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J. Hildenbrand,
J. Wöllenstein, S. Hartwig,
A. Eberhardt,
B. Halford,
M. Moreno,
J. Fonollosa,
L. Fonseca,
J. Santander,
R. Rubio,
I. Gràcia,
C. Cané
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ABSTRACT: Precise and continuous ethylene detection is needed in various fruit ripening applications. The aim of this work is the development
of a miniaturised mid-infrared filter spectrometer for ethylene detection at 10.6μm wavelength. For this reason optical components
and signal processing electronics were developed, tested and integrated in a compact measurement system. The main optical
components, their integration of the optical system, as well as a description of the developed electronics and the first results
of gas measurements are described in this paper. In fact the application conditions demand not a single channel system but
a multichannel one. A silicon-based macroporous IR-emitter, a miniaturised absorption cell and a detector module for the simultaneous
measurement with four channels including, ethylene, two interfering gases and the reference signal were integrated in the
optical system. The new inner architecture of the detector module, consisted of optical filters which were directly attached
by flip-chip technology onto the thermopile-arrays, allowing silicon-based Fresnel multilenses to be attached to the cap of
the detector housing. Because of the high reflection losses at the silicon-air surface the Fresnel lenses were coated with
zinc sulphide antireflection layers. For the signal processing electronics a preamplification stage and a DSP-based lock-in-amplifier
has been developed. Although some of this work is still on-going, first ethylene measurements with the miniaturised gas cell,
silicon-based IR-emitter, a commercial thermopile detector and the self-developed system electronics showed a detection limit
better than 20ppm.
Microsystem Technologies 04/2012; 14(4):637-644. · 0.93 Impact Factor
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[show abstract]
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ABSTRACT: In the present study, bending losses in conventional hollow waveguides (internally Ag/AgI coated) and in photonic bandgap (PBG) hollow waveguides (HWG) are compared based on studies via FT-IR spectroscopy and quantum cascade lasers (QCL). To date, literature on bending losses in hollow waveguides focuses on conventional HWG structures (e.g., silica structural tube with internal Ag/AgI coating), whereas the results discussed here compare relative bending losses in novel photonic bandgap waveguides, a new type of HWG progressively more integrated in gas sensors, versus conventional HWGs for the first time. Photonic bandgap waveguides are expected to exhibit lower polarization-dependent relative bending losses due to radiation propagation via omnidirectional reflection, in contrast to conventional HWGs. Accordingly, photonic bandgap waveguides offer superior flexibility and robustness against bending losses in coiled configurations rendering them promising structures for next-generation miniaturized QCL-based HWG gas sensors.
Sensors, 2007 IEEE; 12/2007
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[show abstract]
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ABSTRACT: To improve the sensitivity of a non-dispersive infrared optical gas sensor, diffractive Fresnel lenses have been designed, fabricated and tested. The target gases determine the wavelengths for the lens design: 10.6 mum, 9.7 mum, 3.5 mum, and 3.9 mum for ethylene, ammonia, ethanol, and the reference band; respectively. Four lenses have been fabricated on the same silicon substrate using reactive ion etching. In order to reduce the number of photolithographic processes, a new design based on sharing sixteen quantization steps through the four lenses is done. Finally, the test of the fabricated device is presented.
Solid-State Sensors, Actuators and Microsystems Conference, 2007. TRANSDUCERS 2007. International; 07/2007
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[show abstract]
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ABSTRACT: In various fruit storage applications precise and continuous ethylene detection is needed. The aim of this work is the development of a miniaturised mid-infrared filter spectrometer for ethylene detection at 10.6 μm wavelength. For this reason optical components and signal processing electronics were developed, tested and integrated in a compact measurement system. The present article describes the optical components, the integration of the optical system, electronics and results of gas measurements. Next to a Silicon-based macroporous IR-emitter, a miniaturised absorption cell and a detector module for the simultaneous measurement at four channels for ethylene, two interfering gases and the reference signal were integrated in the optical system. Optical filters were attached to fourfold thermopile-arrays by flip-chip- technology. Silicon-based Fresnel multilenses were processed and attached to the cap of the detector housing. Because of the high reflection losses at the silicon-air surface the Fresnel lenses were coated with Antireflection layers made of Zinc sulphide. For the signal processing electronics a preamplification stage and a Lock-in-board has been developed. First ethylene measurements with the optical system with miniaturised gas cell, Silicon-based IR-emitter, a commercial thermopile detector and the self-developed system electronics showed a detection limit of smaller than 20ppm.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
05/2007;
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ABSTRACT: Precise and continuous ethylene detection is needed in various fruit storage applications. One of the main goals of the presented work is the development of gas sensor systems for ethylene monitoring based on miniaturized low cost infrared spectroscopy. The work is focused on the development of a novel micromachined IR-emitter, a small multi pass reflection cell and a compact detection module to monitor ethylene and interfering gases at different spectral ranges.
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[show abstract]
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ABSTRACT: The sensitivity of an infrared gas sensor depends on the interaction length between radiation and gas, i . e. a reduction in cell size generally results in a reduced sensitivity, too. Thus miniaturization is physically limited. Use of gas filled hollow fibres is a possibility to realize sensitive compact infrared gas sensors with low gas volumes and relatively long path length. Different types of hollow fibres were characterized for their applicability in gas sensors. Simulation and experimental results for the realization of a compact ethanol sensor show very good agreement.
