Now showing items 1-16 of 16

    • 94.8 km-range direct detection fiber optic distributed acoustic sensor 

      Uyar, Faruk; Uyar, Talha; Ünal, Canberk; Kartaloğlu, Tolga; Özdur, İbrahim; Özbay, Ekmel (Optical Society of America(OSA), 2019)
      This work demonstrates an ultra-long range direct detection fiber optic distributed acoustic sensor which can detect vibrations at a distance of 94.8 km with 10 m resolution along the sensing fiber.
    • Advances in femtosecond single-crystal sum-frequency generating optical parametric oscillators 

      Köprülü, Kahraman G.; Kartaloğlu, Tolga; Dikmelik, Yamaç; Aytür, Orhan (IEEE, 1998)
      The effect of compensating the group velocity mismatch between the orthogonal pump components on the conversion efficiency of the optical parametric oscillators (OPOs) was investigated. A femtosecond single-crystal ...
    • A direct detection fiber optic distributed acoustic sensor with a mean SNR of 7.3 dB at 102.7 km 

      Uyar, Faruk; Onat, Talha; Ünal, Canberk; Kartaloğlu, Tolga; Özbay, Ekmel; Özdür, İ. (Institute of Electrical and Electronics Engineers Inc., 2019)
      In this work, we present the experimental results of a direct detection π-OTDR based distributed acoustic sensor system. The system uses two cascaded acousto-optic modulators in order to generate optical pulses with very ...
    • Femtosecond optical parametric oscillators based on potassium titanyl phosphate crystals 

      Kartaloğlu, Tolga (Bilkent University, 1996)
      In this thesis, we describe our experiments to construct and characterize optical parametric oscillators (OPO) based on a potassium titanyl phosphate (KTP) crystals. The oscillator is synchronously pumped by a ...
    • Field test and fading measurement of a distributed acoustic sensor system over a 50 km-long fiber 

      Uyar, Faruk; Kartaloğlu, Tolga; Özdür, Ibrahim; Özbay, Ekmel (SPIE - International Society for Optical Engineering, 2018)
      In this study, we present a direct detection distributed acoustic sensor based on phase-sensitive optical time domain reflectometer (φ-OTDR) with long sensing range and high signal-to-noise ratio (SNR), which is field-tested ...
    • High-performance ALGaN-based visible-blind resonant cavity enhanced Schottky photodiodes 

      Kimukin, İbrahim; Bıyıklı, Necmi; Kartaloğlu, Tolga; Aytür, Orhan; Özbay, Ekmel (Materials Research Society, 2003-04)
      We have designed, fabricated and tested resonant cavity enhanced visible-blind AlGaN-based Schottky photodiodes. The bottom mirror of the resonant cavity was formed with a 20 pair AlN/AlGaN Bragg mirror. The devices were ...
    • High-performance solar-blind AlGaN photodetectors 

      Özbay, Ekmel; Bıyıklı, Necmi; Kimukin, İbrahim; Tut, Turgut; Kartaloğlu, Tolga; Aytür, Orhan (IEEE, 2004)
      High-performance aluminum gallium nitride (AlGaN)-based solar-blind (SB) photodetectors were demonstrated using different device structures. The Al x-Ga1-xN layers structure were grown by metalorganic chemical vapor ...
    • High-speed 1.3 μm GaAs internal photoemission resonant cavity enhanced photodetector 

      Kimukin, İbrahim; Özbay, Ekmel; Bıyıklı, Necmi; Kartaloğlu, Tolga; Aytür, Orhan; Tuttle, G. (IEEE, 2000)
      Resonant cavity enhanced (RCE) photodetectors offer the possibility of overcoming the low quantum efficiency limitation of conventional photodetectors. The RCE detectors are based on the enhancement of the optical field ...
    • High-speed solar-blind AlGaN Schottky photodiodes 

      Bıyıklı, Necmi; Kimukin, İbrahim; Kartaloğlu, Tolga; Aytür, Orhan; Özbay, Ekmel (Cambridge University Press, 2003)
      We report high-speed solar-blind AlGaN-based Schottky photodiodes. AlGaN/GaN heterostructure device layers were grown on sapphire substrate. The devices were fabricated on AlGaN/GaN heterostructuresusing a microwave ...
    • High-speed solar-blind AlGaN-based metal-semiconductor-metal photodetectors 

      Bıyıklı, Necmi; Kimukin, İbrahim; Kartaloğlu, Tolga; Aytür, Orhan; Özbay, Ekmel (Wiley, 2003)
      Solar-blind AlGaN metal-semiconductor-metal (MSM) photodetectors with fast pulse response have been demonstrated. The devices were fabricated on MOCVD-grown epitaxial Al0.38Ga0.62N layers, using a microwave compatible ...
    • High-speed visible-blind GaN-based ITO-Schottky photodiodes 

      Bıyıklı, Necmi; Kimukin, İbrahim; Kartaloğlu, Tolga; Aytür, Orhan; Özbay, Ekmel (SPIE, 2002)
      In this paper we present our efforts on the design, fabrication and characterization of high-speed, visible-blind, GaN-based ultra-violet (UV) photodiodes using indium-tin-oxide (ITO) Schottky contacts. ITO is known as a ...
    • The investigation of Rayleigh backscattered signal statistics in a φ-OTDR system incorporating optical pre-amplifier 

      Uyar, Faruk; Kartaloğlu, Tolga; Özbay, Ekmel; Özdur, İbrahim (IEEE, 2020)
      We theoretically model and experimentally demonstrate the photon statistics of Rayleigh backscattered signal in a ϕ-OTDR based distributed fiber optical sensor in the presence of amplified spontaneous emission noise caused ...
    • Laser wavelength upconversion with optical parametric oscillators using simultaneously phase-matched crystals 

      Kartaloğlu, Tolga (Bilkent University, 2002)
      In this thesis, we present our work on optical parametric oscillators that employ a single nonlinear crystal that is simultaneously-phase-matched for second-harmonic or sum-frequency generation in order to obtain frequency ...
    • Phase-matched self-doubling optical parametric oscillator 

      Kartaloğlu, Tolga; Köprülü, Kahraman G.; Aytür, Orhan (IEEE, 1996)
      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 ...
    • A Simple method for enhancing the SNR in direct detection φ-OTDR based distributed acoustic sensors 

      Uyar, Faruk; Kartaloğlu, Tolga; Ünal, Canberk; Özbay, Ekmel; Özdur, İbrahim (IEEE, 2020)
      A simple and effective method for increasing the SNR and range in φ-OTDR based direct-detection distributed acoustic sensors is proposed and experimentally verified. The proposed method results in ~11 dB SNR improvement at 66 km.
    • Single-crystal sum-frequency generating optical parametric oscillator 

      Köprülü, Kahraman G.; Kartaloğlu, Tolga; Aytür, Orhan (IEEE, 1997)
      A sum-frequency generating optical parametric oscillator (OPO), where a single crystal is employed for both parametric oscillation and sum frequency generation, is presented. The OPO is based on a KTiOPO4 crystal that is ...