Kırınım ızgaralı girişim ölçer temelli MEMS Fourier dönüşümü kızılötesi spektrometre

Fourier transform infrared (FTIR) spectroscopy is a widely used non-contact optical material characterization method that is used for chemical analysis of solids, fluids, gases, and process flows. FTIR utilizes a black body light source with broad spectrum, moving opto-mechanical components, and a detector. Current FTIR spectrometers offer good spectral resolution (few cm-1 or better); however, they are costly bench top laboratory instruments, require very high opto-mechanical precision, sensitive to vibrations due to interferometric detection principle, and have low measuring speed (few seconds to minutes). A portable FTIR system is needed as it would allow field use and has the potential to open up new research directions and applications.The aim of this project was to build a miniaturized handheld FTIR spectrometer with high measuring speed (1-2msec) and moderate spectral sensitivity (10cm-1) that works across a wide wavelength range in the mid-infrared (2.5-16µm) region. The project is done as a part of the European Commission funded project called MEMFIS within a consortium. A novel lamellar grating interferometer (LGI) based on micro-electro-mechanical-system (MEMS) technology and electrostatic actuation is at the heart of the FTIR system and offers the required precision, speed, and the vibration immunity for a portable system. LGI MEMS device was designed and microfabricated by our group prior to this thesis research. LGI is a dynamic diffraction grating operated at resonance and functions as a high-precision opto-mechanical interferometer with key important advantages compared to other types of interferometers.This thesis mainly focuses on the detailed optical and mechanical characterization of the LGI MEMS device and its integration into a fully functional FTIR system using the source, detector, and IR optics. For this purpose, MEMS devices fabricated in five separate runs are characterized mechanically and optically. For mechanical characterization, two automatized systems based on laser Doppler vibrometry and laser fringe counting are developed using a Labview based controller. Physical optics simulations of the system are performed in MATLAB and ray-tracing simulations are performed in ZEMAX to find the optimum combination of optical components. A fully functional LGI based FTIR spectrometer system is built on an optical table and successfully benchmarked with other FTIR systems using polystyrene film samples. The system can currently achieve about 30cm-1 spectral resolution. This is the best MEMS-based LGI system developed to date considering the spectral resolution and clear aperture size of 10mm2. To increase the mechanical deflection (i.e., improve spectral resolution) and to avoid problems related to electrostatic actuation such as pull-in and nonlinear frequency response, acoustic excitation using a speaker and mechanically-coupled excitation using a piezoelectric-vibrator are introduced as alternative actuation methods. As another application of the FTIR system, measurement of photovoltaic solar cell thin film thickness uniformity is exploited.