Laser beam extraction using a distributed Bragg reflector (DBR) mirror system with a piezoelectric layer

Abstract

The present invention provides laser systems and methods for nuclear fusion energy, as well as related methods, and more specifically, techniques for damping lasers from cavity regions. [Solution] The laser system includes a laser source (CBC, etc.), which is coupled to a first mirror device facing a second mirror device and configured to generate a resonant laser beam between the first mirror and the second mirror. In one example, the system includes a piezoelectric device, which is provided in the second mirror device and characterized by its refractive index, and by applying energy to the piezoelectric device, one or more air gaps are changed to cause a change in the refractive index value (to a value greater than 0.0001, etc.), allowing a resonant laser beam or a portion of the resonant laser to pass through a portion of the second mirror device.

Description

[Technical Field]

[0001] This invention relates in general to fusion energy generation technology. In particular, the invention provides laser systems and methods for fusion energy, and related methods, and more specifically, techniques for damping lasers from cavity regions. For example, the invention can be applied to a variety of applications, including energy generation for power, spacecraft, travel, other land, air and sea vehicles, defense applications (e.g., satellites, aerospace industry, land and missile defense, submarines, boats), biotechnology, chemistry, mechanics, electrical, and communications and / or data applications, but these are merely examples. [Background technology]

[0002] Since prehistoric times, humans have developed energy sources from natural materials such as wood, coal, oil, and gaseous products. Unfortunately, when wood and coal are burned, undesirable carbon particles are released into the atmosphere, sometimes leading to serious pollution problems. Oil and gaseous products have similar limitations and are contributing to "global warming." Renewable energy sources such as nuclear, wind, hydro, and solar power are promising. However, these renewable energy sources also have other drawbacks. Wind power only works when the wind is blowing. Solar power does not work after the sun sets. Hydroelectric power is limited to areas with water. And while nuclear power is promising, it generates waste and has major problems such as the use of reactors that raise issues of reliability and danger. Another promising energy source is nuclear fusion energy.

[0003] Nuclear fusion energy is a type of energy produced when two atomic nuclei fuse together, releasing a large amount of energy during the process. It is considered a clean and abundant potential energy source because the fuel for nuclear fusion (mainly hydrogen) is abundant on Earth, and the reaction does not produce greenhouse gases or other harmful pollutants.

[0004] There are two main approaches to achieving nuclear fusion reactions: inertial confinement fusion (ICF) and magnetic confinement fusion (MCF). [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In inertial confinement fusion (ICF), a high-energy laser or particle beam is used to compress and heat small fuel pellets, causing the fuel to fuse. The main advantage of ICF is that it can potentially generate a fusion reaction using relatively small amounts of fuel and at a relatively low cost. However, this process is still in the experimental stage, and significant technical challenges remain before it can be considered a desirable energy source.

[0006] Magnetic confinement fusion (MCF) involves using a strong magnetic field to confine, heat, and fuse a hydrogen fuel plasma (high-temperature ionized gas). The most common type of MCF is called a tokamak fusion, which uses a toroidal (donut-shaped) chamber to contain the plasma. A strong magnetic field generated by passing an electric current through a set of coil windings around the chamber holds the plasma in the center of the chamber. The plasma is heated by injecting energy into it, either via a particle beam or electromagnetic waves.

[0007] One of the main advantages of MCF is that it can potentially generate fusion reactions on a larger scale, making it more suitable for power generation. However, MCF is a more complex and costly process than ICF, and there are still significant technical challenges to overcome before it can be considered a desirable energy source.

[0008] In recent years, both ICF and MCF have made significant progress, and several experimental facilities around the world are working on these technologies. However, major technical challenges remain in achieving sustained fusion reactions with net energy production (i.e., the energy produced by the fusion reaction is greater than the energy required to initiate and sustain the reaction).

[0009] Other approaches to fusion energy are also being explored, such as magnetization-targeted fusion and muon-catalyzed fusion. However, these approaches are still in the early stages of development. It remains unclear whether fusion energy can survive as an energy source.

[0010] As mentioned above, while nuclear fusion energy has the potential to be a clean and abundant energy source, significant technical challenges must be overcome before it can be considered a practical energy source.

[0011] The present invention generally provides fusion energy generation technology. In particular, the present invention provides laser systems and methods for fusion energy, and related methods, and more specifically, techniques for damping lasers from cavity regions. For example, the present invention can be applied to a variety of applications, including energy generation for power, spacecraft, travel, other land, air, and sea vehicles, defense applications (e.g., satellites, aerospace industry, land and missile defense, submarines, boats), biotechnology, chemistry, mechanics, electrical, and communications and / or data applications. However, these applications are merely illustrative. [Means for solving the problem]

[0012] In one example, the present invention provides a laser system. The laser system includes a laser source (e.g., CBC) coupled to a first mirror device facing a second mirror device, and configured to generate a resonant laser beam between the first mirror and the second mirror. In one example, the laser system includes a piezoelectric device provided in the second mirror device, characterized by its refractive index, and by applying energy to the piezoelectric device, one or more gaps are changed to cause a change in the refractive index value (e.g., greater than 0.0001), allowing a resonant laser beam or portion of the resonant laser to pass through a portion of the second mirror device.

[0013] In one example, this energy is supplied using elastic waves or an electric field. In another example, this energy induces a greater change in refractive index than that in a bulk piezoelectric layer without voids. In another example, the voids include one or more pores, aperture regions, or other structures. In yet another example, the change in value is greater than, for example, 0.01. In yet another example, the piezoelectric device is configured to extract a laser beam from a cavity between a first mirror and a second mirror. In yet another example, the cavity is a Fabry-Perot cavity or an optically enhanced cavity (OEC).

[0014] In one example, the present invention provides a variable reflector. This device comprises a substrate and a piezoelectric (or piezoelectric) material on the substrate. This material is configured to change the refractive index of the substrate so that a laser beam passes through a portion of the substrate. In one example, the substrate includes a distributed Bragg reflector.

[0015] In another example, the present invention provides a variable reflectivity distributed Bragg reflector (VR-DBR) mirror device. The device includes a transparent substrate, for example, an optically transparent substrate. In one example, the device has a plurality of laminates made of materials having at least two different refractive indices, forming a distributed Bragg reflector (DBR) covering the transparent substrate. In one example, the device includes a piezoelectric layer containing a plurality of voids, the piezoelectric layer being composed of one or more laminates such that the piezoelectric layer constitutes a DBR. In one example, the device includes at least one electrical contact point coupled to the piezoelectric layer containing voids and characterized by a conductive material. In one example, the device includes electrical energy (e.g., power) coupled to the electrical contact point and configured to change the refractive index of the piezoelectric layer by supplying an electric field into the piezoelectric layer containing voids, thereby changing the reflection spectrum of the DBR and allowing a laser beam to pass through a portion of the DBR.

[0016] Depending on the embodiment, the present invention can achieve both or one or more of the above benefits and advantages. In one example, the present invention provides a fusion energy system comprising a high-intensity pulsed or CW (Continuous Wave) laser system or continuous-wave laser system configured with a reactor as a compact, spatially efficient system and related method. In one example, the high-intensity pulsed or CW laser system provides sufficient energy to burn and sustain fusion energy within the reactor. In one example, the present invention enables the dumping of the laser beam from the cavity. In one example, the present invention provides the advantage of performing fusion power generation with efficient size, weight, and cost using this high-intensity laser. In one example, the system and method are configured to reduce or eliminate parameter-related instability. Both of the above benefits and advantages, etc., can be achieved by the apparatus and related methods of the present invention. Details of both of the above benefits and advantages can be understood in more detail below throughout this specification.

[0017] A further understanding of the properties and advantages of the present invention will be obtained by referring to the later portions of this specification and the accompanying drawings.

[0018] For a more complete understanding of the present invention, reference is made to the accompanying drawings, which are not intended to limit the scope of the present invention, but which illustrate embodiments described herein and the currently contemplated best mode in greater detail.

