Ultra-compact MEMS FTIR spectrometer

Sabry, Yasser M.; Hassan, Khaled; Anwar, Momen; Alharon, Mohamed H.; Medhat, Mostafa; Adib, George A.; Dumont, Rich; Saadany, Bassam; Khalil, Diaa

doi:10.1117/12.2268078

Cited by 24 publications

(13 citation statements)

References 9 publications

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“…The proposed structure used eight optical fibres for light coupling in and out of the interferometers, which adds some complexity to the system. In principle, the fibres can be replaced by waveguides monolithically integrated on the same chip and a microoptical coupling component 46,47 to achieve the ultimate goal of compactness and low cost.…”

Section: Discussionmentioning

confidence: 99%

On-chip parallel Fourier transform spectrometer for broadband selective infrared spectral sensing

Fathy

Sabry

Nazeer³

et al. 2020

Microsyst Nanoeng

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Optical spectrometers enable contactless chemical analysis. However, decreasing both their size and cost appears to be a prerequisite to their widespread deployment. Chip-scale implementation of optical spectrometers still requires tackling two main challenges. First, operation over a broad spectral range extending to the infrared is required to enable covering the molecular absorption spectrum of a broad variety of materials. This is addressed in our work with an Micro-Electro Mechanical Systems (MEMS)-based Fourier transform infrared spectrometer with an embedded movable micro-mirror on a silicon chip. Second, fine spectral resolution Δλ is also required to facilitate screening over several chemicals. A fundamental limit states that Δλ is inversely proportional to the mirror motion range, which cannot exceed the chip size. To boost the spectral resolution beyond this limit, we propose the concept of parallel (or multi-core) FTIR, where multiple interferometers provide complementary optical paths using the same actuator and within the same chip. The concept scalability is validated with 4 interferometers, leading to approximately 3 times better spectral resolution. After the atmospheric contents of a greenhouse gas are monitored, the methane absorption bands are successfully measured and discriminated using the presented device.

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Section: Discussionmentioning

confidence: 99%

On-chip parallel Fourier transform spectrometer for broadband selective infrared spectral sensing

Fathy

Sabry

Nazeer³

et al. 2020

Microsyst Nanoeng

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“…The MEMS-based FTIR spectrometer (Neospectra, Si-Ware Systems), developed by our group, uses a MEMS-based Michelson interferometer − deeply etched on a silicon substrate using the deep reactive ion etching technique, a long travel range actuator, and a lead selenide (PbSe) detector. This enables it to acquire spectra at a resolution of 66 cm –1 in the wavelength range 1350–4500 nm (wavenumber range 2500–7400 cm –1 ), which includes only the beginning of the mid-infrared range (larger wavenumbers), in contrast to other techniques such as quantum cascade laser-based systems that measure in the middle of the infrared region.…”

Section: Methodsmentioning

confidence: 99%

Detection of Sub-20 μm Microplastic Particles by Attenuated Total Reflection Fourier Transform Infrared Spectroscopy and Comparison with Raman Spectroscopy

et al. 2023

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Microplastics are particulate water contaminants that are raising concerns regarding their environmental and health impacts. Optical spectroscopy is the gold standard for their detection; however, it has severe limitations such as tens of hours of analysis time and spatial resolution of more than 10 μm, when targeting the production of a 2D map of the microparticle population. In this work, through a single spectrum acquisition, we aim at quickly getting information about the whole population of identical particles, their chemical nature, and their size in a range below 20 μm. To this end, we built a compact setup enabling both attenuated total reflection Fourier transform infrared (ATR-FTIR) and Raman spectroscopy measurement on the same sample for comparison purposes. We used monodisperse polystyrene and poly(methyl methacrylate) microplastic spheres of sizes ranging between 6 and 20 μm, also measured collectively using a bench-top FTIR spectrometer in ATR mode. The ATR-FTIR technique appears to be more sensitive for the smallest particles of 6 μm, while the opposite trend is observed using Raman spectroscopy. We use theoretical modeling to simulate and explain the ripples observed in the measured spectra at the shortest wavelength (higher wavenumber) region, which appears as an indicator of the microparticle dimension. The latter finding opens new perspectives for ATR-FTIR for the identification and classification of populations of nearly identical micro-scale bodies, such as bacteria and other micro-organisms, where the same measured spectrum embeds dual information about the chemical nature and the size.

