comprising:

[0007] A substrate; a distributed Bragg reflector is provided on one side of the substrate;

[0008] A spacer layer is disposed on the side of the distributed Bragg mirror away from the substrate; the center of the spacer layer is a gain material;

[0009] A metal layer is disposed on the side of the spacer layer away from the substrate; a metasurface structure is etched on the metal layer; the metasurface structure is an array of metal slit pairs arranged in a helical pattern; the angles between the two slits of a set of metal slit pairs and the radial direction are 45 degrees and 135 degrees, respectively; the metasurface structure achieves chiral selective focusing of the pump light based on the angles between the two slits of each set of metal slit pairs and the radial direction; the radial direction is the direction from the geometric center of the metasurface structure to the center of the current metal slit pair; when pump light matching the chiral mode of the metasurface structure irradiates the metasurface structure, the pump light couples and excites surface plasmons through each metal slit pair, and the gain material radiates photons under the excitation of the surface plasmons; the distributed Bragg mirror, the spacer layer, and the metal layer constitute a Tamm resonant cavity, which is used to resonate and enhance the photons radiated by the gain material to emit laser light.

[0010] The present invention has the following beneficial effects:

[0011] (1) This invention creatively combines a metasurface structure with chiral selective focusing function with a Tamm resonator with a high quality factor. The metasurface structure achieves efficient and chiral selective injection of pump light energy through a circularly polarized sensitive directional surface plasmon focusing effect, making the polarization state of the pump light a "switch" to control laser emission.

[0012] (2) The present invention improves the quality factor of the Tamm resonator and the local field enhancement in the spacer layer, providing an excellent resonant environment for the realization of low threshold laser and enabling highly directional Tamm laser.

[0013] (3) The design proposed in this invention is not limited by specific materials. By adjusting the geometric parameters of the helical shape of the metasurface structure and the thickness of the dielectric layer of each structure in the Tamm resonant cavity, it can be applied to different wavelengths, providing a brand-new technical solution for on-chip integrated lasers. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the circularly polarized pumped Tamm plasmonic laser with an integrated metasurface according to the present invention; wherein, Figure 1 Image (a) is a side view of a circularly polarized pumped Tamm plasmonic laser with an integrated metasurface. Figure 1 (b) is a front view of a circularly polarized pumped Tamm plasmonic laser with an integrated metasurface;

[0015] Figure 2 The above diagram shows the metasurface structure and its oriented surface plasmon coupling ratio distribution obtained from the simulation of this invention; wherein, Figure 2(a) in the diagram is a schematic diagram of the metasurface structure. Figure 2 (b) in the figure is the directional surface plasmon coupling ratio distribution diagram corresponding to the simulation of the metasurface structure;

[0016] Figure 3 This is a schematic diagram of the simulation results of the electric field intensity distribution under circularly polarized light illumination; where... Figure 3 (a) is a schematic diagram of the simulation results of the electric field intensity distribution 30 nm below the metasurface structure when irradiated by right-handed circularly polarized light; Figure 3 (b) is a schematic diagram of the simulation results of the electric field intensity distribution at 30 nm below the metasurface structure when irradiated by left-handed circularly polarized light;

[0017] Figure 4 This is an electrical schematic diagram of the Tamm plasmonic laser of the present invention; wherein, Figure 4 (a) is a diagram showing the distribution of the electric field intensity within the structure when the circularly polarized pumped Tamm plasmonic laser with the integrated metasurface of the present invention generates lasing. Figure 4 (b) is a diagram showing the far-field radiation angle distribution when the circularly polarized pumped Tamm plasmonic laser with the integrated metasurface of the present invention generates lasing.

[0018] In the attached figures, the labels are as follows: 1-substrate; 2-distributed Bragg mirror; 3-spacer layer; 4-gain material; 5-metal layer; 6-metal slit array. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0020] like Figure 1 As shown, the circularly polarized pumped Tamm plasmon laser with integrated metasurface of the present invention includes:

[0021] Substrate 1; a distributed Bragg reflector 2 is provided on one side of substrate 1;

[0022] Spacer layer 3 is disposed on the side of distributed Bragg mirror 2 away from substrate 1; the center of spacer layer 3 is gain material 4;

