阅读说明：本技术 用于环形激光陀螺仪的增强型固态增益介质 (Enhanced solid-state gain medium for ring laser gyroscope ) 是由 艾伦·布鲁斯·塔弛贝里 吴剑峰 兰斯·维里泽 于 2019-07-18 设计创作，主要内容包括：本公开一般涉及用于环形激光陀螺仪的增强型固态增益介质。本发明公开了多层镜、环形激光陀螺仪和方法。例如,多层镜包括多个交替的高折射率光学材料层和低折射率光学材料层,设置在多个交替层上的光学材料的放大层,以及设置在光学材料放大层的最外表面上的抗反射材料涂层。(The present disclosure relates generally to an enhanced solid-state gain medium for a ring laser gyroscope. The invention discloses a multilayer mirror, a ring laser gyroscope and a method. For example, a multilayer mirror includes a plurality of alternating layers of high and low refractive index optical materials, a magnifying layer of optical material disposed on the plurality of alternating layers, and a coating of antireflective material disposed on an outermost surface of the magnifying layer of optical material.)

1. A method, comprising:

forming a plurality of first refractive index optical material layers on a substrate;

forming a plurality of second refractive index optical material layers between the first refractive index optical material layers;

forming an optical amplifying material layer on an outermost layer of the plurality of first refractive index optical material layers; and

forming a coating of an antireflective material on a surface of the layer of optically amplifying material.

2. The method of claim 1, wherein the forming the coating comprises forming a magnesium fluoride coating.

3. A ring laser gyroscope, comprising:

a laser block assembly;

a cavity in the laser block assembly; and

a plurality of multilayer mirrors in the cavity, wherein at least one multilayer mirror of the plurality of multilayer mirrors comprises:

a plurality of alternating layers of high and low index optical materials;

a magnifying layer of optical material disposed on the plurality of alternating layers; and

a coating of an antireflective material disposed on an outermost surface of the optical material amplification layer.

Background

Ring Laser Gyroscopes (RLGs) have been utilized for decades in the field of inertial navigation to measure angular motion or rotation. The concept of measuring angular motion using a ring laser was first published in 1963. Ring lasers utilize a low pressure he-ne gas discharge as the active gain medium and RLGs driven by the he-ne gas discharge gain medium have been utilized since then. However, while existing helium-neon gas discharge RLGs have performed adequately in the field of inertial navigation and other measurements, these helium-neon gas discharge RLGs have significant life, reliability, performance, and size limitations associated with the gas discharge itself. Moreover, helium-neon gas discharge RLGs are expensive to manufacture.

RLGs are known that utilize a solid state gain medium in place of the helium-neon gas mixture. From a manufacturing perspective, such a solid state gain medium RLG may provide significant savings over a helium-neon gas discharge RLG in terms of reduced size, labor, and manufacturing costs. Moreover, such a solid state gain medium RLG may provide significant technical advantages over a helium-neon gas discharge RLG in terms of increased reliability and lifetime.

Neodymium-doped silica (Nd-doped SiO)₂) The layers produce the cavity gain of the solid-state RLG. The Nd-doped silicon dioxide layer is deposited on the top layer of the highly reflective multilayer dielectric mirror in the RLG cavity. However, one significant problem exists in that the refractive index of the neodymium-doped silicon dioxide layer does not match the refractive index of air or vacuum (e.g., in the cavity). As a result, a large portion of the pump light (e.g., laser diode, flash lamp, LED) and the laser signal are lost due to reflection. For example, if the pump light source is a laser, this increase in cavity loss not only increases the laser threshold, but also increases the fundamental laser noise (Schawlow-Townes linewidth).

Accordingly, there is a need for a technique that can be used to reduce the amount of lost photoexcitation energy, and thereby enhance the performance of solid-state RLGs.

Disclosure of Invention

Embodiments disclosed herein propose techniques for enhancing the durability and manufacturability of multilayer interference mirrors used as laser mirrors in RLG devices.

Drawings

Embodiments of the present disclosure may be more readily understood, and further advantages and uses thereof more readily apparent, when considered in view of the description of the preferred embodiments and the following drawings, in which:

FIG. 1 is a simplified block diagram illustrating a multilayer mirror that may be used to implement an exemplary embodiment of the present invention.

Figure 2 is a simplified block diagram illustrating an enhanced gain mirror that may be used to implement an exemplary embodiment of the present invention.

FIG. 3 is a simplified block diagram illustrating an enhanced Ring Laser Gyroscope (RLG) that may be used to implement an exemplary embodiment of the present invention.

FIG. 4 is a flow chart illustrating a method that may be used to implement an exemplary embodiment of the present invention.

In accordance with common practice, the various features described are not necessarily drawn to scale, emphasis instead being placed upon features relevant to the present disclosure. Reference characters denote like elements throughout the figures and text.

Detailed Description

In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific illustrative embodiments in which the embodiments may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, and electrical changes may be made without departing from the scope of the present disclosure. The following detailed description is, therefore, not to be taken in a limiting sense.

