A refractive index modulation structure based on the electric field effect of transparent metal oxide thin films and its application

Abstract

A refractive index modulation structure based on the electric field effect of transparent metal oxide thin films and its applications belong to the fields of integrated photonic devices, optical communication, and optical interconnection. The refractive index modulation structure includes a substrate layer and a TCO thin film layer disposed on the substrate layer. Conductor layers are disposed on both sides of the TCO thin film layer, and the conductor layers and the TCO thin film layer are in contact through a diffusion isolation layer to form a resistive structure, which is a conductor-TCO-conductor connection structure. The TCO thin film layer between the two conductor layers is the refractive index modulation region. This refractive index modulation structure is used to construct high-speed optical waveguide modulators and high-speed spatial light modulators. This invention utilizes the electric field effect of the TCO thin film to achieve efficient and rapid modulation of the real and imaginary parts of the optical constant. The TCO thin film has excellent modulation performance, achieving large-amplitude modulation of the real and imaginary parts of the optical constant using the electric field effect. Continuous high-speed electric field modulation is achieved through low-voltage drive, while the device is short in length and small in size, making it suitable as an electro-optic switch for large-scale high-speed integrated photonic devices.

Description

Technical Field

[0001] This invention belongs to the fields of integrated photonic devices, optical communication, and optical interconnection, and relates to a refractive index modulation structure based on the electric field effect of transparent-conducting-oxide (TCO) thin films and its application. Background Technology

[0002] Electro-optic modulators are fundamental components in photonic integrated circuits, playing a crucial role in optical communication interconnects. Currently, electro-optic modulators mainly utilize plasmon dispersion, thermo-optic, or Pockels effects for modulation, but these methods suffer from limited refractive index modulation ranges. For example, silicon-based electro-optic modulators use plasmon dispersion to modulate the refractive index near the waveguide of a phase shifter, but their extinction ratio and bandwidth performance are somewhat limited. Furthermore, while lithium niobate electro-optic modulators offer relatively fast modulation rates, their large device size, reaching centimeter-scale lengths, hinders miniaturization and integration.

[0003] Transparent metal oxide (TCO) thin films possess both excellent conductivity and transparency, are compatible with CMOS fabrication processes, and are widely used in integrated optoelectronics. Common TCOs include indium tin oxide (ITO), indium oxide, tin oxide, zinc oxide, aluminum-doped zinc oxide, and gallium-doped zinc oxide. The refractive index of these thin film materials can be modulated by controlling the carrier concentration. Some studies have utilized ITO thin films to construct metal-oxide-semiconductor (MOS) capacitor structures, where the carrier concentration in the ITO film can be changed by charging and discharging the capacitor, achieving significant refractive index modulation. However, due to the non-uniform charge distribution in the capacitor, this method can only control the refractive index within a few nanometers, making it difficult to effectively manipulate the optical field. This problem limits the application of TCO materials in electro-optic modulation devices. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention proposes a refractive index control structure based on the electric field effect of TCO thin films and its application. This structure can achieve large-amplitude, high-speed, and wide-range refractive index control through electrical signal driving.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A refractive index control structure based on the electric field effect of a transparent metal oxide thin film is disclosed. The structure includes a substrate layer and a TCO thin film layer disposed on the substrate layer. A conductor layer structure is disposed on the TCO thin film layer, with the connection being conductor-TCO thin film-conductor. The conductor layer is distributed on both sides of the TCO thin film layer, and the conductor layer and the TCO thin film layer are in contact through a diffusion isolation layer to form a resistive structure. The TCO thin film layer between the two conductor layers constitutes the refractive index control region.

[0007] Furthermore, the TCO thin film layer is a transparent metal oxide thin film layer, which may be indium tin oxide, cadmium oxide, indium oxide, tin oxide, zinc oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, fluorine-doped tin oxide, tin indium oxide, tungsten oxide, and related composite multi-component transparent metal oxide materials.

[0008] Furthermore, the thickness of the TCO thin film layer is 5–5000 nm.

[0009] Furthermore, the substrate layer may be an insulating dielectric material or a semiconductor material such as silicon, silicon dioxide, or silicon nitride.

[0010] Furthermore, the conductor layer structure is composed of a conductive thin film made of metallic materials, such as gold, silver, copper, and aluminum, and a diffusion isolation layer composed of titanium and titanium nitride.

[0011] Furthermore, a bias voltage is applied between the two conductor layers, and the magnitude and direction of the bias voltage can be arbitrary.