[0023] Metal layer 5 is disposed on the side of spacer layer 3 away from substrate 1; a metasurface structure is etched on metal layer 5; the metasurface structure is an array of metal slit pairs 6 arranged in a spiral pattern; the angles between the two slits of a set of metal slit pairs and the radial direction are 45° and 135°, respectively; the metasurface structure achieves chiral selective focusing of pump light based on the angles between the two slits of each set of metal slit pairs and the radial direction; the radial direction is the direction from the geometric center of the metasurface structure to the center of the current metal slit pair; when pump light matching the chiral mode of the metasurface structure irradiates the metasurface structure, the pump light couples through each metal slit pair to excite surface plasmons, and the gain material 4 radiates photons under the excitation of surface plasmons;

[0024] The distributed Bragg reflector 2, the spacer layer 3, and the metal layer 5 constitute the Tamm resonant cavity, which is used to resonate and enhance the photons radiated by the gain material 4 to emit laser light.

[0025] Understandably, metasurface structures are used to achieve chiral selective focusing of pump light with a specific circular polarization state, thereby exciting the gain material. How the metasurface structure achieves chiral selective focusing of pump light with a specific circular polarization state depends on the specific radial angles of the two adjacent slits forming the metal slit pair.

[0026] In some embodiments, the position of the metal slit array 6 is determined by the wavelength of the surface plasmons excited at the interface between the metal layer 5 and the spacer layer 3.

[0027] ;

[0028] in, Let be the radial coordinates of the metal slit pair in the polar coordinate system. It is the azimuth angle. The initial inner diameter of the helix. The wavelength of the surface plasmons excited at the interface between the metal layer and the spacer layer.

[0029] In some embodiments, the difference between the inner and outer diameters of each turn of the spiral is one surface plasmon wavelength.

[0030] In some embodiments, the wavelength of the surface plasmons is related to the material at the interface and the wavelength of the pump light, specifically:

[0031] ;

[0032] in, The wavelength of the pump light, The dielectric constant of the dielectric material in the spacer layer at the interface is given. Let be the dielectric constant of the metal layer material at the interface.

[0033] Understandably, the difference between the inner and outer diameters of each turn of the helix is ​​equal to the wavelength of a surface plasmon. This is to compensate for the phase difference generated by circularly polarized light excitation in metal slit pairs at different azimuth angles, enabling coherent and constructive focusing of the inwardly propagating surface plasmons excited by each metal slit pair at the geometric center. The geometric center is the geometric center of the metasurface structure.

[0034] In some embodiments, the major axes of two adjacent slits forming a pair of metal slits are orthogonal to each other.

[0035] In some embodiments, the center-to-center distance between two adjacent slits forming a pair of metal slits in the radial direction is one-quarter of the surface plasmon wavelength.

[0036] In some embodiments, two adjacent slits constituting a pair of metal slits are oriented at angles of 45° and 135° to the radial direction, respectively. The pair of metal slits includes a near-geometric center slit and a far-geometric center slit; the metasurface structure achieves chiral selective focusing of the pump light based on the angles between the far-geometric center slit and the near-geometric center slit and the radial direction; the geometric center is the geometric center of the metasurface structure.

[0037] Specifically, the angles between the two adjacent slits forming a pair of metallic slits and the radial direction are different. If the slit near the geometric center forms a 45° angle with the radial direction, then the slit far from the geometric center forms a 135° angle with the radial direction. These two different cases correspond to right-handed and left-handed circularly polarized light with chiral selection, respectively.

[0038] In some embodiments, when pump light matching the chiral mode of the metasurface structure is irradiated onto the metasurface structure, the pump light is incident on each metal slit pair and is excited by surface plasmons through scattering coupling of each metal slit pair. The surface plasmons propagate along the dielectric interface between the metal layer 5 and the spacer layer 3, and through coherent constructive interference, form a subwavelength focused spot at the geometric center of the metasurface structure, thereby exciting the gain material 4.

[0039] When circularly polarized light is incident on each pair of metal slits, the time phase introduced by the polarization rotation will superimpose with the phase of the surface plasmon propagation itself. This phase superposition effect will form coherent constructive and destructive regions of surface plasmons on both sides of each pair of metal slits, respectively, realizing the directional propagation of surface plasmons. After arranging multiple pairs of metal slits along a spiral shape, all inwardly propagating surface plasmons will undergo coherent constructive propagation at the geometric center of the metastructure surface, completing energy focusing, thereby achieving subwavelength focusing of circularly polarized light with a specific spiral direction below metal layer 5.

