Researcher:
Mestre, Michael

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Michael

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Mestre

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Mestre, Michael

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2009 - 200972010 - 20121

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    Controlled observation of nondegenerate cavity modes in a microdroplet on a superhydrophobic surface
    (Elsevier, 2009) Department of Physics; Department of Physics; Department of Mechanical Engineering; Department of Mechanical Engineering; Department of Physics; Yorulmaz, Saime Çiğdem; Mestre, Michael; Muradoğlu, Metin; Alaca, Burhanettin Erdem; Kiraz, Alper; Master Student; Researcher; Faculty Member; Faculty Member; Faculty Member; Department of Mechanical Engineering; Department of Physics; College of Engineering; College of Engineering; College of Engineering; College of Engineering; College of Sciences; N/A; N/A; 46561; 115108; 22542
    We demonstrate controlled lifting of the azimuthal degeneracy of the whispering gallery modes (WGMs) of single glycerol-water microdroplets standing on a superhydrophobic surface by using a uniform electric field. A good agreement is observed between the measured spectral positions of the nondegenerate WGMs and predictions made for a prolate spheroid. Our results reveal fewer azimuthal modes than expected from an ideal spherical microdroplet due to the truncation by the surface. We use this difference to estimate the contact angles of the microdroplets.
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    Reversible photothermal tuning of single salt-water microdroplets on a superhydrophobic surface
    (Optical Society of America, 2009) N/A; Department of Physics; Department of Physics; Department of Physics; Kiraz, Alper; Yorulmaz, Saime Çiğdem; Mestre, Michael; Faculty Member; Master Student; Researcher; Department of Physics; College of Sciences; College of Sciences; College of Sciences; 22542; N/A; N/A
    We demonstrate large (up to 15 nm) and reversible spectral tuning of the whispering gallery modes of single NaCl-water microdroplets standing on a superhydrophobic surface by local heating with an infrared laser.
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    Probing of ultrahigh optical Q-factors of individual liquid microdroplets on superhydrophobic surfaces using tapered optical fiber waveguides
    (Optical Society of America (OSA), 2012) N/A; Department of Physics; N/A; Department of Physics; Department of Physics; Kiraz, Alper; Karadağ, Yasin; Jonas, Alexandr; Mestre, Michael; Faculty Member; PhD Student; Other; Researcher; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; 22542; N/A; N/A; N/A
    We report measurements of ultrahigh quality factors (Q-factors) of the optical whispering-gallery modes excited via a tapered optical-fiber waveguide in single glycerol-water microdroplets standing on a superhydrophobic surface in air. Owing to the high contact angle of the glycerol-water mixture on the superhydrophobic surface (≥155°), microdroplets with the geometry of a truncated sphere minimally distorted by gravity and contact line pinning effects could be generated. Q-factors up to 2.3 × 106 were observed for such droplets with radii of 100-200 μm exposed to the ambient atmosphere in a closed chamber with controlled relative humidity. Placement of microdroplets in a constant humidity environment permitted prolonged characterization of Q-factors for individual microdroplets. We found that the Q-factors in air were stable over more than 1 h and their measured values were limited mostly by the thermally induced droplet shape fluctuations.
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    High precision size tuning and stabilization of single salt-water microdroplets on a superhydrophobic surface
    (Ieee, 2009) N/A; Department of Physics; Department of Physics; N/A; N/A; N/A; Kiraz, Alper; Mestre, Michael; Karadağ, Yasin; Yorulmaz, Saime Çiğdem; Gündoğan, Mustafa; Faculty Member; Researcher; PhD Student; Master Student; Master Student; Department of Physics; College of Sciences; College of Sciences; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 22542; N/A; N/A; N/A; N/A
    While their spherical geometry is mostly preserved, salt-water microdroplets can be studied in stable experimental conditions when standing on a superhydrophobic surface. Here, we report how the photothermal effect can be used to continuously tune or lock the whispering gallery mode (WGM) spectrum (therefore the size) of salt-water microdroplets on a superhydrophobic surface. The microdroplets are kept in the controlled atmosphere of a humidity chamber. Local heating by an infrared laser focused at the center of the microdroplet causes it to depart from its equilibrium size, shifting the WGM spectrum. This photothermal tuning effect is fully reversible and can be used to tune the microdroplet radius with a precision reaching 1 A by finely controlling the heating laser power. We demonstrate a new spectroscopy method based on this effect, and use it to measure Q-factors of WGM resonances of up to similar to 10(5). Conversely, focusing the heating laser to the microdroplet rim causes it to experience absorption resonances, leading to a hysteretic behavior when increasing and decreasing the laser power. We show that this behavior can be used to lock the size of a microdroplet and make it function as an optically bistable element. WGM resonances of microdroplets locked in such a way are probed using a tunable laser, showing a locking precision reaching < 0.01 nm over tens of minutes. These results indicate that the challenges in terms of position and wavelength stability inherent to liquid microdroplets surrounded by air can be overcome, and that they provide an easily tunable and lockable alternative to solid optical microcavities.
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    Direct measurement of high Q-factors in individual salt-water microdroplets by photothermal tuning spectroscopy
    (Optical Society of America, 2009) N/A; Department of Physics; N/A; Department of Physics; Gündoğan, Mustafa; Kiraz, Alper; Yorulmaz, Saime Çiğdem; Mestre, Michael; Master Student; Faculty Member; Master Student; Researcher; Department of Physics; Graduate School of Sciences and Engineering; College of Sciences; Graduate School of Sciences and Engineering; College of Sciences; N/A; 22542; N/A; N/A