FIG. 1 is a simplified block diagram illustrating an enhanced multilayer mirror 100 that may be used to implement an exemplary embodiment of the present invention. For example, in one embodiment, the multilayer mirror 100 is an interference mirror for a plurality of interference mirrors of an RLG (such as, for example, a solid state gain medium RLG). More specifically, multilayer mirror 100 is a highly reflective mirror stack that includes, for example, an outer layer of a first (e.g., dielectric) material that creates a gain medium for the solid-state RLG, and a top coating of a second (e.g., antireflective) material deposited on the outer layer material to enhance the transmittance of light energy into the outer layer and thereby enhance the emission efficiency of the ring laser of the solid-state RLG.

Referring to the exemplary embodiment shown in FIG. 1, the multilayer mirror 100 includes a plurality of alternating (e.g., staggered) high refractive index (e.g., titanium oxide or TiO) layers formed on a suitable substrate 110₂) Layers 102a-102d and a low refractive index (e.g., silicon oxide or SiO)₂) Layers 104a-104 c. For example, inIn one embodiment, the TiO₂Layers 102a-102d and SiO₂The layers 104a-104c are optical quarter wave (e.g., nominal or substantially quarter wave) structures that are formed using, for example, a suitable sputter deposition process (e.g., an electron beam or ion beam deposition process). It is noted that although a limited number of TiO are shown for this exemplary embodiment₂And SiO₂Layers, but this particular number of layers is for illustrative purposes only, and up to several alternating TiO's may be deposited₂Layer and SiO₂Layers to form the multilayer mirror 100. For example, other suitable high index material layers may also be utilized and coupled with SiO in the multilayer mirror 100₂Layers interleaved, such as zirconia (TiO)₂) Tantalum (Ta)₂O₅) Hafnium (HfO)₂) Or niobium (Nb)₂O₅)。

The enhanced multilayer mirror 100 further includes a layer of material deposited on the TiO₂An outermost (e.g., gain medium) layer 106 on layer 102 a. In one embodiment, the outermost layer 106 is neodymium-doped silicon dioxide (Nd-doped SiO)₂) And (3) a layer. For example, the Nd-doped silicon dioxide layer 106 may be a few half wavelengths (e.g., 2-5 wavelengths) thick. In any case, for this exemplary embodiment, the Nd-doped silicon dioxide layer 106 deposited on top of the multilayer mirror 100 creates a gain mirror that provides optical amplification for the solid state ring laser involved. Notably, because the gain medium is composed of a solid material rather than a helium-neon gas mixture, a conventional post-fabrication plasma scrubbing process, which typically damages the coating material in the helium-neon RLG (e.g., known as etch degradation), is not utilized.

For this exemplary embodiment, multilayer mirror 100 also includes an antireflective coating 108 on the outermost surface of gain medium layer 106. The anti-reflective top coat 108 may be formed by depositing (e.g., sputtering) a layer of material having a suitably low surface reflectivity (e.g., 0.1% to 0.2%). For this embodiment, magnesium fluoride (MgF) is utilized₂) The layer is for an anti-reflective coating 108. In the second embodiment, the anti-reflection may be formed using any suitable material having a low surface reflectance of, for example, 0.1% or lessThe coating 108 is sprayed. For example, in some embodiments, the anti-reflective coating 108 may be formed using a suitable fluoropolymer material. As another example, the antireflective coating 108 can be formed using a suitable material composed of mesoporous silica nanoparticles. Thus, the anti-reflective coating 108 disposed on the gain medium layer 106 functions to increase the number of photons emitted by the Nd-doped silica (circulating within the ring laser cavity), which can re-enter the gain medium layer 106 and thereby stimulate the emission of additional photons. Thus, the emission efficiency, gain, and overall performance of the ring lasers described above are substantially increased (e.g., gain is increased by several percent) compared to those of existing ring lasers.

Fig. 2 is a simplified block diagram illustrating an enhanced gain mirror 200 that may be used to implement an exemplary embodiment of the present invention. For example, in one embodiment, gain mirror 200 is an interference mirror for multiple interference mirrors of an RLG (e.g., a solid state gain medium RLG). Notably, for this exemplary embodiment, the gain mirror 200 is substantially identical in structure and function to the multilayer mirror 100 shown and described above with reference to FIG. 1.

