Polarization controller and optical device

Abstract

The application provides a polarization controller and an optical device, and relates to the technical field of optics.The polarization controller comprises a metal substrate layer, a nanowire and an oxide medium layer; the oxide medium layer is arranged above the metal substrate layer; the nanowire extends along a straight line, the nanowire is arranged inside the oxide medium layer, and the nanowire is parallel to the metal substrate layer; one end of the nanowire is an incident end of unpolarized light, and a gap between the other end of the nanowire and the metal substrate layer is an exit end of polarized light.The polarization controller and the optical device provided by the application can accurately constrain the light field on the nanometer scale, break through the light field limit of the diffraction limit, realize the regulation and control of the polarization state of the light wave on the nanometer scale, and due to the requirement of the plasmonic of the metal substrate layer on the polarization mode, the polarization controller can realize TM polarization, can meet the specific requirements of the light polarization state in different application fields, and has wide application prospects.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and more particularly to a polarization controller and optical device. Background Technology

[0002] A polarization controller is an optical device used to control the polarization state of light waves, and it is widely used in optical communication, optical sensing, laser technology, and other fields. The core function of a polarization controller is to precisely adjust the polarization state of input light to meet specific application requirements.

[0003] Surface plasmon polarization controllers can achieve more precise polarization control in smaller sizes, making them suitable for complex optical systems and high-end applications, especially showing significant advantages in the fields of micro-nano optics and integrated optics.

[0004] However, traditional surface plasmon-based polarization controllers are limited by diffraction limits, making it difficult to achieve precise constraint of the light field at the nanoscale, thus hindering the control of the polarization state of light waves at the nanoscale. Therefore, how to achieve precise constraint of the light field at the nanoscale, thereby enabling the control of the polarization state of light waves at the nanoscale, is a pressing technical problem to be solved in this field. Summary of the Invention

[0005] This invention provides a polarization controller and optical device to solve the problem that traditional polarization controllers in the prior art are unable to achieve precise constraint of the light field at the nanoscale, thus making it difficult to control the polarization state of light waves at the nanoscale. This invention enables precise constraint of the light field at the nanoscale, thereby achieving control of the polarization state of light waves at the nanoscale.

[0006] This invention provides a polarization controller, comprising: a metal substrate layer, nanowires, and an oxide dielectric layer;

[0007] The oxide dielectric layer is disposed above the metal substrate layer; the nanowires extend in a straight line, are disposed inside the oxide dielectric layer, and are parallel to the metal substrate layer;

[0008] One end of the nanowire is the incident end for unpolarized light, and the gap between the other end of the nanowire and the metal substrate is the emitting end for polarized light.

[0009] According to a polarization controller provided by the present invention, the material of the metal substrate is selected from one or more of gold, silver, aluminum, copper and indium.

[0010] According to a polarization controller provided by the present invention, the material of the oxide dielectric layer is silicon dioxide.

[0011] According to a polarization controller provided by the present invention, the nanowire is made of silicon.

[0012] According to a polarization controller provided by the present invention, the distance between the nanowire and the target interface is no greater than 25 nanometers, and the target interface is the interface between the metal substrate layer and the oxide dielectric layer.

[0013] According to a polarization controller provided by the present invention, the nanowire has a circular cross-section and a diameter of 100 to 300 nanometers.

[0014] According to a polarization controller provided by the present invention, the distance between the nanowire and the target interface is 2 to 5 nanometers.

[0015] According to the present invention, a polarization controller operates in transverse magnetic mode TM mode.

[0016] According to a polarization controller provided by the present invention, the wavelength range of the unpolarized light is 800 to 1600 nanometers.

[0017] The present invention also provides an optical device including any of the polarization controllers described above.

