CN-122029413-A - Opto-mechanical pressure measurement system and method for determining ambient pressure level using such an opto-mechanical pressure measurement system

CN122029413ACN 122029413 ACN122029413 ACN 122029413ACN-122029413-A

Abstract

The present disclosure proposes an opto-mechanical pressure measurement system for measuring an ambient pressure level, the system comprising an optical fiber having a first optical fiber end and a second optical fiber end, an opto-mechanical cavity mounted at the first optical fiber end and consisting of a first membrane element and a second membrane element spaced apart from each other, wherein the first membrane element contacts the first optical fiber end, at least one light beam generating device coupled to the second optical fiber end and configured to generate light beams and direct said light beams via the optical fiber onto the opto-mechanical cavity, each light beam having a specific optical frequency, and an optical sensing member coupled to the second optical fiber end, wherein the at least one light beam generating device is configured to direct the first light beam having the first optical frequency onto the opto-mechanical cavity, wherein the first light beam is modulated at a modulation frequency within a bandwidth of a mechanical resonance frequency of the second membrane element, wherein the at least one light beam generating device is configured to direct the second light beam having the second optical frequency onto the opto-mechanical cavity, and wherein the optical sensing member is configured to detect a reflected portion of the second light beam onto the opto-mechanical cavity and determine an ambient pressure change of the opto-mechanical cavity based on an oscillation amplitude of the second membrane element.

Inventors

A. L. Hendricks
A. Fiore

Assignees

埃地沃兹有限公司

Dates

Publication Date: 20260512
Application Date: 20241014
Priority Date: 20231013

Claims (13)

1. An opto-mechanical pressure measurement system for measuring an ambient pressure level, the system comprising: An optical fiber having a first optical fiber end and a second optical fiber end; an opto-mechanical cavity mounted at the first fiber end and consisting of a first membrane element and a second membrane element spaced apart from each other, wherein the first membrane element contacts the first fiber end; At least one light beam generating device coupled to the second fiber end and configured to generate and direct a light beam onto the optomechanical cavity via the optical fiber, each light beam having a particular optical frequency, and A light sensing member coupled to the second optical fiber end, wherein The at least one light beam generating device is configured to direct a first light beam having a first optical frequency onto the opto-mechanical cavity, wherein the first light beam is modulated at a modulation frequency within a bandwidth of a mechanical resonance frequency of the second membrane element, wherein The at least one beam generating device being configured to direct a second beam of light having a second optical frequency onto the opto-mechanical cavity, and wherein The light sensing means is configured for detecting a portion of the second light beam reflected by the opto-mechanical cavity and determining an ambient pressure around the opto-mechanical cavity based on a change in an oscillation amplitude of the second membrane element.
2. The opto-mechanical pressure measurement system according to claim 1, wherein the at least one light beam generating device is configured to direct a first light beam having the modulation frequency only during a first time interval and to direct a second light beam having a second optical frequency at least during a second time interval after the first time interval, and wherein, The light sensing means is configured for detecting a portion of the reflected second light beam as a function of time and determining an ambient pressure based on a time decay of an oscillation of the portion of the reflected second light beam during the second time interval.
3. The optomechanical pressure measurement system of claim 1, wherein the at least one light beam generating device is configured to change a modulation frequency of the first light beam within a bandwidth of the mechanical resonance frequency, and wherein the light sensing means is configured to detect a portion of the reflected second light beam, wherein an amplitude of oscillation in the portion of the reflected second light beam is measured as a function of the modulation frequency, wherein the pressure is measured using a width of a peak of the amplitude of oscillation around the mechanical resonance frequency.
4. An opto-mechanical pressure measurement system according to any one or more of the preceding claims, wherein the opto-mechanical cavity comprises a spacer member configured for orienting the first and second membrane elements at a specific distance from each other.
5. The opto-mechanical pressure measurement system according to claim 4, wherein the spacer member is made of a material selected from the group consisting of at least InGaAs, alGaAs, siO 2 、Si 3 N 4 or other semiconductor or dielectric material.
6. An opto-mechanical pressure measurement system according to claim 4 or 5, wherein the spacer member has a thickness of 200-250 nm.
7. An opto-mechanical pressure measurement system according to any one or more of the preceding claims, wherein the first and second membrane elements are made of a semiconductor material such as silicon or indium phosphide (InP) or gallium arsenide (GaAs) or a dielectric material such as Si 3 N 4 .
8. An opto-mechanical pressure measurement system according to claim 7, wherein the first and second membrane elements have the same thickness, e.g. 150-200nm.
9. The optomechanical pressure measurement system of any one or more of the preceding claims, wherein the first and second film elements are patterned in an array of holes to define a photonic crystal.
10. The optomechanical pressure measurement system of claim 9, wherein the optical frequencies of the first and second light beams are selected to be close to the frequency of the optical resonance of the photonic crystal.
11. An optomechanical pressure measurement system of any one or more of the preceding claims, wherein the mechanical resonance frequency of the optomechanical cavity is between 1-4 MHz.
12. An opto-mechanical pressure measurement system according to any one or more of the preceding claims, wherein the optical fiber is a single mode optical fiber.
13. The opto-mechanical pressure measurement system according to any one or more of the preceding claims, wherein the light sensing means comprises a light detector and a sensing unit, wherein the sensing unit is configured for determining the ambient pressure at the second membrane element based on a change in the amplitude of oscillation of the reflected second light beam detected by the light detector over time or a modulation frequency.