[0012] An application of a refractive index modulation structure based on the electric field effect of transparent metal oxide thin films, wherein the refractive index modulation structure is used to construct high-speed optical waveguide modulators and high-speed spatial light modulators.

[0013] When applied to the construction of high-speed optical waveguide modulators, the ratio of optical power at the two optical outlets can be dynamically adjusted according to the magnitude of the bias voltage applied to the conductor layer.

[0014] When applied to the construction of high-speed spatial light modulators, the wavelength range of the light beam passing through the TCO thin film layer can be dynamically adjusted according to the magnitude of the bias voltage applied to the conductor layer.

[0015] The beneficial effects of this invention are as follows:

[0016] (1) The present invention utilizes TCO thin film to form a conductor-TCO thin film-conductor resistor structure. The electric field intensity in the TCO thin film layer will change dynamically with the change of bias voltage, thereby causing the refractive index of the TCO thin film layer, including the real part and the imaginary part, to change dynamically.

[0017] (2) The refractive index control structure provided by the present invention has the advantages of large control depth, which is not limited to the thickness of the TCO thin film layer, simple structure, small size, and CMOS compatibility. Attached Figure Description

[0018] Figure 1 This is a schematic cross-sectional view of a refractive index-tunable structure based on the electric field effect of TCO thin films.

[0019] Figure 2 The relationship between the bias voltage and the refractive index of the refractive index control structure;

[0020] Figure 3 This is a test diagram of the refractive index modulation speed of the structure.

[0021] Figure 4 This is a specific embodiment 2 high-speed optical waveguide modulator; wherein, Figure 4 (a) is a structural diagram of the device; Figure 4 (b) is a cross-sectional schematic diagram;

[0022] Figure 5 This relates the bias voltage to the optical output power of a high-speed optical waveguide modulator.

[0023] Figure 6 This is a schematic diagram of the high-speed spatial light modulator structure in specific embodiment 3;

[0024] Figure 7 The bias voltage and transmitted beam wavelength range of the high-speed spatial light modulator;

[0025] In the figure: 1-substrate layer, 2-TCO thin film layer, 3-conductor electrode structure and its transition layer, 4-refractive index control structure, 5-interferometer waveguide, 6-silica substrate layer, 7-TCO thin film layer, 8-conductor layer and diffusion isolation layer, 9-substrate layer, 10-TCO thin film layer, 11-conductor layer and diffusion isolation layer, 12-periodic structure dielectric material layer. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments.

[0027] 1. The refractive index control structure and control method of this invention

[0028] A refractive index modulation structure based on the electric field effect of transparent metal oxide thin films, such as... Figure 1 As shown, the structure consists of a TCO thin film layer 2 disposed on a substrate layer 1, and a conductor layer disposed on the TCO thin film layer 2, with the connection method being conductor-TCO thin film-conductor. The conductor layer 3 is divided into a conductive layer and a diffusion isolation layer, with the diffusion isolation layer located between the conductor layer and the TCO thin film layer.

[0029] The conductor layer structure is distributed on both sides of the TCO thin film layer 2, and a bias voltage is applied through a power supply circuit; the middle region of the TCO thin film layer 2 is the control region. By applying a bias voltage to the TCO thin film layer 2, the refractive index of the TCO thin film layer is changed using the field effect. The relationship between the bias voltage and the refractive index of the TCO thin film layer is as follows: Figure 2 As shown. The refractive index of the TCO thin film layer is dynamically controlled by dynamically changing the magnitude of the bias voltage, and the control speed can reach the GHz level, such as... Figure 3 As shown.

[0030] In this embodiment, the TCO thin film layer is indium tin oxide. The thickness of the TCO thin film layer is 100 nm. The substrate layer is silicon. The conductor layer is a conductive thin film made of a metallic material, specifically a 60 nm gold thin film and a diffusion isolation layer composed of titanium and titanium nitride.

[0031] 2. Application in high-speed optical waveguide modulators

[0032] The refractive index modulation structure based on the electric field effect of the TCO thin film layer can be used to construct high-speed optical waveguide modulators. Specific implementation methods are as follows: Figure 4 As shown in (a), the refractive index adjustment structure 4 is placed at the two arms of the interferometer waveguide 5. Its cross-sectional schematic diagram is shown below. Figure 4 As shown in (b), the substrate 6 is silicon dioxide, the interferometer waveguide 5 is a ridge silicon waveguide located on the substrate 6, the TCO thin film layer 7 is located on the interferometer waveguide 5, and the conductor layer and the diffusion isolation layer 8 are located on the TCO thin film 2.