[0018] The present invention provides a polarization controller, optical device, and optical system. The polarization controller includes a metal substrate, nanowires, and an oxide dielectric layer. The oxide dielectric layer is disposed above the metal substrate. The nanowires extend in a straight line and are disposed inside the oxide dielectric layer, parallel to the metal substrate. One end of the nanowires is the incident end for unpolarized light, and the gap between the other end of the nanowires and the metal substrate is the exit end for polarized light. The polarization controller has a simple structure and is easy to fabricate. By forming a low-refractive-index gap between the nanowires and the metal dielectric layer, it can achieve focusing and polarization functions at the nanoscale. Due to the discontinuity of the electric field at the interface between the low-refractive-index gap and the high-refractive-index nanowires, the light field in the low-refractive-index gap between the nanowires and the metal substrate is enhanced and coupled with the plasma waves on the surface of the metal substrate. This enables precise constraint of the light field at the nanoscale, breaking through the diffraction limit of the light field and realizing the control of the polarization state of light waves at the nanoscale. At the same time, due to the polarization mode requirements of the plasmon polaritons in the metal substrate, TM polarization can be achieved, which has broad application prospects. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is one of the structural schematic diagrams of the polarization controller provided by the present invention.

[0021] Figure 2 This is the second schematic diagram of the polarization controller provided by the present invention.

[0022] Figure 3 This is the electric field distribution diagram of the polarization controller provided by the present invention in TM mode.

[0023] Figure 4 This is the electric field distribution diagram of the polarization controller provided by the present invention in TE mode.

[0024] Figure 5 This is a graph showing the correlation between the metal substrates of different materials in the polarization controller provided by this invention and the extinction ratio and transmission loss.

[0025] Figure 6 This is a graph showing the relationship between the diameter of the nanowire and the effective mode field area in the polarization controller provided by this invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] In the description of the invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0028] In the description of this application, the terms "first," "second," etc., are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, without limiting the number of objects; for example, a first object can be one or more. Furthermore, in the description of this application, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects have an "or" relationship.

[0029] It should be noted that the diffraction limit is a fundamental limitation of optical systems, which usually represents the minimum spatial resolution that optical devices such as optical microscopes, imaging systems, or optical waveguides can achieve.

[0030] Traditional optical devices are limited by the diffraction limit, restricting their lateral dimensions to the micrometer scale. This makes it difficult to effectively detect or manipulate optical features smaller than this scale, hindering the integration of traditional optical devices with nanoscale electronic devices and severely impeding the development of integrated photonics. Therefore, overcoming the diffraction limit of traditional optical devices and achieving subwavelength scale beam control is one of the core technological challenges in the field of optical technology.

[0031] Surface plasmons are wave phenomena formed by the interaction of light with free electrons on a metal surface. Surface plasmons can confine light fields to scales much smaller than the wavelength of light. By designing nanostructures, such as metal nanopores and metal nanowires, surface plasmons can excite local strong light fields at subwavelength scales, thereby breaking the diffraction limit of traditional optical devices.

[0032] Optical systems such as coherent optical communication and optical sensing systems rely heavily on the polarization state of light. Therefore, polarization controllers, which are used to control the polarization state of light waves, are widely used in fields such as optical communication, optical sensing, and laser technology.

[0033] Compared to traditional polarizers, surface plasmon polarization controllers can achieve more precise polarization control in a smaller size, making them suitable for complex optical systems and high-end applications, especially demonstrating significant advantages in micro-nano optics and integrated optics. Traditional polarizers, on the other hand, are better suited for simpler, lower-cost polarization control and are typically used in general optical experiments and communication systems.

[0034] Traditional surface plasmon polarization controllers in related technologies include ultra-compact, low-loss TE polarization controllers employing hybrid plasmon ridge waveguide structures. However, traditional surface plasmon polarization controllers focus more on improving polarization performance than on nanometer-scale polarization control and constraint of the optical field. Experiments reduced losses by shortening the device length. Numerical simulation results show that at a wavelength of 1550 nm, the loss is 4.2. The long polarization controller has an extinction ratio of 29.5dB and an insertion loss of 0.18dB, and the extinction ratio exceeds 23dB within a 100nm bandwidth.

[0035] Traditional surface plasmon-based polarization controllers in related technologies can also include nanoscale TM polarization controllers based on TE polarization plasmon absorption, integrated onto silicon waveguides via periodic metal nanoparticle chains. Experimental results show that at 1.59... At a wavelength of 23 dB / , the extinction ratio of the polarization controller is 23 dB / The insertion loss is 2.4 dB / .

