Browsing by Subject "Antireflection coatings"

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    Actively tunable thin films for visible light by thermo-optic modulation of ZnO
    (Wiley-VCH Verlag, 2016) Battal, E.; Okyay, Ali Kemal
    Applications of active control of light matter interactions within integrated photonics, hyper-spectral imaging, reconfigurable lasers, and selective bio-surfaces have enormously increased the demand for realization of optical modulation covering the spectrum from ultraviolet (UV) up to infrared (IR) wavelength range. In this study, we demonstrate ZnO-based actively tunable perfect absorber operating within UV and visible spectrum with more than 5 nm shift in the resonant absorption wavelength. Using spectroscopic ellipsometry technique, we extract temperature-dependent optical constants of atomic layer-deposited ZnO within 0.3-1.6 and 4-40 μm spectra. We also observe bandgap narrowing of ZnO at elevated temperatures due to lattice relaxation verified by the red-shift of phonon-modes. At around its bandgap, refractive index variations up to 0.2 is obtained and ZnO is shown to exhibit thermo-optic coefficient as high as 9.17 × 10-4 K-1 around the bandgap which is the largest among well-known large bandgap materials. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
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    Femtosecond self-doubling optical parametric oscillator based on KTiOAsO4
    (IEEE, 2003) Kartaloğlu, T.; Aytür, O.
    We report a femtosecond intracavity-frequency-doubled optical parametric oscillator that employs a single KTiOAsO4 crystal for both parametric generation and frequency doubling. This device generates a yellow output beam at 575 nm with 39.4% power conversion efficiency when synchronously pumped by a femtosecond Ti:sapphire laser at a wavelength of 796 nm. An intracavity retarder is employed to alleviate temporal pulse overlap problems associated with group velocity mismatch inside the KTiOAsO4 crystal.
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    Phase-matched self-doubling optical parametric oscillator
    (IEEE, 1996) Kartaloğlu, Tolga; Köprülü, Kahraman G.; Aytür, Orhan
    A new self-doubling optical parametric oscillator (OPO) uses a single nonlinear crystal for both parametric generation and frequency doubling. It is based on a KTiOPO4 (KTP) crystal pumped by a Ti:Sapphire laser operating at a wavelength of 739 nm. The crystal is cut such that the signal wavelength of the OPO is at 1064 nm, corresponding to an idler wavelength of 2420 nm. The OPO cavity resonates only the signal wavelength. The signal beam is also phase-matched for second harmonic generation (SHG) at the same crystal orientation. With proper polarization rotation, an output beam at a wavelength of 532 nm can be obtained.