| 1. |
- Ayerden, N.P., et al.
(författare)
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Design, fabrication and characterization of LVOF-based IR microspectrometers
- 2014
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9781628410785 ; 9130
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Konferensbidrag (refereegranskat)abstract
- This paper presents the design, fabrication and characterization of a linear variable optical filter (LVOF) that operates in the infrared (IR) spectral range. An LVOF-based microspectrometer is a tapered-cavity Fabry-Perot optical filter placed on top of a linear array of detectors. The filter transforms the optical spectrum into a lateral intensity profile, which is recorded by the detectors. The IR LVOF has been fabricated in an IC-compatible process flow using a resist reflow and is followed by the transfer etching of this resist pattern into the optical resonator layer. This technique provides the possibility to fabricate a small, robust and high-resolution micro-spectrometer in the IR spectral range directly on a detector chip. In these designs, the LVOF uses thin-film layers of sputtered Si and SiO 2 as the high and low refractive index materials respectively. By tuning the deposition conditions and analyzing the optical properties with a commercial ellipsometer, the refractive index for Si and SiO2 thin-films was measured and optimized for the intended spectral range. Two LVOF microspectrometers, one operating in the 1.8-2.8 μm, and the other in the 3.0-4.5 μm wavelength range, have been designed and fabricated on a silicon wafer. The filters consist of a Fabry-Perot structure combined with a band-pass filter to block the out-of-band transmission. Finally, the filters were fully characterized with an FTIR spectrometer and the transmission curve widening was investigated. The measured transmittance curves were in agreement with theory. The characterization shows a spectral resolution of 35-60 nm for the short wavelength range LVOF and 70 nm for the long wavelength range LVOF, which can be further improved using signal processing algorithms.
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| 2. |
- Ayerden, N.P., et al.
(författare)
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A highly miniaturized NDIR methane sensor
- 2016
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Ingår i: Micro-Optics 2016, Brussels, 4-5 Apr.; (SPIE Proceedings vol. 9888). - : SPIE. - 0277-786X. - 9781510601338 ; 9888, s. art. no. UNSP 98880D-
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Konferensbidrag (refereegranskat)abstract
- The increasing demand for handheld systems for absorption spectroscopy has triggered the development of microspectrometers at various wavelength ranges. Several MEMS implementations of the light source, interferometer/optical filter, and detector have already been reported in the literature. However, the size of microspectrometers is still limited by the required absorption path length in the sample gas cell. This paper presents a compact MEMS linear-variable optical filter (LVOF) where the resonator cavity of the filter is also used as a sample gas cell to measure the absorption of methane at 3392nm wavelength. The physical resonator cavity length is elongated 62.2-fold, using multiple reflections from highly reflective Bragg mirrors to achieve a sufficiently long effective optical absorption path. Although the LVOF would in principle enable operation as a robust portable microspectrometer, here it is used in a miniaturized NDIR methane sensor for wavelength selection and calibration.
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| 3. |
- Ayerden, N.P., et al.
(författare)
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A miniaturized optical gas-composition sensor with integrated sample chamber
- 2016
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Ingår i: Sensors and Actuators, B: Chemical. - : Elsevier BV. - 0925-4005. ; 236:29, s. 917-925
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Tidskriftsartikel (refereegranskat)abstract
- A robust and highly miniaturized optical gas sensor based on optical absorption spectroscopy is presented. By using the resonator cavity of a linear variable optical filter (LVOF) also as a gas chamber, a compact and robust optical sensor is achieved. The device operates at the 15th order in 3.2–3.4 μm wavelength range for distinguishing hydrocarbons. The physical cavity length at the μm-level is translated into an effective optical absorption path length at the mm-level by the use of highly reflective (R > 98%) Bragg mirrors. The optical design using the Fizeau interferometer approach is described. Moreover, the CMOS-compatible fabrication method is explained. In addition to the wideband and single wavelength filter characterization, absorption of methane in the LVOF cavity is demonstrated at 3392 nm and 3416.60 nm wavelengths.
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| 4. |
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| 5. |
- Emadi, A., et al.
(författare)
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An UV linear variable optical filter-based micro-spectrometer
- 2010
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Ingår i: Procedia Engineering, Proc. Eurosensors XXIV, September 5-8, 2010, Linz, Austria. - : Elsevier BV. - 1877-7058. ; 5, s. 416-419
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Konferensbidrag (refereegranskat)abstract
- This paper presents the design, fabrication and spectral measurements of an Ultra-Violet (UV) Linear Variable Optical Filter (LVOF)-based micro-spectrometer operating in the 300 nm - 400 nm wavelength range. The UV LVOF has been fabricated in an IC-Compatible process using resist reflow. Characterization by passing monochromatic light through the LVOF, shows high linearity of the profile. It is expected that using signal processing, spectral resolution better than 0.5 nm can be achieved with this UV LVOF. The filter provides the possibility to have a robust high-resolution micro-spectrometer in the UV on a CMOS chip.
