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Optical Gas Sensing Based on MEMS FTIR Spectrometers
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Book Description

This Spotlight focuses on the use of MEMS Fourier-transform infrared spectrometers as a core building block in optical gas sensing. Micro-optical bench technology is discussed, followed by the basics of the sensing technique. An overview of the system components and their state of the art is given, including the light source, the miniaturized interferometer and gas cell, the optical connectivity, and detection for both the near-infrared and the mid-infrared spectral ranges. A comparison shows the pros and cons of each regime, accounting for the absorption cross-sections of the gases and the signal-to-noise performance of the system components. The impact of the limitation on the signal-to-noise ratio and spectral resolution due to miniaturization on the gas sensor performance is also discussed. An experimental setup to evaluate the sensor performance and extract its sensitivity is explained, and experimental results of detecting acetylene and carbon dioxide gases are presented. The book concludes with a discussion of the foreseen challenges and potential.

Book Details

Date Published: 31 August 2017
Pages: 40
ISBN: 9781510613706
Volume: SL32

Table of Contents
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1 Introduction

2 Gas Sensing
2.1 Market needs
2.2 Sensing technologies
2.3 Gas phase spectra in the IR range

3 Silicon-Based Micro-Optical Bench Technology
3.1 Deep reactive ion etching
3.2 Deeply etched SOI microbenches
3.3 Other technologies for microbenches

4 FTIR Spectrometer
4.1 Michelson interferometer MEMS chip
4.2 FTIR gas sensor
     4.2.1 Light source
     4.2.2 Optical fibers and lenses
     4.2.3 Optical detector
     4.2.4 Gas cell
4.3 Sensing in the NIR range
4.4 Sensing in the MIR range

5 Gas-Sensing Analysis in the NIR range

6 Experimental Results
6.1 C2H2 standard gas-cell measurements
6.2 Gas measurement setup using a MEMS FTIR spectrometer
6.3 Measurements in the NIR spectral range
6.4 Measurements in the MIR spectral range

7 Foreseen Challenges
7.1 Light-diffraction effect
7.2 Silicon dispersion

References

Preface

This Spotlight focuses on the use of microelectromechanical systems Fourier transform infrared (MEMS FTIR) spectrometers as a core building block in optical gas sensing. Micro-optical bench technology is discussed, followed by the basics of the sensing technique. An overview of the system components and their state of the art is given, including the light source, miniaturized interferometer, and gas cell; optical connectivity; and detection for both the near-infrared and mid-infrared spectral ranges. A comparison shows the pros and cons of each range, accounting for the absorption cross-sections of the gases and the signal-to-noise performance of the system components. The impact of the limitation on the signal-to-noise ratio and spectral resolution due to miniaturization on the gas sensor performance is also discussed. An experimental setup to evaluate the sensor performance and extract its sensitivity is explained, and the experimental results of detecting acetylene and carbon dioxide gases are presented. The Spotlight concludes with a discussion of the foreseen challenges and potentials.

Mazen Erfan
Yasser M. Sabry
Marwa M. Ragheb
Diaa A. Khalil
August 2017


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