Brief Description of the Drawings

[0019] [Figure 1] FIG. 1 is a schematic diagram of a (coherent beam combining laser) CBC and an (optically enhanced cavity laser) OEC according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram of the types of layers of a DBR (distributed Bragg reflector) according to an embodiment of the present invention, where (a) shows a DBR structure consisting of layer 1 and layer 2 each having a quarter wavelength thickness, (b) shows a modification where all thin layers each having a quarter wavelength are slightly doped to accommodate ohmic contacts, and (c) and (d) show cases where one of the two thin portions is doped. [Figure 3] FIG. 3 is a diagram showing various types of simplified connections according to an embodiment of the present invention, where (a) shows a parallel connection where both ends of the layer are connected by two contacts, (b) shows a cross connection generally required for a combination of layers of the type shown in FIG. 2(b), where one contact from each layer is shown to be used to send an RF (radio frequency) signal to the semiconductor layer, (c) shows that one side of the layer is used as a contact for RF signal injection, and (d) shows an interdigitated transducer (IDT) type layout, where a thin doped layer is patterned to form an IDT shape such that the RF signal spreads uniformly in the bulk and on the surface. [Figure 4]Figure 4 is a simplified diagram of the surface undulation of a solid piezoelectric layer and a void-containing layer according to an embodiment of the present invention, where (a) shows the net volume change due to SAW (surface acoustic wave) on a completely defined surface, (b) shows voids of random shape, in which case the SAW or BAW (bulk acoustic wave) is heterogeneous and non-uniform due to the crystal sensitivity of the piezoelectric material, causing a net volume change in the voids when RF is applied, and (c), (d), and (e) show the patterns of possible electrical connections in the piezoelectric layer containing voids / pores. [Figure 5] Figure 5 is a simplified diagram illustrating the phenomenon of reflectance spectrum shift when the porosity of a layer changes according to an embodiment of the present invention, and shows (a) a piezoelectric layer containing pores / voids, (b) a change in void volume due to the application of SAW / BAW, and (c) a shift in the reflectance spectrum when a 10% change in porosity is applied. [Figure 6] Figure 6 shows, according to an embodiment of the present invention, (a) an illustration of a DBR mirror layer in which at least one of the layers is a piezoelectric layer containing pores / voids, and (b) a diagram showing a simplified pad configuration in which the sides of the DBR layer are connected to form a simplified DBR chip having two pads. [Figure 7A] Figure 7A illustrates a DBR mirror layer according to an embodiment of the present invention, wherein at least one of the layers is a piezoelectric layer containing pores / voids, and each layer is treated with an electrical connection pad. [Figure 7B] Figure 7B shows a semiconductor DBR mirror chip with 2N pads for a DBR mirror containing N pairs (where N is an integer) DBRs, according to an embodiment of the present invention. [Figure 7C] Figure 7C is a simplified diagram showing a DBR mirror according to an embodiment of the present invention, in which at least one layer is a piezoelectric layer containing pores / voids, and an IDT layout pattern is formed on this layer, thereby forming a pad configuration IDT layout on a specific layer of this laminate. [Figure 7D]Figure 7D shows the IDT layout as viewed from the surface, according to an embodiment of the present invention. [Figure 8] Figure 8 shows, according to an embodiment of the present invention, (a) to (c) simplified diagrams of the proposed DBR mirror system, showing that at least one of the multiple layers is a piezoelectric layer containing voids / pores, and (d) a diagram of the reflection spectrum of the DBR mirror system, showing two traces, one with elastic waves applied and one without. [Figure 9A] Figure 9A is a simplified diagram illustrating the fabrication of intermediate pore / void-containing layers between multiple DBR layers, referred to as DBR laminate 1 and DBR laminate 2, according to an embodiment of the present invention, and shows that the sapphire substrate comprises UID (unintentionally doped) buffer GaN, an etching stop layer (AlN) aluminum nitride, a highly doped semiconductor layer, and a moderately doped semiconductor layer, and has trenches (IDT fingers) etched to spread uniformly with SAW / BAW. [Figure 9B] Figure 9B is a simplified diagram illustrating the manufacturing of intermediate pore / void-containing layers between multiple DBR layers, referred to as DBR laminate 1 and DBR laminate 2, according to an embodiment of the present invention. The diagram shows that a highly doped semiconductor layer is subjected to porosity modification (porosity formation) by an IDT layout, and the first set of DBR laminates is deposited. [Figure 9C] Figure 9C is a simplified diagram illustrating the fabrication of intermediate pore / void-containing layers between multiple DBR layers, referred to as DBR laminate 1 and DBR laminate 2, according to an embodiment of the present invention, and shows laser lift-off and chemical etching. [Figure 9D] Figure 9D is a simplified diagram illustrating the manufacturing of intermediate pore / void-containing layers between multiple DBR layers, referred to as DBR laminate 1 and DBR laminate 2, according to an embodiment of the present invention, showing that a second set of DBR laminates is deposited. [Figure 9E]Figure 9E is a simplified diagram illustrating the fabrication of intermediate pore / void-containing layers between multiple DBR layers, referred to as DBR laminate 1 and DBR laminate 2, according to an embodiment of the present invention, and shows GaN and AlN layers on a SiC (silicon carbide) substrate fabricated using an IDT layout. [Figure 9F] Figure 9F is a simplified diagram illustrating the manufacturing of intermediate pore / void-containing layers between multiple DBR layers, referred to as DBR Laminate 1 and DBR Laminate 2, according to an embodiment of the present invention, and shows the first laminate of DBR layers deposited after porosity formation. [Figure 9G] Figure 9G is a simplified diagram illustrating the manufacturing of intermediate pore / void-containing layers between multiple DBR layers, referred to as DBR laminate 1 and DBR laminate 2, according to an embodiment of the present invention, and shows the removal of the SiC substrate. [Figure 9H] Figure 9H is a simplified diagram illustrating the manufacturing of the intermediate pore / void-containing layer between multiple DBR layers, referred to as DBR laminate 1 and DBR laminate 2, according to an embodiment of the present invention, and shows the deposited second DBR laminate. [Figure 10] Figure 10 is a schematic diagram showing a method for creating porosity or voids according to an embodiment of the present invention, and (a) a diagram showing alternating layers of piezoelectric material and metal composite layer, (b) a diagram showing that the metal areas are selectively etched using a chemical substance, leaving voids in the composite piezoelectric layer, and (c) a diagram showing that two DBR laminates are deposited on the upper and lower parts of the void-containing layer. [Figure 11] Figure 11 shows, according to an embodiment of the present invention, (a) a simplified diagram showing electrical connection and porosity, in which the DBR layer may be of dielectric or semiconductor type, unlike other structures, and the central porous layer is a piezoelectric semiconductor layer that matches the refractive index of the DBR layer at that location; and (b) a diagram showing the IDT layout of the porous layer, in which the electrical connection pads are metal and the fingers are semiconductor layers or transparent conductive layers such as ITO. [Figure 12]Figure 12 is a simplified diagram showing the reflection spectrum of a GaN / void-containing GaN layer laminate of a DBR according to an embodiment of the present invention, in which there are, for example, 55 pairs in total, and the center wavelength is adjusted to, for example, 987 nm, so that the wavelength of 1040 nm remains at the edge of the stopband, and the diagram shows two further trajectories when the refractive index of the pore / void-containing layer changes from the reference layer to, for example, 0.023, and (b) a magnified view of the edge of the stopband, showing that the induced refractive index contrast in the void-containing layer shifts the reflection spectrum. [Figure 13] Figure 13 is a simplified diagram showing a DBR cavity structure according to an embodiment of the present invention, in which the thickness of the void / pore-containing layer is half the thickness of one wavelength of the DBR laminate layer. [Figure 14] Figure 14 shows, according to an embodiment of the present invention, (a) a simplified diagram of a DBR cavity structure having an IDT layout sandwiched between an upper DBR laminate and a lower DBR laminate, and (b) a diagram of an IDT layout structure having metal electrodes and semiconductor / TCO fingers. [Figure 15] Figure 15 shows, according to an embodiment of the present invention, (a) a schematic diagram of the Ta2O5 / SiO2 layers of a DBR laminate on both sides of a piezoelectric layer containing pores / voids and having an effective refractive index np; (b) a diagram showing the reflectance spectrum of a cavity DBR structure with several traces showing refractive index np ranging, for example, between 1.24 and 1.28; and (c) a magnified diagram showing a dip in the reflectance spectrum of the system for broadening refractive index, showing a change Δnp between ±0.02. [Figure 16] Figure 16 shows a simplified diagram of the configuration of a DBR (a) and a DBR cavity (b) according to an embodiment of the present invention, both of which feature a pore-containing piezoelectric layer with connections for the application of an electric field. [Figure 17] Figure 17 is a diagram illustrating various types of porous layers according to embodiments of the present invention. [Modes for carrying out the invention]

[0020] The present invention generally provides technologies related to fusion energy generation. In particular, the present invention provides laser systems and methods for fusion energy, and related methods, and more specifically, technologies for damping lasers from cavity regions. For example, the present invention can be applied to a variety of applications, including energy generation for power, spacecraft, travel, other land, air and sea vehicles, defense applications (e.g., satellites, aerospace industry, land and missile defense, submarines, boats), biotechnology, chemistry, mechanics, electrical, and communications and / or data applications, but these are merely examples.

[0021] This invention describes a system that enables the rapid removal or "damping" of laser light accumulated in a cavity. The laser cavity is formed by two mirrors with a free space between them. The laser cavity can be used to amplify the power of an input laser. This can be achieved by controlling the timing and phase of the input laser, thereby injecting and accumulating multiple pulses into the cavity as a single high-energy pulse.

[0022] The cavity consists of two concave mirrors (or concave mirrors), both mounted at opposite ends of the cavity, with free space between them and equipped with finely adjustable mounts. When the augmented cavity is driven by a pre-amplified laser pulsed at a megahertz repetition rate, pulses that propagate increasingly strongly are generated between the mirrors of the cavity.

