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| 2. |
- Mandon, J., et al.
(författare)
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A photonic microsystem for hydrocarbon gas analysis by mid-infrared absorption spectroscopy
- 2017
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Ingår i: Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS). - 1084-6999. ; , s. 1052-1055
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Konferensbidrag (refereegranskat)abstract
- This paper demonstrates the functional integration of a linear variable optical filter (LVOF) and a gas cell at the wafer level, i.e. a gas-filled LVOF, where the resonator cavity of the filter is also used for storing the gas sample. A mm-level effective optical absorption path length is achieved from a μm-level physical path length, by exploiting multiple reflections from highly reflective Bragg mirrors and the high-order operation of the filter. The wideband spectral response of the device is ensured by using a tapered cavity, where the cavity length changes linearly along the length of the filter. Therefore, combined with a detector array and a light source, the gas-filled LVOF enables wideband operation and long absorption path in a single MEMS device, thus ensuring a highly sensitive on-chip gas absorption microspectrometer.
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| 3. |
- Silva, M. F., et al.
(författare)
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Magnesium fluoride as low-refractive index material for near-ultraviolet filters applied to optical sensors
- 2020
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Ingår i: Vacuum. - : Elsevier BV. - 0042-207X. ; 181
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Tidskriftsartikel (refereegranskat)abstract
- This article describes the fabrication of MgF2 and MgO thin-film-based optical filters and compares the optical transmission of the filters over UV. The MgF2 thin-films were deposited by use of an e-beam technique and their optical properties were characterised by ellipsometry. The effect of substrate temperature on the optical properties was studied. The MgF2 optimum refractive indices were obtained with a substrate temperature between 200 °C and 300 °C. Optical simulations were performed to compare the performance of MgF2 and MgO in the fabrication of near-UV narrow bandpass optical filters. While MgO-based optical filters result in a higher transmittance peak intensity, especially at 350 nm, the MgF2 optical filters are narrower, present lower values of FWHM, a mean value of 20 nm. This feature could be especially relevant for specific applications on fluorescent optical sensors. Finally, a Fabry-Perot based on a MgF2/TiO2 optical filter was deposited, using an e-beam technique for the MgF2 thin-films and RF-sputtering technique for the TiO2 thin-films. The MgF2/TiO2 optical filter peak transmittance is approximately 70% close to 400 nm, as expected. The results are discussed with focus on applications in fluorescent optical sensors for peaks at 350, 370, 380 and 400 nm, respectively.
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| 4. |
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| 5. |
- 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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| 6. |
- 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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| 7. |
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| 8. |
- Ghaderi, Mohammadamir, 1986, et al.
(författare)
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CMOS Compatible Fabrication of Mid Infrared Microspectrometers Based on an Array of Metamaterial Absorbers
- 2019
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Ingår i: 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems and Eurosensors XXXIII, TRANSDUCERS 2019 and EUROSENSORS XXXIII. ; June 2018, s. 1580-1583
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Konferensbidrag (refereegranskat)abstract
- The design of a mid-infrared micro-spectrometer based on an array of differently tuned narrow-band metamaterial absorbers is presented. The spectral response is tailored by the design of the unit cell. Each spectral band is composed of a thermopile detector with a 300 ×180 μm2 Al-based metamaterial absorber fabricated in a CMOS compatible post-process. The challenges in the fabrication of the sub-μm features within the unit cell over a several mm2 absorber area by equipment that is part of the standard infrastructure of a MEMS facility is addressed. The design and fabrication method utilized here for the first time enables the CMOS fabrication of integrated large-area plasmonic components on thermal detectors.
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| 9. |
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| 10. |
- Ghaderi, Mohammadamir, 1986, et al.
(författare)
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Fabrication and characterization of MEMS airgap-based optical filters for the UV spectral range
- 2017
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Ingår i: TRANSDUCERS 2017 - 19th International Conference on Solid-State Sensors, Actuators and Microsystems. - 9781538627310 ; , s. 1959-1962
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Konferensbidrag (refereegranskat)abstract
- This paper presents the design, fabrication, and characterization of MEMS airgap-based optical filters designed for the ultraviolet (UV) spectral range. Optical design, process conditions, and material choice have been optimized for obtaining large-area and optically flat membranes. Several distributed Bragg reflectors centered at λ=400 nm were designed using silicon oxide and nitride layers as the membrane materials. Airgap Bragg reflectors with up to 80% fill-factor were fabricated in standard Si technology and the spectral reflectance of the reflectors were compared. The optical characterization demonstrated a high reflectance (up to 80%) with only a few number of layers over a bandwidth of up to 175 nm in the UV spectral range.
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