Mark Fralick

Development of a MEMS-based Raman spectrometer

This paper discusses the development of a Raman spectrometer incorporated into a MEMS device for use in environmental monitoring against chemical and biological agents. The current design incorporates a 1525 nm laser diode as an optical pump source, and a tunable Fabry-Pérot interferometer as the wavelength selection element.

Optimization of kinetic energy harvester for low amplitude vibration

This paper presents the steps involved in optimizing the design of an electromagnetic kinetic energy harvester (KEH). The KEH device is conceptually a highly non-linear device. There are numerous dependent variables involved in the design of a KEH which are reliant upon the specific environmental conditions in which the KEH will be deployed. Furthermore, the non-linear nature of the device leads to an iterative design process. The environment that the KEH is deployed into also dictates the overall design and power per volume achieved by the device.

Design and analysis of a novel electro-optical MEMS gyroscope for navigation applications

A novel gyroscope design is presented that has potential to reach navigation-grade performance, i.e. bias instability < 0.01 °/hr and Angle Random Walk (ARW) < 0.001 °/√hr. The design is based on the incorporation of an optical transduction mechanism used to decouple drive and sense signals, a dual crystalline silicon spring fabrication approach along with a large drive mass and small sense mass to enhance Coriolis displacement.

Powering of wireless sensors through the exclusive use of kinetic energy

This paper demonstrates the powering of wireless sensor nodes with the exclusive use of a novel kinetic energy harvester (KEH). This KEH is designed to operate under low accelerations which are practical to find in a typical environment where a sensor would be deployed. Four different sensor types were powered with accelerations ranging between 17–300mg.

Factors influencing the noise floor and stability of a time domain switched inertial device

A new paradigm in inertial sensing is presented based on measurement of accurate time intervals using physical proximity switches deposed on a resonating beam structure. This paper discusses the time domain sensing concept and noise sources that can influence the performance of the sensor. The ultimate noise floor (-178 dB/√Hz)is limited by the accuracy of a time-to-digital convertor.

Characterization and optimization of a novel electromagnetic transduction technique for rotational energy harvesting

A novel transduction technique that converts mechanical rotation energy to usable electrical energy using condensed magnetic flux is tested and characterized for a wind source. This rotation harvester is compared to the power output of a commercially available generator for a fixed wind source. Optimization of the rotation harvester is discussed in terms of various parameters, such as magnet spacing, number of excitation arms, rotation frequency, and harvester resonance.

Design of highly reflective subwavelength diffraction gratings for use in a tunable spectrometer

The design of highly reflective subwavelength gratings (SWGs) for use in a micro-electromechanical system (MEMS) tunable spectrometer is presented. The SWGs are designed to be polarization independent at an incident wavelength of 1.5 µm with high reflectivity over a 200 nm bandwidth. Two designs are considered; Model 1: a silicon layer with periodic air holes and Model 2: a stacked Si-SiO2-Si design with the last Si layer a periodic array of columns. The designs are simulated using a commercial rigorous coupled wave analysis (RCWA) software package. The RCWA software aids in the design of SWGs that have higher reflectance than traditional dielectric mirrors. Model 1 has a reflectance (R)≫0.99 for lambda 1.37–1.6 µm. Model 2 has a R≫0.99 for lambda 1.46–1.69 µm. Finally, both designs are modeled to create a Fabry-Perot cavity, and at an incident wavelength 1.5 µm, the designs have a reflection finesse of 1707 and 4452 for Model 1 and Model 2, respectively.