[0023] For example, by utilizing coherent beam combining (CBC) and optical enhancement cavities (OEC), high-power laser beams can be generated by stretching, amplifying, and then compressing laser pulses, achieving dramatic peak powers ranging from gigawatts (GW) [Non-Patent Literature 1] to petawatts (PW). These high-power laser beams have spurred the development of compact electron and ion accelerators [Non-Patent Literature 2], X-ray sources [Non-Patent Literature 3], and antimatter jet generation [Non-Patent Literature 4]. Despite these remarkable advances, limitations remain in certain applications due to the physical constraints and damage thresholds of the optical components used in current laser systems. The intensity limit of solid-state optics is approximately 10 12 W / cm 2 This is very close to the ionization threshold of most materials. This proximity means that even with advancements in optical coatings, there are limits to how much improvement can be achieved. 10 13 W / cm 2 To achieve strengths exceeding [a certain level], alternative methods are needed that can circumvent the limitations of solid-state optical systems.

[0024] In this application, the inventors propose a method for extracting a high-power laser beam from one of several DBR mirrors in an OEC. A hybrid distributed Bragg reflector (DBR) mirror system is provided, in which photoelastic phenomena are used to alter the reflection spectrum of the DBR layer. This method can create a tunable piezoelectric opticmechanical (or piezo-optomechanical) cavity system by introducing surface acoustic waves (SAWs), bulk acoustic waves (BAWs), or an electric field (or field) into the DBR layer. Under the operation of these acoustic waves (or sound waves), a Bragg mirror containing at least one layer having piezoelectric properties can be effectively coupled to the generated wave. Conventional acousto-optic modulators (AOMs) or piezoelectric modulators provide a refractive index contrast of only 0.0001, which is insufficient for significant reflection spectral shifts in the DBR mirror unless the magnitude of the contrast changes by a factor of 100. As a result, when AOM is used with DBR mirrors, it introduces unnecessary absorption losses, reducing system efficiency. Accessing the laser beam through a DBR mirror system is practical because it allows for increasing the mirror size to more than 2 inches, thereby diluting the energy density on the mirror material.

[0025] To address this problem, the inventors focus on extracting a high-power laser beam through one or more of a plurality of DBR mirrors, particularly through the mirror opposite the coherent beam-coupled (CBC) laser injection mirror. For elastic waves or electric fields in a piezoelectric crystal to achieve a significant reflectivity shift, a refractive index contrast greater than 0.001 is required. DBR mirrors can handle higher energy levels by increasing the mirror area, thereby making the manipulation, deflection, or transmission of high-power laser beams ideal. This method leverages the inherent advantages of DBR mirrors when handling high-power lasers, ensuring efficient and effective extraction (or extraction) of the laser beam by transmitting it through the DBR mirror. The inventors propose achieving a greater refractive index contrast by (intentionally) introducing pores or voids using at least one piezoelectric crystal layer. This comprehensive approach overcomes the limitations of current DBR systems, paving the way for next-generation high-power lasers and numerous electro-optical applications in fields such as nuclear fusion where precise control of high-power laser beams is desired.

[0026] In the field of optoelectronics, nanoporous semiconductors are emerging as important materials, particularly due to their ability to alter the refractive index through the introduction of porosity. Semiconductors such as GaN [Non-Patent Literature 4], GaAs, LiNbO3, LiTaO3, and ZnO exhibit desirable optical properties when porous. The introduction of nanopores (typically voids with diameters ranging from 5 to 15 nanometers) significantly alters the refractive index and optical behavior of the material. These nanopores are formed randomly and reflect the crystal structure of the material, resulting in a highly variable and tunable refractive index. As a result, nanoporous semiconductors are versatile materials in a variety of fields, including sensors, optical devices (or photonic devices), and high-reflectivity coatings for lasers.

[0027] Several advanced techniques are used in the process of creating porous semiconductors. One common method is electrochemical etching, which uses electric current to dissolve a portion of the semiconductor material and form pores. In this method, etching parameters such as voltage, current density, and etching time can be adjusted to precisely control the size and distribution of the pores. Another technique involves ion implantation followed by thermal annealing, in which ions are implanted into the semiconductor substrate to cause damage, and subsequent annealing helps to form pores. In addition, metal-assisted chemical etching (MACE) is used [Non-Patent Literature 5], in which a metal catalyst accelerates the etching process, resulting in the formation of a porous structure. These methods make it possible to manufacture nanoporous semiconductors with properties tailored to specific applications.

[0028] Surface acoustic waves (SAWs), bulk acoustic waves (BAWs), and electric fields play desirable roles in modulating the optical properties of nanoporous semiconductors. SAWs are mechanical waves (or mechanical undulations) that travel along the surface of piezoelectric materials, causing periodic undulations (or swells). Depending on their frequency and intensity, these waves can reach heights of several hundred picometers. While SAWs cause surface undulations in bulk materials, in nanoporous semiconductors, these waves interact with irregularly shaped voids, resulting in complex surface and volume modulations. Bulk acoustic waves, on the other hand, propagate within the material. In nanoporous semiconductors, BAWs interact with voids, causing changes in the material's mechanical and optical properties. The interaction between elastic waves and the nanoporous structure results in dynamic modulation of the refractive index, significantly influencing the optical behavior of the material.

[0029] In nanoporous semiconductors, the introduction of pores or voids lowers the average refractive index because the voids are filled with air or other low refractive index materials, creating a composite medium with a lower effective refractive index than the bulk material. For example, in nanoporous GaN, the refractive index can be significantly lower than that of bulk GaN, which is approximately 2.3. The refractive index of nanoporous materials can be calculated using volume-average theory (VAT), which takes into account the porosity and refractive index of the constituent materials. When multiple SAWs or BAWs move through a nanoporous semiconductor, they cause mechanical deformations within and around the multiple pores. These deformations can enhance or attenuate wave propagation depending on the crystal orientation of the void surface, resulting in dynamic modulation of the refractive index. This change in refractive index (often greater than 0.001) is sufficient to shift the reflection spectrum of a DBR or alter the resonance peak of an optical cavity.

[0030] Introducing porosity into semiconductors often yields several advantages compared to the corresponding non-porous cases. The high surface area of ​​nanoporous semiconductors enhances photomatter interaction, making them ideal for sensors and photodetectors. Porosity and the ability to modulate the refractive index via elastic waves enable the design of tunable optical devices. Furthermore, the porous structure facilitates better heat dissipation, enabling improved thermal management. Nanoporous semiconductors can also be used to produce high-reflectance deep beam fibers (DBRs), which are desirable in high-power laser and optical cavity applications. The high refractive index contrast between bulk and nanoporous materials allows for the development of efficient DBRs with low lattice mismatch. As a result, nanoporous DBRs are superior to conventional semiconductor DBRs in terms of reflectivity and durability. The ability to fine-tune the refractive index via porosity and elastic waves further enhances the performance of these DBRs, making them ideal for a wide range of optoelectronic applications.

[0031] Piezoelectric materials are selected for their desirable properties. In one example, they affect the efficiency and properties of the surface acoustic waves (SAWs) generated.

[0032] Lithium niobate (LiNbO3) Sound velocity: 3,730 m / s Piezoelectric coupling coefficient: 19×10 -12 C / m 2

[0033] Lithium tantalate (LiTaO3) Sound velocity: 3,360 m / s Piezoelectric coupling coefficient: 19×10 -12 C / m 2

[0034] Quartz (SiO2) Sound velocity: 3,150 m / s Piezoelectric coupling coefficient: 2.3×10 -12 C / m 2

[0035] Zinc oxide (ZnO) Sound velocity: 2,680 m / s Piezoelectric coupling coefficient: 12.3×10 -12 C / m 2

[0036] Aluminum nitride (AlN) Sound velocity: 5,800 m / s Piezoelectric coupling coefficient: 5.5×10 -12 C / m 2

[0037] Gallium nitride (GaN) [[ID=六十]] Sound velocity: 5,970 m / s Piezoelectric coupling coefficient: 3.1×10 -12 C / m 2

[0038] For example, gallium nitride (GaN) is desirable for acousto-optical applications due to its excellent thermal stability, wide bandgap, and high electron mobility. The elastic wave amplitude in GaN varies depending on the crystal orientation. In the C-plane (0001) direction, GaN exhibits strong piezoelectric coupling, resulting in a high SAW amplitude of approximately 200–300 pm / V for Rayleigh waves. In the A-plane (11–20) direction, it supports shear horizontal SAWs (SH-SAWs) with amplitudes of approximately 150–200 pm / V, which are suitable for sensor applications. In the M-plane (1–100) direction, polarization effects are minimized, allowing for significant flexibility and producing a SAW amplitude of approximately 250 pm / V. These properties make GaN suitable for high-frequency and high-power applications, including filters and sensors.