[0040] Based on the circularly polarized pumped Tamm plasmon laser of the integrated metasurface of the present invention, when the near geometric center slit is at a 45° angle to the radial direction and the far geometric center slit is at a 135° angle to the radial direction, if right-hand circularly polarized light (RCP) is incident perpendicularly on the metasurface as pump light, the surface plasmons excited by each set of metal slits will converge at the medium interface between the metal layer 5 and the spacer layer 3, forming a subwavelength focused spot, which in turn excites the internal gain material. When left-hand circularly polarized light (LCP) is incident perpendicularly on the same metasurface structure, the plasmons in each path coherently cancel each other out, and cannot form an effective focused spot. If the angles of the near geometric center slit and the far geometric center to the radial direction are opposite, then the situation is also reversed.

[0041] In some embodiments, when the pump light is a right-hand circularly polarized 532nm pump light, the major axis dimension of a single metal slit in a pair of metal slits is 120nm, the minor axis dimension is 30nm, and the inner diameter of a single helical slit is 3300nm.

[0042] The parameters in the above embodiments were repeatedly adjusted and verified using three-dimensional finite-difference time-domain simulation software to optimize the size of the slit in the above embodiments. Under the size of the slit in the above embodiments: the screening ratio of target polarized light that can be screened and the directional propagation surface plasmons that can be excited is 67.91; the energy ratio of incident light converted into directional surface plasmons is about 1.2%; the entire metasurface structure can efficiently convert circularly polarized light into surface plasmons that propagate in a fixed direction.

[0043] In some embodiments, when the pump light is a right-handed circularly polarized 532nm pump light, the distributed Bragg reflector 2 is composed of 10 pairs of alternately grown silicon nitride and silicon dioxide dielectric layers, wherein the side closest to the spacer layer 3 is a silicon nitride layer; the thickness of one silicon nitride dielectric layer is 80 nm, and the thickness of one silicon dioxide dielectric layer is 115 nm. The metal layer 5 is made of silver and has a thickness of 200 nm. The center of the spacer layer 3 forms a microcylinder; the diameter of the microcylinder is 2 μm, and the height of the microcylinder and the thickness of the spacer layer 3 are both 110 nm.

[0044] To ensure the efficient directional coupling performance of the metasurface structure, this invention utilizes a three-dimensional finite-time difference method to simulate the aforementioned metasurface structure and optimize its parameters. The simulated metasurface structure is as follows: Figure 2 As shown in (a), the length and width of a single slit in a pair of metal slits are L and W, respectively. The period of two adjacent slit pairs in the direction of surface plasmon propagation is related to the wavelength of the surface plasmons. The period of the non-surface plasmon propagation direction is 260 nm. The metasurface structure was perpendicularly irradiated with left-handed circularly polarized light at a wavelength of 532 nm. Multiple sets of comparative tests were conducted by adjusting the length and width of the slit. The coupling efficiency of the surface plasmons propagating in the left and right directions was statistically determined, and the two values ​​were divided to obtain the desired result. Figure 2 The directional coupling ratio distribution results are shown in (b) of the figure. As can be seen from the distribution figure, when the size of a single slit is set to 120 nm in length and 30 nm in width, the directional selection ratio reaches a peak value of 67.91. The structure of this slit can realize unidirectional and efficient excitation of surface plasmons.

[0045] Figure 3 (a) Figure 3 Figure (b) shows the simulation results of the electric field intensity distribution at 30 nm below the metasurface structure when irradiated by 532 nm pump light of right-handed and left-handed circularly polarized light, respectively. As can be seen from the figure, only under right-handed circularly polarized light (RCP) irradiation, a bright focused spot with a diameter approximately equal to the wavelength of the surface plasmon polariton is generated at the center of the helix, while under left-handed circularly polarized light (LCP) irradiation, a dark spot appears at the same position, clearly verifying the chiral selectivity of the structure for focusing the pump light.

[0046] Figure 4 (a) Figure 4 (b) shows the internal electric field distribution and far-field radiation angle distribution of the XZ section of the circularly polarized pumped Tamm plasmonic laser with integrated metasurface during lasing. It can be seen that the laser is emitted perpendicularly into free space through the distributed Bragg reflector below, with a radiation divergence angle of less than 5°, exhibiting highly directional radiation characteristics.

[0047] Understandably, based on the above parameters, efficient excitation of the Tamm mode at 630 nm can be achieved, and the overlap factor between the mode in spacer layer 3 and gain material 4 is 0.32, enabling efficient coupling and conversion from gain material 4 to radiation mode.