[0036] Traditional surface plasmon polarization controllers in related technologies can also include low-loss hybrid plasmon TM polarization controllers based on polarization mode conversion, employing silicon hybrid plasmon slot waveguides (HPSWs). This polarization controller uses HPSWs to convert the TE fundamental mode to higher-order TM modes, suppressing the TE mode while retaining the TM fundamental mode. At 1550 nm, this device exhibits an insertion loss as low as 0.4 dB and an extinction ratio of 28.3 dB.

[0037] Traditional surface plasmon polarization controllers in related technologies mainly focus on improving the extinction ratio and reducing insertion loss. However, these traditional surface plasmon polarization controllers are difficult to achieve precise constraint of the light field at the nanoscale, making it difficult to control the polarization state of nanoscale light waves. This makes it difficult to integrate polarization controllers with nanoscale electronic devices, thus restricting the miniaturization of optical systems and the development of high-density photonic integration technology.

[0038] Figure 1 This is one of the structural schematic diagrams of the polarization controller provided by the present invention. Figure 2 This is the second schematic diagram of the polarization controller provided by the present invention. The following is in conjunction with… Figure 1 and Figure 2 The polarization controller provided by this invention will be described. For example... Figure 1 and Figure 2 As shown, the polarization controller 101 includes: a metal substrate layer 102, nanowires 103, and an oxide dielectric layer 104.

[0039] An oxide dielectric layer 104 is disposed above a metal substrate layer 102; a nanowire 103 extends in a straight line and is disposed inside the oxide dielectric layer 104, and the nanowire 103 is parallel to the metal substrate layer 102.

[0040] One end of the nanowire 103 is the incident end for unpolarized light, and the gap between the other end of the nanowire 103 and the metal substrate layer 102 is the emitting end for polarized light.

[0041] It should be noted that the polarization controller 101 supports a novel hybrid plasma TM mode while also satisfying the TE mode cutoff condition.

[0042] Based on Maxwell's equations, the normal component of the electric displacement vector is continuous at the boundary. Therefore, as the diameter of the nanowire 103 decreases, the light field will leak from the high-refractive-index nanowire 103 to the low-refractive-index oxide dielectric layer 104, and the normal component of the electric field intensity will have a significant jump.

[0043] A low-refractive-index gap composed of an oxide dielectric layer 104 is formed between the metal substrate layer 102 and the nanowire 103. The light field entering the low-refractive-index gap will couple with the plasmons on the surface of the metal substrate layer 102, resulting in a novel hybrid plasma TM mode in the low-refractive-index gap. This mode no longer exhibits the characteristics of the TM waveguide mode and the SPP mode, but achieves capacitive energy storage through a low dielectric constant thin film, confining the light energy in the nanoscale dielectric film. This enables the hybrid TM mode to achieve low-loss long-range transmission in the low dielectric constant region. The mode field of this hybrid mode can be strictly confined to a range much smaller than the wavelength, achieving light field confinement that breaks through the diffraction limit.

[0044] In this embodiment of the invention, the interface between the metal substrate layer 102 and the oxide dielectric layer 104 can be defined as the target interface. By adjusting the diameter of the nanowire 103 and the distance between the nanowire 103 and the target interface (i.e., the width of the aforementioned low-refractive-index gap), the device can cut off the TE polarization mode. Therefore, the polarization controller 101 provided by this invention has nanoscale optical field confinement capability and polarization selection effect, as well as advantages such as high extinction ratio, low loss, and small device size.

[0045] It should be noted that the cross-section of the nanowire 103 in this embodiment of the invention is circular.

[0046] Specifically, after unpolarized light is incident from one end of the nanowire 103, the polarization controller 101 generates a novel hybrid plasma TM mode. Its light energy is distributed in the oxide film 104 between the nanowire 103 and the metal substrate 102. When the thickness of the oxide film 104 is reduced to the nanoscale, the TM hybrid mode is strongly confined within the oxide film 104, exhibiting a light field focusing capability that breaks the diffraction limit. When the diameter of the nanowire 103 is reduced, the TE mode in the nanowire 103 can be cut off, and the TE mode light energy rapidly leaks outside the polarization controller 101. However, the novel TM hybrid plasma mode remains unaffected, and its light energy is still strongly confined within the oxide film, achieving a nanoscale focused TM polarized light field.