[0039] For example, zinc oxide (ZnO) is desirable due to its high piezoelectric constant and ease of thin-film deposition. In the C-axis (0001) direction, ZnO exhibits excellent SAW properties, with elastic wave amplitudes reaching 300-400 pm / V for Rayleigh waves, making it ideal for high-sensitivity sensors and high-frequency SAW devices. In the A-axis (11-20) direction, it supports SH-SAW, providing a wave amplitude of approximately 200-300 pm / V, which is beneficial for biosensors and chemical sensors where horizontal polarization is advantageous. Furthermore, M-plane (1-100)ZnO provides a substantial elastic wave amplitude of approximately 250-350 pm / V, giving it versatility for various acoustic applications, including transducers and actuators.

[0040] For example, lithium niobate (LiNbO3) is desirable due to its strong piezoelectric and electro-optical properties and is an important material in acousto-optical and piezoelectric devices. The Z-cut (0001) direction of LiNbO3 is optimal for longitudinal bulk elastic waves, with amplitudes reaching up to 200-300 pm / V, making it ideal for high-power optical modulators. The Y-cut (11-20) direction is excellent for generating high-amplitude SAWs, typically having values ​​of around 150-250 pm / V, and is widely used in SAW filters and resonators. The 128° Y-cut direction is particularly outstanding for maximizing SAW amplitude, achieving high values ​​of 300-400 pm / V, and is widely used in high-performance SAW devices. These variations in elastic wave amplitude across different crystal directions enhance the suitability of LiNbO3 for precision elastic wave applications in communications and sensor technologies.

[0041] For example, gallium arsenide (GaAs) is another important material used in acousto-optical devices due to its high electron mobility and direct bandgap. In the C-plane (100) direction, GaAs can produce a significant SAW amplitude of approximately 150–200 pm / V, making it suitable for high-frequency applications. In the A-plane (110) direction, it supports a moderate SAW amplitude of approximately 100–150 pm / V, which is applicable to various sensor applications. In the Z-plane (111) direction, it is used in certain high-efficiency SAW devices, providing amplitudes in the range of 150–250 pm / V. These properties make GaAs versatile for use in both communication and sensor technologies, especially when high frequency and high efficiency are required.

[0042] The following describes the outlines of several drawings in one embodiment.

[0043] Figure 1 shows examples of coherent beam coupling (CBC) and optically enhanced cavity (OEC). The OEC includes two distributed Bragg reflector (DBR) mirrors, the radius of curvature of each mirror configured to focus the beam to the center of the OEC's length. In this configuration, the high-power beam is concentrated between the two mirrors. The desired cavity length for such a system can range from 0.5 meters to 200 meters. One DBR mirror is on the CBC side, and the other DBR mirror is on the opposite side.

[0044] In one example, the refractive index of this mirror is changed, allowing the propagating beam resonating within the cavity to pass through a second mirror outside the cavity, thereby damping the beam outside the cavity.

[0045] Figure 2 illustrates various types of DBR layers. Figure 2(a) shows an example of a DBR mirror in which pairs of materials are stacked together. In this example, each pair contains material 1 with refractive index n1 and material 2 with refractive index n2. Each material in this pair has thicknesses of λ / 4n1 and λ / 4n2, respectively, where λ is the wavelength of a high-power laser. By stacking several of these pairs, a high reflectivity is obtained. Figures 2(b) to 2(d) show various combinations of quarter-wavelength layers of semiconductors, which can be stacked without deviating from the reflection spectrum. In the combination shown in Figure 2(b), the thin portion of each quarter-wavelength layer is moderately doped, so that when an electric field is applied, the refractive index is changed by carrier injection. In the configurations shown in Figures 2(c) and 2(d), only one of the two layers is moderately doped.

[0046] Figure 3 shows various types of available electrical connections. In one example of a parallel connection configuration, moderately doped layers help spread the electric field uniformly across the entire layer. This is even more effective in the case of a cross connection shown in Figure 3(b). In the connection shown in Figure 3(c), only the sides of the layers are connected. When multiple DBR layers are placed to form a mirror, a manufacturing process is carried out that exposes the sides of all layers, and then metal is deposited to spread the RF field during stacking. In the most effective configuration, IDTs are placed on top of one of the multiple semiconductor layers, allowing SAW / BAW to propagate across the entire thickness of the layer with little attenuation and without changing the refractive index of the layer.

[0047] Figure 4 shows a conceptual diagram of a pore / void layer and coupled elastic waves in one example. Figure 4(a) illustrates the propagation of surface elastic waves on a piezoelectric crystalline material. Surface elastic waves generate surface waves according to the crystal direction, with amplitudes of several hundred picometers. Figure 4(b) shows randomly formed voids within a layer, where selective etching is performed according to the doping concentration to promote current within the layer and create surface relief on the inner surface of the voids. The amplitude of the reliefs changes in different directions based on the unspecified crystal direction of the voids. Figures 4(c), (d), and (e) illustrate various connection patterns of this void layer.

[0048] Figure 5 shows the photoacoustic effect in a piezoelectric crystal layer containing pores / voids in one embodiment. Figure 5(a) shows a piezoelectric crystal layer containing pores, where the pores / voids are represented as circles and simplified. Figure 5(c) shows the reflection spectrum of the layer (bright solid line). When elastic waves are applied using one of the connection methods described above, the net volume (or actual volume) of the pores changes based on the generated surface relief. Figure 5(b) shows a schematic diagram of this effect. The reflection spectrum in Figure 5(c) assumes a net volume contraction of 10%, and the pore size changes from 10 nm to 9.5 nm, corresponding to an average contraction of 250 pm from the inner surface of the voids. Figure 5(c) shows the resulting reflection spectral shift.

[0049] Figures 6 and 7 show a lateral layer connection pattern and a pattern enabling individual content referencing for injecting elastic waves into multiple DBR layers in one embodiment. The method in Figure 6 is similar to volume Bragg diffraction, but in this case, it involves diffracting light through a periodic change in refractive index across the entire volume using a three-dimensional periodic structure known as a volume Bragg grating (VBG). In the field of laser systems, VBGs are highly efficient. In piezoelectric crystals, their desirable properties allow for dynamic control of the refractive index within the VBG. When an electric field is applied to the piezoelectric crystal, mechanical strain occurs, changing the periodic structure of the VBG and effectively adjusting its diffraction characteristics. The refractive index contrast, which is the difference in refractive index between regions of the grating, can be dynamically adjusted when an electric field is applied. This process changes the atomic structure and arrangement within the crystal lattice, resulting in a change in refractive index. In this embodiment, a one-dimensional periodic refractive index change exists, which is already present in the DBR layer. When elastic waves are applied from the side, a three-dimensional refractive index change occurs, acting as a volume backgrowth (VBG). Volume Bragg diffraction in piezoelectric crystals provides a powerful method for controlling light through refractive index modulation. Figure 7 shows connection patterns for processing multiple semiconductor DBR layers individually, and semiconductor chips fabricated for processing each layer.

[0050] Figures 8(a) to 8(d) illustrate the proposed DBR mirror systems, which, as an example, are configured to shift the reflection spectrum by dynamically coupling elastic waves to a piezoelectric layer containing pores / voids. Figure 8(a) shows a method of connecting multiple layers at the sides to ensure efficient coupling of elastic waves. Figure 8(b) shows that each pore-containing layer in the DBR structure can be processed individually to enable precise control of the elastic wave interaction. Figure 8(c) shows a DBR mirror system in which only one layer contains pores / voids, and the other layers can be either semiconductors or dielectrics. The pore-containing layer has piezoelectric properties, and its porosity (or degree of porosity) is adjusted to obtain the precise refractive index required to complete the DBR pair. The IDT layout activates the elastic waves and simplifies the overall DBR structure. The void-containing layer is prepared first, and then the remaining DBR layers are placed at the bottom and top to form the collective DBR system. Figure 8(d) shows a comparison of the effects when an RF signal is applied and when it is not, illustrating the mechanism by which the reflection spectrum of the DBR mirror is shifted.

[0051] Figures 9 and 10 show, as an example, a procedure that may be used to obtain a sandwich (or void) containing a piezoelectric crystal layer in the center of a DBR laminate. One procedure is based on electrochemical etching, and the other is based on selective chemical etching of composite metal atoms. In both procedures, the thickness of the void-containing / pore-containing layer is controlled to a quarter wavelength or the required thickness.

[0052] Figure 11(a) shows the thickness of one-quarter wavelength and the refractive index n. p A schematic diagram of a clamping structure having a pore / void-containing layer is shown, which in one embodiment coincides with one of the DBR mirror layers. If one of the DBR laminates is formed from a dielectric material, its porosity can be adjusted to precisely match the refractive index of the layers within the DBR laminate.

