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Quartile: search.filters.quartile.Q2Subject: search.filters.subject.Photonics

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    PublicationOpen Access
    Detection of aflatoxin M1 by fiber cavity attenuated phase shift spectroscopy
    (Optical Society of America (OSA), 2021) Ghauri, M. Daniyal; Hussain, Syed Zajif; Ullah, Ubaid; Saleem, Rahman Shah Zaib; Cheema, M. Imran; N/A; Department of Physics; Ayaz, Rana Muhammed Armaghan; Kiraz, Alper; Faculty Member; Department of Physics; Graduate School of Sciences and Engineering; College of Sciences; N/A; 22542
    Aflatoxin M1 (AFM1) is a carcinogenic compound commonly found in milk in excess of the WHO permissible limit, especially in developing countries. Currently, state-of-the-art tests for detecting AFM1 in milk include chromatographic systems and enzyme-linked-immunosorbent assays. Although these tests provide fair accuracy and sensitivity, they require trained laboratory personnel, expensive infrastructure, and many hours to produce final results. Optical sensors leveraging spectroscopy have a tremendous potential of providing an accurate, real-time, and specialist-free AFM1 detector. Despite this, AFM1 sensing demonstrations using optical spectroscopy are still immature. Here, we demonstrate an optical sensor that employs the principle of cavity attenuated phase shift spectroscopy in optical fiber cavities for rapid AFM1 detection in aqueous solutions at 1550 nm. The sensor constitutes a cavity built by two fiber Bragg gratings. We splice a tapered fiber of < 10 μm waist inside the cavity as a sensing head. For ensuring specific binding of AFM1 in a solution, the tapered fiber is functionalized with DNA aptamers followed by validation of the conjugation via FTIR, TGA, and EDX analyses. We then detect AFM1 in a solution by measuring the phase shift between a sinusoidally modulated laser input and the sensor output at resonant frequencies of the cavity. Our results show that the sensor has the detection limit of 20 ng/L (20 ppt), which is well below both the U.S. and the European safety regulations. We anticipate that the present work will lead towards a rapid and accurate AFM1 sensor, especially for low-resource settings.
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    PublicationOpen Access
    Pupil steering holographic display for pre-operative vision screening of cataracts
    (Optica Publishing Group, 2021) Ulusoy, Erdem; Department of Electrical and Electronics Engineering; Kavaklı, Koray; Aydındoğan, Güneş; Kesim, Cem; Hasanreisoğlu, Murat; Şahin, Afsun; Ürey, Hakan; Teaching Faculty; Faculty Member; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Sciences and Engineering; School of Medicine; College of Engineering; Koç University Hospital; N/A; N/A; N/A; 182001; 171267; 8579
    Cataract is the most common cause of preventable blindness and vision loss where the only treatment is surgical replacement of the natural lens with an intraocular lens. Computergenerated holography (CGH) enables to control phase, size, and shape of the light beam entering through the eye-pupil. We developed a holographic vision simulator to assess visual acuity for patients to experience the postoperative corrected vision before going through surgery. A holographically shaped light beam is directed onto the retina using small non-cataractous regions of the lens with the help of a pupil tracker. A Snellen chart hologram is shown to subjects at desired depth with myopia and hyperopia correction. Tests with 13 patients demonstrated substantial improvements in visual acuity and the simulator results are consistent with the post-operative vision tests. Holographic simulator overperforms the existing vision simulators, which are limited to static pinhole exit pupils and incapable of correcting aberrations.