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[show abstract]
[hide abstract]
ABSTRACT: In various fruit storage applications precise and continuous ethylene detection is needed. The aim of this work is the development of a miniaturised mid-infrared filter spectrometer for ethylene detection at 10.6 µm wavelength. For this reason optical components and signal processing electronics were developed, tested and integrated in a compact measurement system. The present article describes the optical components, the integration of the optical system, electronics and results of gas measurements. Next to a Silicon-based macroporous IR-emitter, a miniaturised absorption cell and a detector module for the simultaneous measurement at four channels for ethylene, two interfering gases and the reference signal were integrated in the optical system. Optical filters were attached to fourfold t hermopile-arrays by flip-chip-technology. Silicon-based Fresnel multilenses were processed and attached to the cap of the detector housing. Because of the high reflection losses at the silicon-air surface the Fresnel lenses were coated with Antireflection layers made of Zinc sulphide. For the signal processing electronics a preamplification stage and a Lock-in-board has been developed. First ethylene measurements with the optical system with miniaturised gas cell, Silicon-based IR-emitter, a commercial thermopile detector and the self-developed system electronics showed a detection limit of smaller than 20ppm.
Fraunhofer IPM.
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[show abstract]
[hide abstract]
ABSTRACT: In the present study, bending losses in conventional hollow waveguides (internally Ag/AgI coated) and in photonic bandgap (PBG) hollow waveguides (HWG) are compared based on studies via FT-IR spectroscopy and quantum cascade lasers (QCL). To date, literature on bending losses in hollow waveguides focuses on conventional HWG structures (e.g., silica structural tube with internal Ag/AgI coating), whereas the results discussed here compare relative bending losses in novel photonic bandgap waveguides, a new type of HWG progressively more integrated in gas sensors, versus conventional HWGs for the first time. Photonic bandgap waveguides are expected to exhibit lower polarization dependent relative bending losses due to radiation propagation via omnidirectional reflection, in contrast to conventional HWGs. Accordingly, photonic bandgap waveguides offer superior flexibility and robustness against bending losses in coiled configurations rendering them promising structures for next-generation miniaturized QCL-based HWG gas sensors.
Fraunhofer IPM.
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[show abstract]
[hide abstract]
ABSTRACT: To improve the sensitivity of a non-dispersive infrared optical gas sensor, diffractive Fresnel Lenses have been designed, fabricated and tested. The target gases determine the wavelengths for the lens design: 10.6µm, 9.7µm, 3.5µm, and 3.9µ m for ethylene, ammonia, ethanol, and the reference band; respectively. Four lenses have been fabricated on the same silicon substrate using Reactive Ion Etching. In order to reduce the number of photolithographic processes, a new design based on sharing sixteen quantization steps through the four lenses is done. Finally, the test of the fabricated device is presented.
Fraunhofer IPM.
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[show abstract]
[hide abstract]
ABSTRACT: Hollow fibers can be used for compact infrared gas sensors. The guided light is absorbed by the gas introduced into the hollow core. High sensitivity and a very small sampling volume can be achieved depending on fiber parameters i.e. attenuation, flexibility, and gas exchange rates. Different types of infrared hollow fibers including photonic bandgap fibers were characterized using quantum cascade lasers and thermal radiation sources. Obtained data are compared with available product specifications. Measurements with a compact fiber based ethanol sensor are compared with a system simulation. First results on the detection of trace amounts of the explosive material TATP using hollow fibers and QCL will be shown .
Fraunhofer IPM.
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ABSTRACT: The sensitivity of an infrared gas sensor depends on the interaction length between radiation and gas, i.e. a reduction in cell size generally results in a reduced sensitivity, too. However, low group velocity regions in the bandstructure of photonic crystals should enable the realization of very compact gas sensors. Using photonic crystals based on macroporous silicon experimental results with CO2 show an increase of the gas sensitivity in the photonic crystal compared to an empty cell of same dimensions. For practical applications the results are compared with gas measurements using conventional multireflection cells and hollow fiber setups.
Fraunhofer IPM.
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[show abstract]
[hide abstract]
ABSTRACT: To improve the sensitivity of a non-dispersive infrared optical gas sensor, diffractive Fresnel lenses have been designed, fabricated with silicon microtechnologies, and tested. The target gases (for fruit storage applications) determine the wavelengths for the lens design: 10.6 μm, 9.7 μm, 3.5 μm, and 3.9 μm for ethylene, ammonia, ethanol, and the reference band, respectively. Four lenses are fabricated on the same silicon substrate in a combined multi-lens. In order to reduce the number of photolithographic steps, a new design based on sharing up to sixteen quantization steps by the four lenses is done. Due to the high reflection losses at the silicon–air surfaces, some multi-lenses have been coated with zinc sulphide antireflection layers. The difference between the measured and the target focal length is smaller than 5%. Alignment fixtures have been fabricated to assemble the Fresnel lenses chip on the detector lid in the correct orientation.
Sensors and Actuators B: Chemical.