[0047] It should be noted that in TM mode (Transverse Magnetic Mode), the magnetic field vector is completely perpendicular to the direction of electromagnetic wave propagation, and the longitudinal magnetic field component is zero. In TE mode (Transverse Electric Mode), the electric field vector is completely perpendicular to the direction of electromagnetic wave propagation, and the longitudinal electric field component is zero.

[0048] As an alternative embodiment, the material of the metal substrate is selected from one or more of gold, silver, aluminum, copper, and indium.

[0049] It should be noted that, with the diameter of the nanowire 103 and the distance between the nanowire 103 and the metal substrate 102 remaining constant, the aluminum substrate has the highest extinction ratio, followed by the silver and copper substrates, while the gold and indium substrates have the lowest extinction ratios.

[0050] With the structural parameters of the metal substrates remaining constant, the gold substrate exhibits the lowest propagation loss, followed by the silver and aluminum substrates, while the copper and indium substrates show the highest propagation loss. Comparing subwavelength confinement strength, the aluminum substrate performs best, followed by the silver and copper substrates, while the gold and indium substrates perform the worst.

[0051] In summary, silver is the preferred material for metal substrates.

[0052] As an alternative embodiment, the oxide dielectric layer 104 is made of silicon dioxide.

[0053] It should be noted that when the material of the oxide dielectric layer 104 is silicon dioxide, the refractive index of the oxide dielectric layer 104 is 1.444.

[0054] As an alternative embodiment, the nanowire 103 is made of silicon.

[0055] As an alternative embodiment, the nanowire 103 has a circular cross-section and a diameter of 100 to 300 nanometers.

[0056] As an alternative embodiment, the diameter of the nanowire 103 is 180 to 220 nanometers.

[0057] It should be noted that when the material of nanowire 103 is silicon, the refractive index of nanowire 103 is 3.476.

[0058] As an optional embodiment, the distance between the nanowire 103 and the target interface is no more than 25 nanometers, and the target interface is the interface between the metal substrate layer 102 and the oxide dielectric layer 104.

[0059] As an alternative embodiment, the distance between the nanowire 103 and the target interface is 2 to 5 nanometers.

[0060] As an optional embodiment, the polarization controller 101 operates in transverse magnetic mode TM mode.

[0061] As an alternative embodiment, the wavelength range of the unpolarized light is 800 to 1600 nanometers.

[0062] It should be noted that the wavelength range of unpolarized light in the embodiments of the present invention can be determined based on the 1550nm communication band. For example, the wavelength range of unpolarized light can be 1500 to 1600nm.

[0063] As the wavelength of unpolarized light increases, the extinction ratio of the polarization controller 101 increases, as does the transmission loss of the polarization controller 101. The effective mode area of ​​the polarization controller 101 first decreases and then increases. Overall, the changes caused by the increasing wavelength of unpolarized light are consistent with the changes in the diameter of the nanowire 103 while keeping the distance between the nanowire 103 and the target interface constant and the wavelength of unpolarized light constant.

[0064] When the wavelength of the incident unpolarized light is 1550 nm, the polarization controller 101 achieves a polarization extinction ratio greater than 7.6675 dB / μm, a transmission loss less than 1.2553 dB / μm, and a mode field area of ​​0.0682393 μm. 2 (≈) (less than the free space diffraction limit) .

[0065] The polarization controller 101 provided by this invention has a specific nanowire 103 diameter, a specific low refractive index slit width, and a specific operating mode. At a wavelength of 1550nm, it exhibits nanoscale light confinement capability, low loss, and high extinction ratio performance, and will play a role in fields such as coherent optical communication, fiber optic gyroscopes, micro-nano optics, nonlinear optics, and polarization imaging.