    We present measurements of high quality (Q) factors in liquid microdroplets standing on a superhydrophobic surface using the new photothermal tuning spectroscopy technique. Q-factors up to ~105 are observed from degenerate whispering gallery modes. © 2009 Optical Society of America.
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    Photothermal tuning and size locking of salt-water microdroplets on a superhydrophobic surface
    (Taylor and Francis inc, 2009) N/A; Department of Physics; N/A; N/A; N/A; Department of Physics; Mestre, Michael; Karadağ, Yasin; Yorulmaz, Saime Çiğdem; Gündoğan, Mustafa; Kiraz, Alper; Researcher; PhD Student; Master Student; Master Student; Faculty Member; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; N/A; 22542
    Liquid microdroplets are attractive as optical microcavities with tunable resonances for applications in quantum optics and biological sensing, owing to their flexible nature and spherical shape. Salt-water microdroplets can be used in such experiments while standing on a superhydrophobic surface that preserves their spherical geometry. Here, we report how the photothermal effect enables continuous tuning or locking of the whispering gallery mode (WGM) spectrum and size of salt-water microdroplets on a superhydrophobic surface. Local heating by an infrared laser focused at the center of a microdroplet causes it to depart from its equilibrium size, shifting the WGM spectrum. This photothermal tuning effect is fully reversible and can be used to tune the microdroplet radius with a precision reaching 1 angstrom. We combine this effect with fluorescence excitation spectroscopy using a fixed wavelength laser to measure Q-factors of up to similar to 10(5). Conversely, focusing the heating laser to the microdroplet rim reveals absorption resonances, leading to a hysteretic behavior when cycling the laser power. We show that this behavior can be used to lock the size of a microdroplet and make it exhibit optical bistability. WGM resonances of locked microdroplets are probed using a tunable laser, showing a spectral locking precision reaching <0.01 nm over tens of minutes. these results indicate that the wavelength stability and positioning challenges inherent to liquid microdroplets in air can be overcome, providing an easily tunable and lockable alternative to solid optical microcavities and making them potential candidates for studies in cavity optomechanics.
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    High precision size tuning and stabilization of single salt-water microdroplets on a superhydrophobic surface
    (2009) N/A; Department of Physics; N/A; Department of Physics; Gündoğan, Mustafa; Kiraz, Alper; Yorulmaz, Saime Çiğdem; Mestre, Michael; Master Student; Faculty Member; Master Student; Researcher; Department of Physics; Graduate School of Sciences and Engineering; College of Sciences; Graduate School of Sciences and Engineering; College of Sciences; N/A; 22542; N/A; N/A
    While their spherical geometry is mostly preserved, salt-water microdroplets can be studied in stable experimental conditions when standing on a superhydrophobic surface. Here, we report how the photothermal effect can be used to continuously tune or lock the whispering gallery mode (WGM) spectrum (therefore the size) of salt-water microdroplets on a superhydrophobic surface. The microdroplets are kept in the controlled atmosphere of a humidity chamber. Local heating by an infrared laser focused at the center of the microdroplet causes it to depart from its equilibrium size, shifting the WGM spectrum. This photothermal tuning effect is fully reversible and can be used to tune the microdroplet radius with a precision reaching 1 Å by finely controlling the heating laser power. We demonstrate a new spectroscopy method based on this effect, and use it to measure Q-factors of WGM resonances of up to - 10 5. Conversely, focusing the heating laser to the microdroplet rim causes it to experience absorption resonances, leading to a hysteretic behavior when increasing and decreasing the laser power. We show that this behavior can be used to lock the size of a microdroplet and make it function as an optically bistable element. WGM resonances of microdroplets locked in such a way are probed using a tunable laser, showing a locking precision reaching andlt; 0.01 nm over tens of minutes. These results indicate that the challenges in terms of position and wavelength stability inherent to liquid microdroplets surrounded by air can be overcome, and that they provide an easily tunable and lockable alternative to solid optical microcavities. © 2009 IEEE.
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    Photothermal self-stability and optical bistability of single nacl-water microdroplets on a superhydrophobic surface
    (Royal Soc Chemistry, 2009) N/A; N/A; Department of Physics; Department of Physics; Karadağ, Yasin; Mestre, Michael; Kiraz, Alper; PhD Student; Other; Faculty Member; Department of Physics; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; 22542
    A self-stabilization mechanism locking the size of single inorganic salt (NaCl)–water microdroplets that are standing on a superhydrophobic surface and kept in a humidity-controlled chamber is demonstrated. The effect is based on the hysteretic behavior of a photothermal tuning cycle caused by the whispering gallery mode (WGM) absorption resonances that are observed when scanning the power of an infrared laser focused at the rim of a microdroplet. When locked, the microdroplet size and WGM spectrum are resilient to environmental perturbations and can be maintained for hours as the mechanism does not rely on a photobleachable dye. The bistable nature of the system is also demonstrated, enabling reversible switching between two sizes. A rate equation-based thermodynamical model of the hysteretic behavior is provided, giving good agreement with the experimental results. Our results may be used to establish stable experimental conditions for ultrahigh resolution spectroscopy of microdroplets. Other optical and biological applications that require exactly size-matched microdroplets can also benefit from the demonstrated self-stabilization mechanism.