The use of spectroscopy in the field of biomedical science has increased in recent years. Many biological samples such as viruses and bacteria could be detected using FTIR spectroscopy in the MIR range. An important challenge arises when analyzing samples with low concentrations is that they might not be detected or accurately predicted within the capabilities of the instrument’s signal-to-noise ratio. To overcome such challenge, absorption signal enhancement techniques can be used to improve the detectability of the samples. One of such techniques is the use of quantum dots (QDs) that are particles of crystal structure with sizes ranging from a few to tens of nanometers, which exhibit interesting optical properties. In this work, we apply a multi-scale modeling approach to describe the enhancement of QDs starting with an atomistic simulator to extract the absorption lines by solving Schrödinger’s equation. Next, the optical constants of the QDs and biological samples are extracted using Kramer-Kronig’s (KK) relations and Fresnel coefficients, followed by using Maxwell Garnett model in an effective medium approximation. Then, a transfer matrix method (TMM) is used to model layered media containing biological samples mixed with QDs. Using this theoretical description, an enhancement of about 2.5x in a transmission configuration is predicted by simulations for a sample with refractive index representing a saliva sample mixed with mercury telluride (HgTe) QDs. This model can be used to predict the enhancement of different types of QDs with different types of samples, which enhances the detection of various biological samples. Then, the QDs are synthesized experimentally using a two-step injection method. Finally, a practical measurement of the attenuated total reflection (ATR) spectrum in the range of 400-4000 cm-1 of a dried saliva sample mixed with HgTe QDs is carried showing an absorption enhancement of about 1.3x.
The conventional methods used for the diagnostics of viral infection are either expensive and time-consuming or not accurate enough and dependent on consumable reagents. In the presence of pandemics, a fast and reagent-free solution is needed for mass screening. Recently, the diagnosis of viral infections using infrared spectroscopy has been reported as a fast and low-cost method. In this work a fast and low-cost solution for corona viral detection using infrared spectroscopy based on a compact micro-electro-mechanical systems (MEMS) device and artificial intelligence (AI) suitable for mass deployment is presented. Among the different variants of the corona virus that can infect people, 229E is used in this study due to its low pathogeny. The MEMS ATR-FTIR device employs a 6 reflections ZnSe crystal interface working in the spectral range of 2200-7000 cm-1. The virus was propagated and maintained in a medium for long enough time then cell supernatant was collected and centrifuged. The supernatant was then transferred and titrated using plaque titration assay. Positive virus samples were prepared with a concentration of 105 PFU/mL. Positive and negative control samples were applied on the crystal surface, dried using a heating lamp and the spectrum was captured. Principal component analysis and logistic regression were used as simple AI techniques. A sensitivity of about 90 % and a specificity of about 80 % were obtained demonstrating the potential detection of the virus based on the MEMS FTIR device.
In this work, we report a novel notch optical filter based on the imaging properties of a MEMS-based Multimode Interference (MMI) waveguide. The concept is based on the dependence of the imaging lengths on the different wavelengths, where each wavelength exits the waveguide at a different lateral position. Thus, by properly choosing the output waveguide position, it is possible to have a good selective optical filter as well as a good notch optical filter (the complementary response). To validate this concept an MMI structure is fabricated using Deep Reactive Ion Etching (DRIE) technology on a silicon-on-insulator (SOI) wafer. The walls of the waveguide are metalized with Aluminum to decrease the insertion loss. The design makes use of the compactness of the parabolic butterfly shape to reduce the MMI length. The structure is fed by a 9/125 single-mode fiber and the Amplified Spontaneous Emission ASE out of a Semiconductor Optical Amplifier is used as a wideband source for the optical response characterization. The output is measured on an optical spectrum analyzer demonstrating a notch filter response around 1550 nm with about 20-dB rejection ratio. The reported results open the door for integrated, low-cost and fabrication insensitive optical MEMS notch filter.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.