Laterally deformable optical NEMS grating transducers for inertial sensing applications

et al. 2018

Sensors

Optical coupling between subwavelength grating pairs allows for the precise measurement of lateral or vertical displacement of grating elements and gives rise to different types of displacement and inertial sensors. In this paper, we demonstrate a design for a nano-optomechanical accelerometer based on a subwavelength grating pair that can be easily fabricated by a single Silicon-on-insulator (SOI) chip. The parameters of the subwavelength grating pair-based optical readout, including period, duty cycle, thickness of grating and metal film, and the distance of the air gap, were optimized by combining a genetic algorithm and rigorous coupled wavelength analysis (RCWA) to obtain the optimal sensitivity to the displacement of suspended grating element and the acceleration. A corresponding mechanical design was also completed to meet the highly sensitive acceleration measurement requirement while considering the mechanical cross-axis sensitivity, dynamic range, bandwidth, and fabrication feasibility. This device was verified by both RCWA and finite-different-time-domain methods, and a tolerance analysis was also completed to confirm that it is able to achieve the extremely high optical displacement sensitivity of 1.8%/nm, acceleration-displacement sensitivity of 1.56 nm/mg, and acceleration measurement sensitivity of more than 2.5%/mg, which is almost one order of magnitude higher than any reported counterparts. This work enables a single SOI-based high performance accelerometer, and provides a theoretical basis and fabrication guides for the design.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Single Chip-Based Nano-Optomechanical Accelerometer Based on Subwavelength Grating Pair and Rotated Serpentine Springs

Bai

et al. 2018

Sensors

“…Wood's anomaly was first discovered in 1902, which manifests itself as a considerable increase or decrease in the intensity of reflective waves from a grating due to the small variation of the grating structure [63][64][65][66]. Since 2003, Krishnamoorthy and Carr at the Sandia National Laboratory and Symphony Acoustics used this effect to measure small motion [67][68][69][70][71]. Their work was underpinned with rigorous analysis [67], experimental verification [68] as well as an application to an optical accelerometer [69][70][71].…”

Section: Optical Mems Accelerometersmentioning

confidence: 99%

“…Since 2003, Krishnamoorthy and Carr at the Sandia National Laboratory and Symphony Acoustics used this effect to measure small motion [67][68][69][70][71]. Their work was underpinned with rigorous analysis [67], experimental verification [68] as well as an application to an optical accelerometer [69][70][71]. Their integrated sub-wavelength optical nano-grating MEMS accelerometers demonstrated a sensitivity of 590 V/g and a noise floor of 17 ng/ √ Hz (at 1 Hz).…”

Section: Optical Mems Accelerometersmentioning

confidence: 99%

Micromachined Accelerometers with Sub-µg/√Hz Noise Floor: A Review

Chen

et al. 2020

Sensors

This paper reviews the research and development of micromachined accelerometers with a noise floor lower than 1 µg/√Hz. Firstly, the basic working principle of micromachined accelerometers is introduced. Then, different methods of reducing the noise floor of micromachined accelerometers are analyzed. Different types of micromachined accelerometers with a noise floor below 1 µg/√Hz are discussed. Such sensors can mainly be categorized into: (i) micromachined accelerometers with a low spring constant; (ii) with a large proof mass; (iii) with a high quality factor; (iv) with a low noise interface circuit; (v) with sensing schemes leading to a high scale factor. Finally, the characteristics of various micromachined accelerometers and their trends are discussed and investigated.

“…Typical examples of such application are optical filter [4], guided-mode resonant filter (GMRF) [5][6], high speed laser scanning [7]. Recently, Dustin presented a novel grating design based on Wood's anomaly and demonstrated his work with rigorous analysis [8], experimental test [9] as well as following application in an optical accelerometer [10][11]. This device gives out rapid variation of reflective intensity with small lateral displacement in nanometer scale and is quite sensitive to incident wavelength, which make it very suitable for small displacement detection and beamsplitting switch.…”

Section: Introductionmentioning

confidence: 99%

Analysis and optimization of a novel laterally deformable optical NEMS grating transducer

2014

This paper discusses the analysis and optimization of a novel optomechanical structure based on a Wood's type anomaly, in which tiny changes in the spacing of the nanostructured grating elements lead to a dramatic increase or decrease of the optical reflection amplitude. With this special feature, this structure is an ideal sensor component to observe very small amount of relative motion. This device is very sensitive to light source wavelength, the period and the width of the grating. Here, we analyze the performance of the structure with different parameters and incident light of different wavelengths through 3-D Finite Difference Time Domain method (FDTD). Simulation gives out the respective influence of those parameters and the optimized structure designs for different wavelengths which are most possible to fabricate with current surface micromachining processing similar to that used for the fabrication of polysilicon MEMS. The calculated data enables us to apply the structure into fields required for different sensitivities and dynamic ranges with different grating designs and thus broadens the further usage of such novel structure.