The University of Southampton
University of Southampton Institutional Repository

Mid-infrared liquid spectroscopy using chalcogenide optical waveguide

Mid-infrared liquid spectroscopy using chalcogenide optical waveguide
Mid-infrared liquid spectroscopy using chalcogenide optical waveguide
Biochemical analysis for medical diagnostics is normally carried out by trained operators in sophisticated laboratories using large instruments. These techniques are out of reach to many people living in remote areas or are too slow for critically ill patients who need urgent care. A rapid, automated, compact, low cost and disposable integrated lab on a chip device which can be operated by a minimally trained person is required not only for the detection and diagnosis of the diseases, but also for water, food and environmental safety. Optical waveguide devices allow integration of various optoelectronic and microfluidic components to help in realizing sensing of liquid analytes and require 3-6 orders less sample volume compared with many conventional medical tests. The mid-infrared (mid-IR) spectral window covering wavelengths from 2 to 14 µm is ideal for biochemical analysis due to the fundamental fingerprint molecular absorption, and waveguide evanescent field based spectroscopy can potentially offer rapid high sensitivity, real-time measurement of complex mixtures to identify and quantify species in clinical samples for point of care diagnosis without any biomarkers. To realize such devices, mid-IR transparent chalcogenide materials are used to fabricate optical waveguides. In our previous work, we have demonstrated waveguiding in the mid-IR region using germanium telluride (GeTe 4) waveguide cores on zinc selenide (ZnSe) substrates [1]. In this work, ZnSe rib waveguides were fabricated on oxidized silicon with the dimensions shown in Fig 1(a). ZnSe films were deposited by thermal evaporation and the ribs were fabricated using photolithography and Ar + ion-beam etching. Light from a tunable optical parametric oscillator (M-squared) operating between 2.5-3.7 µm wavelengths was butt-coupled into the waveguide using a single mode ZrF 4 fibre (core diameter ~ 9 µm) and the waveguide output was collected using a multimode InF 3 fibre (core diameter ~100 µm), directed onto a TE cooled Mercury Cadmium Telluride detector (MCT, Vigo System) and recorded on a computer. After optimizing coupling into the waveguide by imaging the waveguide output using a mid-IR camera from above, as shown in Fig 1(b), two spectral scans were recorded, one of the output power from the waveguide alone and the other with a10 µL DI water droplet on the waveguide surface of length ~0.6 cm shown in Fig 1(c) inset. The ratio, representing the waveguide absorption spectrum of water, is plotted in Fig 1(c) (black points) and compared with a numerical model of the water-coated waveguide (blue line) using the published complex refractive index of water [2], for a waveguide length of 0.6 cm. These preliminary experimental results are in good agreement with the theoretical results. The elevated transmission in the absorption band is due to substrate radiation and the transmission above unity is due to reduction in waveguide scattering loss with the water cladding. Future work will study the absorption spectra of clinically relevant analytes. Fig. 1 (a) Theoretical mode profile of ZnSe rib waveguide, (b) Infrared camera image of the guiding rib waveguide sample with a water drop on its surface and (c) Experimental and theoretical IR-spectra of water on the surface of a ZnSe waveguide (inset: photograph of waveguide sample while taking measurements).
Mittal, Vinita
fd5ee9dd-7770-416f-8f47-50ca158b39b0
Wilkinson, James
73483cf3-d9f2-4688-9b09-1c84257884ca
Murugan, G.S.
a867686e-0535-46cc-ad85-c2342086b25b
Mittal, Vinita
fd5ee9dd-7770-416f-8f47-50ca158b39b0
Wilkinson, James
73483cf3-d9f2-4688-9b09-1c84257884ca
Murugan, G.S.
a867686e-0535-46cc-ad85-c2342086b25b

Mittal, Vinita, Wilkinson, James and Murugan, G.S. (2016) Mid-infrared liquid spectroscopy using chalcogenide optical waveguide. EMN Meeting on Photonics 2016, Barcelona, Spain. 19 - 23 Sep 2016. 2 pp .