[0033] The high-speed optical waveguide modulator described above can dynamically adjust the ratio of optical power at the two optical outlets according to the magnitude of the bias voltage applied to the conductor layer, such as... Figure 5 As shown.

[0034] Furthermore, the interferometer waveguide can also be other waveguide device structures such as micro-ring resonator, linear waveguide, photonic crystal waveguide, and topological waveguide.

[0035] Furthermore, the materials constituting the interferometer waveguide, besides silicon, can be any transparent material with a refractive index greater than 1, such as silicon nitride, lithium niobate, group IV materials, and chalcogenides.

[0036] 3. Application in high-speed spatial light modulators

[0037] The refractive index modulation structure based on the electric field effect of TCO thin films can be used to construct high-speed spatial light modulators. Specific implementation methods are as follows: Figure 6As shown. A periodic structure dielectric material layer is placed above the refractive index control structure. A TCO thin film layer 10 is placed on the substrate layer 9, and a conductive layer, a diffusion isolation layer 11, and a periodic structure dielectric material layer 12 are placed on the TCO thin film layer 10.

[0038] The high-speed spatial light modulator described above can dynamically adjust the wavelength range of the light beam transmitted through the TCO thin film layer 2 according to the magnitude of the bias voltage applied to the conductor layer, such as... Figure 7 As shown.

[0039] Furthermore, the periodic structure medium material layer 12 can also be a stacked structure composed of multiple material thin films.

[0040] Furthermore, the adjustable beam wavelength range can also include other optical parameter control functions such as beam deflection angle, polarization state, and field distribution.

[0041] The above-described embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A refractive index modulation structure based on the electric field effect of transparent metal oxide thin films, characterized in that, The refractive index modulation structure includes a substrate layer and a TCO thin film layer disposed on the substrate layer. The TCO thin film layer is a transparent metal oxide thin film layer, and a conductor layer is disposed on the TCO thin film layer. The modulation structure is a conductor-TCO-conductor connection structure. The conductor layer is distributed on both sides of the TCO thin film layer. The structure of the conductor layer is composed of a conductive thin film made of a metallic material and a diffusion isolation layer composed of titanium and titanium nitride. The TCO thin film layer between the two conductor layers is the refractive index modulation region.

2. The refractive index modulation structure based on the electric field effect of a transparent metal oxide thin film according to claim 1, characterized in that, The TCO thin film layer is made of indium tin oxide, cadmium oxide, indium oxide, tin oxide, zinc oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, fluorine-doped tin oxide, tin indium oxide, tungsten oxide, or a composite multi-component transparent metal oxide material.

3. The refractive index control structure based on the electric field effect of a transparent metal oxide thin film according to claim 1, characterized in that, The thickness of the TCO thin film layer is 5~5000nm.

4. The refractive index control structure based on the electric field effect of a transparent metal oxide thin film according to claim 1, characterized in that, The substrate layer is silicon, silicon dioxide, silicon nitride, or a semiconductor material.

5. The refractive index modulation structure based on the electric field effect of a transparent metal oxide thin film according to claim 4, characterized in that, The metallic materials mentioned include gold, silver, copper, or aluminum.

6. The refractive index control structure based on the electric field effect of a transparent metal oxide thin film according to claim 1, characterized in that, A bias voltage is applied between the two conductor layers.

7. An application of the refractive index control structure based on the electric field effect of a transparent metal oxide thin film as described in any one of claims 1-6, characterized in that, The aforementioned refractive index modulation structure is used to construct high-speed optical waveguide modulators or high-speed spatial light modulators.

8. The application of the refractive index modulation structure based on the electric field effect of a transparent metal oxide thin film according to claim 7, characterized in that, When applied to the construction of high-speed optical waveguide modulators, after applying a bias voltage to the conductor layer, the ratio of optical power at the two optical outlets is dynamically adjusted according to the magnitude of the voltage.

9. The application of the refractive index modulation structure based on the electric field effect of a transparent metal oxide thin film according to claim 7, characterized in that, When applied to the construction of high-speed spatial light modulators, after applying a bias voltage to the conductor layer, the wavelength range of the light beam passing through the TCO thin film layer is dynamically adjusted according to the magnitude of the voltage.

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