[0066] Distance between nanowire 103 and the target interface h With a diameter of 200 nm for the nanowire 103 and a diameter of 2 nm for the nanowire 103, the mode field distribution of the polarization controller 101 provided by the present invention is calculated using the finite-difference time-domain method. Figure 3 This is an electric field distribution diagram of the polarization controller 101 provided by the present invention in TM mode. Figure 4 This is an electric field distribution diagram of the polarization controller 101 provided by the present invention in TE mode.

[0067] Figure 3 and Figure 4 The circular white dashed line in the image indicates the location of nanowire 103. Figure 3 and Figure 4 The straight white dashed line in the diagram represents the target interface.

[0068] like Figure 3 and Figure 4 As shown, when the wavelength of the incident unpolarized light is 1550 nm, the TM electric field distribution diagram of the polarization controller 101 provided by the present invention shows that a strong electric field appears in the low refractive index gap. However, the TE mode field distribution diagram shows that the polarization controller 101 produces almost no light in the low refractive index gap.

[0069] To further analyze the light field characteristics of the mode, the calculations were performed along x=0 and y= in the current case. The full width at half maximum (FWHM) in both directions is 0.1512 μm (low-refractive-index slit). In TM mode, the FWHM along the x=0 direction is smaller than the width of the low-refractive-index slit. When the width of the low-refractive-index slit is 2 nm, the FWHM along the x=0 direction is less than 2 nm, fully reaching the nanometer scale. Along y= The full width at half maximum (FWHM) in the 0.1512μm direction is 6.48nm.

[0070] Therefore, whether along x=0 or y= The optical field in TM mode reaches the nanometer scale, with a full width at half maximum (FWHM) of less than 2 nm in the x=0 direction. In contrast, the electric field distribution at the low-refractive-index slit along the x=0 direction in TE mode is almost non-existent in the overall electric field distribution, and along the y= At 0.1512 μm, the electric field does not react with the metal. The wider the low-refractive-index slit, the smaller the electric field strength, which is almost zero at x=0.

[0071] Furthermore, the diameters of the nanowires 103 in the polarization controller 101 were respectively... d The distance between the nanowire 103 and the target interface h Analysis was performed. While maintaining the diameter of the nanowire 103...d With the nanometer diameter remaining constant at 200 nm, the distance between the nanowire 103 and the target interface. h As the wavelength of polarization controller 101 decreases from 25 nm to 2 nm, its transmission loss continuously increases from 1.2553 dB / μm to 2.0781 dB / μm, its extinction ratio continuously increases from 4.4951 dB / μm to 7.6675 dB / μm, and its mode field area continuously decreases from 0.11829 μm. 2 (≈) The size decreased to 0.0682393 μm. 2 (≈) ).

[0072] Maintaining the distance between nanowire 103 and the target interface h With a diameter of 2nm, the nanowire 103 has a diameter of 2nm. d As the wavelength increases from 100 nm to 300 nm, the transmission loss of polarization controller 101 continuously increases, from 0.55715 dB / μm to 4.445 dB / μm. The extinction ratio of polarization controller 101 also continuously increases, from 1.19235 dB / μm to 11.117 dB / μm. The mode field area of ​​polarization controller 101 first decreases and then increases, from 0.273007 μm... 2 (≈) The size decreased to 0.0682393 μm. 2 (≈) ), and then increased to 0.087898μm 2 (≈) ).

[0073] Taking all factors into consideration, the diameter of nanowire 103... d Preferably, the distance between the nanowire 103 and the target interface is 200 nm. h Preferably, the wavelength is 2-5nm.

[0074] Figure 5 This is a graph showing the relationship between different metal substrate materials, extinction ratio, and transmission loss of the polarization controller 101 provided by this invention. Figure 6 This is a graph showing the relationship between the diameter of the nanowire 103 and the effective mode field area in the polarization controller 101 provided by the present invention.

[0075] like Figure 5 As shown, while maintaining the diameter of nanowire 103 d The distance between the nanowire 103 and the target interface h Under the same conditions, the extinction ratio of aluminum and silver substrates is higher than that of metal substrates of other materials 102, and the transmission loss is also relatively low.