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| 6. |
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| 7. |
- Emadi, A., et al.
(författare)
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Design, fabrication and measurements with a UV Linear-Variable Optical Filter microspectrometer
- 2012
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9780819491312 ; 8439, s. Art. no. 84390V-
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Konferensbidrag (refereegranskat)abstract
- An IC-Compatible Linear-Variable Optical Filter (LVOF) for application in the UV spectral range between 310 nm and 400 nm has been fabricated using resist reflow and an optimized dry-etching. The LVOF is mounted on the top of a commercially available CMOS camera to result in a UV microspectrometer. A special calibration technique has been employed that is based on an initial spectral measurement on a Xenon lamp. The image recorded on the camera during calibration is used in a signal processing algorithm to reconstruct the spectrum of the Mercury lamp and the calibration data is subsequently used in UV spectral measurements. Experiments on fabricated LVOF-based microspectrometer with this calibration approach implemented reveal a spectral resolution of 0.5 nm.
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| 8. |
- Emadi, A., et al.
(författare)
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Fabrication and characterization of IC-Compatible Linear Variable Optical Filters with application in a micro-spectrometer
- 2010
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Ingår i: Sensors and Actuators, A: Physical. - : Elsevier BV. - 0924-4247. ; 162:2; Sp. Iss. SI, s. 400-405
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on an IC-Compatible process for the fabrication of Linear Variable Optical Filter (LVOF). The LVOF is integrated with a detector array to result in a micro-spectrometer. The technological challenge in fabrication of an LVOF is fabrication of a well-controlled tapered cavity layer. Very small taper angles, ranging from 0.001 degrees to 0.1 degrees. are fabricated in a resist layer by just one lithography step and a subsequent reflow process. The 3D pattern of resist structures is subsequently transferred into SiO2 by an appropriate etching. Complete LVOF fabrication involves CMOS-compatible deposition of a lower dielectric mirror using a stack of dielectrics on the wafer, tapered layer formation and the deposition of the top dielectric mirror. The design principle, IC-Compatible processing and the characterization results on fabricated LVOFs are presented. (C) 2010 Elsevier B.V. All rights reserved.
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| 9. |
- Emadi, A., et al.
(författare)
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Linear variable optical filter-based ultraviolet microspectrometer
- 2012
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 51:19, s. 4308-4315
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Tidskriftsartikel (refereegranskat)abstract
- An IC-compatible linear variable optical filter (LVOF) for application in the UV spectral range between 310 and 400 nm has been fabricated using resist reflow and an optimized dry-etching. The LVOF is mounted on the top of a commercially available CMOS camera to result in a UV microspectrometer. A special calibration technique has been employed that is based on an initial spectral measurement on a xenon lamp. The image recorded on the camera during calibration is used in a signal processing algorithm to reconstruct the spectrum of the mercury lamp and the calibration data is subsequently used in UV spectral measurements. Experiments on a fabricated LVOF-based microspectrometer with this calibration approach implemented reveal a spectral resolution of 0.5 nm.
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| 10. |
- Emadi, Arvin, et al.
(författare)
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Spectral measurement using IC-compatible linear variable optical filter
- 2010
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Ingår i: Proc. of SPIE. - : SPIE. ; 7716
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Konferensbidrag (refereegranskat)abstract
- This paper reports on the functional and spectral characterization of a microspectrometer based on a CMOS detectorarray covered by an IC-Compatible Linear Variable Optical Filter (LVOF). The Fabry-Perot LVOF is composed of 15dielectric layers with a tapered middle cavity layer, which has been fabricated in an IC-Compatible process using resistreflow. A pattern of trenches is made in a resist layer by lithography and followed by a reflow step result in a smoothtapered resist layer. The lithography mask with the required pattern is designed by a simple geometrical model and FEMsimulation of reflow process. The topography of the tapered resist layer is transferred into silicon dioxide layer by anoptimized RIE process. The IC-compatible fabrication technique of such a LVOF, makes fabrication directly on aCMOS or CCD detector possible and would allow for high volume production of chip-size micro-spectrometers. TheLVOF is designed to cover the 580 nm to 720 spectral range. The dimensions of the fabricated LVOF are 5×5 mm2. TheLVOF is placed in front of detector chip of a commercial camera to enable characterization. An initial calibration isperformed by projecting monochromatic light in the wavelength range of 580 nm to 720 nm on the LVOF and thecamera. The wavelength of the monochromatic light is swept in 1 nm steps. The Illuminated stripe region on the cameradetector moves as the wavelength is swept. Afterwards, a Neon lamp is used to validate the possibility of spectralmeasurement. The light from a Neon lamp is collimated and projected on the LVOF on the camera chip. After dataacquisition a special algorithm is used to extract the spectrum of the Neon lamp.
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