Description

Opto-mechanical pressure measurement system and method for determining ambient pressure level using such an opto-mechanical pressure measurement system Technical Field The present disclosure relates to techniques for determining an ambient pressure level, and in particular, techniques for determining an ambient pressure level inside a deposition and measurement system operating at low pressure (below atmospheric pressure). Background Low pressure control is essential for deposition processes (e.g., electron beam evaporation, chemical vapor deposition, molecular beam epitaxy) to be performed in an accurate and controlled manner in the semiconductor industry. It is also required that the measurement system involves an electron beam or ion beam (e.g. electron microscope) or is operated at low temperature (cryostat). The measurement of low pressures mostly requires large pressure gauges (e.g. Pirani and capacitive gauges) that occupy valuable space inside the vacuum system. In addition, these meters may be subject to electromagnetic interference and, in some cases, corrosion (e.g., in plasma systems). The field involving interactions between light and nanomechanical motion conducted by radiation pressure provides a very promising alternative to accurate pressure level measurement. However, the practical application of these nano-opto-mechanical structures is hampered by the complexity of the sensor and the limited efficiency of light coupling to the sensor, which is related to the strong optical limitations and narrow linewidths that are commonly employed. It is therefore an object of the present disclosure to provide an improved opto-mechanical pressure measurement system capable of accurately measuring low ambient pressure levels while enabling large coupling efficiencies without any external optics. The opto-mechanical structure according to the present disclosure can be easily used in related sensing applications, such as in particular inside deposition and measurement systems. Disclosure of Invention According to a first example of the present disclosure, an opto-mechanical pressure measurement system for measuring an ambient pressure level is presented. The system includes an optical fiber having a first optical fiber end and a second optical fiber end, an opto-mechanical cavity mounted at the first optical fiber end and composed of a first membrane element and a second membrane element spaced apart from each other, wherein the first membrane element contacts the first optical fiber end, at least one light beam generating device coupled to the second optical fiber end and configured to generate light beams and direct the light beams onto the opto-mechanical cavity via the optical fiber, each light beam having a specific optical frequency, and a light sensing member coupled to the second optical fiber end. In particular, in an opto-mechanical pressure measurement system according to the present disclosure, the at least one light beam generating device is configured for directing a first light beam having a first optical frequency onto the opto-mechanical cavity, wherein the first light beam is modulated at a modulation frequency within a bandwidth of a mechanical resonance frequency of the second membrane element, wherein the at least one light beam generating device is configured for directing a second light beam having a second optical frequency onto the opto-mechanical cavity, and wherein the light sensing means is configured for detecting a portion of the second light beam reflected by the opto-mechanical cavity and determining an ambient pressure around the opto-mechanical cavity based on a change in an oscillation amplitude of the second membrane element. By way of this example, an opto-mechanical cavity mounted to the tip of an optical fiber is presented. The first and second membrane elements are patterned to form an optical resonance with an electromagnetic field extending across the two membrane elements. When the first light beam is modulated at a frequency close to the mechanical resonance frequency of the second film element, the second film element forms a mechanical oscillator that can be excited by the first light beam by optical or photo-thermal forces. The opto-mechanical cavity is excited at that particular mechanical resonance frequency by illuminating the opto-mechanical cavity with a first light beam having a modulation frequency within the mechanical resonance frequency bandwidth of the second membrane element. This is achieved by selecting the modulation frequency of the first light beam within said bandwidth such that it coincides (is almost equal) to the specific mechanical resonance frequency of the second membrane element. The displacement of the vibrating second membrane element results in a change of the optical resonance frequency and this change can be monitored by measuring the reflection of a second light beam which has been directed towards the opto-mechanical cavity by t