[0053] A thin doped semiconductor layer is added on top of the piezoelectric porous layer, ensuring that the combined thickness of the porous layer and the doped layer does not exceed a quarter wavelength. This doped layer is formed during the IDT layout. Alternatively, a transparent conductive oxide layer such as ITO can be used to form the IDT. To improve conductivity, metal pads are deposited at the ends of the IDT fingers. Figure 11(b) shows the top surface of the porous piezoelectric layer with the IDT. The first stack of DBRs is positioned within the rectangular solid lines, ensuring that the high-power laser is incident only on areas away from the metal pads.

[0054] Figure 12(a) shows the simulation results of a DBR laminate containing GaN and porous GaN layers, similar to the structure shown in Figure 8(b) as an example. The reflection spectra of structures for GaN / porous GaN layers with thicknesses of 105 nm and 145.2 nm, respectively, were investigated. The refractive index of the porous GaN layer is 1.6994 at 40% porosity. A total of 55 periods were used in the simulation, targeting a central wavelength of 987 nm. The edge of the stopband of the reflection spectrum includes a wavelength of 1040 nm; in this case, the reflectance can be reduced by changing the refractive index from 1.6994 to 1.6761, thus obtaining a refractive index contrast of 0.023. Figure 12(b) shows the spectral shift when the refractive index is changed, with an enlarged view of the trace (trajectory) at one end. Elastic waves in piezoelectric materials can induce the necessary contrast in the porous layer.

[0055] Figure 13 shows the proposed DBR cavity structure as one of several embodiments, in which the thickness of the cavity layer has been changed from a quarter wavelength to a half-wavelength thickness in one embodiment. Two DBR mirror stacks are positioned on either side of this cavity layer. This combined structure exhibits cavity resonance, or a dip, in the reflection spectrum. This dip can be corrected by changing the refractive index of the cavity layer. Two DBR stack layers are positioned above and below the pore-containing layer, introducing a cavity resonance dip into the reflection spectrum of the DBR cavity. This dip can be manipulated by applying elastic waves to the pore / void-containing layer. Figure 14(a) shows a cross-sectional view of this structure, and Figure 14(b) shows an IDT layout structure, which is formed on a slightly doped semiconductor layer. Alternatively, a thin, transparent conductive layer can be separately positioned and then formed into the IDT shape.

[0056] Figure 15 shows, as an example, the simulation results of a DBR cavity structure composed of Ta2O5 / SiO2 layered structures. The cavity layer (or void layer) has a refractive index n p The porous material has a thickness of half the wavelength. Figure 15(b) shows the reflectance spectrum of a DBR cavity structure with the introduced cavity layer. Figure 15(c) shows a magnified view of the reflectance spectrum, highlighting the trace when the refractive index of the cavity layer changes by only 0.02 from the original value. By introducing a change in refractive index through the coupling of elastic waves to a piezoelectric layer containing pores / voids, the dip in the reflectance spectrum can be dynamically adjusted, effectively creating transparency at the dip wavelength.

[0057] Referring again to the drawings, the void / pore piezoelectric crystal layer shown in Figures 4 and 5 of the present invention will be described below as one embodiment. In one embodiment, the enhancement of the laser peak power intensity by pulse stacking in the optical enhancement cavity (OEC) is estimated to reach 100,000 times after 100,000 round trips between two distributed Bragg reflector (DBR) mirrors. As a result, the laser in the OEC is expected to produce a peak power in the terawatt (TW) or petawatt (PW) class. Figure 1 shows a schematic diagram of an OEC with two DBR mirrors.

[0058] For example, making a thin piezoelectric layer porous (e.g., porous) reduces its refractive index, which can improve the performance of optoelectronic devices, sensors, and acoustic devices. Porosification involves creating a porous structure within a material to alter its optical, electrical, and mechanical properties. Several methods exist for achieving porosity, including electrochemical etching, ion implantation followed by thermal annealing, and metal-assisted chemical etching (MACE).

[0059] Electrochemical etching is used for porosity formation, particularly for semiconductors such as silicon, GaAs, and GaN (gallium nitride). In this method, an electric current is applied to a semiconductor immersed in an electrolyte. The current causes dissolution of the semiconductor material, forming multiple pores. The size and distribution of these pores can be controlled by adjusting etching parameters such as voltage, current density, and etching time. For example, porous silicon can be formed with pore sizes ranging from a few nanometers to a few micrometers, depending on the electrochemical conditions. This method allows for precise control of porosity and is suitable for a variety of applications.

[0060] Another technique used to form porous structures in semiconductor and piezoelectric materials is ion implantation followed by thermal annealing. In this process, high-energy ions are implanted into the semiconductor substrate, causing damage and generating defects. Subsequent thermal annealing induces the formation of multiple pores as the material recrystallizes. This method is particularly effective for materials such as GaAs (gallium arsenide) and ZnO (zinc oxide). For example, ion implantation and subsequent annealing of GaAs can produce nanoporous structures that significantly improve the optical properties of the material.

[0061] Metal-assisted chemical etching (MACE), as shown in Figure 11, is a technique that uses a metal catalyst to carry out the etching process and promote the formation of porous structures. In this method, a thin layer of metal, such as silver or gold, is deposited on the semiconductor surface. When the metal is exposed to an etching solution, such as a mixture of hydrofluoric acid and hydrogen peroxide, it undergoes an etching reaction, leading to the formation of a porous structure. This method is particularly effective for forming high aspect ratio pores in materials such as silicon.

[0062] Porousing GaN (gallium nitride) involves several specific steps to form a desired porous structure, which can significantly improve its optical and piezoelectric properties. GaN may be doped or undoped, and the choice affects the porosification process and the properties of the resulting material. Doped GaN is introduced with specific impurities, which alter its electrical and optical properties. For example, n-type doping can be obtained using silicon (Si) or germanium (Ge). In n-type doping, a typical doping concentration is 10⁻¹⁰. 18 from 10 19 cm -3 It is within the range up to that point.

[0063] Electrochemical etching of GaN involves cleaning and preparing the GaN layer, whether doped or undoped, to deposit metal contacts (usually gold or platinum) on the surface to enable electrical connection. The prepared GaN sample is immersed in an electrolyte solution (usually a mixture of hydrofluoric acid, ethanol, potassium hydroxide, etc.). An electric current is applied between the GaN in the electrolyte solution and a counter electrode. The current density and voltage are carefully controlled to obtain the desired porosity. Typically, higher current densities result in larger pores, but this porosity level ranges from 10% to 75%. Ion implantation and subsequent thermal annealing of GaN involves implanting high-energy ions, such as argon or nitrogen, into the GaN substrate. This process creates defects and damage in the crystal structure. The implanted GaN is then exposed to high temperatures in a controlled environment, typically in a nitrogen or argon atmosphere, ranging from about 800°C to 1000°C. This step allows the material to recrystallize and form nanopores.

[0064] For example, highly efficient surface acoustic wave (SAW) apparatus can be created using porous GaN or GaAs. By introducing multiple pores, the refractive index of GaN or GaAs can be dynamically modulated. For instance, with porous GaN, a refractive index contrast between 0.1 and 0.95 can be achieved as the porosity increases from 10% to 75%. Even a 1% change in porosity can result in a refractive index contrast of 0.01, which is significant in applications requiring precise control of optical properties.

[0065] Figure 4(a) illustrates surface wave (SAW) on the piezoelectric layer 401. Since the wavy portion has a common reference point at both maximum and minimum amplitude, no net change occurs on the surface. This wave amplitude varies according to the different crystal orientations of the piezoelectric material used. Figure 4(b) illustrates a single void / pore 402 affected by an elastic wave. Because the void shape is random, various crystal orientations are combined on its inner surface. As a result, some directions are favorable for increasing amplitude, while others are not, leading to a net volume change within a single pore. When this phenomenon is amplified in several pores / voids within the layer, the layer as a whole exhibits refractive index contrast when an elastic wave is applied. The elastic wave has an amplitude of several picometers, and the pore has an inner diameter of approximately 5 nm to 15 nm. Therefore, an amplitude of 250 pm from a void of only 10 nm induces porosity of up to approximately 15%. Even a 1% change induces a refractive index contrast of 0.01, which is virtually impossible to achieve with elastic waves introduced into a bulk piezoelectric layer. Bulk piezoelectric layers typically exhibit refractive index contrast changes from 0.0001 to 0.0003. Therefore, the present invention, which introduces elastic waves into a pore-containing piezoelectric layer, can advance many applications in the field of optics. One of these is the field of laser fusion (or laser bonding), where a high-energy laser beam needs to be extracted from a cavity. By changing the refractive index by a second order higher than conventional methods, it can be used in many applications in the field of electro-optical devices.

[0066] Hereinafter, with reference to Figures 9 and 14, an embodiment of the present invention will be described as a method for sandwiching a piezoelectric layer containing pores / voids. This method involves integrating a porous piezoelectric layer between two distributed Bragg reflector (DBR) laminates to form a highly efficient optical and acoustic modulation system.