Referring to FIG. 2, the gain mirror 200 includes a plurality of alternating layers 202a-202d of high index material and layers 204a-204c of low index material. A gain medium (e.g., Nd-doped silicon dioxide) layer 206 is located on the outermost (e.g., high index of refraction) layer 202a, and an antireflective material (e.g., MgF)₂) Layer 208 is located on gain medium layer 206. The alternating layers 202a-204c are formed on a (e.g., highly polished) substrate 210. For this exemplary embodiment, each of the interleaved layers 202a-204c is substantially 1/4 optical wavelengths thick, and the gain medium layer 206 (e.g., Nd-doped silicon dioxide) is an integer of substantially 1/2 optical wavelengths thick. A pump light source (e.g., laser diode, flash lamp, LED)214 transmits pump light 216 to the gain medium layer 206 via a suitable focusing optics assembly 212. It is noted that for this exemplary embodiment, although the pump light source 214 is depicted pumping light from the "back" (e.g., substrate) side of the gain mirror 200, in a second exemplary embodiment, the pump light source 214 (e.g., and optics assembly 212) may be located at the left of FIG. 2Side to pump light from the opposite or "front" side of the gain mirror 200. Notably, the anti-reflective coating 208 functions to increase the number of photons emitted by Nd doped silicon dioxide that can re-enter the gain medium layer 206 (e.g., photons circulating within the ring laser cavity and shown by arrowed lines CW and CCW) and thereby stimulate the emission of additional photons in accordance with the above teachings of the present disclosure.

Fig. 3 is a simplified block diagram illustrating an enhanced RLG300 that may be used to implement an exemplary embodiment of the present invention. For this exemplary embodiment, RLG300 is a solid state gain medium RLG. Referring to fig. 3, an exemplary RLG300 includes three highly reflective multi-layer dielectric mirrors 302a, 302b, 302 c. The mirrors are mounted to a block of polished, stable material 304 and positioned to define closed-loop optical cavities 306a-306c through which the counter-propagating laser beams pass. The beam combining optics and detector 308 measure the difference in frequency of the counter-propagating laser beam, which is proportional to the rotation of the RLG 300. A thin amorphous layer 310 of Nd-doped silicon dioxide is deposited on the mirror 302a, resulting in a gain mirror 302a that provides optical frequency amplification. Notably, in accordance with the above teachings of the present disclosure, an anti-reflective coating 312 (e.g., magnesium fluoride) is deposited on the (e.g., gain medium) layer 310 to increase the number of photons emitted by the Nd-doped silicon dioxide (circulating within the ring laser cavities 306a-306 c), which can re-enter the gain medium layer 310 and thereby stimulate the Nd-doped silicon dioxide to emit additional photons. A pump light source (e.g., a laser diode) 313 and an optical lens assembly 314 provide the optical excitation energy 316 required to produce lasing action in the optical cavities 306a-306 c.

Fig. 4 is a flow chart illustrating a method 400 that may be used to implement an exemplary embodiment of the present invention. With reference to the exemplary embodiment shown in FIG. 1, an exemplary method begins with forming a plurality of first high index optical materials (such as, for example, TiO)₂) Layers 102a-102d, (402), and also forming a plurality of second low index optical materials (such as, for example, SiO) between layers 102a-102d₂) Layers 104a-104c (404). More specifically, as shown in FIG. 1, on a substrate 110 (e.g., using an electron beam or ion beam)Deposition process) depositing the first TiO₂Layer 102 d. Then on the first TiO₂Depositing a first SiO on the exposed surface of layer 102d (e.g., also using an electron beam or ion beam deposition process)₂And a layer 104 c. Next, in the first SiO₂Depositing a second TiO on the exposed surface of layer 104c₂Layer 102c, and then on the second TiO₂Depositing a second SiO on the exposed surface of layer 102c₂Layer 104 b. Next, in the second SiO₂Depositing a third TiO on the exposed surface of layer 104b₂Layer 102b, and then on a third TiO₂Depositing a third SiO on the exposed surface of layer 102b₂Layer 104 a. Then in the third SiO₂Depositing a fourth TiO on the layer 104a₂Layer 102 a. Notably, although the exemplary embodiment shown in FIG. 1 depicts four TiO s₂Layers 102a-102d and three SiO₂Layers 104a-104c, the present disclosure is not intended to impose an upper or lower limit on the number of layers that may be utilized in other embodiments. Moreover, although the exemplary embodiment shown in FIG. 1 depicts TiO for layers 102a-102d and 104a-104c₂And SiO₂Layers, but the present disclosure is not intended to limit the high and low index optical materials to only TiO that may be used in other embodiments₂And SiO₂And (3) a layer.

Returning to method 400, TiO, a high refractive index optical material₂On the exposed surface of the outermost layer 102a (e.g., using an electron beam or ion beam deposition process) is deposited a layer 106(406) of a suitable optical amplifying material (e.g., Nd-doped silicon dioxide in this embodiment). Layer 106 provides a solid-state gain medium for the ring laser and thus for the concerned RLG. Next, an anti-reflective coating 108 (e.g., magnesium fluoride) is deposited 408 on the (e.g., gain medium) layer 110. As described above with reference to fig. 1, in accordance with the above teachings of the present disclosure, the anti-reflective coating 108 increases the number of photons emitted by the Nd-doped silicon dioxide layer 106 (e.g., circulating within the ring laser cavities 306a-306c in fig. 3), which may re-enter the gain medium layer 110 and thereby stimulate the emission of additional photons through the Nd-doped silicon dioxide layer.

It should be understood that the elements of the above-described embodiments and the illustrative figures can be used in various combinations with each other to produce other embodiments that are explicitly intended to be within the scope of the present disclosure.

Exemplary embodiments