Abstract
An optically enabled z-axis micro-disk inertia sensor is presented, which consists of a disk-shaped proof mass integrated on top of an optical waveguide. Numerical simulations show that the optical power of laser beam propagating in a narrow silicon nitride (Si3N4) waveguide located under the disk is attenuated in response to the vertical movement of the micro-disk. The high leakage power of the TM mode can effectively be used to detect a dynamic range of 1 g‒10 g (g=9.8 m/s2). At lest, the waveguide is kept at a nominal gap of 1 µm from the proof mass. It is adiabatically tapered to a narrow dimension of W×H = 350×220 nm2 in a region where the optical mode is intended to interact with the proof mass. Furthermore, the bottom cladding is completely etched away to suspend the waveguide and improve the optical interaction with the proof mass. The proposed optical inertia sensor has a high sensitivity of 3 dB/g when a 50 µm-long waveguide is used (normalized sensitivity 0.5 dB/µm2) for the vertical movement detection.
Highlights
Silicon micro-electro-mechanical systems (MEMS) devices are widely used for inertia and pressure sensing applications
The sensitivity has a low value for a gap more than 1 m, as the disk becomes closer to the waveguide with gap spacing below 1 m, the transverse magnetic (TM) mode becomes highly sensitive, which is possible to calculate the gap spacing by monitoring the intensity of each polarization or the ratio between them
Numerical simulations are used to compute the leakage of the transverse electric (TE) and TM polarizations propagating in a 50 m-long waveguide as a function of gap between the two wafers and for a scan of waveguide width
Summary
Silicon micro-electro-mechanical systems (MEMS) devices are widely used for inertia and pressure sensing applications. DUSHAQ et al.: Micro-Opto-Mechanical Disk for Inertia Sensing sensors are able to achieve sub nm/g resolution with smaller masses [1, 2] Those optical detection based systems employ optical resonators or photonics crystal cavities with a narrow transmission bandwidth. The serpentine springs are designed to provide a low spring constant and optimized to allow the maximum displacement in the out-of-plane direction This movement is detected using birefringent suspended waveguides hybrid integrated under the proof mass. This shows that the easiest energy of the system is in the z-direction, in addition it indicates a very tiny displacement in the in-plane direction under this z-loaded force recording ~1.3% cross axis sensitivity. (e) Fig. 3 Vibrational and steady state analysis of the sensor: (a) mode 1 with 2.1 kHz, (b) mode 2 with 3.6 kHz, (c) mode 3 with 3.6 kHz, (d) the maximum displacement of out-of-plane loaded inertia sensor, and (e) the maximum displacement of in-plane loaded inertia sensor
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