US-12627934-B2 - Diamond cantilever-based optical microphones and related systems and methods

US12627934B2US 12627934 B2US12627934 B2US 12627934B2US-12627934-B2

Abstract

This invention unveils an optical microphone utilizing diamond cantilevers and its associated acoustic sensing system. The core component is a diamond cantilever, featuring a diamond diaphragm with a centrally located U-shaped groove. The manufacturing process involves several key steps: initially preparing the diamond diaphragm using silicon in a chemical vapor deposition setup, where methane and hydrogen are reacted under specific temperature and pressure conditions to form a diamond polycrystalline film on the silicon. This film is then separated from the substrate to create the diaphragm. Subsequently, a U-shaped groove is crafted on the diaphragm by applying a dry etching template and etching, resulting in the formation of the diamond cantilever, with a thickness ranging from 10 to 100 μm. This method establishes a novel approach to creating sensitive and durable optical microphones.

Inventors

Chongxin SHAN
Shen Tian
Lei Li
Chaonan LIN
Yingying Qiao
Mingqi JIAO
Mingyang FENG
Mu LIANG

Assignees

ZHENGZHOU UNIVERSITY

Dates

Publication Date: 20260512
Application Date: 20240307
Priority Date: 20230922

Claims (8)

1 . An optical microphone based on a diamond microcantilever, characterized in that it comprises: a diamond microcantilever component, wherein the diamond microcantilever component comprises a diamond diaphragm; a U-shaped groove is provided at a central position of the diamond diaphragm, and a diamond microcantilever is formed by the diamond diaphragm inside the U-shaped groove; and a preparation method of the diamond microcantilever component comprises: S1—preparing a diamond diaphragm using silicon as a silicon substrate, placed in a chemical vapor deposition device; adjusting a heating temperature and a pressure of the chemical vapor deposition device, and introducing a certain amount of methane and hydrogen for chemical vapor deposition reaction to obtain a diamond polycrystalline film on the silicon substrate; and separating the diamond polycrystalline film from the silicon substrate to obtain the diamond diaphragm; and S2—preparing a diamond microcantilever covering the obtained diamond diaphragm with a dry etching template with a U-shaped groove; etching the diamond diaphragm covered with the dry etching template to form a U-shaped groove on the diamond diaphragm, obtaining the diamond microcantilever, and a thickness of the diamond microcantilever is 10-100 μm; wherein the optical microphone further comprises: a base, with a first cavity opened at a central position of the base; a support, positioned above the base to support the diamond diaphragm; a second cavity is opened at a central position of the support, and the first cavity is connected to the second cavity; the diamond diaphragm is adaptively positioned on the support, when the diamond microcantilever corresponds to the second cavity; a pressure plate, positioned above the support, used to fix the diamond diaphragm in cooperation with the support; a third cavity is opened at a central position of the pressure plate, and the third cavity corresponds to the second cavity; optical fiber and ceramic insert, adaptively positioned in the first cavity; and an Fabry-Perot (F-P) interference cavity is formed between the optical fiber and ceramic insert and the diamond microcantilever; and wherein an interference sensitivity Si of the F-P interference cavity is expressed as: S i = 8 ⁢ π ⁢ ξ ⁢ R 1 ⁢ R 2 λ ⁢ I i ⁢ sin ⁢ 4 ⁢ π ⁢ d λ wherein, R 1 is a reflectance of the optical fiber and ceramic insert, R 2 is the reflectance of the diamond microcantilever, λ is a wavelength of an incident light, ξ is an optical coupling coefficient, I i is an intensity of the incident light, d is a static cavity length of the F-P interference cavity, wherein the optical coupling coefficient ξ is expressed as: ξ = 4 [ 1 + ( 2 ⁢ λ ⁢ d π ⁢ n 0 ⁢ ω ) 2 ] [ 2 + ( 2 ⁢ λ ⁢ d π ⁢ n 0 ⁢ ω 2 ) 2 ] 2 wherein, n 0 is a refractive index of air, n 0 =1, ω is a mode field radius of the optical fiber and ceramic insert.
2 . The optical microphone based on the diamond microcantilever according to claim 1 , characterized in that through-holes are set on a side wall of the base, and the through-holes are used to connect the first cavity with the outside of the base.
3 . The optical microphone based on the diamond microcantilever according to claim 1 , characterized in that diameters of the first cavity, the second cavity, and the third cavity are the same.
4 . The optical microphone based on the diamond microcantilever according to claim 1 , characterized in that a resonant frequency ω 0 of the diamond microcantilever is expressed as: ω 0 = 1.875 2 L 2 EI ρ ⁢ S ⁡ ( 1 - σ 2 ) = 1.875 2 h L 2 ⁢ E 12 ⁢ ρ wherein, L is a length of the diamond microcantilever, h is the thickness of the diamond microcantilever, S is a cross-sectional area of the diamond microcantilever, I is a moment of inertia of the diamond microcantilever, E is a Young's modulus of the diamond microcantilever, σ represents a Poisson's ratio, and ρ is a density of the diamond microcantilever.
5 . The optical microphone based on the diamond microcantilever according to claim 4 , characterized in that a mechanical sensitivity S m of the diamond microcantilever is expressed as: S m = 3 ⁢ L 2 ( 1 - σ ) Eh 2
6 . The optical microphone based on the diamond microcantilever according to claim 1 , characterized in that when the static cavity length of the F-P interference cavity satisfies d=(2n+1)λ/8, the interference sensitivity of the F-P interference cavity is maximized, wherein n is a natural number.
7 . The optical microphone based on the diamond microcantilever according to claim 1 , characterized in that the diamond microcantilever is rectangular.
8 . An optical sound transmission system based on a diamond microcantilever, characterized in that it comprises the optical microphone according to claim 1 .