[0067] As shown in Figure 9, a thin porous piezoelectric layer of a quarter wavelength or a thick piezoelectric crystal layer containing pores / voids of a half wavelength is sandwiched between two DBR laminates. The DBR laminate can consist of alternating layers of dielectric materials or semiconductor alloys. The piezoelectric crystal layer can be patterned using a thin doping layer of each piezoelectric material or by depositing a thin transparent conductive oxide (TCO) material, and then patterned within the fingers of an interdigital transducer (IDT) before mounting the first laminate of DBR mirror layers. Typically, metals such as gold or platinum are used to uniformly spread the RF field. However, when metals are used, laser energy is absorbed. For this reason, only the outer region of the fingers is made of metal so that the incident laser does not interact with the metal portion of the modified DBR mirror system.

[0068] Here, the preparation of a nanoporous sandwich between two DBR laminates is described in detail. In the first embodiment, a sapphire substrate is used, on which a buffer GaN layer and an etching stop layer (such as AlN) are deposited, followed by the deposition of a highly doped GaN layer and a moderately doped GaN layer. The combined thickness of the doped GaN layer and the etching stop layer is adjusted to either half a wavelength or a quarter wavelength of the desired reflection spectrum of the DBR laminate. The porosization process begins with the formation of a finger layout etched by photolithography on the piezoelectric material. These fingers can also function as a contact layer during the porosization process. The GaN layer, including the substrate, is embedded in a chemical solution to form an electrical circuit between the chemical used and the finger layout. After creating multiple pores within the highly doped GaN layer, the first DBR laminate is deposited. The sapphire substrate is then removed using laser lift-off technology. Then, after a series of chemical and / or reactive ion etching treatments, another laminate of DBR mirrors is attached to expose the etching stop layer.

[0069] In another example, a porous GaN layer is grown on a SiC substrate, subjected to a porosity treatment, and then a first set of DBR laminates is deposited. The SiC substrate is removed chemically or mechanically. Next, a second set of DBR laminates is deposited to obtain a DBR cavity or DBR mirror system containing a porous piezoelectric layer. This method can effectively create high-performance optical and acoustic modulation systems by leveraging the desired properties of the nanoporous piezoelectric material and the reflection efficiency of the DBR mirror. Integrating a nanoporous piezoelectric layer between two DBR laminates provides significant advantages when modulating light and elastic waves. The porosity of the piezoelectric layer allows for dynamic changes in its refractive index, increasing the tunability of the DBR system. This dynamic modulation is desirable in applications requiring precise control of optical properties, such as laser fusion, where it is necessary to efficiently extract a high-energy laser beam from the cavity. By integrating the porous piezoelectric layer, the system can achieve higher efficiency and better performance compared to conventional bulk piezoelectric layers that exhibit limited refractive index contrast changes.

[0070] Referring to Figure 8 of the present invention, another example illustrates the shift in the reflectance spectrum of a DBR system by changing the refractive index of a piezoelectric layer containing pores / voids using elastic waves. Figure 8(a) illustrates a DBR mirror system in which pairs of DBR layers are semiconductor layers, and at least one layer contains voids / pores. The sides of the DBR laminate are exposed by etching, and electrical connections are established at the edges. Applying elastic waves can shift the reflectance spectrum of the DBR mirror system. Elastic waves induce a refractive index contrast of at least 0.001, which is sufficient to shift the reflectance spectrum of the DBR system. As a result, wavelengths with reflectances of approximately 99.999% or 99.9999%, initially at the edges of the spectral stopband, can be reduced to less than 1%, thereby making those wavelengths transparent to the DBR system.

[0071] Similarly, Figure 8(b) shows a DBR mirror system, in which one layer of each DBR pair is a piezoelectric layer containing pores / voids. Each layer can be treated with separate pairs of electrodes to transmit elastic waves through it. As described above, when elastic waves induce refractive index contrast, wavelengths at the edges of the stopband of the DBR mirror system can become transparent.

[0072] Figure 8(c) shows a DBR mirror system, in which at least one of the DBR laminates may be dielectric, or both may be dielectric material systems. However, the thickness of the piezoelectric layer containing the central pores / voids is adjusted to match one of the DBR pairs in the system. The electrical pads formed during the IDT layout allow the wavelength of highest reflectivity to shift when elastic waves are applied, reducing it to low reflectivity and making it transparent. Figure 8(d) shows schematic diagrams of the reflectance spectra with and without elastic waves applied.

[0073] Referring to Figures 13, 14, and 15 of the present invention, another example is shown in which the reflection spectrum of the DBR system is shifted by changing the refractive index of a piezoelectric layer containing pores / voids using elastic waves. Figure 14(a) shows a cross-section of a DBR mirror cavity system in which a single piezoelectric cavity layer containing pores / voids is adjusted to a thickness of half the wavelength of the center frequency of the reflection spectrum of the DBR cavity system. The refractive index of the cavity layer can be controlled by adjusting the porosity of the cavity layer. An IDT layout structure is formed on the cavity layer for the injection of elastic waves. Figure 14(b) shows details of the IDT layout structure on the cavity layer. This DBR cavity system structure exhibits a dip in the reflection spectrum. The wavelength of this dip can be shifted by changing the refractive index of the cavity layer through the application of elastic waves.

[0074] Figure 15 shows the simulation results of a DBR cavity system, in which two DBR stacks of Ta2O5 / SiO2 are formed on both sides of the DBR cavity layer. The DBR cavity layer is a piezoelectric layer containing pores / voids. Figure 15(b) shows the reflectance spectrum of the DBR cavity system, and a dip in the reflectance spectrum can be observed. This dip can be manipulated by changing the refractive index of the cavity layer within a range of plus or minus 0.02 (±0.02). An enlarged view of the dip manipulation in the reflectance spectrum is shown, and it is shown that dip wavelengths with lower reflectance can be transparent in this system. As shown in Figure 15(c), the OEC laser introduced from the back surface of the first high-reflection mirror is amplified 100,000 times after 100,000 back-and-forth reflections by the two high-reflection DBR mirrors in the OEC. In this case, the peak wavelength of the 1037 nm laser beam is located in the high-reflection region 5 nm away from the reflection dip at 1042 nm where Δnp=0 of the second high-reflection DBR mirror. Next, as shown in Figure 15(c), when the elastic wave is turned on, the reflection dip at 1042 nm where Δnp=0 shifts to the wavelength position at 1037 nm where Δnp=-0.013 of the laser's peak wavelength, and the reflectivity of the laser changes from 99.999% to 10%. Thus, the 100,000-fold amplified laser beam passes through a portion of the second mirror and is effectively extracted through the second high-reflection mirror with a loss of less than 10%. When the length of the OEC cavity is 150m, the round-trip time of the laser beam in the OEC is 1 microsecond. Therefore, the response time of the cavity damper, which changes the reflectivity of the DBR mirror containing a piezoelectric material with voids or pores by applying an elastic wave or electric field, must be faster than 1 microsecond. When the length of the OEC cavity is 15m, the response time of the cavity damper must be faster than 0.1 microseconds. As the cavity length decreases, the response time of the cavity damper should become even faster.

[0075] Referring to Figure 16, (a) and (b) respectively illustrate the application of electric fields to two types of distributed Bragg reflectors (DBRs). The layer containing pores or voids is a piezoelectric material having an effective refractive index np. This layer is configured to have a wavelength of one-quarter or half of the center wavelength of the DBR, which is equal to the laser wavelength.

[0076] In a quarter-wavelength configuration, electrical contacts are positioned on a piezoelectric layer containing pores. When an electric field is applied, the volume of the pores changes, which in turn changes the refractive index of the layer. This change in refractive index creates a contrast that affects the DBR spectrum, causing fluctuations in the reflectance spectrum.

[0077] In a half-wavelength configuration, also known as a DBR cavity configuration, the central resonance peak of the spectrum shows a dip, indicating a decrease or zero reflectance at the central wavelength. This configuration is particularly sensitive to changes in the electric field, allowing the position of the dip in the spectrum to be shifted. By applying an electric field to the pore-filled layer at the central half-wavelength, the system can dynamically change the central wavelength of the reflectance, thereby providing a tunable optical response.

[0078] The aforementioned adjustability is beneficial in applications requiring precise control of light reflection and transmission characteristics, such as optical filters, sensors, communication devices, and laser energy extraction for nuclear fusion experiments. The ability to modulate the refractive index and the resulting spectral characteristics with an electric field provides remarkable flexibility in the design and operation of optical components.

[0079] Referring to Figure 17, an example of a porous layer included in the present invention is shown, in which the piezoelectric semiconductor layer contains three different types of pores.

[0080] Type 1) Three-dimensionally distributed pores or voids, due to their random and wide distribution, provide desirable interactions with light and elastic waves, making them suitable for dynamic modulation of optical properties.

[0081] Type 2) Pores or voids embedded in the piezoelectric semiconductor layer facilitate modulation of the refractive index, making it possible to achieve desired reflectivity variations. These pores affect the mechanical strength, thermal conductivity, electrical properties, and optical properties of the material.