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“…Proposed on-chip FT-IR spectrometer designs have been unable to translate the high-resolution laboratory optical design into a miniaturized package and have focused principally on the near infrared regime using off-chip infrared sources, as described by Sabry et. al 1 . Other on-chip FT-IR interferometers have been proposed that rely on thermo-optic or electro-optic modulation to change the OPL in a waveguide, such as described by Zheng 2 using a tunable micro-ring resonator filter, or Souza 3 using a thermo-optic nonlinearity and dispersion correction.…”

Section: Introductionmentioning

confidence: 98%

Near Centimeter-scale FT-MIR Spectrometer based on NZIM Perfect Absorption using Inverted TanCirc Conformal Mapping Geometry

Swett

2021

Preprint

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A long sought objective of MEMS research within the oil & gas industry has been the realization of “FT-IR on a chip,” which could hold the potential to migrate laboratory grade chemical spectroscopy into downhole sensor suites. A fundamental obstacle to this research has been the cooling demands of conventional technologies which conflict with the miniaturized sensor volumes required in downhole logging systems and environmental conditions that routinely exceed 125 • C. Near centimeter scale spectroscopic devices are required by a majority of downhole sensor suites, which stands in stark contrast to multiple-decimeter size conventional devices. Here we report a near-centimeter scale FT-MIR ATR spectrometer compatible with downhole volumetric and temperature constraints. The spectrometer is based upon a high-temperature broadband mid-infrared metasurface detector/source combination derived from a geometric inversion of a set of conformal mapping contours. The metasurface elemental structure is derived from a geometric inversion of the canonical TanCirc conformal mapping contours and was found to exhibit a near zero index metamaterial (NZIM) behavior over a spectral range of interest for downhole chemical spectroscopy. The NZIM properties of the metasurface lead to an absorption phenomenon characterized by surface plasmon resonances which confine the absorption mechanism within the ultrathin (λ /300) metasurface plane and make the absorption properties of the microbolometer design relatively insensitive to the material properties of the remaining laminae. This unusual feature allows the metasurface to be integrated on a single VO 2 material thermometric layer and operated at elevated downhole temperatures despite corresponding to the VO2 metal-insulator-transition (MIT) region. Within this transition region however the VO2 layer exhibits a substantially beneficial property in that the VO 2 layer exhibits more than an order of magnitude enhancement in its ambient thermometric properties, leading to an uncooled microbolometer design with predicted maximum detectivity D * = 1.5 × 10 10 cm √ Hz/W and noise equivalent difference temperature NEDT of 1 mK at a modulation frequency of 500 Hz. A sub-millimeter scale thermal infrared source with intrinsic mid-infrared band-limited emission is formed from the same cellular geometric building block, enabling the spectrometer miniaturization. These performance parameters compare well with lower tier laboratory grade FT-MIR spectroscopic instruments and could represent a significant step in the effort towards deploying miniaturized high-temperature mid-infrared spectroscopy into oilfield downhole logging applications.

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Ultra-compact MEMS FTIR spectrometer

Cited by 24 publications

References 9 publications

On-chip parallel Fourier transform spectrometer for broadband selective infrared spectral sensing

On-chip parallel Fourier transform spectrometer for broadband selective infrared spectral sensing

Detection of Sub-20 μm Microplastic Particles by Attenuated Total Reflection Fourier Transform Infrared Spectroscopy and Comparison with Raman Spectroscopy

Near Centimeter-scale FT-MIR Spectrometer based on NZIM Perfect Absorption using Inverted TanCirc Conformal Mapping Geometry

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