[0048] This invention is not limited to the embodiments described above. Any equivalent substitutions or modifications made based on the technical solutions of this invention should fall within the protection scope of this invention. The above descriptions are merely specific embodiments of this invention, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, this invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An integrated metasurface circularly polarized pump Tamm plasmon laser, characterized in that, include: A substrate; a distributed Bragg reflector is provided on one side of the substrate; A spacer layer is disposed on the side of the distributed Bragg mirror away from the substrate; the center of the spacer layer is a gain material; A metal layer is disposed on the side of the spacer layer away from the substrate; a metasurface structure is etched on the metal layer; the metasurface structure is an array of metal slit pairs arranged in a helical pattern; the angles between the two slits of a pair of metal slits and the radial direction are 45° and 135°, respectively; the metasurface structure achieves chiral selective focusing of the pump light based on the angles between the two slits of each pair of metal slits and the radial direction; the radial direction is the direction from the geometric center of the metasurface structure to the center of the current metal slit pair. When pump light matching the chiral mode of the metasurface structure is irradiated onto the metasurface structure, the pump light couples and excites surface plasmons through each metal slit, and the gain material radiates photons under the excitation of the surface plasmons. The distributed Bragg reflector, the spacer layer, and the metal layer constitute a Tamm resonant cavity, which is used to resonate and enhance the photons radiated by the gain material to emit laser light.

2. The circularly polarized pumped Tamm plasmonic laser with integrated metasurface according to claim 1, characterized in that, The position of the metal slit array is determined by the wavelength of the surface plasmons excited at the interface between the metal layer and the spacer layer. ； in, Let be the radial coordinates of the metal slit pair in the polar coordinate system. It is the azimuth angle. The initial inner diameter of the helix. The wavelength of the surface plasmons excited at the interface between the metal layer and the spacer layer.

3. The circularly polarized pumped Tamm plasmonic laser with integrated metasurface according to claim 2, characterized in that, The difference between the inner and outer diameters of each spiral is equal to one surface plasmon wavelength.

4. The circularly polarized pumped Tamm plasmonic laser with integrated metasurface according to claim 2, characterized in that, The major axes of two adjacent slits that form a pair of metal slits are orthogonal to each other.

5. The circularly polarized pumped Tamm plasmonic laser with integrated metasurface according to claim 4, characterized in that, The center-to-center distance between two adjacent slits forming a pair of metal slits in the radial direction is one-quarter of the wavelength of the surface plasmon resonance.

6. The circularly polarized pumped Tamm plasmonic laser with integrated metasurface according to claim 5, characterized in that, A pair of metal slits includes a near-geometric center slit and a far-geometric center slit; the metasurface structure achieves chiral selective focusing of the pump light based on the angle between the far-geometric center slit and the near-geometric center slit and the radial direction; the geometric center is the geometric center of the metasurface structure.

7. The circularly polarized pumped Tamm plasmonic laser with integrated metasurface according to claim 6, characterized in that, When pump light matching the chiral mode of the metasurface structure is irradiated onto the metasurface structure, the pump light is incident on each metal slit pair and excited by surface plasmons through scattering coupling of each metal slit pair. The surface plasmons propagate along the dielectric interface between the metal layer and the spacer layer, and through coherent constructive interference, form a subwavelength focused spot at the geometric center of the metasurface structure, thereby exciting the gain material.

8. The circularly polarized pumped Tamm plasmonic laser with integrated metasurface according to claim 7, characterized in that, When the pump light is a right-handed circularly polarized 532nm pump light, the major axis dimension of a single slit in a pair of metal slits is 120nm and the minor axis dimension is 30nm.

9. The circularly polarized pumped Tamm plasmonic laser with integrated metasurface according to claim 8, characterized in that, When the pump light is a right-hand circularly polarized 532nm pump light, the distributed Bragg reflector is composed of 10 pairs of alternately grown silicon nitride and silicon dioxide dielectric layers, wherein the side closest to the spacer layer is a silicon nitride layer; the thickness of one silicon nitride dielectric layer is 80 nm, and the thickness of one silicon dioxide dielectric layer is 115 nm; the metal layer is made of silver, and the thickness of the metal layer is 200 nm.

10. The circularly polarized pumped Tamm plasmonic laser with integrated metasurface according to claim 9, characterized in that, When the pump light is a right-handed circularly polarized 532nm pump light, the center of the spacer layer forms a micro-cylinder; the diameter of the micro-cylinder is 2μm, and the height of the micro-cylinder and the thickness of the spacer layer are both 110nm.

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