Monolithic Silicon Photonics Interferometer for Ultra-sensitive MEMS Sensors

用于超灵敏 MEMS 传感器的单片硅光子干涉仪

• 批准号: ST/M000427/1
• 负责人: Giles Hammond
• 金额: $ 6.31万
• 依托单位: University of Glasgow
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2014
• 资助国家: 英国
• 起止时间: 2014 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FM000427%2F1
• 关键词: Monolithic; Silicon; Photonics; Interferometer; Ultra

Interferometers are devices which can provide accurate position measurements. They work by comparing the distance travelled by light in two (typically) perpendicular arms. When the light from the two beams is combined and interfered, the change in intensity can be compared to a fraction of the wavelength of light. If both light waves are in-phase the light output is a maximum, while if the light waves are out of phase the intensity will be zero. This project will develop a miniaturised on-chip interferometer suitable for use in Micro-Electro-Mechanical System (MEMS) sensors. The entire interferometer will occupy a size below 10 mm x 10 mm. The light source will be an off-chip 1550 nm laser which is coupled to on-chip silicon waveguides, polarising beamsplitters and Ge photodetectors which are fabricated by reactive ion etching of commercial silicon-on-insulator (SOI) wafers. The interferometer utilises the polarisation of the incoming laser beam to operate two separate interferometers within the same Si components. This is achieved by shifting one of the beams by 90 degrees with respect to the other one with a phaseplate. By plotting the two outputs from the interferometer we achieve a circular pattern whereby the circle is traversed every time the mirrors are moved a relative separation equal to one half the wavelength of light (or lambda/2). If the circle can be subdivided into 1000 sections, the sensitivity is of the order 700 picometres for 1550 nm laser light. In principle it is possible to do even better by accurate modelling of the shape of the resulting circular pattern and we propose to demonstrate a sensitivity of 100 picometres.Current MEMS sensors are typically monitored with simple electrostatic sensors which measure the capacitance between micro-structured electrodes. Whilst being a relatively simple component, this method has limitations in the achievable sensitivity, and also challenges as electrostatic voltage causes spurious forces which can destabilises the delicate MEMS device and cause it to lock. The on-chip interferometer which is described in this proposal will be combined with a MEMS accelerometer in order to provide an ultra-sensitive device able to sense tiny changes in gravity. To give quantitative measure of the sensitivity, MEMS accelerometers found in iPhones typically have an acceleration sensitivity of 0.015 ms-2 and are able to sense the direction of the screen. The accelerometer we propose here has sensitivity approximately 1 million times better than an iPhone accelerometer. This will allow the opportunity to utilise the optical readout MEMS to monitor the gravitational effects of a variety of bodies. This could include dense objects being smuggled through ports of entry, hidden subterranean tunnels, the location of carbon sequestered under the ground or the location of buried nuclear waste. The device thus has a wide range of applications in the areas of precision sensing and monitoring, detecting hidden dense masses and buried objects/tunnels, and the monitoring of carbon/nuclear waste in geological repositories.

干涉仪是可以提供精确位置测量的设备。他们的工作原理是比较光在两个（通常）垂直臂中传播的距离。当两束光合并并发生干涉时，强度的变化可以与光波长的一小部分进行比较。如果两个光波同相，则光输出最大，而如果光波异相，则强度为零。该项目将开发一种适用于微机电系统（MEMS）传感器的小型化片上干涉仪。整个干涉仪的尺寸将低于10毫米×10毫米。光源将是片外 1550 nm 激光器，与片上硅波导、偏振分束器和 Ge 光电探测器耦合，这些探测器是通过商业绝缘体上硅 (SOI) 晶圆的反应离子蚀刻制造的。干涉仪利用入射激光束的偏振来操作同一硅组件内的两个独立的干涉仪。这是通过使用相位板将其中一束光相对于另一束光移动 90 度来实现的。通过绘制干涉仪的两个输出，我们获得了一个圆形图案，每次镜子移动相对间隔等于光波长的一半（或 lambda/2）时，都会穿过该圆。如果圆可以细分为 1000 个部分，则 1550 nm 激光的灵敏度约为 700 皮米。原则上，通过对所得圆形图案的形状进行精确建模，可以做得更好，我们建议展示 100 皮米的灵敏度。当前的 MEMS 传感器通常使用简单的静电传感器进行监控，这些传感器测量微结构电极之间的电容。虽然是一个相对简单的组件，但该方法在可实现的灵敏度方面存在局限性，并且还存在挑战，因为静电电压会产生寄生力，从而破坏精密 MEMS 设备的稳定性并导致其锁定。该提案中描述的片上干涉仪将与 MEMS 加速度计相结合，以提供能够感知重力微小变化的超灵敏设备。为了定量测量灵敏度，iPhone 中的 MEMS 加速度计通常具有 0.015 ms-2 的加速度灵敏度，并且能够感应屏幕的方向。我们在此建议的加速计的灵敏度比 iPhone 加速计高约 100 万倍。这将使我们有机会利用光学读出 MEMS 来监测各种物体的重力效应。这可能包括通过入境口岸走私的密集物体、隐藏的地下隧道、地下碳封存的位置或埋藏的核废料的位置。因此，该设备在精密传感和监测、检测隐藏的致密物质和掩埋物体/隧道以及监测地质处置库中的碳/核废物等领域具有广泛的应用。

项目成果

A 19 day earth tide measurement with a MEMS gravimeter.

使用 MEMS 重力计进行的 19 天地球潮测量。

• DOI: http://dx.10.1038/s41598-022-16881-1
• 发表时间: 2022
• 期刊: Scientific reports
• 影响因子: 4.6
• 作者: Prasad A

Measurement of the Earth tides with a MEMS gravimeter.

使用 MEMS 重力计测量地球潮汐。

• DOI: http://dx.10.1038/nature17397
• 发表时间: 2016
• 期刊: Nature
• 影响因子: 64.8
• 作者: Middlemiss RP

A Simulation Study of the Temperature Sensitivity and Impact of Fabrication Tolerances on the Performance of a Geometric Anti-Spring Based MEMS Gravimeter

温度敏感性和制造公差对几何抗弹簧 MEMS 重力计性能影响的仿真研究

• DOI: http://dx.10.1109/inertial53425.2022.9787761
• 发表时间: 2022
• 作者: Belwanshi V

Microelectromechanical system gravimeters as a new tool for gravity imaging.

微机电系统重力仪作为重力成像的新工具。

• DOI: http://dx.10.1098/rsta.2017.0291
• 发表时间: 2018
• 期刊: Philosophical transactions. Series A, Mathematical, physical, and engineering sciences
• 作者: Middlemiss RP

Field Tests of a Portable MEMS Gravimeter.

便携式 MEMS 重力计的现场测试。

• DOI: http://dx.10.3390/s17112571
• 发表时间: 2017
• 期刊: Sensors (Basel, Switzerland)
• 作者: Middlemiss RP