[0082] Type 3) Pores or voids are formed throughout the entire layer using a mask by wet etching or dry etching, creating small, uniform openings or gaps that significantly affect the material properties. Openings of random or uniform size can be precisely controlled to improve the performance of Variable Reflectance Distributed Bragg Reflectors (VR-DBRs). The figure shows random void sizes. A mask is used for etching, and in one example, uniform void sizes can be created.

[0083] These three types of pores or voids can be realized by various etching techniques. Selective physical etching involves selectively removing material using physical processes such as ion milling or laser ablation to form pores. Selective chemical etching uses a chemical etchant (or etching solution) to selectively dissolve a portion of the material, and by adjusting parameters such as concentration, temperature, and exposure time, pores of precise size and distribution are formed. In electrochemical etching, an electric current is applied to a semiconductor immersed in an electrolyte solution, causing the material to dissolve and pores to form. In this method, the degree of porosity can be finely controlled by adjusting the current density and voltage.

[0084] One technique for creating pores or cavities involves distributing silicon nanopowder with particle sizes ranging from 5 nm to 20 nm on a piezoelectric semiconductor layer and subjecting it to selective reactive ion etching to form cavities, gaps, or pores within the layer. This process can be uniform and scaled to larger sizes. The distribution of nanopowder on the semiconductor layer can be carried out by spin coating for uniform diffusion. The process of creating porosity in semiconductors involves several advanced techniques. One common method is electrochemical etching, which uses electric current to dissolve a portion of the semiconductor material to form pores. In this method, the size and distribution of pores can be precisely controlled by adjusting etching parameters such as voltage, current density, and etching time. Another technique involves the use of ion implantation followed by thermal annealing, in which ions are implanted into the semiconductor substrate to cause damage, and subsequent annealing helps in pore formation. Furthermore, metal-assisted chemical etching (MACE) is used, in which a metal catalyst accelerates the etching process, resulting in the formation of a porous structure.

[0085] The constructed porous layer can also function as a photonic crystal. In the photonic crystal, a photonic band gap is introduced, which can be dynamically adjusted by applying an electric field or elastic wave. In the above structure, the effective transmission or reflection spectrum of the photonic crystal can be modulated, making it possible to precisely control the optical properties of the VR-DBR system. This feature is important in applications requiring highly efficient optical manipulation, such as laser fusion, optical filtering, and advanced sensor technologies. The present invention aims to create a highly tunable and efficient optical device by utilizing the desirable properties of nanoporous semiconductors and combining them with elastic waves or electric fields.

[0086] In one example, the present invention provides a laser system. The laser system includes a laser source (e.g., CBC) which is coupled to a first mirror apparatus facing a second mirror apparatus and configured to generate a resonant laser beam between the first mirror and the second mirror. In one example, the system includes a piezoelectric device (or piezoelectric apparatus) provided in the second mirror apparatus, which is characterized by its refractive index. In this case, energy is applied to the piezoelectric device to change one or more gaps, causing a change in the refractive index value, for example, to a value greater than 0.0001, allowing a resonant laser beam or portion of the resonant laser to pass through a portion of the second mirror apparatus.

[0087] In one example, energy is supplied using elastic waves or an electric field. In one example, this energy induces a larger change in refractive index compared to that in a bulk piezoelectric layer without voids. In one example, the voids include one or more pores, aperture regions, or other structures. In one example, the change in value is, for example, greater than 0.01. In one example, the piezoelectric device is configured to extract a laser beam from a cavity between a first mirror and a second mirror. In one example, the cavity is a Fabry-Perot cavity or an optically enhanced cavity (OEC).

[0088] In one example, the present invention provides a variable reflectivity distributed Bragg reflector (VR-DBR) mirror device. The device includes a transparent substrate, which is, for example, optically transparent. In one example, the device has a plurality of laminates made of materials having at least two different refractive indices to form a distributed Bragg reflector (DBR) covering the transparent substrate. In one example, the device includes a piezoelectric layer containing a plurality of voids, composed of one or more laminates, so that the piezoelectric layer is provided on the DBR. In one example, the device has at least one electrical contact coupled to the void-containing piezoelectric layer, the electrical contact being characterized by a conductive material. In one example, the device is configured such that the electrical contact is coupled with electrical energy (e.g., power) to supply an electric field into the void-containing piezoelectric layer, thereby changing the refractive index of the piezoelectric layer and changing the reflection spectrum of the DBR, allowing a laser beam to pass through a portion of the DBR.

[0089] In one example, the DBR has an initial reflectivity of, for example, over 99% at the wavelength of the laser emission of the laser beam, but this is changed to, for example, a reflectivity of 30% or less. In one example, electrical energy is applied on and off at a repetition rate of, for example, 0.1 Hz to 10 Hz. In one example, the device is configured to have an optically enhanced cavity characterized by a laser peak wavelength in the range of 1020 nm to 1070 nm. In one example, the laser beam passing through the DBR constitutes laser nuclear fusion, which includes laser-induced magnetized inertial fusion (MagLIF). In one example, the device is configured to form a Fabry-Perot cavity.

[0090] In one example, multiple voids are formed by one or more arbitrary shapes and one or more volume contractions, accompanied by heterogeneous modulation generated within these voids. In one example, these voids are pores. In one example, electrical contacts (electrical connections) are configured for side injection or cross coupling. In one example, the reflectance spectrum of the DBR is tuned by shifting the wavelength of the laser emission, for example from 2 nm to 20 nm, thereby shifting the reflectance spectrum near the edge of the reflection stopband from a high reflectance of over 99% to a low reflectance of, for example, less than 30%. In one example, the piezoelectric layer includes multiple interdigital transducers (IDTs), which are formed on the piezoelectric layer, and each of the multiple IDTs is characterized by multiple comb-like structures containing conductive material, which are coupled to an RF signal to generate one or more elastic waves. In one example, the electrical contacts of the multiple IDTs are formed on doped piezoelectric material or on a transparent conductive oxide (TCO) material deposited on the piezoelectric layer. In one embodiment, the laminate includes a dielectric selected from the group consisting of silicon dioxide (SiO2), titanium dioxide (TiO2), tantalum oxide (Ta2O5), and hafnium oxide (HfO2). In one example, the laminate includes gallium arsenide (GaAs) and an alloy of gallium, aluminum, and arsenic (Al x Ga 1-x The semiconductor material is selected from the group consisting of (As)(1≧x>0). In one example, the multilayer is gallium arsenide (GaAs) and an alloy of gallium, aluminum, and arsenide (Al x Ga 1-x The material includes a void-containing semiconductor material selected from the group consisting of As)(1≧x>0). In one example, the multilayer includes a void-containing semiconductor material having gallium nitride (GaN). In another example, the DBR is composed of a multilayer pair of dielectric materials or semiconductor layers.

[0091] In one example, the piezoelectric layer is a single piezoelectric layer containing multiple voids sandwiched between a pair of DBRs. In another example, the piezoelectric layer is characterized by the thickness of a single piezoelectric layer, where the thickness is between a quarter wavelength (λ / 4n) and a half wavelength (λ / 2n), where λ is the laser emission peak wavelength and n is the refractive index of the piezoelectric layer. In yet another example, the piezoelectric layer is one of multiple layers of a pair of DBRs having a quarter wavelength thickness (λ / 4n), where λ is the laser emission peak wavelength and n is the refractive index of the piezoelectric layer. In yet another example, the multiple voids within the piezoelectric layer are characterized by one or more arbitrary shapes, the inner surface of which consists of a combination of two or more crystal planes. In yet another example, the voids in the piezoelectric layer reduce the refractive index of one or more bulk piezoelectric materials, thereby causing electrical energy to trigger a response in the voids, for example, inducing a refractive index change between 0.0001 and 0.05. In yet another example, the refractive index change is greater than, for example, 0.0001. For example, the piezoelectric layer is selected from the group consisting of lithium niobate (LiNbO3), lithium tantalate (LiTaO3), quartz (SiO2), zinc oxide (ZnO), aluminum nitride (AlN), gallium arsenide (GaAs), and gallium nitride (GaN).

[0092] In one example, the device features a resonant reflectivity dip (less than 30%) within a high reflectivity region of over 99% at the wavelength of the laser emission. This resonant reflectivity dip is caused by electrical energy that generates one or more elastic waves or electric fields.

[0093] In one example, voids within the piezoelectric layer are formed using electrochemical etching. In another example, the piezoelectric layer is formed by epitaxially growing one or more piezoelectric materials on a substrate selected from, for example, GaN, sapphire, SiC, and ZnO. In yet another example, voids within the piezoelectric layer are formed using one or more electrochemical etching methods. In this process, an electric current is applied to a semiconductor immersed in an electrolyte solution to dissolve a portion of the semiconductor material and form voids. Ion implantation is followed by thermal annealing. In this process, one or more high-energy ions are implanted into the semiconductor substrate to form damaged regions, which then trigger void formation through subsequent annealing, and then metal-assisted chemical etching (MACE) is performed. In this process, a metal catalyst accelerates the etching process and triggers the formation of one or more voids.