Description

TECHNICAL FIELD The present invention pertains to the field of acoustical signal sensing technology, specifically involving an optical microphone and acoustic sensing system based on diamond cantilevers. BACKGROUND A microphone is an acoustic sensor that converts sound wave signals into electrical signals and is widely applied in industrial equipment fault diagnosis, material defect identification, ultrasonic medical applications, and other fields. Traditional electronic microphones, which are based on energy conversion principles, are mainly categorized as capacitive, piezoelectric, or microelectromechanical system (MEMS) types. Traditional electronic microphones commonly face challenges such as insufficient sensitivity, susceptibility to electromagnetic interference, and difficulty adapting to high-temperature, high-humidity, or corrosive environments. Currently, a novel optical microphone based on Fabry-Perot (F-P) interference has emerged. It consists of a ceramic end face at the fiber optic end and a rigid diaphragm employing an “acoustic signal-optical signal-electrical signal” energy conversion mechanism. Incident light enters through the optical fiber, where it undergoes multiple reflections between the end face of the optical fiber and the inner side of the rigid diaphragm, thereby leading to F-P interference. The acoustic signal acts on the diaphragm, causing elastic deformation of the diaphragm surface. This deformation leads to a phase change in the inner interference light, thus converting the acoustic signal into an optical signal. The interference light can be received by a highly sensitive photoelectric detector, and after optical signal collection, it is converted into a voltage signal output. F-P microphones exhibit advantages such as compact structure, high signal-to-noise ratio (SNR), and resistance to electromagnetic interference. In the current design of F-P microphones, the rigid diaphragm is a critical factor in microphone performance, but it commonly suffers from performance limitations. Typically, metal materials are used as rigid diaphragms. However, when the material thickness is reduced to the micron or nanometer scale to achieve high sensitivity, the mechanical strength of metal materials decreases, and residual stresses may occur, limiting sensitivity. Metal material thin films have low resonance frequencies, restricting the bandwidth of the frequency response, which is unfavorable for sound wave signal conversion. Prolonged exposure to acoustic vibrations may also lead to metal fatigue. Additionally, metal materials exhibit poor chemical stability, increasing susceptibility to corrosion from acidic gases, such as HF, SO2, and SF6, in industrial environments. SUMMARY In view of the above, some embodiments disclose an optical microphone based on diamond cantilevers, comprising a diamond cantilever component. The diamond cantilever component included a diamond diaphragm, with a U-shaped groove positioned at the middle of the diaphragm, forming the diamond cantilever within the U-shaped groove. The preparation method for the diamond cantilever component includes the following steps: S1, preparing a diamond diaphragm by setting silicon as a substrate in a chemical vapor deposition device; adjusting the heating temperature and pressure of the chemical vapor deposition device; introducing methane and hydrogen for the chemical vapor deposition reaction; obtaining a diamond polycrystalline thin film on the silicon substrate; and separating the diamond polycrystalline thin film from the silicon substrate to obtain the diamond diaphragm.S2: The diamond cantilever was prepared by covering the obtained diamond diaphragm with a dry etching template with a U-shaped groove; the diamond diaphragm was etched to form a U-shaped groove on the diamond diaphragm, yielding a diamond cantilever with a thickness of 10 to 100 μm. Some embodiments of the optical microphone based on diamond cantilevers also include a base with a first cavity at the middle position, a support base above the base for supporting the diamond diaphragm, and a clamping plate above the support base for fixing the diamond diaphragm. An optical fiber and ceramic insert in the first cavity form an F-P interference cavity with the diamond cantilever. The sidewall of the base in some embodiments of the optical microphone based on diamond cantilevers has through-holes for external communication with the first cavity. The diameters of the first cavity, second cavity, and third cavity in some embodiments of the optical microphone based on diamond cantilevers are the same. The resonance frequency ω0 of the diamond cantilever in some embodiments of the optical microphone based on diamond cantilevers is expressed as: ω0=1.8⁢7⁢52L2⁢E⁢IρS⁡(1-σ2)=1.8⁢7⁢52⁢hL2⁢E12⁢ρwhere L denotes the length of the diamond cantilever, h denotes the thickness of the diamond cantilever, S denotes the cross-sectional area of the diamond cantilever, I denotes th