Record type: Conference or Workshop Item (Other)

Abstract

Biochemical analysis for medical diagnostics is normally carried out by trained operators in sophisticated laboratories using large instruments. These techniques are out of reach to many people living in remote areas or are too slow for critically ill patients who need urgent care. A rapid, automated, compact, low cost and disposable integrated lab on a chip device which can be operated by a minimally trained person is required not only for the detection and diagnosis of the diseases, but also for water, food and environmental safety. Optical waveguide devices allow integration of various optoelectronic and microfluidic components to help in realizing sensing of liquid analytes and require 3-6 orders less sample volume compared with many conventional medical tests. The mid-infrared (mid-IR) spectral window covering wavelengths from 2 to 14 µm is ideal for biochemical analysis due to the fundamental fingerprint molecular absorption, and waveguide evanescent field based spectroscopy can potentially offer rapid high sensitivity, real-time measurement of complex mixtures to identify and quantify species in clinical samples for point of care diagnosis without any biomarkers. To realize such devices, mid-IR transparent chalcogenide materials are used to fabricate optical waveguides. In our previous work, we have demonstrated waveguiding in the mid-IR region using germanium telluride (GeTe 4) waveguide cores on zinc selenide (ZnSe) substrates [1]. In this work, ZnSe rib waveguides were fabricated on oxidized silicon with the dimensions shown in Fig 1(a). ZnSe films were deposited by thermal evaporation and the ribs were fabricated using photolithography and Ar + ion-beam etching. Light from a tunable optical parametric oscillator (M-squared) operating between 2.5-3.7 µm wavelengths was butt-coupled into the waveguide using a single mode ZrF 4 fibre (core diameter ~ 9 µm) and the waveguide output was collected using a multimode InF 3 fibre (core diameter ~100 µm), directed onto a TE cooled Mercury Cadmium Telluride detector (MCT, Vigo System) and recorded on a computer. After optimizing coupling into the waveguide by imaging the waveguide output using a mid-IR camera from above, as shown in Fig 1(b), two spectral scans were recorded, one of the output power from the waveguide alone and the other with a10 µL DI water droplet on the waveguide surface of length ~0.6 cm shown in Fig 1(c) inset. The ratio, representing the waveguide absorption spectrum of water, is plotted in Fig 1(c) (black points) and compared with a numerical model of the water-coated waveguide (blue line) using the published complex refractive index of water [2], for a waveguide length of 0.6 cm. These preliminary experimental results are in good agreement with the theoretical results. The elevated transmission in the absorption band is due to substrate radiation and the transmission above unity is due to reduction in waveguide scattering loss with the water cladding. Future work will study the absorption spectra of clinically relevant analytes. Fig. 1 (a) Theoretical mode profile of ZnSe rib waveguide, (b) Infrared camera image of the guiding rib waveguide sample with a water drop on its surface and (c) Experimental and theoretical IR-spectra of water on the surface of a ZnSe waveguide (inset: photograph of waveguide sample while taking measurements).

Text
EMN_Spain_paperVM.pdf - Other
Restricted to Registered users only
Available under License Creative Commons Attribution.
Download (62kB)
Request a copy

More information

Published date: 19 September 2016
Venue - Dates: EMN Meeting on Photonics 2016, Barcelona, Spain, 2016-09-19 - 2016-09-23
Organisations: Optoelectronics Research Centre

Identifiers

Local EPrints ID: 400881
URI: http://eprints.soton.ac.uk/id/eprint/400881
PURE UUID: d81d0a12-3383-497a-88c9-432ac2270880
ORCID for Vinita Mittal: ORCID iD orcid.org/0000-0003-4836-5327
ORCID for James Wilkinson: ORCID iD orcid.org/0000-0003-4712-1697
ORCID for G.S. Murugan: ORCID iD orcid.org/0000-0002-2733-3273

Catalogue record

Date deposited: 04 Oct 2016 15:26
Last modified: 15 Mar 2024 03:23

Export record

Contributors

Author: Vinita Mittal ORCID iD
Author: James Wilkinson ORCID iD
Author: G.S. Murugan ORCID iD

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×