[0094] In one example, the wavelength of the electric field or elastic wave is approximately equal to (λ / n) the peak wavelength of the laser emission, where λ is the peak wavelength of the laser emission and n is the refractive index of the piezoelectric layer. In another example, the frequency of the electric field or elastic wave is, for example, between 1 MHz and 100 GHz.

[0095] In this invention, the terms “pore” and / or “void” are used as illustrative examples. These terms are intended to be interpreted in their usual sense, and they may be used in one or more descriptions relating to one or more examples. [Prior art documents] [Non-patent literature]

[0096] [Non-Patent Document 1] Towards Ultimate High-Power Scaling: Coherent Beam Combining of Fiber Lasers, Photonics, 8(21), 566 (2021) [Non-Patent Document 2] High-quality electron beams from a laser wakefield accelerator using plasma-channel guiding, Nature 431, 538 (2004). [Non-Patent Document 3] The X-ray emission effectiveness of plasma mirrors: Reexamining power-law scaling for relative high-order harmonic generation, Sci. Rep. 10, 5154 (2020). [Non-Patent Document 4] Investigation and optimization of N-polar porosification for regrowth of smooth, hillocks-free GaN films, Appl. Phys. Lett, 119, 042105 (2021) [Non-Patent Document 5] Nanoporous SiO2 thin films made by atomic layer deposition and atomic etching, Nanotechnology, 27, 255603, (2016).

[0097] In one embodiment, further details of an optically enhanced cavity using a Fabry-Perot cavity can be found in U.S. Patent Application No. 18 / 319,368, “Fast Ignition Fusion System and Method,” filed May 17, 2023, by Shuji Nakamura and Hiroaki Ohta, which is incorporated herein by reference in its entirety.

[0098] While specific examples have been adequately described above, various modifications, substitutions, and equivalents are applicable. In one example, the system, method, and apparatus may include any combination of the components described above, as well as components not described herein. In one example, a high-intensity laser uses the structural interference of each laser beam to form a resonator between a pair of mirror devices. In one example, the first path of the high-intensity pulsed laser is located within the resonator device. In one example, the present invention provides a system and method for generating a concentric or spherical resonator within a reaction region so as to focus the laser beam to the center of the reactor. Furthermore, the terms first, second, third, and last do not imply an order in one or more embodiments. Accordingly, the above description and illustrations should not be taken as limiting the scope of the present invention as defined by the appended claims.

Claims

1. A laser system comprising a laser source and a piezoelectric device, The laser source is coupled to a first mirror device facing a second mirror device and is configured to generate a resonant laser beam between the first mirror and the second mirror. The piezoelectric device is provided in the second mirror device and is characterized by its refractive index, wherein applying energy to the piezoelectric device changes one or more air gaps, causing a change in the refractive index value, thereby allowing a portion of the resonant laser beam to pass through a portion of the second mirror device. Laser system.

2. The system according to claim 1, wherein the energy is provided using elastic waves or an electric field, and the piezoelectric device is configured such that the change in the refractive index value is greater than 0.0001.

3. The system according to claim 1, wherein the void comprises one or more pores, and the laser source generates a continuous-wave laser beam or a pulsed laser beam.

4. The system according to claim 1, wherein the change in the aforementioned value is greater than 0.

01.

5. The system according to claim 1, wherein the piezoelectric device is configured to extract a laser beam from the cavity between the first mirror and the second mirror.

6. The system according to claim 1, wherein the cavity is a Fabry-Perot cavity or an optically enhanced cavity (OEC).

7. A variable reflectance distributed Bragg reflector (VR-DBR) mirror device, Transparent substrate and A plurality of laminates made of materials having at least two different refractive indices, forming a distributed Bragg reflector (DBR) that covers the transparent substrate, A piezoelectric layer containing multiple voids, wherein the piezoelectric layer is composed of one or more laminates such that it is formed in the DBR, The piezoelectric layer is coupled to at least one electrical contact portion characterized by a conductive material, A device is configured to be coupled to the electrical contact portion and to supply an electric field into the piezoelectric layer including the air gap, thereby changing the refractive index of the piezoelectric layer and altering the reflection spectrum of the DBR, thereby enabling the laser beam to pass through a portion of the DBR, and to provide electrical energy. A device equipped with the following features.

8. The apparatus according to claim 7, wherein, at the wavelength of the laser emission of the laser beam, the DBR has an initial reflectance of more than 99%, which can be changed to a reflectance of 30% or less.

9. The apparatus according to claim 7, wherein the electrical energy is applied to the device in an on / off state with a repetition rate from 0.1 Hz to 10 Hz.

10. The apparatus is configured using an optical enhancement cavity, or The laser beam passing through the DBR constitutes laser fusion, including laser-induced magnetized inertial fusion (MagLIF). The apparatus according to claim 7.

11. The apparatus according to claim 7, wherein the apparatus is configured to form a Fabry-Perot cavity.

12. The void is formed by one or more arbitrary shapes and one or more volume contractions accompanied by non-uniform modulation generated within the void, or The apparatus according to claim 7, wherein the void is a pore.

13. The apparatus according to claim 7, wherein the DBR has a reflectance spectrum, and by shifting the wavelength of the laser emission from 2 nm to 20 nm, the reflectance spectrum near the edge of the reflection stop band is shifted from a high reflectance of over 99% to a low reflectance of less than 30%.

14. The apparatus according to claim 7, wherein the piezoelectric layer comprises a plurality of interdigital transducers (IDTs) formed on the piezoelectric layer, each of the plurality of IDTs being characterized by a plurality of comb-like structures containing a conductive material, and coupled with an RF signal to generate one or more elastic waves.

15. The aforementioned laminate is made of silicon dioxide (SiO ２ ), titanium dioxide (TiO ２ ), tantalum oxide (Ta ２ O ５ ), and hafnium oxide (HfO ２ Includes a dielectric material selected from the group consisting of ) Or, The aforementioned layer is made of gallium arsenide (GaAs), and an alloy of gallium, aluminum, and arsenide (Al ｘ Ga １－ｘ A semiconductor material selected from the group consisting of As (1 ≥ x > 0), or gallium nitride, The apparatus according to claim 7.

16. The apparatus according to claim 7, wherein the DBR is composed of a multilayer pair of dielectric materials or semiconductor layers.

17. The apparatus according to claim 7, wherein the piezoelectric layer is a single piezoelectric layer containing voids and is sandwiched between a pair of DBRs.

18. The apparatus according to claim 7, wherein the piezoelectric layer is characterized by the thickness of a single piezoelectric layer, the thickness being between a quarter wavelength (λ / 4n) and a half wavelength (λ / 2n), where λ is the laser emission peak wavelength and n is the refractive index of the piezoelectric layer.

19. The apparatus according to claim 7, wherein the piezoelectric layer is one of a plurality of layers of DBR pairs having a quarter-wavelength thickness (λ / 4n), where λ is the laser emission peak wavelength and n is the refractive index of the piezoelectric layer.

20. The apparatus according to claim 7, wherein the voids in the piezoelectric layer are characterized by one or more arbitrary shapes, and their inner surfaces are a combination of two or more crystal planes.

21. The apparatus according to claim 7, wherein the gaps in the piezoelectric layer reduce the refractive index of one or more bulk piezoelectric materials, thereby causing the electrical energy to trigger a response in the gaps and induce a change in refractive index between 0.0001 and 0.

05.

22. The piezoelectric layer is lithium niobate (LiNbO ３ ), lithium tantalate (LiTaO ３ ), quartz (SiO ２ ), zinc oxide (ZnO), aluminum nitride (AlN), gallium arsenide (GaAs), and gallium nitride (GaN), and the device according to claim 7, which is selected from the group consisting of

23. The apparatus according to claim 7, wherein the wavelength of the electric field or elastic wave is approximately equal to (λ / n) of the laser emission peak wavelength, where λ is the laser emission peak wavelength and n is the refractive index of the piezoelectric layer.

24. The apparatus according to claim 7, wherein the frequency of the electric field or elastic wave is between 1 MHz and 100 GHz.

25. A variable reflectance distributed Bragg reflector (VR-DBR) mirror device, circuit board and A plurality of first laminates made of materials having at least two different refractive indices for forming a first distributed Bragg reflector (DBR1) covering the transparent substrate, A plurality of second laminates made of materials having at least two different refractive indices for forming a second distributed Bragg reflector (DBR2), A piezoelectric layer containing a plurality of voids is formed between the first distributed Bragg reflector and the second distributed Bragg reflector, The piezoelectric layer is coupled to at least one electrical contact portion characterized by a conductive material, The electrical energy coupled to the electrical contact portion, wherein an electric field is supplied into the piezoelectric layer containing the air gap, thereby changing the refractive index of the piezoelectric layer and altering the reflection spectrum of the VR-DBR mirror device, allowing the laser beam to pass through a portion of the VR-DBR mirror device. A device equipped with the following features.

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