[0076] like Figure 6 As shown, with the diameter of nanowire 103... d As the polarization controller 101 increases, its effective mode field area first decreases and then increases, relative to the diameter of the nanowire 103. d The binding strength is highest when the wavelength is 200 nm.

[0077] When the metal substrate 102 of the polarization controller 101 is made of precious metal nanomaterials such as gold, silver, aluminum, copper, and indium, the light confinement intensity can break through the diffraction limit, achieving nanoscale light confinement, and the fluctuation range of its mode area is within the range of to Less than the diffraction limit in vacuum .

[0078] The polarization controller in this embodiment of the invention includes a metal substrate, nanowires, and an oxide dielectric layer. The oxide dielectric layer is disposed above the metal substrate. The nanowires extend in a straight line and are located inside the oxide dielectric layer, parallel to the metal substrate. One end of the nanowire is the incident end for unpolarized light, and the gap between the other end of the nanowire and the metal substrate is the exit end for polarized light. The polarization controller has a simple structure and is easy to fabricate. By adjusting the diameter of the nanowires, the TE mode in the nanowires can be cut off, realizing a TM polarized light field. By forming a low-refractive-index gap between the nanowires and the metal layer, focusing and polarization functions can be achieved at the nanoscale. Due to the discontinuity of the electric field at the interface between the low emissivity gap and the high refractive index nanowire, the light field in the low emissivity gap between the nanowire and the metal substrate is enhanced and coupled with the plasmon waves on the surface of the metal substrate. This enables precise constraint of the light field at the nanoscale, breaking through the diffraction limit of the light field and realizing the control of the polarization state of light waves at the nanoscale. At the same time, due to the polarization mode requirements of the plasmon polaritons in the metal substrate, a nano-focused TM polarized light field can be realized. This device has broad application prospects.

[0079] The polarization controller provided by this invention not only has advantages such as nanoscale light confinement capability, low-loss propagation, high extinction ratio and small device size, but also has a wide wavelength application range, which can meet the specific requirements of different application fields for light polarization state, thereby promoting the miniaturization of photonic devices and driving the development of high-density photonic integration technology.

[0080] Based on the above embodiments, an optical device includes: a polarization controller 101 as described in any of the above embodiments.

[0081] The optical device in this embodiment of the invention includes the polarization controller 101 as described above, which can be better integrated with nanoscale electronic devices, realize a high-performance, compact optoelectronic integrated system, provide an innovative solution for the next generation of optoelectronic integrated systems, realize the deep integration of nanophotonics and electronics, and better promote the development of high-performance, miniaturized optoelectronic devices.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A polarization controller, characterized in that, include: Metal substrate, nanowires, and oxide dielectric layer; The oxide dielectric layer is disposed above the metal substrate layer; The nanowires extend in a straight line, are disposed inside the oxide dielectric layer, and are parallel to the metal substrate layer; One end of the nanowire is the incident end for unpolarized light, and the gap between the other end of the nanowire and the metal substrate is the emitting end for TM polarized light. The diameter of the nanowire is set to meet the cutoff condition of the transverse electric TE mode, so that the transverse electric TE mode light energy leaks out of the polarization controller. The light field entering the gap will couple with the plasmons on the surface of the metal substrate, so that a mixed plasma transverse magnetic TM mode appears in the gap. The light energy is still strongly confined in the oxide medium layer, realizing the nano-focused TM polarized light field, and propagating to the output end through the gap. The nanowire has a circular cross-section and a diameter of 100 to 300 nanometers. The distance between the nanowire and the target interface is 2 to 5 nanometers. The target interface is the interface between the metal substrate layer and the oxide dielectric layer.

2. The polarization controller according to claim 1, characterized in that, The material of the metal substrate is selected from one or more of gold, silver, aluminum, copper, and indium.

3. The polarization controller according to claim 1, characterized in that, The material of the oxide dielectric layer is silicon dioxide.

4. The polarization controller according to claim 1, characterized in that, The nanowires are made of silicon.

5. The polarization controller according to any one of claims 1 to 4, characterized in that, The wavelength range of the unpolarized light is 800 to 1600 nanometers.

6. An optical device, characterized in that, include: The polarization controller as described in any one of claims 1 to 5.

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